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A Collection of Biographies Geophysics

A Collection of Biographies Geophysics

A Collection of Biographies with special emphasis on

by

Wolfgang A. Lenhardt

Lenhardt – Biographies 1 Foreword

This presentation of biographies is far from complete and kept very brief for each person relevant to geophysics. Most texts are taken from Wikipedia and respective links are stated at the bottom of each page. The biographies are sorted in chronological order according respective years of birth and show pictures (when possible from their haydays) of these scientists and engineers. Their countries of birth and death are given in historical context (England <> G.B. >> U.K., Prussia <> , Austro-Hungarian Empire >> , Yugoslavia <> Serbia, Croatia, etc.) thus might to appear erratic, but are deemed to be correct.

It seems appropriate to mention the many achievements in geophysics which were not accomplished by a single person alone – as it happens in all other scientific disciplines. Therefore, collaborations are briefly addressed in some slides. In addition, the sequence of biographies is supplemented by slides describing two significant natural events, which altered almost immediately the course of geophysical understanding of our .

Each person has been allocated a specific main achievement or topic related to geophysics. Sometimes, these allocations are incomplete, like for e.g. Gauss, Laplace or Young, which were truly multi-talented. Hence, some of the headlines might be considered not to the point by some readers. I apologize for that. Please let me know, where I did very wrong.

[email protected] /Austria 21st of December, 2020

Lenhardt – Biographies 2 Brief Overview of

13th cent. Petrus Peregrinus Compass 1596 Geographer, shapes of continents match! 1600 William Gilbert magnetism 1635 Henry Gellibrand Secular variation (movement of geomagnetic field) 1735 Pierre Bouguer Abnormal gravity at Chimborazo (Andes) 1831-1843 Carl Friedrich Gauss Separation of the inner and outer Earth‘s magnetic field 1858 Antonio Snider-Pellegrini Similarities of fossils in coal seams 1895 Pierre Curie Loss of magnetism of rocks at high temperatures 1906 Bernard Brunhes Inversion of magnetic field 1908 Frank Bursley Taylor Geology, movement of continents, shape 1915 “Die Entstehung der Kontinente und Ozeane” 1926 Harold Jeffreys Rejects 1927 Arthur Holmes Drift, convection due to heat 1933 Kiyoo Wadati Deep in Japan 1937 Alexander du Toit “Our Wandering Continents“, 1941 Beno Gutenberg & Charles Frederic Richter Subduction? - Already half of the geologists accept continental drift 1950 Patrick Blackett & Keith Runcorn Local magnetic field orientation relates to continental drift 1959/1962 Harry Hess Sea floor topography, “Sea Floor Spreading“ 1963 Drummond Mathews & Local inversions of magnetic field at sea floor (Carlsberg Ridge) 1963/65 John Tuzo-Wilson Hotspots und transform-faults in oceans

Lenhardt – Biographies 3 Ptolemeic World – 2nd century

After 's book Geography, written c. 150. Based on an inscription in several of the earliest surviving manuscripts, it is traditionally credited to Agathodaemon of Alexandria (2nd century A.D). See also: https://en.wikipedia.org/wiki/Ptolemy%27s_world_map

Lenhardt – Biographies 4 Deep Time

Aristotle

(384 in Stagira/Macedonia – 322 BC in Euboea/Macedonia) was a Greek philosopher and polymath during the Classical period in Ancient Greece. He was the founder of the Lyceum and the Peripatetic School of Philosophy and Aristotelian tradition. Along with his teacher Plato, he has been called the “Father of Western Philosophy”. His writings cover almost all subjects such as , biology, zoology, metaphysics, logic, ethics, esthetics, poetry, theatre, music, rhetoric, psychology, linguistics, economics, politics and government. Aristotle provided a complex synthesis of the various philosophies existing prior to him, and it was above all from his teachings that the West inherited its intellectual lexicon, as well as problems and methods of inquiry. As a result, his philosophy has exerted a unique influence on almost every form of knowledge in the West and it continues to be a subject of contemporary philosophical discussion. Meanwhile, many of Aristotle’s findings (e.g. the speed of a free falling object depends on its weight) have been disproved. The philosopher Bertrand Russell argued that “almost every serious intellectual advance has had to begin with an attack on some Aristotelian doctrine”. Russell called Aristotle's ethics “repulsive”, and labelled his logic ”as definitely antiquated as Ptolemaic ”. Russell stated that these errors made it difficult to do historical justice to Aristotle, until one remembered what an advance he made upon all of his predecessors. Geosciences: Aristotle was one of the first people to record any geological observations. He stated that geological change was too slow to be observed in one person's lifetime. The geologist Charles Lyell noted that Aristotle described such change, including “lakes that had dried up” and “deserts that had become watered by rivers”, giving as examples the growth of the Nile delta since the time of Homer, and "the upheaving of one of the Aeolian islands, previous to a volcanic eruption“. Hence, he anticipated the concept of “deep time” which was put forward by John McPhee in 1981.

See also: https://de.wikipedia.org/wiki/Aristoteles https://en.wikipedia.org/wiki/Deep_time

Lenhardt – Biographies 5 Earth Size

Eratosthenes of Cyrene

(c. 276 BC in Cyrene/today Libya – c. 195/194 BC in Alexandria/Egypt) was a Greek polymath: a mathematician, geographer, astronomer, poet, and music theorist. He was a man of learning, becoming the chief librarian at the Library of Alexandria. His work is comparable to what is now known as the study of geography, and he introduced some of the terminology still used today. He is best known for being the first person to calculate the circumference of the Earth, which he did by comparing angles of the mid-day Sun at two places, a known North-South distance apart. His calculation was remarkably accurate. He was also the first to calculate the tilt of the Earth's axis, again with remarkable accuracy. Additionally, he may have accurately calculated the distance from the Earth to the Sun and invented the leap day. He created the first global projection of the world, incorporating parallels and meridians based on the available geographic knowledge of his era. was the founder of scientific chronology; he endeavoured to revise the dates of the chief literary and political events from the conquest of Troy. Eratosthenes dated “The Sack of Troy” to 1183 BC. In number theory, he introduced the sieve of Eratosthenes, an efficient method of identifying prime numbers. He was a figure of influence in many fields. According to an entry in the Suda (a 10th century encyclopedia), his critics scorned him, calling him Beta (the second letter of the Greek alphabet) because he always came in second in all his endeavors. Nonetheless, his devotees nicknamed him Pentathlos after the Olympians who were well rounded competitors, for he had proven himself to be knowledgeable in every area of learning. Eratosthenes yearned to understand the complexities of the entire world.

See also: https://en.wikipedia.org/wiki/Eratosthenes

Lenhardt – Biographies 6 Seismoscope

Zhang Heng

(張衡; AD 78 in Nanyang/China – 139 in Luoyang/China), formerly romanized as Chang Heng, was a Chinese polymathic scientist and statesman from Nanyang who lived during the Han dynasty. Educated in the capital cities of Luoyang and Chang'an, he achieved success as an astronomer, mathematician, seismologist, hydraulic engineer, inventor, geographer, cartographer, ethnographer, artist, poet, philosopher, politician, and literary scholar. In 132, Zhang introduced an intricate seismoscope to the court, which he claimed could detect the precise cardinal direction of a distant . On one occasion his device indicated that an earthquake had occurred in the northwest. As there was no perceivable tremor felt in the capital his political enemies were briefly able to relish the failure of his device, until a messenger arrived shortly afterwards to report that an earthquake had occurred about 400 km to 500 km northwest of Luoyang in Gansu province. During the Han Dynasty, many learned scholars — including Zhang Heng — believed in the “oracles of the winds”. These oracles of the occult observed the direction, force, and timing of the winds, to speculate about the operation of the cosmos and to predict events on Earth. These ideas influenced Zhang Heng's views on the cause of earthquakes.

See also: https://en.wikipedia.org/wiki/Zhang_Heng

Lenhardt – Biographies 7 Compass

Petrus Peregrinus de Maricourt

or Pierre Pelerin de Maricourt (French), or Peter Peregrinus of Maricourt (1240 in Maricourt/ – date of death and place not known), was a 13th-century French scholar who conducted experiments on magnetism and wrote the first extant treatise describing the properties of magnets. His work is particularly noted for containing the earliest detailed discussion of freely pivoting compass needles, a fundamental component of the dry compass soon to appear in medieval navigation. He also wrote a treatise on the construction and use of a universal astrolabe. The Epistola de magnete is divided into two parts. Part One discusses the physical (but not the occult) properties of the lodestone (= magnetite) and provides the first extant written account of the polarity of magnets. He was thus the first to use the word “pole” in this context. There, he provides methods for determining the opposing poles of a magnet, and he describes the effects magnets have upon one another, showing that like poles repel each other and unlike poles attract each other. He also treats the attraction (magnetization) of iron by lodestones (= magnetites) and the ability to reverse the polarity in such an induced magnet. Peregrinus attributed the Earth's magnetism to the action of celestial poles, rather than to the terrestrial poles of the planet itself - where he failed. Part Two describes three devices that utilize the properties of magnets. He treats the practical applications of magnets, describing the “wet” floating compass as an instrument in common use, and proposing a new “dry” pivoted compass in some detail. He also attempts to prove that with the help of magnets it is possible to realize perpetual motion. His device is a toothed wheel which passes near a lodestone so that the teeth are alternately attracted by one pole and repelled by the other. One of his disciples was Roger Bacon.

See also: https://en.wikipedia.org/wiki/Petrus_Peregrinus_de_Maricourt

Lenhardt – Biographies 8 Match of Continents Abraham Ortelius

(April 14, 1527 in /Habsburg – June 28, 1598 in Antwerp/Spanish Netherlands) was a Brabantian cartographer and geographer, conventionally recognized as the creator of the first modern , the (Theatre of the World). Ortelius is often considered one of the founders of the Netherlandish school of cartography and one of the most notable figures of the school in its golden age (approximately 1570s – 1670s). The publication of his atlas in 1570 is often considered as the official beginning of the Golden Age of Netherlandish cartography. He is also believed to be the first person to imagine that the continents were joined before drifting to their present positions. In 1578 he laid the basis of a critical treatment of ancient geography by his Synonymia geographica – issued by the Plantin press at Antwerp and republished in expanded form as Thesaurus Geographicus in 1587 and again expanded in 1596. In this last edition, Ortelius considers the possibility of continental drift, a hypothesis proved correct only centuries later. Ortelius was the first to underline the geometrical similarity between the coasts of America and Europe-Africa and to propose continental drift as an explanation. Jaquelyne Kious (1996) described Ortelius's thoughts in this way: “Abraham Ortelius in his work Thesaurus Geographicus … suggested that the Americas were “torn away from Europe and Africa … by earthquakes and floods” and went on to say: “The vestiges of the rupture reveal themselves, if someone brings forward a map of the world and considers carefully the coasts of the three [continents].” See also: https://en.wikipedia.org/wiki/Abraham_Ortelius

Lenhardt – Biographies 9 Earth´s Magnetism

William Gilbert

also known as Gilberd (May 24, 1544 in Colchester/England – November 30, 1603 in London/England),, was an English physician, physicist and natural philosopher. He passionately rejected both the prevailing Aristotelian philosophy and the Scholastic method of university teaching. He is credited as one of the originators of the term “electricity”. He is regarded by some as the father of electrical engineering or electricity and magnetism. His primary scientific work — much inspired by earlier works of Robert Norman — was De Magnete, Magneticisque Corporibus, et de Magno Magnete Tellure (On the Magnet and Magnetic Bodies, and on the Great Magnet the Earth) published in 1600. In this work, he describes many of his experiments with his model Earth called the “terrella”. From these experiments, he concluded that the Earth was itself magnetic and that this was the reason compasses point north (previously, some believed that it was the pole star (Polaris) or a large magnetic island on the north pole that attracted the compass). He was the first to argue, correctly, that the centre of the Earth was made of iron, and he considered an important and related property of magnets was that “they can be cut, each forming a new magnet with north and south poles”.

See also: https://en.wikipedia.org/wiki/William_Gilbert_(astronomer)

Lenhardt – Biographies 10 Gravity

Galileo di Vincenzo Bonaulti de Galilei

(February 15, 1564 in Pisa/Italy – January 8, 1642 in Arcetri/Italy) was an Italian astronomer, physicist and engineer, sometimes described as a polymath, from Pisa. Galileo has been called the “father of observational astronomy”, the “father of modern physics”, the "father of the scientific method", and the “father of modern science”. Galileo studied speed and velocity, gravity and free fall, the principle of relativity, inertia, projectile motion and also worked in applied science and technology, describing the properties of pendulums and “hydrostatic balances”, inventing the thermoscope and various military compasses, and using the telescope for scientific observations of celestial objects. His contributions to observational astronomy include the telescopic confirmation of the phases of Venus, the observation of the four largest satellites of Jupiter, the observation of 's rings, and the analysis of sunspots. Galileo's championing of heliocentrism and Copernicanism was controversial during his lifetime, when most subscribed to geocentric models such as the Tychonic system. He met with opposition from astronomers, who doubted heliocentrism because of the absence of an observed stellar parallax. The matter was investigated by the Roman Inquisition in 1615, which concluded that heliocentrism was “foolish and absurd in philosophy, and formally heretical since it explicitly contradicts in many places the sense of Holy Scripture”.

See also: https://en.wikipedia.org/wiki/Galileo_Galilei

Lenhardt – Biographies 11 Planetary Motion

Johannes Kepler

(December 27, 1571 in Weil der Stadt/Germany – November 15, 1630 in Regensburg/Germany) was a German astronomer, mathematician, and astrologer. He is a key figure in the 17th century , best known for his laws of planetary motion, and his books Astronomia nova, Harmonices Mundi, and Epitome Astronomiae Copernicanae. These works also provided one of the foundations for Newton's theory of universal gravitation. Kepler was a mathematics teacher at a seminary school in /Austria, where he became an associate of Prince Hans Ulrich von Eggenberg. Later he became an assistant to Tycho Brahe in Prague, and eventually the imperial mathematician to Emperor Rudolf II and his two successors Matthias and Ferdinand II. He also taught mathematics in Linz, and was an adviser to General Wallenstein. Additionally, he did fundamental work in the field of optics, invented an improved version of the refracting (or Keplerian) telescope, and was mentioned in the telescopic discoveries of his contemporary Galileo Galilei. He was a corresponding member of the Accademia dei Lincei in Rome. Kepler lived in an era when there was no clear distinction between astronomy and astrology, but there was a strong division between astronomy (a branch of mathematics within the liberal arts) and physics (a branch of natural philosophy). Kepler also incorporated religious arguments and reasoning into his work, motivated by the religious conviction and belief that God had created the world according to an intelligible plan that is accessible through the natural light of reason. Kepler described his new astronomy as “celestial physics", as "an excursion into Aristotle's Metaphysics“. As a “supplement to Aristotle's On the Heavens” he transformed the ancient tradition of physical cosmology by treating astronomy as part of a universal mathematical physics.

See also: https://en.wikipedia.org/wiki/Johannes_Kepler

Lenhardt – Biographies 12 Refraction

(born Willebrord Snel Royen, June 13, 1580 in /Spanish Netherlands – October 30, 1626 in Leiden/) was a Dutch astronomer and mathematician, known in the English-speaking world as “Snell”. In the west, especially the English speaking countries, his name is attached to the law of refraction of light. In 1613 he succeeded his father, Rudolph Snel van Royen (1546 – 1613) as professor of mathematics at the University of Leiden. In his work The terrae Ambitus vera quantitate (1617) under the author's name (“The Dutch Eratosthenes”) Snellius describes the methods he used to determine the Earth’s circumference. He came up with an estimate of 28,500 Rhineland rods – in modern units 107.37 km for one degree of . 360 times 107.37 then gives a circumference of the Earth of 38,653 km. The actual circumference is 40,075 kilometers, hence Snellius underestimated the circumference of the Earth by just 3.5 %. Snell's law (also known as Snell–Descartes law and the law of refraction) is a formula used to describe the relationship between the angles of incidence and refraction, when referring to light or other waves passing through a boundary between two different isotropic media, such as water, glass, or air. Snell's window (also called Snell's circle or optical man-hole) is a phenomenon by which an underwater viewer sees everything above the surface through a cone of light of width of about 96 degrees. This phenomenon is caused by refraction of light entering water, and is governed by Snell's Law. The area outside Snell's window will either be completely dark or show a reflection of underwater objects by total internal reflection. See also: https://en.wikipedia.org/wiki/Willebrord_Snellius

Lenhardt – Biographies 13 Reflection and Refraction

René Descartes

(March 31, 1596 in La Haye en Touraine/France – February 11, 1650 in Stockholm/Sweden) was a French philosopher, mathematician, and scientist. A native of the Kingdom of France, he spent about 20 years (1629 – 1649) of his life in the Dutch Republic after serving for a while in the Dutch States Army of Maurice of Nassau, Prince of Orange and the Stadtholder (chief magistrate) of the United Provinces. One of the most notable intellectual figures of the , Descartes is also widely regarded as one of the founders of modern philosophy. Descartes laid the foundation for 17th century continental rationalism, later advocated by Spinoza and Leibniz, and was later opposed by the empiricist school of thought consisting of Hobbes, Locke, Berkeley, and Hume. Leibniz, Spinoza, and Descartes were all well-versed in mathematics as well as philosophy, and Descartes and Leibniz contributed greatly to science as well. Descartes' Meditations on First Philosophy (1641) continues to be a standard text at most university philosophy departments. Descartes' influence in mathematics is equally apparent; the Cartesian coordinate system was named after him. He is credited as the father of analytical geometry, the bridge between algebra and geometry – used in the discovery of infinitesimal calculus and analysis. Descartes was also one of the key figures in the Scientific Revolution. Descartes also made contributions to the field of optics. He showed by using geometric construction and the law of refraction (also known as Descartes' law or more commonly known as Snell's law) that the angular radius of a rainbow is 42°. He also independently discovered the law of reflection, and his essay on optics was the first published mention of this law.

See also: https://en.wikipedia.org/wiki/Ren%C3%A9_Descartes#Natural_science

Lenhardt – Biographies 14 Change of Magnetic Field

Henry Gellibrand

(November 17, 1597 in London/England – February 16, 1636 in London/England) was an English physicist. Gellibrand discovered the secular change in magnetic declination. He attempted to solve the problem of . His Appendix concerning Longitude in Thomas James Strange and Dangerous Voyage, 1633, attempted to draw on observable celestial events as a means to establish longitude. Gellibrand completed Briggs' Trigonometria Britannica (1633). He composed Astronomia lunaris, which survived in manuscript. Posthumous a longer work of the same name in Latin, together with applications to navigation and astronomy, was published in 1652. He is also known for having written a Treatise of Building of Ships. His Epitome of Navigation appeared in 1698, long after his death.

See also: https://en.wikipedia.org/wiki/Henry_Gellibrand and http://galileo.rice.edu/Catalog/NewFiles/gelibrnd.html

Lenhardt – Biographies 15 Earth´s Interior

Athanasius Kircher

(May 2, 1602 in Geisa/Germany – 28 November 28, 1680 in Rome/Italy) was a German Jesuit scholar and polymath who published around 40 major works, most notably in the fields of comparative religion, geology, and medicine. On a visit to southern Italy in 1638, the ever-curious Kircher was lowered into the crater of Vesuvius, then on the brink of eruption, to examine its interior. He was also intrigued by the subterranean rumbling which he heard at the Strait of Messina. His geological and geographical investigations culminated in his Mundus Subterraneus of 1664, in which he suggested that the tides were caused by water moving to and from a subterranean ocean (!?). Kircher was also puzzled by fossils. He understood that fossils were the remains of animals. He ascribed large bones to giant races of humans. Not all the objects which he was attempting to explain were in fact fossils, hence the diversity of explanations. He interpreted mountain ranges as the Earth's skeletal structures exposed by weathering. Kircher's map of Atlantis, oriented with south at the top, from Mundus Subterraneus. Mundus Subterraneus includes several pages about the legendary island of Atlantis including a map with the Latin caption Situs Insulae Atlantidis, a Mari olim absorpte ex mente Egyptiorum et Platonis Description, translating as “Site of the island of Atlantis, in the sea, from Egyptian sources and Plato's description.”

See also: https://en.wikipedia.org/wiki/Athanasius_Kircher

Lenhardt – Biographies 16 Hydrodynamics

Blaise Pascal

(June 19, 1623 in Clermont-Ferrand/France – August 19, 1662 in Paris/France) was a French mathematician, physicist, inventor, writer and Catholic theologian. Pascal's work in the fields of the study of hydrodynamics and hydrostatics centered on the principles of hydraulic fluids. His inventions include the hydraulic press (using hydraulic pressure to multiply force) and the syringe. He proved that hydrostatic pressure depends not on the weight of the fluid but on the elevation difference. He demonstrated this principle by attaching a thin tube to a barrel full of water and filling the tube with water up to the level of the third floor of a building. This caused the barrel to leak, in what became known as Pascal's barrel experiment. In the face of criticism that some invisible matter must exist in Pascal's empty space, Pascal, in his reply to Estienne Noel, gave one of the 17th century's major statements on the scientific method, which is a striking anticipation of the idea popularised later by Karl Popper (1934) that scientific theories are characterised by their falsifiability: "In order to show that a hypothesis is evident, it does not suffice that all the phenomena follow from it; instead, if it leads to something contrary to a single one of the phenomena, that suffices to establish its falsity.“

See also: https://en.wikipedia.org/wiki/Blaise_Pascal

Lenhardt – Biographies 17 Elasticity

Robert Hooke

(July 28 [O.S. July 18], 1635 on Isle of Wight/England – March 3, 1703 in London/England) was an English natural philosopher, architect and polymath. His adult life comprised three distinct periods: as a scientific inquirer lacking money; achieving great wealth and standing through his reputation There is no picture of for hard work and scrupulous honesty following the great fire of 1666 in Robert Hooke, although London, but eventually becoming ill and party to jealous intellectual there are few circulating disputes, which may have contributed to his relative historical obscurity in the internet. outside of his association with Newton in particular. Hooke's law is a principle of physics that states that the force F needed to extend or compress a spring by some distance X is proportional to that distance. That is: F = k x, where k is a constant factor and characteristic of the spring – known as stiffness, and x is small displacement compared with the full length of the spring.

See also: https://en.wikipedia.org/wiki/Robert_Hooke

Lenhardt – Biographies 18 Gravitation

Isaac Newton

(December 25, 1642 in Woolsthorpe-by-Colsterworth/England – March 20, 1726/27 in Kensington/G.B.) was an English physicist and mathematician (described in his own day as a ‘natural philosopher’) who is widely recognized as one of the most influential scientists of all time and a key figure in the scientific revolution. His book on Mathematical Principles of Natural Philosophy, first published in 1687, laid the foundations for classical mechanics. He shares credit with Gottfried Wilhelm Leibniz for the development of calculus and the laws of gravity. In Principia, Newton formulated the laws of motion and universal gravitation that formed the dominant scientific viewpoint until it was superseded by the theory of relativity. Newton used his mathematical description of gravity to prove Kepler's laws of planetary motion, account for tides, the trajectories of comets, the precession of the equinoxes and other phenomena, eradicating doubt about the Solar System's heliocentricity. He demonstrated that the motion of objects on Earth and celestial bodies could be accounted for by the same principles. Newton's inference that the Earth is an oblate spheroid was later confirmed by the geodetic measurements. Newton built the first practical reflecting telescope and developed a sophisticated theory of colour based on the observation that a prism separates white light into the colours of the visible spectrum. His work on light was collected in his highly influential book Opticks, published in 1704. He also formulated an empirical law of cooling, made the first theoretical calculation of the speed of sound, and introduced the notion of a Newtonian fluid. In Newtonian fluids (typically water and solutions containing only low molecular mass material) the viscosity is independent of shear strain rate.

See also: https://en.wikipedia.org/wiki/Isaac_Newton

Lenhardt – Biographies 19 Aurorals and Magnetic Field Edmond Halley

(or Edmund Halley, November 8 [O.S. 29 October 29], 1656 in Haggerston, Middlesex/England – January 25, 1742 [O.S. 14 January 14, 1741] in Greenwich, Kent/G.B.) was an English astronomer, geophysicist, mathematician, meteorologist, and physicist. He was the second Astronomer Royal in Britain, succeeding John Flamsteed in 1720. From an observatory, he constructed on Saint Helena in the midst of the Atlantic, Halley recorded a transit of Mercury across the Sun. He realized a similar transit of Venus could be used to determine the size of the Solar System. He also used his observations to expand contemporary star maps. He aided in observationally proving Isaac Newton's laws of motion, and funded the publication of Newton's influential Philosophiæ Naturalis Principia Mathematica. From his September 1682 observations, he used the laws of motion to compute the periodicity of comets in his 1705 Synopsis of the Astronomy of Comets. It was named after him upon its predicted return in 1758, which he did not live to see (“Halley’s Comet”). In 1686, Halley published the second part of the results from his Helenian expedition, being a paper and chart on trade winds and monsoons. The symbols he used to represent trailing winds still exist in most modern day weather chart representations. In this article he identified solar heating as the cause of atmospheric motions. He also established the relationship between barometric pressure and height above sea level. Strange, in 1692 Halley put forth the idea of a hollow Earth consisting of a shell about 500 miles (800 km) thick, two inner concentric shells and an innermost core (possibly inhabitated!). He suggested that atmospheres separated these shells, and that each shell had its own magnetic poles, with each sphere rotating at a different speed. Halley proposed this scheme to explain anomalous compass readings. He suggested, "Auroral rays are due to particles, which are affected by the magnetic field, the rays parallel to Earth’s magnetic field“. Beginning in 1698, he conducted sailing expeditions and observations on the conditions of terrestrial magnetism.

See also: https://en.wikipedia.org/wiki/Edmond_Halley Lenhardt – Biographies 20 Local Gravity

Pierre Bouguer

(February 16, 1698 in Croisic/France – August 15, 1758 in Paris/France) was a French mathematician, geophysicist, geodesist, and astronomer. He is also known as "the father of naval architecture". In 1729 he published Essai d'optique sur la gradation de la lumière, the object of which is to define the quantity of light lost by passing through a given extent of the atmosphere, and became the first known discoverer of what is now more commonly known as the Beer-Lambert law. He found the light of the sun to be 300 times more intense than that of the moon, and thus made some of the earliest measurements in photometry. In 1735 Bouguer sailed with Charles Marie de La Condamine on a scientific mission to Peru, to measure a degree of the meridian arc near the equator. Ten years were spent in this operation, a full account of which was published by Bouguer in 1749, La figure de la terre. In 1746 he published the first treatise of naval architecture, Traité du navire, which among other achievements first explained the use of the metacenter as a measure of ships' stability. His later writings were nearly all upon the theory of navigation and naval architecture. The term “Bouguer anomaly”, referring to small regional variations in the Earth's gravity field resulting from density variations in underlying rocks, is named after him.

See also: https://en.wikipedia.org/wiki/Pierre_Bouguer

Lenhardt – Biographies 21 Aurora Borealis

Anders Celsius

(November 27, 1701 in Uppsala/Sweden – April 25, 1744 in Uppsala/ Sweden) was a Swedish astronomer, physicist and mathematician. He was professor of astronomy at Uppsala University from 1730 to 1744. In 1730, Celsius published the Nova Methodus distantiam solis a terra determinandi (New Method for Determining the Distance from the Earth to the Sun). His research also involved the study of auroral phenomena, which he conducted with his assistant Olof Hiorter, and he was the first to suggest a connection between the aurora borealis and changes in the magnetic field of the Earth. He observed the variations of a compass needle and found that larger deflections correlated with stronger auroral activity. At Nuremberg in 1733, he published a collection of 316 observations of the aurora borealis made by himself and others over the period 1716–1732. In 1738, he published the De observationibus pro figura telluris determinanda (Observations on Determining the Shape of the Earth). He travelled from 1732 to 1735 visiting notable observatories in Germany, Italy and France. He founded the Uppsala Astronomical Observatory in 1741, and in 1742 proposed (an inverted* form of) the Centigrade temperature scale which was later renamed Celsius in his honour.

* Originally his temperature scale was “upside down”. 0°C = water boils, 100°C = water freezes. Jean-Pierre Christin proposed the scale’s reversal in 1743 shortly thereafter.

See also: https://en.wikipedia.org/wiki/Anders_Celsius

Lenhardt – Biographies 22 Ellipsoid

Alexis Claude Clairaut

(May 13, 1713 in Paris/France – May 17, 1765 in Paris/France) was a French mathematician, astronomer, and geophysicist. He was a prominent Newtonian whose work helped to establish the validity of the principles and results that Sir Isaac Newton had outlined in the Principia of 1687. Clairaut was one of the key figures in the expedition to Lapland that helped to confirm Newton's theory for the ellipsoid figure of the Earth. In that context, Clairaut worked out a mathematical result now known as "Clairaut's theorem". He also tackled the gravitational three-body problem, being the first to obtain a satisfactory result for the apsidal precession of the Moon's . The unravelling of the problem of three bodies also had practical importance. It allowed sailors to determine the longitudinal direction of their ships, which was crucial not only in sailing to a location, but finding their way home as well. This held economic implications as well, because sailors were able to find destinations of trade based on the longitudinal measures more easily. In mathematics he is also credited with Clairaut's equation and Clairaut's relation.

See also: https://en.wikipedia.org/wiki/Alexis_Clairaut

Lenhardt – Biographies 23 1755 Lisbon

https://www.laphamsquarterly.org/roundtable/finding-words-describe-disaster Lenhardt – Biographies 24 1755 Lisbon

The “1755 Lisbon earthquake”, also known as the “Great Lisbon Earthquake” or “All Saints’ earthquake”, took place on November 1, 1755, at 9:40 in the morning. It was one of the most destructive and deadly earthquakes in history, claiming approximately 12.000 lives. The earthquake was followed by a tsunami and fire, resulting in the near-total destruction of Lisbon. The earthquake accentuated political tensions in Portugal and profoundly disrupted the country's 18th century colonial ambitions. The event was widely discussed by European Enlightenment philosophers (Kant, Descartes, Leibniz, Goethe), and inspired major developments in theodicy and in the philosophy of the sublime. As the first earthquake studied scientifically for its effects over a large area, it signaled the birth of modern . Joao Fonseca (2020) estimates the “Lisbon earthquake” magnitude to 7.7, with an epicenter in the Atlantic Ocean about 200 km west- southwest of Cape St. Vincent.

See also: https://www.newworldencyclopedia.org/entry/Lisbon_earthquake_1755, and https://pubs.geoscienceworld.org/ssa/bssa/article-abstract/110/1/1/579967/A-Reassessment-of-the-Magnitude-of-the-1755-Lisbon

Lenhardt – Biographies 25 Questionnaire Sebastião José de Carvalho e Melo

1st Marquis of Pombal, 1st Count of Oeiras (May 13, 1699 in Lisbon/Portugal – May 8, 1782 in Pombal/Portugal), popularly known as the Marquis of Pombal was an 18th century Portuguese statesman. He was Secretary of the State of Internal Affairs of the Kingdom (the equivalent of a Prime Minister today) in the government of Joseph I of Portugal from 1750 to 1777. Apart from being the most prominent minister in the government, he has also been considered to have been its de facto head. He implemented sweeping economic policies in Portugal to regulate commercial activity and standardise quality throughout the country, and was instrumental in weakening the grip of the Inquisition. Pombal was notable for his swift and competent leadership in the aftermath of the 1755 Lisbon earthquake. The city was razed by the earthquake and ensuing tsunami and fires. Pombal survived by a stroke of luck and, unshaken, immediately took upon the task of rebuilding the city, with his famous quote: “What now? We bury the dead and heal the living.” The buildings and major squares of todays “Pombaline Downtown” of Lisbon are one of its main attractions, and they are the world's first earthquake-resistant buildings based on strategic town design. Pombal made also an important contribution to the study of seismology, by designing a survey that was sent to every parish in the country. The questionnaire was split in three parts: the first, comprised 27 questions about the settlement; the second, 13 questions about the local landforms, specifically mountains; and the third, 20 questions about the local watercourses. All three parts ended by asking if there was anything else that was worthy of memory, in an effort to collect more information about the parishes' local peculiarities.

See also: https://en.wikipedia.org/wiki/Sebastião_José_de_Carvalho_e_Melo,_1st_Marquis_of_Pombal https://en.wikipedia.org/wiki/Parochial_Memories_of_1758 Lenhardt – Biographies 26 Earthquakes – Magnetism – Gravity John Michell

(December 25, 1724 in Eakring/Nottinghamshire/G.B. – April 21, 1793 in Thornhill/Yorkshire/G.B.) was an English natural philosopher and clergyman who provided pioneering insights into a wide range of scientific fields including astronomy, geology, optics, and gravitation. Considered “one of the greatest unsung scientists of all time”, he was the first person known to offer the following concepts: proposed the So far, no picture is existence of black holes; suggested that earthquakes propagate as (seismic) waves; known from Michell. explained how to manufacture an artificial magnet; and, recognizing that double stars were a product of mutual gravitation, he was the first to apply statistics to the study of the cosmos. He invented an apparatus to measure the mass of the Earth. He has been called the father both of seismology and of magnetometry. Until the late 20th century Michell was considered important primarily because of his work on geology. His most important geological essay, written after the 1755 Lisbon earthquake, was entitled Conjectures concerning the Cause and Observations upon the Phaenomena of Earthquakes (Philosophical Transactions, li. 1760). In this paper he introduced the idea that earthquakes spread out as waves through the Earth and that they involve the offsets in geological strata now known as faults. He was able to estimate both the epicentre and the focus of the Lisbon earthquake, and may also have been the first to suggest that a tsunami is caused by a submarine earthquake. His 1750 paper Treatise of Artificial Magnets, which was written for seamen and instrument makers and intended as a practical manual on how to make magnets, included a list of the Properties of Magnetical Bodies that represented a major contribution to the understanding of magnetism. Michell also devised a torsion balance for measuring the mass of the Earth, but died before he could use it. His instrument passed into the hands of his lifelong friend Henry Cavendish, who first performed in 1798 the experiment now known as the Cavendish Experiment.

See also: https://en.wikipedia.org/wiki/John_Michell Lenhardt – Biographies 27 Gravitational Constant Henry Cavendish

(October 10, 1731 in Nice/Kingdom of Sardinia – February 24, 1810 in London/U.K.) was an English natural philosopher, scientist, and an important experimental and theoretical chemist and physicist. He is noted for his discovery of hydrogen, which he termed "inflammable air". He described the density of inflammable air, which formed water on combustion, in a 1766 paper On Factitious Airs. Antoine Lavoisier later reproduced Cavendish's experiment and gave the element its name. A notoriously shy man, Cavendish was nonetheless distinguished for great accuracy and precision in his researches into the composition of atmospheric air, the properties of different gases, the synthesis of water, the law governing electrical attraction and repulsion, a mechanical theory of heat, and calculations of the density (and hence the mass) of the Earth. His experiment to measure the density of the Earth has come to be known as the Cavendish experiment. The apparatus Cavendish used for weighing the Earth was a actually modification of the torsion balance built by John Michell, who died before he could begin the experiment. The apparatus was sent in crates to Cavendish, who completed the experiment in 1797 – 1798. The experimental apparatus consisted of a torsion balance with a pair of 2-inch 1.61-pound lead spheres suspended from the arm of a torsion balance and two much larger stationary lead balls (350 pounds). Cavendish intended to measure the force of gravitational attraction between the two. Using this equipment, Cavendish calculated the attraction between the balls from the period of oscillation of the torsion balance, and then he used this value to calculate the mean density of the Earth and found it 5.48 times greater than that of water (which is within 1 percent accurate of today’s value). Cavendish's work initiated others to determine the gravitational constant (G) and the Earth's mass. The bulk of Cavendish’ electrical experiments did not become known until they were collected and published by James Clerk Maxwell a century later, in 1879.

See also: https://en.wikipedia.org/wiki/Henry_Cavendish Lenhardt – Biographies 28 Friction

Charles-Augustin de Coulomb

(June 14, 1736 in Angoulême/France – August 23, 1806 Paris/France) was a French physicist. He was best known for developing Coulomb's law, the definition of the electrostatic force of attraction and repulsion, but also did important work on friction. The SI unit of electric charge, the Coulomb, was named after him. The Coulomb model of friction, or the Amonton-Coulomb model of friction, or Coulomb friction, refers to a simple model of dry friction that is fairly accurate empirically. Specifically, it is a model that helps predict the direction and magnitude of the friction force between two bodies with dry surfaces in contact, depending on their of surface. The Coulomb model predicts that in the static case, this is true for the limiting value of frictional force, with the constant of proportionality being the limiting coefficient of static friction, while in the kinetic case, it is directly true, with the constant of proportionality being the coefficient of kinetic friction. Coulomb‘s law is applied in seismology and rock mechanics.

See also: https://en.wikipedia.org/wiki/Charles-Augustin_de_Coulomb

Lenhardt – Biographies 29 Potential Theory Pierre-Simon Laplace

(March 23, 1749 in Beaumont-en-Auge/France – March 5, 1827 in Paris/France) was a French scholar whose work was important to the development of engineering, mathematics, statistics, physics, astronomy, and philosophy. He summarized and extended the work of his predecessors in his five-volume Mécanique Céleste (Celestial Mechanics) (1799 – 1825). This work translated the geometric study of classical mechanics to one based on calculus, opening up a broader range of problems. In statistics, the Bayesian interpretation of probability was developed mainly by Laplace. Laplace formulated Laplace's equation, and pioneered the Laplace transform which appears in many branches of mathematical physics, a field that he took a leading role in forming. The Laplacian differential operator, widely used in mathematics, is also named after him. He restated and developed the nebular hypothesis of the origin of the solar system and was one of the first scientists to postulate the existence of black holes and the notion of gravitational collapse. He is also known for his idea of earth flattening, potential theory, spherical harmonics, tidal equations, probability functions, and last but not least the Laplace demon (knowing all forces would enable us to predict the future > earthquake prediction!). Laplace is remembered as one of the greatest scientists of all time. Sometimes referred to as the French Newton or Newton of France. He has been described as possessing a phenomenal natural mathematical knowledge to that of any of his contemporaries. He was Napoleon's examiner when Napoleon attended the École Militaire in Paris in 1784. Laplace became a count of the Empire in 1806 and was named a marquis in 1817, after the Bourbon Restoration.

See also: https://en.wikipedia.org/wiki/Pierre-Simon_Laplace Lenhardt – Biographies 30 Wave Spectrum and Heat Flow

Jean-Baptiste Joseph Fourier

(March 21, 1768 in Auxerre/France – May 16, 1830 in Paris/France) was a French mathematician and physicist, and best known for initiating the investigation of Fourier series, which eventually developed into Fourier analysis and harmonic analysis, and their applications to problems of heat transfer and vibrations. The Fourier transform and Fourier's law of conduction are also named in his honour. Fourier is also generally credited with the discovery of the greenhouse effect, as he considered the possibility that the Earth's atmosphere might act as an insulator of some kind. In 1822 Fourier published his work on heat flow in Théorie analytique de la chaleur (The Analytical Theory of Heat), in which he based his reasoning on Newton's law of cooling, namely, that the flow of heat between two adjacent molecules is proportional to the extremely small difference of their temperatures. There were three important contributions in this work, one purely mathematical, two essentially physical. In mathematics, Fourier claimed that any function of a variable, whether continuous or discontinuous, can be expanded in a series of sines of multiples of the variable. One important physical contribution in the book was the concept of dimensional homogeneity in equations; i.e. an equation can be formally correct only if the dimensions match on either side of the equality*. The other physical contribution was Fourier's proposal of his partial differential equation for conductive diffusion of heat. This equation is still a standard in mathematical physics.

* This is a prime test in physics even today to see, whether derived formulae in physics make sense.

See also: https://en.wikipedia.org/wiki/Joseph_Fourier

Lenhardt – Biographies 31 Magnetic Anomalies

Friedrich Wilhelm Heinrich Alexander von Humboldt

(September 14, 1769 in Berlin/Germany – May 6, 1859 in Berlin/Germany) was a Prussian polymath, geographer, naturalist, explorer, and proponent of Romantic philosophy and science. He was the younger brother of the Prussian minister, philosopher, and linguist Wilhelm von Humboldt (1767 – 1835). Humboldt's quantitative work on botanical geography laid the foundation for the field of biogeography. Humboldt's advocacy of long-term systematic geophysical measurement laid the foundation for modern geomagnetic and meteorological monitoring. Between 1799 and 1804, Humboldt travelled extensively in the Americas, exploring and describing them for the first time from a modern scientific point of view. His description of the journey was written up and published in an enormous set of volumes over 21 years. Humboldt also proposed that the lands bordering the Atlantic Ocean were once joined (South America and Africa in particular). Humboldt resurrected the use of the word “cosmos” from the ancient Greek and assigned it to his multivolume treatise Kosmos in which he sought to unify diverse branches of scientific knowledge and culture. This important work also motivated a holistic perception of the universe as one interacting entity. He was the first person to describe the phenomenon and cause of human-induced climate change, in 1800 and again in 1831, based on observations during his travels.

See also: https://en.wikipedia.org/wiki/Alexander_von_Humboldt

Lenhardt – Biographies 32 Seismic Catalogue

Karl Ernst Adolf von Hoff

(November 1, 1771 in Gotha/Germany – 24 May 24, 1837 in Gotha/Germany) was a German natural historian and geologist. After studying law, physics and natural history, in 1791 he was appointed to a diplomatic post by Ernest II, Duke of Saxe-Gotha-Altenburg. From 1832 onwards he was the director of Gotha's royal science and art collections and he also wrote the five-volume Geschichte der durch Überlieferung nachgewiesenen natürlichen Veränderungen der Erdoberfläche (History of natural changes in the earth's surface proven by tradition) from 1822 to 1841. This work justified the principle of actuality in departure from the catastrophe theory (cataclysm theory) and cleared the way for the scientific nature of geology. Another independent author of the principle of actuality is James Hutton in Scotland. Charles Lyell, widely regarded as a developer of uniformitarianism and generally acknowledging him, found it independent of Hoff, but later acknowledged Hoff's priority. Between 1826 and 1834 von Hoff published the first annual global seismic catalogues for the years 1821 – 1832, listing 2225 seismic events. Soon, he became superseded by Alexis Perrey’s catalogue stating 21.000 events.

See also: https://en.wikipedia.org/wiki/Karl_Ernst_Adolf_von_Hoff

Lenhardt – Biographies 33 Elasticity and much more

Thomas Young

(June 13, 1773 in Milverton/G.B. – May 10, 1829 in London/U.K.) was a British polymath and physicist. Young made notable scientific contributions to the fields of vision, light, solid mechanics, energy, physiology, language, musical harmony, and Egyptology. He developed a number of original and insightful innovations in the decipherment of Egyptian hieroglyphs (specifically the Rosetta Stone) before Jean-François Champollion eventually expanded on his work. He was mentioned by, among others, William Herschel, Hermann von Helmholtz, James Clerk Maxwell, and Albert Einstein. Young has been described as "The Last Man Who Knew Everything". Young is credited with establishing the wave theory of light, influenced in his experiments by those of Isaac Newton. His work was subsequently supported by the work of Augustin-Jean Fresnel. Young described the characterization of elasticity that came to be known as Young's modulus, denoted as “E”, in 1807, and further described it in his Course of Lectures on Natural Philosophy and the Mechanical Arts. However, the first use of the concept of Young's modulus in experiments was by Giordano Riccati in 1782 — predating Young by 25 years. Furthermore, the idea can be traced to a paper by Leonhard Euler published in 1727, some 80 years before Thomas Young's 1807 paper. At the age of fourteen Young had already learned Greek and Latin and was acquainted with French, Italian, Hebrew, German, Aramaic, Syriac, Samaritan, Arabic, Persian, Turkish and Amharic (= 14 languages including his mother- language).

See also: https://en.wikipedia.org/wiki/Thomas_Young_(scientist)

Lenhardt – Biographies 34 Inner– and External Magnetic Field

Carl Friedrich Gauss

(April 30, 1777 in Brunsbüttel/Germany – February 23, 1855 in Göttingen/ Germany) was a German mathematician and physicist who made significant contributions to many fields in mathematics and sciences. He is sometimes referred to as the “Princeps mathematicorum” (Latin for “the foremost of mathematicians”, similar to Laplace) and “the greatest mathematician since antiquity”, Gauss had an exceptional influence in many fields of mathematics and science, and is ranked among history's most influential mathematicians. Gauss was a child prodigy. When Gauss was barely three years old he corrected a math error his father made; and that when he was seven, he confidently solved an arithmetic series problem faster than anyone else in his class of 100 students. In 1831, Gauss developed a fruitful collaboration with the physics professor Wilhelm Weber, leading to new knowledge in magnetism (including finding a representation for the unit of magnetism in terms of mass, charge, and time) and the discovery of Kirchhoff's circuit laws in electricity. It was during this time that he formulated his namesake law. Together with Weber, he constructed the first electromechanical telegraph in 1833, which connected the observatory with the Institute for Physics in Göttingen. Gauss ordered a magnetic observatory to be built in the garden of the observatory, and founded the “Magnetischer Verein” (“magnetic association”) with Weber, which supported measurements of Earth's magnetic field in many regions of the world. He developed a method of measuring the horizontal intensity of the magnetic field which was in use well into the second half of the 20th century, and worked out the mathematical theory for separating the inner and outer (magnetospheric) sources of Earth's magnetic field. In addition, he proposed to take the sea level of the Earth as reference shape of the planet, known today as geoid.

See also: https://en.wikipedia.org/wiki/Carl_Friedrich_Gauss

Lenhardt – Biographies 35 Electric and Magnetic Field Interaction

Hans Christian Ørsted

(often rendered Oersted in English; August 14, 1777 in Rudkøbing/Denmark – March 9, 1851 in Copenhagen/Denmark ) was a Danish physicist and chemist who discovered that electric currents create magnetic fields, which was the first connection found between electricity and magnetism. Oersted's law and the oersted (Oe) are named after him. A leader of the Danish Golden Age, Ørsted was a close friend of Hans Christian Andersen and the brother of politician and jurist Anders Sandøe Ørsted, who served as Prime Minister of Denmark from 1853 to 1854. On 21 April 1820, Ørsted published his discovery that a compass needle was deflected from magnetic north by a nearby electric current, confirming a direct relationship between electricity and magnetism. The often reported story that Ørsted made this discovery incidentally during a lecture is a myth. He had, in fact, been looking for a connection between electricity and magnetism since 1818, but was quite confused by the results he was obtaining. His initial interpretation was that magnetic effects radiate from all sides of a wire carrying an electric current, as do light and heat. Three months later, he began more intensive investigations and soon thereafter published his findings, showing that an electric current produces a circular magnetic field as it flows through a wire. Ørsted's findings stirred much research into electrodynamics throughout the scientific community, influencing French physicist André-Marie Ampère's developments of a single mathematical formula to represent the magnetic forces between current-carrying conductors. Ørsted's work also represented a major step toward a unified concept of energy and the dynamo.

See also: https://en.wikipedia.org/wiki/Hans_Christian_%C3%98rsted

Lenhardt – Biographies 36 Physics and Statistics

Siméon Denis Poisson

(June 21, 1781 in Pithiviers/France – April 25, 1840 Sceaux/France) was a French physicist, essentially an allrounder. He authored major works in optics, statistics, mathematics and mechanics. The ratio of the horizontal to vertical strain – the Poisson’s ratio “n”– as well as the Poisson distribution and probability theory was named after him. It was in the application of mathematics to physics that his greatest services to science were performed. Perhaps the most original, and certainly the most permanent in their influence, were his memoirs on the theory of electricity and magnetism, which virtually created a new branch of mathematical physics. In this treatise he described the concept of a magnetic and electric dipole moment. A translation of Poisson's Treatise on Mechanics was published in London in 1842 posthumous.

n = -x/z

See also: en.wikipedia.org/wiki/List_of_things_named_after_Siméon_Denis_Poisson

Lenhardt – Biographies 37 Elasticity and Fluids

Claude-Louis Navier

(February 10, 1785 in Dijon/France – August 21, 1836 Paris/France), was a French engineer and physicist who specialized in mechanics. He directed the construction of bridges at Choisy, Asnières and Argenteuil in the Department of the Seine, and built a footbridge to the Île de la Cité in Paris. His 1824 design for the Pont des Invalides failed to leave a safety margin on top of his calculations, and after cracking the bridge had to be dismantled, destroying Navier's bridge-building reputation. He was chastised by a government committee for relying too much on mathematics. Navier formulated the general theory of elasticity in a mathematically usable form (1821), making it available to the field of construction with sufficient accuracy for the first time. In 1819 he succeeded in determining the zero line of mechanical stress, finally correcting Galileo Galilei's incorrect results, and in 1826 he established the elastic modulus as a property of materials independent of the second moment of area. Navier is therefore often considered to be the founder of modern structural analysis. His major contribution however remains the Navier-Stokes equations (1822), central to fluid mechanics.

See also: https://en.wikipedia.org/wiki/Claude-Louis_Navier

Lenhardt – Biographies 38 Magnetic Network

Edward Sabine

(October 14, 1788 in Dublin/Ireland – June 26, 1883 in London/U.K.) was an Irish astronomer, geophysicist, ornithologist, explorer, soldier (from 1870 holding the rank of a general) and the 30th president of the Royal Society. He led the effort to establish a system of magnetic observatories in various parts of British territory all over the globe. Much of his life was devoted to their direction, and to analysing their observations. Other research focused on the birds of Greenland, ocean temperatures, the Gulf Stream, barometric measurement of heights, arc of the meridian, glacial transport of rocks, the volcanoes of the Hawaiian Islands, and various points of meteorology. During the decades that the Royal Navy and Royal Society devoted much energy to magnetic variation and its problems, magnetism came to be seen as an eminently "British" science. There was intense interest in figuring out what many called "the great remaining physical mystery since Newton's work on gravitation". In 1852, Sabine recognized from magnetic records taken in Toronto that magnetic variations could be divided into a regular diurnal cycle and an irregular portion. The irregularity correlated very closely with fluctuations in the number of sunspots, whose cyclic nature had been discovered by the German amateur astronomer Heinrich Schwabe in 1843. Sabine was the first to recognize that solar disturbances affected the Earth's magnetic environment. On 6 April 1852, he announced that the Sun's 11-year sunspot cycle was "absolutely identical" to the Earth's 11-year geomagnetic cycle.

See also: https://en.wikipedia.org/wiki/Edward_Sabine

Lenhardt – Biographies 39 Potential

George Green

(July 14, 1793 in Sneinton/G.B. – May 31, 1841 in Nottingham/U.K.) was a British mathematical physicist who wrote An Essay on the Application of Mathematical Analysis to the Theories of Electricity and Magnetism in 1828. The essay introduced several important concepts, among them a theorem similar to the modern Green's theorem, the idea of potential functions as currently used in physics, and the concept of what are now called Green's functions. Green was the first person to create a mathematical theory of electricity and magnetism and his theory formed the foundation for the work of other scientists such as James Clerk Maxwell, William Thomson, and others. His work on potential theory ran parallel to that of Carl Friedrich Gauss. Green's work on the motion of waves in a canal (resulting in what is known as Green's law) anticipates the WKB* approximation of quantum mechanics, while his research on light-waves and the properties of the ether produced what is now known as the Cauchy-Green tensor. Green's theorem and functions were important tools in classical mechanics, and were revised by Julian Schwinger's 1948 work on electrodynamics that led to his 1965 Nobel prize (shared with Feynman and Tomonaga). Green's functions later also proved useful in analysing superconductivity. On a visit to Nottingham in 1930, Albert Einstein commented that Green had been 20 years ahead of his time. The theoretical physicist Julian Schwinger who used Green's functions in his ground-breaking works, published a tribute entitled The Greening of Quantum Field Theory: George and I in 1993.

*Wentzel-Kramers-Brillouin

See also: https://en.wikipedia.org/wiki/George_Green_(mathematician)

Lenhardt – Biographies 40 Hypocentral Distance William Hopkins

(February 2, 1793 in Kingston-on-Soar/G.B. – October 13, 1866 in Cambridge/U.K.) was an English mathematician and geologist. He is famous as a private tutor of aspiring undergraduate Cambridge mathematicians, earning him the sobriquet (nickname) the "senior-wrangler maker.*“ He became interested in geology through his acquaintance with the celebrated Cambridge geology professor Adam Sedgwick (1785 – 1873), who was also trained in mathematics. But it was Hopkins who seriously sought to place geological theory on a mathematical footing. In 1848, he published, that waves could be analogous to the vibrations of sound waves, dependent changes in pressure generating longitudinal pressure waves (called “normal” waves by Hopkins, or P-waves today); and waves that might be compared to those occurring on the surface of water, with transverse wave motions (called “tangential” waves, or S-waves today). Consequently these waves might be expected to travel at different velocities, the pressure waves travelling more rapidly. Thus he conceived the idea of what was later addressed as P (primary or OP = V t pressure) and S (secondary or shear) waves. The distance (“OP”) of an earthquake 1 1 OP = VStS (“O”; origin) from a point of observation (P) is thus dependent on the time difference and tS – tP= T of P- and S-wave arrivals. then OP (1/VS– 1/VP) = T Today, this OP-distance is estimated by the time difference between the S- and P-wave whence OP = T {VPVS/(VP– VS)} arrivals, given standard wave propagation velocities in the continental crust apply, simply multiplied by the factor of 8 (units in km, seconds and km/s, respectively). • Top mathematics undergraduate at Cambridge University in England, a position which has been described as "the greatest intellectual achievement attainable in Britain”.

See also: https://en.wikipedia.org/wiki/William_Hopkins; Oldroyd et al. 2007. The study of earthquakes in the hundred years following the Lisbon earthquake of 1755. Earth sciences history: Journal of the History of the Earth Sciences Society. Hopkins W 1848. Report on the geological theories of elevation and earthquakes. 17th Meeting Br. Assoc. Adv. Sci. in Oxford, 1847:33–92. Lenhardt – Biographies 41 Elasticity Parameters

Gabriel Lamé

(July 22, 1795 in Tours/France – May 1, 1870 in Paris/France) was a French mathematician who contributed to the theory of partial differential equations by the use of curvilinear coordinates, and the mathematical theory of elasticity (for which linear elasticity and finite strain theory elaborate the mathematical abstractions). He worked on a wide variety of different topics. Often problems in engineering led him to study mathematical questions and to develop the elasticity theory (e.g. on the stability of vaults and on the design of suspension bridges). Another example is his work on the conduction of heat which culminated in his theory of curvilinear coordinates. In continuum mechanics, the Lamé parameters (also called the Lamé coefficients, Lamé constants or Lamé moduli) are two material-dependent quantities denoted by λ and μ that arise in strain-stress relationships. In general, λ and μ are individually referred to as Lamé's first parameter and Lamé's second parameter, respectively. Other names are sometimes employed for one or both parameters, depending on context. For example, the parameter “μ” is referred to in fluid dynamics as the dynamic viscosity of a fluid (not the same units); whereas in the context of elasticity, “μ” is called the shear modulus, and is sometimes denoted by “G” instead of “μ”. Typically the notation “G” is seen paired with the use of Young's modulus “E”, and the notation “μ” is paired with the use of “λ”, or with the bulk modulus “K”.

See also: https://en.wikipedia.org/wiki/Gabriel_Lam%C3%A9

Lenhardt – Biographies 42 Mountain Roots George Biddell Airy

(July 27, 1801 in Alnwick/U.K. – January 2, 1892 in London/U.K.) was an English mathematician and astronomer, Astronomer Royal from 1835 to 1881. His many achievements include work on planetary , measuring the mean density of the Earth, a method of solution of two-dimensional problems in solid mechanics and establishing Greenwich as the location of the prime meridian. One of the most remarkable of Airy's researches was his determination of the mean density of the Earth. In 1826, the idea occurred to him of attacking this problem by means of pendulum experiments at the top and bottom of a deep mine at the Harton pit near South Shields in northern England in 1854. Their immediate result was to show that gravity at the bottom of the mine exceeded that at the top by 1/19286 of its amount, the depth being 383 m. From this he was led to the final value of Earth's specific density of 6.566, which was astounding 19 % larger than the currently accepted value of 5.51 kg/m³. Note, that Cavendish’s estimate from 1798 was much better. George Airy came up with the explanation that the roots of the mountain go deep into the earth. He compared it with a heap of logs in water and suggested that when a log juts higher above the water, a greater amount of it must be submerged. In 1830, Airy calculated the lengths of the polar radius and equatorial radius of the earth using measurements taken in the U.K. Although his measurements were superseded by more accurate radius figures (such as those used for GRS 80 and WGS84) his Airy geoid (strictly a reference ellipsoid, OSGB36) is still used by Great Britain's Ordnance Survey for mapping of England, Scotland and Wales because it better fits the local sea level (about 80 cm below world average).

See also: https://en.wikipedia.org/wiki/George_Biddell_Airy Lenhardt – Biographies 43 Geomagnetism

Johann von Lamont

(December 13, 1805 in Corriemulzie/U.K. – August 6, 1879 in /Germany), born John Lamont, was a Scottish-German astronomer and physicist. The son of Robert Lamont (forester to Earl Fife) and Elizabeth Ewan, his education began at the local school in Inverey, near Braemar in Scotland. In 1817 his father died and John was sent to be educated at St. James' monastery (Scots Benedictine College) at Ratisbon, Germany. He began to work in astronomy and joined the Bogenhausen Observatory, became its director in 1835, took his doctorate of philosophy in 1830 and became professor of astronomy in 1852 at Munich University. At the observatory he undertook the task of creating a star catalogue that had about 35,000 entries. His most important work was on the magnetism of the Earth. He performed magnetic surveys in Bavaria and northern Germany, France, , and Denmark. He discovered a magnetic decennial period (ten-year cycle) and the electric current in the Earth closing the electric "circuit" creating the magnetic field in 1850, matching and confirming the sunspot cycle discovered by Heinrich Schwabe in 1843. He calculated the orbits of the moons of and Saturn, obtaining the first value for Uranus' mass. By chance he observed in 1845 and twice in 1846, but did not recognize the object as being a new planet. Lamont is the author of Handbuch des Erdmagnetismus (1849).

See also: https://en.wikipedia.org/wiki/Johann_von_Lamont Lenhardt – Biographies 44 Earthquake Prediction?

Alexis Perrey

(July 6, 1807 in Sexfontaines/France – December 29, 1882 in Paris/France) was a seismologist and compiler of earthquake catalogues. He is considered a pioneer in this area, having published a paper on earthquakes in Algeria as early as 1848, in the journal Mémoires de l'Académie des Sciences, Arts et Belles-Lettres de Dijon. He continued to post annual observations on Algerian earthquakes until 1871 and compiled an impressive earthquake catalogue from 1843-1871 stating 21.000 events He suspected a correlation between the moon and seismic activity on earth, and developed his theory with the use of statistics. He found that earth tremors occurred most frequently during full and new moons, when the Earth is between the sun and moon, when the moon is between the Earth and Sun, and when the moon is closest in its orbit to the Earth. He also found indications in some cases that the moon had crossed the meridian of affected localities at the time of the earthquake. His idea, that earthquakes are related to the relative position of celestial bodies, has been proven wrong almost instantly – but re-appears every now and then as a new idea to explain the initiation of earthquakes. If it would be that easy, earthquake prediction would have been possible and used since long ago (see Laplace‘s demon). Dubious other persons who carried on to believe in tidal triggering of earthquakes were e.g. among many others the climatologist/ biologist/philosopher Iben Browning, who predicted an earthquake in New Madrid for December 3, 1980 (which did not turn up) and the geologist James Berkland.

See also: https://en.m.wikipedia.org/wiki/Alexis_Perrey Lenhardt – Biographies 45 and Geothermal Heat

James David Forbes

(April 20, 1809 in Edinburgh/U.K. – December 31, 1868 in Edinburgh/U.K.) was a Scottish physicist and glaciologist who worked extensively on the conduction of heat and seismology. Forbes was a resident of Edinburgh for most of his life, educated at its University and a professor there from 1833 until he became principal of the United College of St. Andrews in 1859. He is known for constructing the "first“ proper seismometer in 1842 which was essentially an inverted pendulum – and should better referred to as a "seismoscope“. He concentrated on glaciology, however. Forbes was also interested in geology, and published memoirs on the thermal springs of the Pyrenees, on the extinct volcanoes of the Vivarais (Ardêche), on the geology of the Cuchullin and Eildon hills, etc. In 1846 he began experiments on the temperature of the earth at different depths and in different soils near Edinburgh, which yielded determinations of the thermal conductivity of trap-tufa, sandstone and pure loose sand. Towards the end of his life he was occupied with experimental inquiries into the laws of the conduction of heat in iron bars, and his last piece of work was to show that the thermal conductivity of iron diminishes with increase of temperature. His attention was directed to the question of the flow of glaciers in 1840 when he met Louis Agassiz at the meeting of the British Association, and in subsequent years he made several visits to Switzerland, where he was particularly impressed by Bernhard Studer's theories, and also to Norway for the purpose of obtaining accurate data. His observations led him to the view that a glacier is an imperfect fluid or a viscous body which is urged down slopes of a certain inclination by the mutual pressure of its parts, and involved him in some controversy with Tyndall and others both as to priority and to scientific principle. A notable defender of Forbes in this controversy was John Ruskin, the two having first met by coincidence in 1844 during a study tour of the Alps.

See also: https://en.wikipedia.org/wiki/James_David_Forbes

Lenhardt – Biographies 46 Crustal Balance

John Henry Pratt

(June 4, 1809 in London/U.K. – December 28, 1871 in India) was a British clergyman, astronomer and mathematician. A Cambridge Apostle, he joined the British East India Company in 1838 as a chaplain and later became Archdeacon of Calcutta. A gifted mathematician who worked on problems of and earth science, he was approached by the Surveyor General of India to examine the errors in surveys resulting from the attraction of the plumb-line to the mass of the Himalayan mountains. This led him to develop a theory based on a fluid earth of crustal balance which became the basis for the isostasy principle. He died in India of cholera. Pratt suggested that there was a lower density beneath mountains below sea- level (actually refined later and termed the depth of compensation) and that this is offset by the mass above sea-level. Pratt's explanation assumes a variation in density whereas Airy assumed a constant crustal density. Pratt found with Airy's idea as it assumed a thinner crust (14 km) than that estimated by William Hopkins (1,100 – 1,400 km) and also that the crust is lighter. Pratt said that the crust cools from the solid interior and should therefore be denser. Airy did not defend his view but Samuel Haughton used the debate to claim that mathematics was a useless tool for speculation. Pratt suggested that the crust would be depressed in the cooler parts of the world and suggested that the plumb deflection was caused by anomalous high density in the oceans south of the Himalayas. Essentially Pratt was right. A more elaborated explanation gave Vening Meinesz. The term “isostasy” was coined later by the America geologist Clarence Edward Dutton (1841–1912).

See also: https://en.wikipedia.org/wiki/John_Pratt_(Archdeacon_of_Calcutta) Lenhardt – Biographies 47 Isostasy

Isostasy (Greek ísos "equal", stásis "standstill") is the state of gravitational equilibrium between Earth's crust (or lithosphere) and mantle such that the crust "floats" at an elevation that depends on its thickness and density.

The three types of isostasy: a) Pratt-Hayford: Equal density and unequal mass for different crustal sections. b) Airy-Heiskanen: Predicts topography after different densities of crustal sections with an equal mass. c) Vening Meinesz: Flexural isostasy calculates the lithosphere compensation to a certain load, where “Te” is the flexural rigidity of the lithosphere and λ the flexural wavelength (which has nothing in common with Lame’s parameter).

Airy and Pratt isostasy are statements of buoyancy, but flexural isostasy is a statement of buoyancy when deflecting a sheet of finite elastic strength.

After Watts, A. B. 2001. Isostasy and flexure of the lithosphere. Cambridge University Press. and https://en.wikipedia.org/wiki/Isostasy

Lenhardt – Biographies 48 Earthquake Map

Robert Mallet

(June 3, 1810 in Dublin/Ireland – November 5, 1881 in London/U.K.), Irish geophysicist, civil engineer, and inventor who distinguished himself in research on earthquakes. In 1851 he published an earthquake catalogue 1606 BC – 1850 including 6,831 events. His Report on the Great Neapolitan Earthquake of 1857 was a major scientific work and made great use of the then new research tool of photography to record the devastation caused by the earthquake.

Together with his son John William (who worked as geologist in India) he published the first Seismographic map of the world in 1858 (as earlier works by Heinrich Berghaus (1845) and Keith Johnston (1948) were less conclusive) and he conducted seismic experiments to examine the velocities of energy passing through various materials including rocks at Killiney Beach near Dublin in 1849. He coined the names “isoseismal” and “epicentre”. The latter term may also be attributed to Johannes Friedrich Julius Schmidt (1825 – 1884) from Germany, however. He also was the first to use the See also: https://en.wikipedia.org/wiki/Robert_Mallet term “seismology” in print. Lenhardt – Biographies 49 Continental Drift

Osmond Fisher

(November 17, 1817 in Osmington, Dorset/U.K. – July 12, 1914, Huntingdon/U.K.) was an English geologist and geophysicist. Fisher worked on the geomorphology of Norfolk, as well as the stratigraphy and invertebrate fossils of Dorset. He had published The Physics of the Earth’s Crust in 1881, in which he postulated a non-homogenous composition of the Earth. He speculated that the crust may sit on top of a liquid layer. This was the most prominent work on the topic since Alexander von Humboldt, however it went largely ignored until the work of Alfred Wegener. Much of his work into continental drift went ridiculed, while other geologists of the time clung to their “Solid State Theory”. However his observations were all based on careful scientific deductions rather than simple speculation. He also published theories on the moon, proposing that the was the mark left where the moon split from the earth. However, the Pacific Ocean is both chemically dissimilar and much younger than the moon and the seas were subject to plate drifts over billions of years, hence his assumption was wrong. He was also the author of the first geophysical textbook, named Physics of the Earth's Crust, published in 1881.

See also: https://en.m.wikipedia.org/wiki/Osmond_Fisher

Lenhardt – Biographies 50 Fluids

George Gabriel Stokes

(August 13, 1819 in Skreen/Ireland – February 1, 1903 in Cambridge/U.K.) was an Anglo-Irish physicist and mathematician. Born in County Sligo, Ireland, Stokes spent all of his career at the University of Cambridge, where he was the Lucasian Professor of Mathematics from 1849 until his death in 1903. As a physicist, Stokes made seminal contributions to fluid mechanics, including the Navier– Stokes equations and to physical optics, with notable works on polarization and fluorescence. As a mathematician, he popularised "Stokes' theorem" in vector calculus and contributed to the theory of asymptotic expansions. Stokes, along with Felix Hoppe-Seyler, first demonstrated the oxygen transport function of hemoglobin and showed colour changes produced by aeration of hemoglobin solutions. His first published papers, which appeared in 1842 and 1843, were on the steady motion of incompressible fluids and some cases of fluid motion. These were followed in 1845 by one on the friction of fluids in motion and the equilibrium and motion of elastic solids, and in 1850 by another on the effects of the internal friction of fluids on the motion of pendulums. To the theory of sound he made several contributions, including a discussion of the effect of wind on the intensity of sound and an explanation of how the intensity is influenced by the nature of the gas in which the sound is produced. These inquiries together put the science of fluid dynamics on a new footing, and provided a key not only to the explanation of many natural phenomena, such as the suspension of clouds in air, and the subsidence of ripples and waves in water, but also to the solution of practical problems, such as the flow of water in rivers and channels, and the skin resistance of ships.

See also: https://en.wikipedia.org/wiki/Sir_George_Stokes,_1st_Baronet Lenhardt – Biographies 51 Isoseismals Georg Heinrich Otto Volger

(January 30, 1822 in Lüneburg/Kingdom of Hannover – October 18, 1897 in Sulzbach/Germany) was a German geologist. From 1851 to 1856 he was a professor of natural history at the ETH Zurich, and afterwards taught geology at the Forschungsinstitut Senckenberg. From 1859 to 1881 he taught geology and mineralogy at the Freie Deutsche Hochstift in Frankfurt-am-Main. Volger made contributions in the fields of mineralogy and crystallography, and was particularly interested in earthquakes. He did extensive study of earthquakes in Switzerland; researching their origins, periodicity, meteorological and environmental factors, as well as the spread of quake effects. Volger advocated the theory of neptunism. Independent of geologist Robert Mallet, he created his own neptunistic theory of wave propagation of earthquakes. Volger believed that most earthquakes in Switzerland were subsidence quakes caused by collapse of layers of hollow strata in the Earth. In July 1855 there was a substantial earthquake at Visp in the Rhone Valley of Switzerland. Volger studied the earthquake’s effects intensively, making detailed enquiries from witnesses, which eventually enabled him to write a three-volume treatise on the event, making it one of the most thoroughly described and best-known of 19th-century earthquakes from a qualitative rather an instrumental perspective. In essence, his map was "up-side“ down in terms of today‘s macroseimic intensity, as the greatest effect near the epicentre was attributed to zone 1, and decaying intensity-degrees were associated with zones up to 5 (where no damage of effects were observed). Volger‘s scale concentrated on damage to buildings in terms of "importance“. Later, Robert Mallet turned this classification around, which essentially is used today. It should be noted, that similar maps (1810 – Hungary; 1828, 1846 – Germany etc.) had been published earlier, but at much lesser detail.

See also: https://de.wikipedia.org/wiki/Otto_Volger; and Oldroyd et al. 2007. The study of earthquakes in the hundred years following the Lisbon earthquake of 1755. Earth sciences history: journal of the History of the Earth Sciences Society. Lenhardt – Biographies 52 First Concise Macroseismic Map

The map by Volger shows the combined effects of four earthquakes in Switzerland in 1855. Colours follow "intensity“. Red = Intense damage, beyond Orange = no damage.

See also: https://de.wikipedia.org/wiki/Otto_Volger; and Oldroyd et al. 2007. The study of earthquakes in the hundred years following the Lisbon earthquake of 1755. Earth sciences history: journal of the History of the Earth Sciences Society.

Lenhardt – Biographies 53 Carrington Event Richard Christopher Carrington

(May 26, 1826 in London/U.K. – November 27, 1875 in Churt/U.K.) was an amateur astronomer whose 1859 astronomical observations demonstrated the existence of solar flares as well as suggesting their electrical influence upon the Earth and its aurorae; and whose 1863 records of sunspot observations revealed the differential rotation of the Sun. On September 1, 1859, Carrington and Richard Hodgson, another English amateur astronomer, independently made the first observations of a solar flare. Because of a simultaneous "crochet" observed in the Kew Observatory magnetometer record by Balfour Stewart and a geomagnetic storm observed the following day, Carrington suspected a solar-terrestrial connection.

Worldwide reports on the effects of the geomagnetic storm of 1859 were compiled and published by Elias Loomis which support the observations of Carrington and Balfour Stewart. For this reason, the geomagnetic storm of 1859 is often referred to as the “Carrington event”. The solar fare recording at Kew Gardens near London went simply out of bounds (right figure). Even though he did not discover the 11-year sunspot activity cycle, Carrington's observations of sunspot activity after he heard about Heinrich Schwabe's work (which dealt solely with sun spot observations) led to the numbering of the cycles with Carrington's name. For example, the sunspot maximum of 2002 was Carrington Cycle No. 23. See also: https://en.wikipedia.org/wiki/Richard_Christopher_Carrington Lenhardt – Biographies 54 Ancient Continents

Eduard Suess

(August 20, 1831 in London/U.K. – April 26, 1914 in Vienna/Austria)

1856 Professor for Palaeontology in Vienna, from 1861 Professor for Geology 1883-1904 Several editions of Das Antlitz der Erde 1896 Receives Wollaston-Medal from the Geological Society in London

Being a member of the town council in Vienna and of the provincial government of Lower Austria, Suess advocated the regulation of the Danube river bed and the establishment of the “Wiener Hochquellenwasserleitung”. Suess coined the term “” after the ancient people of the Gonds in India for a super-continent, which encompassed South America, Africa and India, as certain plants (Glossopteris) could be found on these continents. This continent also included landmasses, which Suess assumed to have subsided since the Tertiary and form the oceans. Suess was convinced, that oceans were relative young. He also introduced terms such as “Lithosphere”, “Hydrosphere”, “Sial”, “Sima”, and “Laurentia” (Canadian shield, – later referred to as “Laurasia” by the South African geologist Alexander de Toit), Suess interpreted volcanism as a result of the genesis of mountains, in contrast to Leopold von Buch und James Hutton. He advocated the idea of cooling and shrinking of the Earth – where he was wrong. He also introduced the term “Thermenlinie” and “Kamptal-Linie” in Austria, which he supposed, were the cause of frequent earthquakes as he was not aware of what is known today as soil-amplification.

See also: https://en.wikipedia.org/wiki/Eduard_Suess

Lenhardt – Biographies 55 Publisher

Georg Cornelius Karl Gerland

(January 29, 1833 in Kassel/Germany – February 16, 1919 in Strasbourg/France) was a German anthropologist and geophysicist.

He studied classical philology, Germanistics and anthropology at the universities of Berlin and Marburg. From 1856 to 1875 he successively worked as a gymnasium teacher in Kassel, Hanau, Magdeburg and Halle an der Saale, and in 1875 was named a professor of ethnology and geography at the University of Strasbourg. In 1900 he became director of the Imperial Central Bureau for Earthquake Research in Strasbourg. Gerland presented ideas of German seismologist Ernst von Rebeur-Paschwitz at the 6th International Geographic Conference in London in 1895, and organized the first International Conference of Seismology in Strasbourg in 1901. It was the start of international cooperation in seismology and led to the founding two years later of the International Seismological Association (since 1951 the International Association of Seismology and Physics of the Earth’s Interior – IASPEI). By the way: The geologist and revolutionary Carl Ferdinand Julius Fröbel (1805 –1893) coined the word “Geophysik” in 1834. It was used occasionally used in the next few decades, but did not really stick on until journalists turned to the subject with the appearance of Beiträge zur Geophysik in 1887 by Gerland.

See also: https://en.wikipedia.org/wiki/Georg_Gerland

Lenhardt – Biographies 56 Stress Conditions

Christian Otto Mohr

(October 8, 1835 in Wesselburen in Holstein/Germany – October 2, 1918 in Dresden/Germany) was a civil engineer. Mohr was an enthusiast for graphical tools and developed the method, for visually representing stress in three dimensions, previously proposed by Carl Culmann. In 1882, he famously developed the graphical method for analysing stress known as Mohr's circle and used it to propose an early theory of strength based on shear stress. He also developed the Williot-Mohr diagram for truss displacements and the Maxwell-Mohr method for analysing statically indeterminate structures, it can also be used to determine the displacement of truss nodes and forces acting on each member. The Maxwell-Mohr method is also referred to as the virtual force method for redundant trusses. Mohr's circle is often used in calculations relating to mechanical engineering for materials' strength, geotechnical engineering for strength of soils and, structural engineering for strength of built structures respectively. It is also used for calculating stresses in many planes by reducing them to vertical and horizontal components. These are called principal planes in which principal stresses are calculated; Mohr's circle can also be used to find the principal planes and the principal stresses in a graphical representation. Note, that focal solutions used in seismology do not provide the directions of principal stresses but indicate their quadrants.

See also: https://en.wikipedia.org/wiki/Mohr%27s_circle

Lenhardt – Biographies 57 Rayleigh Wave

John William Strutt, 3rd Baron Rayleigh

(November 12, 1842 in Maldon/U.K. – June 30, 1919 in Witham/U.K.), was a British scientist who made extensive contributions to both theoretical and experimental physics. He spent all of his academic career at the University of Cambridge. Among many honors, he received the 1904 Nobel Prize in Physics "for his investigations of the densities of the most important gases and for his discovery of argon in connection with these studies." He served as President of the Royal Society from 1905 to 1908 and as Chancellor of the University of Cambridge from 1908 to 1919. Rayleigh provided the first theoretical treatment of the elastic scattering of light by particles much smaller than the light's wavelength, a phenomenon now known as "Rayleigh scattering", which notably explains why the sky is blue. He studied and described transverse surface waves in solids (1885), now known as "Rayleigh waves“, denoted “R” for short. He contributed extensively to fluid dynamics, with concepts such as the Rayleigh number (a dimensionless number associated with natural convection), Rayleigh flow, the Rayleigh–Taylor instability, and Rayleigh's criterion for the stability of Taylor–Couette flow. He also formulated the circulation theory of aerodynamic lift. In optics, Rayleigh proposed a well known criterion for angular resolution. His derivation of the Rayleigh–Jeans law for classical black-body radiation later played an important role in birth of quantum mechanics (see Ultraviolet catastrophe). Rayleigh's textbook The Theory of Sound (1877) is still used today by acousticians and engineers. See also: https://en.wikipedia.org/wiki/John_William_Strutt,_3rd_Baron_Rayleigh Lenhardt – Biographies 58 Landscape Changes

Grove Karl Gilbert

(May 6, 1843 in Rochester, New York/U.S.A. – May 1, 1918 in Jackson, Michigan/U.S.A.) was an American geologist. He published an important monograph, The Geology of the Henry Mountains (1877). After the creation of the U.S. Geological Survey in 1879, he was appointed to the position of Senior Geologist and worked for the U.S.G.S. until his death (including a term as acting director). In 1891, Gilbert examined the origins for a crater in Arizona, now known as “Meteor Crater”. Gilbert's calculations showed that the volume of the crater and the debris on the rim were roughly equal, and no magnetic anomalies were found. Gilbert argued that the meteorite fragments found on the rim were just “coincidence”, as he believed, that the crater was volcanic origin (1895). Subsequent investigations would reveal that it was in fact a meteor crater, but that interpretation was not well established until the mid-20th century. Two weeks after the 1906 earthquake, Gilbert took a series of famous photographs documenting the damage along the from Inverness to Bolinas in California. Gilbert is considered one of the giants of the sub-discipline of geomorphology, having contributed to the understanding of landscape evolution, erosion, river incision and sedimentation. Gilbert was a planetary science pioneer, correctly identifying lunar craters as caused by impacts, and carrying out early impact- cratering experiments.

See also: https://en.wikipedia.org/wiki/Grove_Karl_Gilbert Lenhardt – Biographies 59 Gradient of Gravity

Loránd Eötvös de Vásárosnamény

(July 27, 1848 in Buda/Austro-Hungarian Empire – April 8, 1919 in Budapest/Hungary), more commonly called “Baron Roland von Eötvös” in English literature, was a Hungarian physicist. He is remembered today largely for his work on gravitation and surface tension, and the invention of the torsion pendulum. His experimental work on gravity, in particular his study of the equivalence of gravitational and inertial mass (the so-called weak equivalence principle) and his study of the gravitational gradient on the Earth's surface was ground-breaking. The weak equivalence principle plays a prominent role in relativity theory and the Eötvös experiment was cited by Albert Einstein in his 1916 paper The Foundation of the General Theory of Relativity. Measurements of the gravitational gradient are important in Applied Geophysics. The CGS unit for gravitational gradient is named the Eötvös in his honour. The Eötvös torsion balance, an important instrument of geodesy and geophysics throughout the whole world, studies the Earth's physical properties. It is used for mine exploration, and also in the search for minerals, such as oil, coal and ores. The Eötvös pendulum was never patented, but after the demonstration of its accuracy and numerous visits to Hungary from abroad, several instruments were exported worldwide, and the richest oilfields in the United States were discovered by using it. The Eötvös pendulum was used to prove the equivalence of the inertial mass and the gravitational mass accurately. This equivalence was used later by Albert Einstein in setting out the theory of general relativity.

See also: https://en.wikipedia.org/wiki/Lor%C3%A1nd_E%C3%B6tv%C3%B6s

Lenhardt – Biographies 60 Earth Oscillations

Horace Lamb

(November 27, 1849 in Stockport/U.K. – December 4, 1934 in Cambridge/U.K.) was a British applied mathematician and author of several influential texts on classical physics, among them Hydrodynamics (1895) and Dynamical Theory of Sound (1910). Both of these books remain in print. The word “vorticity” (a.k.a. turbulence today) was coined by Lamb in 1916. Lamb waves propagate in solid plates or spheres. They are elastic waves whose particle motion lies in the plane that contains the direction of wave propagation and the plane normal (the direction perpendicular to the plate). The wave properties turned out to be quite complex. An infinite medium supports just two wave modes traveling at unique velocities; but plates support two infinite sets of Lamb wave modes, whose velocities depend on the relationship between wavelength and plate thickness, hence they exhibit velocity dispersion; that is, their velocity of propagation “c” depends on the frequency (or wavelength), as well as on the elastic constants and density of the material. Physically, the key parameter is the ratio of plate thickness “d” to wavelength “λ”. This concept leads to free oscillations of a plate. In 1882, Lamb showed that free vibrations of an elastic sphere can be classified into two groups: torsional and spheroidal oscillations. The earthquake in Chile in 1960 served as an excellent example to study these free oscillations of the Earth. Since the 1990s, the understanding and utilization of Lamb waves has advanced greatly, thanks to the rapid increase in the availability of computing power. Lamb's theoretical formulations have found substantial practical application, especially in the field of nondestructive testing.

See also: https://en.wikipedia.org/wiki/Horace_Lamb

Lenhardt – Biographies 61 Intensity Scales

Giuseppe Mercalli

(May 21, 1850 in Milan/Italy – March 19, 1914 in Naples/Italy) was an Italian volcanologist and Catholic priest. He is known best for the Mercalli intensity scale for describing earthquake effects. Mercalli devised two earthquake intensity scales, both modifications of the Rossi-Forel (RF) scale. The first now largely forgotten, had six degrees whereas the Rossi-Forel scale had ten. The second, now known as the Mercalli intensity scale, had ten degrees, and elaborated the descriptions in the Rossi-Forel scale. The Italian physicist Adolfo Cancani expanded the ten- degree Mercalli scale with the addition of two degrees at the more intense of the scale: XI (catastrophe) and XII (enormous catastrophe). This scale was later modified by the German geophysicist August Heinrich Sieberg and became known as the Mercalli-Cancani-Sieberg (MCS) scale. This scale was modified again and published in English by Harry O. Wood and Frank Neumann during 1931 as the Mercalli-Wood-Neumann (MWN) scale. It was later improved by Charles Richter, developer of the Richter scale. The scale is known now as the Modified Mercalli intensity scale (MM or MMI) and is mainly used in the U.S.A. In Europe the European Macroseismic Scale (EMS) has been introduced in 1998. The latter scale builds on the Medvedev-Sponheuer-Karnik (MSK) from 1964, which itself is again based on the MCS.

See also: https://en.wikipedia.org/wiki/Giuseppe_Mercalli

Lenhardt – Biographies 62 Earthquake Categories

Rudolf Hoernes

(October 7, 1850 in Vienna/Austro-Hungarian Empire – August 20, 1912 in Judendorf-Straßengel in Styria/ Austro-Hungarian Empire) was an Austrian geologist and palaeontologist. His daughter Tanna was married to the artist Luigi Kasimir. In 1876, he became a.o. Professor for Geology at the University in Graz. During his term as regional geologist at the Geological Survey (based in Vienna), he travelled frequently to and between South Tyrol and Venetia. He also covered palaeontology and compared fossils from the Tertiary, and described the appearances of fossils from Croatia, Southern Styria, Hungary and from the Vienna Basin. Most of his discoveries were published in the Mitteilungen des naturwissenschaftlichen Vereines für Steiermark, which he edited for several years. From 1878 onwards, Hoernes showed extreme interest in earthquakes. He became a referent for Styria and published numerous papers on historic and recent earthquakes. In his work Erdbebenkunde (1893) he grouped earthquakes in three categories according to their cause:

1. Tectonic 2. Volcanic 3. Collapse

Today, owing to the industrial exploitation and usage for waste deposals, we may add a fourth category: induced seismic events.

See also: https://de.wikipedia.org/wiki/Rudolf_Hoernes

Lenhardt – Biographies 63 Horizontal Seismograph

John Milne

(December 30, 1850 in Liverpool/U.K. – July 31, 1913 in Shide/Isle of Wight/U.K.) was a British geologist and mining engineer who worked on a horizontal seismograph. Milne was hired by the Meiji government of the as a foreign advisor and professor of mining and geology at the Imperial College of Engineering in Tokyo from 8 March 1876, where he worked under Henry Dyer and with William Edward Ayrton and John Perry. Partly from a sense of adventure and partly because he suffered from seasickness, he travelled overland across Siberia taking three months to reach Tokyo. In 1880, Sir James Alfred Ewing, Thomas Gray and , all British scientists working in Japan, began to study earthquakes following a very large tremor which struck the area that year. They founded the Seismological Society of Japan (SSJ). The society funded the invention of seismographs to detect and measure the strength of earthquakes. Although all three men worked as a team on the invention and use of seismographs, John Milne is generally credited with the invention of the horizontal pendulum seismograph in 1880. Milne's instruments permitted to detect different types of earthquake waves, estimate velocities and microseisms. In addition, the foreign professors trained Japanese students including Seikei Sekiya who would become the world’s first professor of seismology at the Imperial University, and his successor, Fusakichi Omori, who refined Milne's instruments to detect and record finer vibrations.

See also: https://en.wikipedia.org/wiki/John_Milne

Lenhardt – Biographies 64 Crust-Mantle Boundary Andrija Mohorovičić

(January 23, 1857 in Volosko near Opatjia/Austro-Hungarian Empire – December 18, 1936 in Zagreb/Croatia) was a Croatian meteorologist and seismologist. He is best known for the eponymous Mohorovičić discontinuity and is considered as one of the founders of modern seismology. He made systematic studies and both invented and constructed instruments to observe precipitation in Croatia and Slavonia. In 1892 he became a head of the Meteorological Observatory in Grič and established a service for all Croatia, while teaching geophysics and astronomy at the university. On October 8, 1909 an earthquake occurred in the Kupa valley in the Pokuplje district in Croatia, 39 km southeast of Zagreb. A number of seismographs had been installed beforehand and these provided invaluable data, upon which he made new discoveries. By analysing data from more observation posts, Mohorovičić concluded that the Earth has several layers above a core. He was the first to establish, based on the evidence from seismic waves, the discontinuity that separates the Earth's crust from its mantle. This is now called the Mohorovičić discontinuity or (because of the complexity of that name) “Moho” for short. He estimated the “Moho” to exist a depth of approx. 60 km. This erroneous estimate can be attributed to massive clock corrections, which he was ware of. Therefore, he recommended to use far distant stations (> 300 – 400 km, where the time-correction would be less relevant) for locating earthquakes. Today, the “Moho”-depth has been ascertained to exist at a depth of around 30 km in continental areas, but may reach down almost twice as deep below the Alps. Mohorovičić's theories were visionary and were only truly understood many years later from detailed observations of the effects of earthquakes on buildings, deep focus earthquakes, locating earthquake epicenters, Earth models, seismographs, harnessing the energy of the wind, hail defence and other related elements related to geoscience.

See also: https://en.wikipedia.org/wiki/Andrija_Mohorovi%C4%8Di%C4%87

Lenhardt – Biographies 65 Earth´s Core

Richard Dixon Oldham

(July 31, 1858 in Dublin/Ireland – July 15, 1936 in Llandrindod Wells/U.K.) was a British geologist who made the first clear identification of the separate arrivals of P-waves, S-waves and surface waves on seismograms and the first clear evidence that the Earth has a central core. In 1879 Oldham became an assistant-superintendent with the Geological Survey of India, working in the Himalayas. He wrote about 40 publications for the Survey on geological subjects including hot springs, the geology of the Son Valley and the structure of the Himalayas and the Ganges plain. His most famous work was in seismology. His report on the 1897 Assam earthquake went far beyond reports of previous earthquakes. It included a description of the Chedrang fault, with uplift up to 11 m and reported accelerations of the ground that had exceeded the Earth's gravitational acceleration. His most important contribution to seismology was the first clear identification of the separate arrivals of P-waves, S-waves and surface waves on seismograms. Since these observations agreed with theory for elastic waves, they showed that the Earth could be treated as elastic in studies of seismic waves. In 1906 he wrote a paper analysing seismic arrival times of various recorded earthquakes. He concluded that the Earth has a core and estimated its radius to be less than 0.4 times the radius of the Earth. Oldham also favored the idea, that deep earthquakes occur as a result of recristallisation in the crust – an issue of ongoing debate.

See also: https://en.m.wikipedia.org/wiki/Richard_Dixon_Oldham

Lenhardt – Biographies 66 Magnetic Behaviour

Pierre Curie

(May 15, 1859 in Paris/France – April 19, 1906 in Paris/France) was a French physicist, a pioneer in crystallography, magnetism, piezoelectricity, and radioactivity. In 1903, he received the Nobel Prize in Physics with his wife, Marie Skłodowska-Curie, and Henri Becquerel, "in recognition of the extraordinary services they have rendered by their joint researches on the radiation phenomena discovered by Professor Henri Becquerel". Prior to his famous doctoral studies on magnetism, he designed and perfected an extremely sensitive torsion balance for measuring magnetic coefficients. Variations on this equipment were commonly used by future workers in that area. Pierre Curie studied ferromagnetism, paramagnetism, and diamagnetism for his doctoral thesis, and discovered the effect of temperature on paramagnetism which is now known as Curie's law. The material constant in Curie's law is known as the Curie constant. He also discovered that ferromagnetic substances exhibited a critical temperature transition, above which the substances lost their ferromagnetic behaviour. This is now known as the Curie temperature. The Curie temperature is used to study plate tectonics, treat hypothermia, measure caffeine, and to understand extraterrestrial magnetic fields.

See also: https://en.wikipedia.org/wiki/Pierre_Curie

Lenhardt – Biographies 67 Elastic Rebound

Harry Fielding Reid

(May 18, 1859 in Baltimore/U.S.A. – June 18, 1944 in Baltimore/U.S.A.) was an American geophysicist. He was notable for his contributions to seismology, particularly his theory of elastic rebound that related faults to earthquakes. Despite his interest in glaciology, he switched to seismology in 1902 when collecting seismological data for the U.S.G.S. At that time the science of seismology was extremely new, and there were only a handful of working seismographs anywhere in the world. The 1906 San Francisco earthquake offered Reid the chance to take his interest in seismology to a new level. Through a close examination of how different points of land along the California coast and nearby inland had moved over the course of the previous half century - here his access to U.S.G.S. data was crucial - Reid was able to determine that the earthquake was a result of forces he identified as “elastic strain release.” This strain had built up slowly but unequally at points along the “San Andreas Fault”*, and it took a massive tremblor to release the strain at that point along the fault where the greatest energy had accumulated. During the previous generation European scientists had begun to wonder if faults were related to earthquakes, and vice versa, but it was him who established that there was a clear and dynamic relationship. He would call his new theory “Elastic Rebound,” and it remains even into the 21st century at the foundation of modern tectonic studies. In this context, it should be fair to mention, that John Fillmore Hayford and A. L. Baldwin came forward with a similar idea in 1908 – not to mention Grove Karl Gilbert in 1884.

* The name “San Andreas Fault” was actually coined by the geologist Andrew Cowper Lawson in 1895, who published the so-called “Lawson Report” on the “1906 San Francisco earthquake” in 1908.

See also: https://en.wikipedia.org/wiki/Harry_Fielding_Reid Lenhardt – Biographies 68 Continental Drift

Frank Bursley Taylor

(November 23, 1860 in Fort Wayne/U.S.A. – June 12, 1938 Fort Wayne/U.S.A.) was a geologist. He was a Harvard dropout who studied privately financed in large part by his wealthy father. He became a specialist in the glacial geology of the Great Lakes, and proposed to the Geological Society of America on December 29, 1908 that the continents moved on the Earth's surface, that a shallow region in the Atlantic marks where Africa and South America were once joined, and that the collisions of continents could uplift mountains. His ideas were based on his studies on mountain ranges as the Andes, Rockies, Alps and Himalayas, concluding that these mountains could have been formed only as a result of titanic lateral pressures that thrust the earth's surface upward. His theory was either ignored or opposed by other scientists of his time. He wrote a total ten papers on the subject of continental drift. Taylor's ideas about continental drift were independently discovered by Alfred Wegener in Germany in 1912. Later, he proposed that this occurred as the plates are being dragged towards the equator by tidal forces during the hypothesized capture of the moon, resulting in "general crustal creep" toward the equator. His own proposition was that the moon was captured by the Earth's gravity during the Cretaceous period 100 million years ago, and came so close to the earth that its tidal pull dragged the continents toward the Equator. This lacked evidence. Although his proposed mechanism was wrong, he was the first to come to the insight that one of the effects of continental motion would be the formation of mountains due to the collision of continental plates. But even with Wegener's extensive extra research the idea of continental drift did not achieve acceptance until the 1960s when evidence had accrued via Harry Hess, Frederick Vine, Drummond Matthews and Keith Runcorn.

See also: https://en.wikipedia.org/wiki/Frank_Bursley_Taylor Lenhardt – Biographies 69 Teleseims

Ernst von Rebeur-Paschwitz

(August 9, 1861, Frankfurt a.d. Oder/Germany – October 1, 1895, Merseburg/Germany) was an astronomer, geophysicist and seismologist. On 17 April 1889, he recorded very strong deflections of the vertical axis on both instruments at the time when a strong earthquake occurred near Tokyo in Japan. 64 minutes after its impulse was recorded in Tokyo, Rebeur- Paschwitz observed disturbances on his instruments at Potsdam and Wilhelmshaven in Germany, which means that the seismic waves had gone a distance of almost 9000 km through the inside of the Earth at the average speed of more than 1600 m per second. Rebeur-Paschwitz was the first to detect earthquake vibration that had passed through the inside of the Earth. Even though the shaking of local earthquakes was recorded several times before, this was the first time when the waves of a faraway earthquake had been registered. The realization that strong earthquakes can be recorded at great distances helped usher in the modern era in the field of seismology and the physics of the Earth’s interior. Georg C. K. Gerland presented Rebeur-Paschwitz’s ideas at the 6th International Geographic Conference in London in 1895, and organized the 1st International Conference of Seismology in Strasbourg in 1901. It was the start of international cooperation in seismology and led to the founding two years later of the International Seismological Association (since 1951 the International Association of Seismology and Physics of the Earth’s Interior – IASPEI).

See also: https://en.wikipedia.org/wiki/Ernst_von_Rebeur-Paschwitz

Lenhardt – Biographies 70 Seismograph

Emil Johann Wiechert

(December 26, 1861 in Tilsit/Prussia – March 19, 1928 in Göttingen/Germany) was a German physicist and geophysicist who made many contributions to both fields, including presenting the first model of a layered structure of the Earth and being among the first to discover the electron. Wiechert studied at the University of Königsberg (Kaliningrad/Russia). In 1898, he was appointed to the world's first Chair of Geophysics at the University of Göttingen. Wiechert was also interested in fields outside of fundamental physics and in 1896, he published the first verifiable model of the Earth's interior as a series of shells. Here he concluded that the difference between the density of the Earth's surface rocks and the mean density of the Earth meant that the Earth must have a heavy iron core. These were the foundations that one of Wiechert's students, Beno Gutenberg, used to discover the three-layered Earth in 1914. Another student of Wiechert was Karl Bernhard Zöppritz. During his career he made many other important contributions, writing a number of scientific papers, including a pioneering work on how seismic waves propagate through the Earth. He also devised an improved seismograph and created the field of geological prospecting using small, artificially-created earthquakes. Wiechert was also interested in theoretical physics, such as the theory by Albert Einstein. He discussed the role of the ether and related questions with Hendrik Antoon Lorentz and others. It appears, that Wiechert's seismograph became handy (also it weighted 1 ton at least), as he used paper to record earthquakes. Earlier seismographs (e.g. Rebeur-Paschwitz) used expensive photographic paper with very little paper advance. This property did not permit the study of seismic waves in great detail.

See also: https://en.wikipedia.org/wiki/Emil_Wiechert Lenhardt – Biographies 71 Epicentres

Radó von Kövesligethy

(in Hungarian usage Kövesligethy Radó, September 1, 1862 in Verona/Austro- Hungarian Empire – October 11, 1934 in Budapest/Hungary), was a Hungarian physicist, astronomer and geophysicist. The first successful spectral equation of black body radiation was his theory of the continuous spectra of celestial bodies in 1885 in Hungarian and in 1890 in German. He derived a spectral equation with the following properties: the spectral distribution of radiation depends only on the temperature, the total irradiated energy is finite (15 years before Max Planck!), the wavelength of the intensity maximum is inversely proportional to the temperature (eight years before Wilhelm Carl Werner Otto Fritz Franz Wien!). Using his spectral equation, he estimated the temperature of several celestial bodies, including the Sun. He also formulated laws to establish the epicenters of earthquakes (based on macroseismic observations), and was an assistant to Loránd Eötvös.

See also: https://en.wikipedia.org/wiki/Rad%C3%B3_von_K%C3%B6vesligethy

Lenhardt – Biographies 72 Love Wave

Augustus Edward Hough Love

(April 17, 1863 in Weston-super-Mare/U.K. – June 5, 1940 in Oxford/U.K.), often known as A. E. H. Love, was a mathematician famous for his work on the mathematical theory of elasticity. He also worked on wave propagation and his work on the structure of the Earth in Some Problems of Geodynamics won for him the Adams prize in 1911 when he developed a mathematical model of surface waves known as Love waves. Love also contributed to the theory of tidal locking and introduced the parameters known as Love numbers*, which are widely used today. These numbers are also used in problems related to the tidal deformation of the Earth due to the gravitational attraction of the Moon and Sun.

* The Love numbers h, k, and l are dimensionless parameters that measure the rigidity of a planetary body and the susceptibility of its shape to change in response to a tidal potential.

See also: https://en.wikipedia.org/wiki/Augustus_Edward_Hough_Love Lenhardt – Biographies 73 Geomagnetic Field Reversal

Antoine Joseph Bernard Brunhes

(July 3, 1867 in Toulouse/France – May 10, 1910 in Clermont-Ferrand/ France) was a French geophysicist known for his pioneering work in palaeomagnetism, in particular, his 1906 discovery of . The Brunhes-Matuyama reversal is named for him. In November 1900, he was appointed as head of the Puy-de-Dôme Observatory, built on an extinct volcano in the Auvergne region of France, where he worked until his death in 1910. It was during his time at the observatory that he made the crucial observation that led to his discovery of geomagnetic reversal. In 1905, he found that rocks in an ancient lava flow at Pontfarin in the commune of Cézens (part of the Cantal département) were magnetised in a direction almost opposite to that of the present-day magnetic field. From this, he deduced that the magnetic North Pole of the time was close to the current geographical South Pole, which could only have happened if the magnetic field of the Earth had been reversed at some point in the past. He was correct, though it took another 50 years before his theory was fully accepted by the scientific community.

See also: https://en.wikipedia.org/wiki/Bernard_Brunhes

Lenhardt – Biographies 74 Rate

Fusakichi Omori

(大森 房吉, Ōmori Fusakichi, October 30, 1868 in Fukui/Japan – November 8, 1923 in Tokyo/Japan) was a pioneer Japanese seismologist, second chairman of seismology at the Imperial and president of the Japanese Imperial Earthquake Investigation Committee. On October 28, 1891 the provinces of Mino and Owari were devastated by earthquakes; their fault lines were traced by Bunjiro Koto (1856 – 1935), another professor at Imperial University. He found the strike-slip fault intersected the surface for at least 60 km and that the north-east side had been shifted relative to the other side by 1 – 2 metres. Some areas had 6 – 7 m high scarps, others looked like a mole had been at work. This earthquake provided an initial data set which, when correlated with other earthquakes, revealed that aftershock frequency decreases by approximately the reciprocal of time after the main shock, a mathematical formula now called "Omori's law". Omori later continued this research and is recognized in as the first to research the effects of earthquakes on man-made structures through implementing the usage of shaking tables and comparing experimental results with measurements during actual earthquakes. This earthquake firmly established the faulting origin (Bunjiro Kato, 1893). On the occasion of the 1908 Messina earthquake, Omori noted the large loss of life, perhaps 75,000, and he stated that 99 percent of those had died because their houses were not built to withstand earthquakes.

See also: https://en.wikipedia.org/wiki/Fusakichi_Omori

Lenhardt – Biographies 75 Earthquake Geography

Ferdinand de Montessus de Ballore

(May 20, 1870 in Villeurbanne/France – January 26, 1937 in Arcachon, France). He was a pioneer at the same level of Perrey, Mallet, Milne and Omori. He became familiar with earthquakes and volcanoes in Central America (1881 – 1885). After his experience in El Salvador his interest for understanding earthquakes and volcanoes determined the rest his life. Back in France he worked out a most complete world catalogue of earthquakes with 170.000 events (1885 – 1907), and completed his career being the head of the Chilean Seismological Service (1907 – 1923). Many of his ideas were in advance of later discoveries. He was an exceptional writer and published more than 30 books and hundreds of papers. He became known for his work on the Global distribution of earthquakes.

See also: https://hal.archives-ouvertes.fr/hal-00533421/document

Lenhardt – Biographies 76 Ray Parameter

Hans Benndorf

(December 13, 1870 in Zürich/Switzerland – February 11, 1953 in Graz/Austria) was an Swiss/Austrian physicist. He was the son of archaeologist and the grandson of physiologist Rudolf Wagner. He made several contributions in the field of seismology and in his research of atmospheric electricity. In a mine-shaft at Pribram (Czechia) he was able to distinguish long-distance earthquakes from local seismic activity with the use of . He was also the first scientist to solve the problem regarding refraction of seismic rays in spherical layers. The term “Benndorf’s relationship” (“Benndorf’scher Satz”) is used to describe the constancy of the ray parameter “p” across the spherical layers. A device known as a "Benndorf electrometer" is used for atmospheric electrical measurements.

See also: https://en.wikipedia.org/wiki/Hans_Benndorf

Lenhardt – Biographies 77 Earthquake Catalogue and Intensity Scale

August Heinrich Sieberg

(December 23, 1875 in Aachen/Germany – November 18, 1945 in Jena/Germany) was a geophysicist. He researched mainly in the field of seismology and developed a seismic intensity scales as well as a tsunami intensity scale. As a seismologist he was concerned with the compilation of earthquake catalogues and the geographical distribution of earthquakes. Further fields of research were tectonics and the analysis of macroseismic data. Sieberg was aware that the nature of the building ground and the construction method have a strong influence on the damage caused by an earthquake, and he was showed keen interest in social impacts of earthquakes. In 1912 Sieberg introduced the twelve-degree Mercalli-Cancani-Sieberg intensity scale as an improvement of the previous Mercalli-Cancani scale. The scale is constructed in such a way that each scale division corresponds approximately to twice the horizontal basic acceleration of the previous one. In 1927 he developed the Sieberg-Scale, a six-degree scale for assessing the strength of tsunamis on the basis of their effects on humans, buildings and nature, which was adapted in 1962 by Nicholas Ambraseys in the form of the Sieberg-Ambraseys Tsunami Intensity Scale to the usual twelve-degree earthquake scales. In 1939 Sieberg published the first earthquake catalogue of Germany and neighbouring areas.*

* The first earthquake compendium – covering a period from 34 A.D. and 1687 – was prepared by D. Vincenzo Magnati in 1688.

See also: https://en.wikipedia.org/wiki/August_Heinrich_Sieberg Lenhardt – Biographies 78 Upper- and Lower Crust

Victor Conrad

(August 25, 1876 in Vienna/Austro-Hungarian Empire – April 25, 1962 in Cambridge, Mass./U.S.A.) was an Austrian-American physicist, seismologist and meteorologist. In 1896, when he started working on his degree, Sigmund Exner, realized his pupil's talent for experimental work, and encouraged Conrad to take up the study of physics. Conrad became a University assistant at the "K.K. Centralanstalt für Meteorologie und Erdmagnetismus" (the “Zentralanstalt für Meteorologie und Geodynamik” today) in Vienna/Austria 1901, working at the Sonnblick high-altitude observatory for the next three years. In 1904, when the Seismological Service of Austria was established, Conrad was appointed head of the new department responsible for monitoring the seismicity in the Austro-Hungarian Empire. Among his first programs was a microseismic* survey in 1905 and the installation of a seismic station in Vienna. Earthquakes in the Tauern massif (1923) and near Schwadorf (1927) led him to interpret specific seismic onsets to be refractions from a horizontal discontinuity separating the Earth’s crust, later to be coined Conrad discontinuity. Harold Jeffreys, at the same time, observed similar signals from Jersey-earthquakes, thus confirming Conrad’s observations. Conrad was politically victimized twice, in 1919 for his ethnicity and in 1934 as a socialist. He emigrated to the United States in 1938, continuing his academic career in New York, California and at Cambridge. Conrad's scientific work is documented in more than 240 papers concerning meteorology, climatology and seismology.

*Note, that the meaning of “microseismics” has undergone a change. Then, “microseismicity” was understood as to study seismic recordings of earthquakes which otherwise went unnoticed. “Macroseismic” studies deal with observed effects. Today, the term “microseismics” is used to describe meteorological effects in seismograms.

See also: https://en.wikipedia.org/wiki/Victor_Conrad

Lenhardt – Biographies 79 Borehole Geophysics

Conrad & Marcel Schlumberger

François “Conrad” (October 2, 1878 in Guebwiller/France – May 9, 1936 in Stockholm/Sweden) was a French geophysicist, and Marcel Henri Émile "Marcel" (June 21, 1884, Guebwiller/France – August 19, 1953, Val-Richer/France), bottom picture) worked initially as an engineer for the French Railways (SNCF). In 1919, with financial support of their father, they both developed a scientific method and a mobile equipment for a ”wireline logging method“ to conduct borehole measurements. This measuring principle is referred to as “Schlumberger method” for determining electrical resistivity in boreholes. It must not be mixed up with the “Method de Champenoise” of the “Schlumberger Sekt”, which was introduced by Robert Alwin Schlumberger, Edler von Goldeck (September 12, 1814 – July 13, 1879) in Austria. Both family trees can be traced back to Ulm in Germany in the 16th century, however. Afterwards, Conrad and Marcel established an office near Crèvecœur-en-Auge, where the company "Schlumberger" still resides. Together, with his brother Marcel, he conducted borehole measurements worldwide. In 1931, they founded CGG (Compagnie générale de géophysique) und 1934 der ”Schlumberger Well Corporation“ in Houston, U.S.A.

One of his siblings, Paul Conrad Nicolas "Jean" Schlumberger, founded the Nouvelle Revue française. “Jean” (not shown here) was laid to rest in San Michele in Venice.

See also: https://de.wikipedia.org/wiki/Conrad_Schlumberger

Lenhardt – Biographies 80 Long-Term Climate Change

Milutin Milanković

(May 28, 1879 in Dalj/Austro- Hungarian Empire – December 12, 1958 in Belgrade/Yugoslavia) was a Serbian mathematician, astronomer, climatologist, geophysicist, civil engineer, doctor of technology, university professor and popularizer of science. Milanković gave two fundamental contributions to global science. The first contribution is the Canon of the Earth’s Insolation, which characterizes the climates of all the of the Solar system. The second contribution is the explanation of Earth's long-term climate changes caused by changes in the position of the Earth in comparison to the Sun, now known as “Milankovitch cycles”.

See also: https://en.wikipedia.org/wiki/Milutin_Milankovi%C4%87

Lenhardt – Biographies 81 1906 San Francisco

Photograph by Grove Karl Gilbert Lenhardt – Biographies 82 1906 San Francisco

The 1906 San Francisco earthquake struck the coast of at 5:12 a.m. on Wednesday, April 18 with an estimated moment magnitude of 7.9 and a maximum Mercalli intensity of XI (Extreme). High-intensity shaking was felt from Eureka on the North Coast to the Salinas Valley, an agricultural region to the south of the San Francisco Bay Area. Devastating fires (”Ham and Eggs Fire”) soon broke out in the city and lasted for several days. More than 3,000 people died. Over 80 percent of the city of San Francisco was destroyed. The events are remembered as one of the worst and deadliest earthquakes in the history of the United States. The death toll remains the greatest loss of life from a natural disaster in California's history and high on the lists of American disasters. Between 227,000 and 300,000 people were left homeless out of a population of about 410,000; half of those who evacuated fled across the bay to Oakland and Berkeley. Newspapers described Golden Gate Park, the Presidio, the Panhandle and the beaches between Ingleside and North Beach as covered with makeshift tents. More than two years later, many of these refugee camps were still in operation. The 1908 “Lawson Report”, a study of the 1906 quake led and edited by Professor Andrew Lawson of the University of California, showed that the same San Andreas Fault which had caused the disaster in San Francisco ran close to Los Angeles as well. The earthquake was the first natural disaster of its magnitude to be documented by photography and motion picture footage and occurred at a time when the science of seismology was blossoming. See also: https://en.wikipedia.org/wiki/1906_San_Francisco_earthquake Lenhardt – Biographies 83 1906 San Francisco

View to the north across the Dogtown trench site showing the alluviated valley of upper Pine Gulch Creek and the Strain Ranch with its offset fence. (U.S.G.S. Archives). The fence on the Strain Ranch that was offset a total of 3.4 m (8.5 ft) in the 1906 earthquake. The camera was aligned with the straight part of the fence beyond the fault zone. Location is 1 km northwest of Woodville (Dogtown), 25 km NW of the Golden Gate Bridge. Photos by G. K. Gilbert.

Hall, N.T. & T.M. Niemi, 2008. The 1906 Earthquake Fault Rupture and Paleoseismic Investigation of the Northern San Andreas Fault at the Dogtown Site, Marin County, California. Bull. Seism. Soc. Amer., Vol. 98, No. 5, pp. 2191–2208.

Lenhardt – Biographies 84 Head Waves Ludger Mintrop

(July 18, 1880 in Essen-Werden/Germany – January 1, 1956 in Essen/Germany) was a mine surveyor and geophysicist and disciple of Emil Wiechert. Mintrop is considered the inventor of the seismic method for exploration of hydrocarbons and minerals (Patent 1916) through the seismic refraction method. Among the many accolades and awards in recognition of his seminal work in seismic prospecting Mintrop was awarded SEG honorary Membership. In 1911 he obtained his doctorate under Wiechert with a study: On the propagation of ground oscillations produced by the pressure of the mass of a large gas machine. The seismogram of an artificial earthquake produced by dropping a four-ton steel ball – a donation by the Krupp Company – from a height of 14 m is also to be found in his thesis. The First World War saw Mintrop in the prime of life. First he served as a physicist with the Airship Division and later with the Artillery Control Commission. He long tried in vain to convince the general staff that he was in a position with his portable seismographs to determine quickly and accurately the position of enemy gunfire. Only after the bloody Somme massacre was Mintrop able to convince Ludendorff’s general staff of the possibilities of locating artillery positions with seismic means. As a consequence, a demonstration of his method was made toward the end of 1916 at the Wahn artillery firing range. Mintrop located the “enemy battery” with such precision that General Ludendorff approved 100 locating crews and wanted them at the front in 1917. Mintrop founded SEISMOS on April 4, 1921, and went on to work for oil companies (e.g. TEXACO) outlining potential oil traps near salt domes. He retired from SEISMOS in 1933 and carried on to lecture at the University of Breslau. He retired in 1948. The “head wave“ in refraction seismics is also referred to as “Mintrop wave“.

See also: https://wiki.seg.org/wiki/Ludger_Mintrop Lenhardt – Biographies 85 Plate Drift

Alfred Wegener

(November 1, 1880 in Berlin/Germany – November ?, 1930 in Greenland)

1905 Doctorate in Astronomy 1906 1st Greenland expedition 1909 Habilitation in Marburg

1911- Summary of ideas about 1914 continental drift

1915 First publication of Die Entstehung der Kontinente und Ozeane During his lifetime Wegener 1919 Head of the Department of was primarily known for his Theoretical Meteorology achievements in meteorology of the Deutsche Seewarte und and as pioneer of polar a.o. Prof. in Hamburg research, but today he is most 1921 Die Entstehung der Mondkrater remembered as the originator (impact) of the theory of continental 1924 Professorship in Graz for drift by hypothesizing in 1912 Meteorology and Geophysics that the continents are slowly 1930 4th and last expedition to drifting across the Earth. Greenland See also: https://en.wikipedia.org/wiki/Alfred_Wegener

Lenhardt – Biographies 86 Converted Waves

Karl Bernhard Zöppritz

(October 22, 1881 in Mergelstetten near Heidenheim an der Brenz/Germany – July 20, 1908 in Göttingen/Germany) was a geophysicist who made important contributions to seismology, in particular the formulation of the Zöppritz equations. These equations relate the amplitudes of P-waves and S-waves at each side of an interface, between two arbitrary elastic media, as a function of the angle of incidence and are largely used in reflection seismology for determining structure and properties of the subsurface and are widely used by the oil-industry. Using Wiechert's theoretical work and data from earthquakes including the 1905 Kangra earthquake, 1905 Calabria earthquake and the 1906 San Francisco earthquake. Zöppritz's most important early contribution was the construction of travel time curves - and their associated velocity-depth functions – for P-waves, S- waves and surface waves, recognizing for the first time that body waves are reflected and converted at discontinuities. These curves were later used by other members of the research group, Ludwig Carl Geiger and Beno Gutenberg, as well as the British astronomer and seismologist Herbert Hall Turner at the International Seismological Summary. The related ill-posed inverse problem of inferring a discrete velocity distribution, representing the layers of the crust and mantle, was solved by fellow Göttingen mathematician Gustav Herglotz.

See also: https://en.wikipedia.org/wiki/Karl_Bernhard_Zoeppritz

Lenhardt – Biographies 87 Vertical Velocity Distribution

Gustav Herglotz

(February 2, 1881 in Wallern in Bohemia/Austro-Hungarian Empire – March 22, 1953 in Göttingen/Germany) was a German/Bohemian physicist. He is best known for his works on the theory of relativity and seismology. In 1904, Herglotz defined relations for the electrodynamic potential which are also valid in special relativity even before that theory was fully developed. Hermann Minkowski (during a conversation reported by Arnold Sommerfeld) pointed out that the four-dimensional symmetry of electrodynamics is latently contained and mathematically applied in Herglotz' paper. In 1907, he became interested in the theory of earthquakes, and together with Emil Wiechert, he developed the “Wiechert–Herglotz method” for the determination of the velocity distribution of the Earth's interior from the known propagation times of seismic waves (an inverse problem). There, Herglotz solved a special integral equation of the Abelian type. The “Herglotz-Noether” theorem stated by Herglotz in 1909 (and independently by Fritz Noether the same year), was used by Herglotz to classify all possible forms of rotational motions satisfying the “Born rigidity”. In 1911, he formulated the “Herglotz representation theorem” regarding holomorphic functions “f” on the unit disk “D”, with Re f ≥ 0 and f(0) = 1, represented as an integral over the boundary of “D” with respect to a probability measure μ, and formulated a relativistic theory of elasticity.

See also: https://en.wikipedia.org/wiki/Gustav_Herglotz

Lenhardt – Biographies 88 Earthquake Location

Ludwig Carl Geiger

(September 16, 1882 in Basel/Switzerland – November 26, 1966 in Basel/Switzerland) was a seismologist. He developed a method for locating the hypocentre of earthquakes. On January 1, 1913, Geiger was hired by the “Göttingen Academy of Sciences and Humanities” to work as an observational astronomer for geophysics and meteorology at the Göttingen Samoa Observatory for one year, where he stayed longer because of the incipient World War I. Back then, the Samoan Islands in the South Pacific were a German colony referred to as a protectorate. Geiger worked on both theoretical and applied problems. In Göttingen, he was part of Emil Wiechert’s innovative working group. Between 1907 and 1910, Geiger was in charge of the annual seismological bulletin of the Göttingen station, where he also supervised the operation of the station and the evaluation of the seismic recordings. During his work at the observatory, he developed a keen sense of observing and interpreting seismic phases. Together with Karl Zöppritz, he improved the then-known travel time curves and used seismological observations to decipher the global structure of the terrestrial body. After Zöppritz’s early death, Geiger continued some of these investigations using evaluations started by Zöppritz. Together with Emil Wiechert, Geiger used what is known today as the “Wiechert-Herglotz Inversion” to determine the velocity structure in the Earth’s interior for the first time, and for his iterative procedure to locate earthquakes. Gustav Herglotz had solved the related mathematical problem and Wiechert subsequently found a more practicable formula. Wiechert’s derivation and the first application to the then-known travel time curves were then published in 1910.

See also: https://www.erdbebenwarte.de/en/ludwig-carl-geiger-1882-1966/

Lenhardt – Biographies 89 Tomography

Johann Radon

(December 16, 1887 in Děčín in Bohemia/Austro-Hungarian Empire – May 25, 1956 in Vienna/Austria) was an Austrian mathematician. His doctoral dissertation in 1910 at the was on the calculus of variations. In mathematics, the Radon transform is the integral transform which takes a function “f” defined on the plane to a function “Rf” defined on the (two- dimensional) space of lines in the plane, whose value at a particular line is equal to the line integral of the function over that line. The transform was introduced in 1917 by Johann Radon, who also provided a formula for the inverse transform. Radon further included formulas for the transform in three dimensions, in which the integral is taken over planes (integrating over lines is known as the X-ray transform). It was later generalized to higher- dimensional Euclidean spaces, and more broadly in the context of integral geometry. The complex analogue of the Radon transform is known as the Penrose transform. The Radon transform is widely applicable to tomography, the creation of an image from the projection data associated with cross- sectional scans of an object.

Based on Radon’s transform, Allan MacLeod Cormack (1924 – 1998) and Godfrey Newbold Hounsfield (1919 – 2004) received the Noble Prize for Physiology and Medicine for their work X-ray computed tomography (CT) in 1979 .

See also: https://en.wikipedia.org/wiki/Johann_Radon https://en.wikipedia.org/wiki/Radon_transform Lenhardt – Biographies 90 Ocean Trenches – Gravity Sinks

Felix Andries Vening Meinesz

(July 30, 1887 in /The Netherlands – August 10, 1966 in Amersfoort/The Netherlands) was a geophysicist and geodesist. He is known for his invention of a precise method for measuring gravity. Thanks to his invention, it became possible to measure gravity at sea, which led him to the discovery of gravity anomalies above the ocean floor. He later attributed these anomalies to continental drift. The vast amounts of data that his expeditions yielded were analysed and discussed together with other leading Dutch Earth scientists of the time J. H. F. Umbgrove, B. G. Escher and Ph. H. Kuenen, the results were published in 1948. An important result was the discovery of elongated belts of negative gravity anomalies along the oceanic trenches. The mean gravity force appeared to be the same on land and at sea, which was in agreement with the principle of isostasy. Vening Meinesz was especially intrigued by the oceanic trenches. The coexistence of active volcanism, large negative gravity anomalies and the sudden difference in terrain elevation could only be explained by assuming the Earth's crust was somehow pushed together at these places. As a geophysicist, he was prejudiced that the crust was too rigid to deform at that scale in such a way. His discoveries could be explained only with the development of the theory of plate tectonics in the 1950s.

See also: https://en.wikipedia.org/wiki/Felix_Andries_Vening_Meinesz Lenhardt – Biographies 91 Magnetosphere and Magnetic Storms

Sidney Chapman

(January 29, 1888 in Eccles/U.K. – June 16, 1970 in Boulder/U.S.A.) was a British mathematician and geophysicist. His work on the kinetic theory of gases, solar- terrestrial physics, and the Earth's ozone layer has inspired a broad range of research over many decades. He began his research in pure mathematics under G. H. Hardy, but later that year was asked by Sir Frank Dyson to be his chief assistant at the Royal Greenwich Observatory. Chapman is recognized as one of the pioneers of solar-terrestrial physics. This interest stemmed from his early work on the kinetic theory of gases. Chapman studied magnetic storms and aurorae, developing theories to explain their relation to the interaction of the Earth's magnetic field with the solar wind. He disputed and ridiculed the work of Kristian Birkeland and Hannes Alfvén, later adopting Birkeland's theories as his own. Chapman and his first graduate student, V. C. A. Ferraro, predicted the presence of the magnetosphere in the early 1930s. They also predicted characteristics of the magnetosphere that were confirmed 30 years later by the Explorer 12 satellite. In 1940, Chapman and a German colleague Julius Bartels published a book in two volumes on geomagnetism, which was to become the standard text book for the next two decades. In 1946 Chapman coined the term: Aeronomy, which is used today to describe the scientific field of high-altitude research into atmosphere/space interaction. Chapman was President of the Special Committee for the International Geophysical Year (IGY). The idea of the IGY stemmed from a discussion in 1950 between Chapman and scientists including James Van Allen.

See also: https://en.wikipedia.org/wiki/Sydney_Chapman_(mathematician)

Lenhardt – Biographies 92 Solid Inner Core

Inge Lehmann

(May 3, 1888 in Østerbro/Denmark – February 21, 1993 in Copenhagen/Denmark) was a Danish seismologist and geophysicist. In 1936, she discovered that the Earth has a solid inner core inside a molten outer core. Before that, seismologists believed Earth's core to be a single molten sphere, being unable, however, to explain careful measurements of seismic waves from earthquakes, which were inconsistent with this idea. Lehmann analysed the seismic wave measurements and concluded that Earth must have a solid inner core and a molten outer core to produce seismic waves that matched the measurements. Other seismologists tested and then accepted Lehmann's explanation. In 1925 Lehmann's seismology career began as she became an assistant to the geodesist Niels Erik Nørlund. She began the task of setting up seismological observatories in Denmark and Greenland. In the meantime, she studied seismology on her own. She went abroad for three months to study seismology with leading experts in the field such as Beno Gutenberg, who had determined the distance to the core-mantle boundary within 15 km of the present value. In a paper titled P' in 1936, Lehmann was the first to interpret P wave arrivals — which inexplicably appeared in the P wave shadow of the Earth's core — as reflections from an inner core, for example from the strong 1929 Murchison earthquake in New Zealand. Other leading seismologists of the time, such as Beno Gutenberg, Charles Richter, and Harold Jeffreys, adopted this interpretation within two or three years, but it took until 1971 for the interpretation to be shown correct by computer calculations.

Strange: A new beetle species was named after her: Globicornis (Hadrotoma) ingelehmannae.

See also: https://en.m.wikipedia.org/wiki/Inge_Lehmann

Lenhardt – Biographies 93 Seismic Energy

Beno Gutenberg

(June 4, 1889 in Darmstadt/Germany – January 25, 1960 in Pasadena/ California/U.S.A.) was a German seismologist who developed the seismic energy scale (together with Charles Francis Richter) and detected the core-mantle boundary. He obtained his doctorate in physics from the University of Göttingen in 1911. His advisor was Emil Wiechert. During World War I, Gutenberg served in the German army as a meteorologist in support of gas warfare operations. Since Gutenberg could not sustain a career of scientific work in Germany (attributed to his Jewish background), he accepted a position as Professor of Geophysics at the California Institute of Technology in Pasadena in 1930, becoming founding director of the Seismological Laboratory when it was transferred to Caltech from Carnegie. Gutenberg, especially in his collaboration with Charles Francis Richter, made the California Institute of Technology Seismological Laboratory the leading seismological institute worldwide. Collaborating with Richter, Gutenberg developed a relationship between seismic magnitude M and seismic energy Es, represented in this equation:

log Es [in Joule] = 4.8 + 1.5 M

He also worked on determining the depth of the core-mantle boundary (CMB) as well as other properties of the of the Earth’s interior.

See also: https://en.wikipedia.org/wiki/Beno_Gutenberg

Lenhardt – Biographies 94 Probability

Harold Jeffreys

(April 22, 1891 in Fatfield/County Durham/U.K. – March 18, 1989 in Cambridge/U.K.) was an English mathematician, statistician, geophysicist, and astronomer. His book, “Theory of Probability”, which was first published in 1939, played an important role in the revival of the objective Bayesian view of probability. By 1924 Jeffreys had developed a general method of approximating solutions to linear, second-order differential equations, including the Schrödinger equation. Although the Schrödinger equation was developed two years later, Wentzel, Kramers and Brillouin (“WKB”) were apparently unaware of this earlier work, so Jeffreys is often neglected when credit is given for the WKB approximation. From 1939 to 1952 he was established as Director of the International Seismological Summary further known as International Seismological Centre (ISC). He corresponded with when he also suspected a horizontal discontinuity in the Earth‘s crust, which later became known as “Conrad discontinuity“. Like most of his contemporaries, Jeffreys was a strong opponent of continental drift as proposed by Alfred Wegener, Arthur Holmes, and even into the 1960s his Cambridge contemporaries. For him, continental drift was “out of the question” because no force even remotely strong enough to move the continents across the Earth's surface was evident. As geological and geophysical evidence for continental drift and plate tectonics mounted in the 1960s and after, to the point where it became the unifying concept of modern geology, Jeffreys remained a stubborn opponent of the theory to his death.

See also: https://en.m.wikipedia.org/wiki/Harold_Jeffreys

Lenhardt – Biographies 95 Ionosphere

Edward Victor Appleton

(September 6, 1892 in Bradford/U.K. – April 21, 1965 in Edinburgh/U.K.) was an English physicist, Nobel Prize winner (1947) for his seminal work proving the existence of the ionosphere during experiments carried out in 1924, and pioneer in radiophysics. Appleton had observed that the strength of the radio signal from a transmitter on a frequency such as the medium wave band and over a path of a hundred miles or so was constant during the day but that it varied during the night. This led him to believe that it was possible that two radio signals were being received. One was travelling along the ground, and another was reflected by a layer in the upper atmosphere. The fading or variation in strength of the overall radio signal received resulted from the interference pattern of the two signals. The existence of a reflecting atmospheric layer was not in itself a completely new idea. Balfour Stewart had suggested the idea in the late 19th century to explain rhythmic changes in the earth’s magnetic field. Using this theory and further experiments, he showed that the so-called Kennelly-Heaviside layer was heavily ionised and thus conducting. This led to the term “ionosphere” which had a much more complex structure than first anticipated. The lower level was labelled “E–Layer”, reflected longer wavelengths and was found to be at an altitude of approximately 125 km. The high level, which had much higher electron density, was labelled “F–Layer” and could reflect much shorter wavelengths that penetrated the lower layer. It is situated 300 – 400 km above the Earth’s surface. It is this which is often referred to as the Appleton Layer as is responsible for enabling most long range short wave telecommunication.

See also: https://en.wikipedia.org/wiki/Edward_Victor_Appleton

Lenhardt – Biographies 96 Interface Waves

Robert Stoneley

(May 14, 1894 London/U.K. – February 2, 1976 in Cambridge/U.K.) was a British seismologist, who worked in the U.K. and the U.S.A. A Stoneley wave is a type of boundary wave (or interface wave) that propagates along a solid- fluid boundary or, under specific conditions, also along a solid-solid boundary. Amplitudes of Stoneley waves have their maximum values at the boundary between the two contacting media and decay exponentially towards the depth of each of them. These waves can be generated along the walls of a fluid-filled borehole, being an important source of coherent noise in VSPs and making up the low frequency component of the source in sonic logging. Stoneley waves are most commonly encountered during borehole sonic logging and vertical seismic profiling. They propagate along the walls of a fluid-filled borehole. They make up a large part of the low-frequency component of the signal from the seismic source and their attenuation is sensitive to fractures and formation permeability. Hence, Stoneley waves can be used to estimate these rock properties.

See also: https://royalsocietypublishing.org/doi/pdf/10.1098/rsbm.1976.0020

Lenhardt – Biographies 97 First Motions

Perry Byerly

(May 28, 1897 in Clarinda/U.S.A. – September 26, 1978 in Oakland/U.S.A.) developed the method of determining fault parameters from the polarities of first motions on the seismogram. He authored an early textbook: Seismology (Prentice-Hall, New York, 1942), and he was the first to point out the significance of what came to be called the “20-degree discontinuity”. He used both earthquakes and blasts to study crustal structures. He was the first to demonstrate by seismic studies that there is a root under the Sierra Nevada Mountains. He was also the first to demonstrate that water-well pressure can be used to record earthquakes, and he studied the energy of earthquakes, dispersion of seismic waves, discontinuities in the Earth, earthquake swarms, and the T-phase of Hawaiian earthquakes as well as studies of many individual earthquakes and quarry blasts. He was an instructor of physics at the University of Nevada from 1924 to 1925, then became the first director of Berkeley’s Seismograph Station, which he expanded into a sixteen-station network including the first use of telemetering of data to the central station of the network in the early 1960s.

See also: International Handbook of Earthquake and Engineering Seismology (Part B), 2003, and http://www.nasonline.org/publications/biographical-memoirs/memoir-pdfs/byerly-perry.pdf Lenhardt – Biographies 98 Crustal Strain

Hugo Benioff

(September 14, 1899 in Los Angeles/U.S.A. – February 29, 1968 in Mendocino/U.S.A.) was an American seismologist and a professor at the California Institute of Technology. He is best remembered for his work in charting the location of deep earthquakes in the Pacific Ocean. Benioff is considered a genius in the design of earthquake instruments. One of his first instruments, created in 1932, was the Benioff seismograph, which senses the movement of the Earth – these instruments were used almost worldwide. Equally famous is the Benioff strain instrument, which records the stretching of the Earth's surface. One of his latest accomplishments was a refined version of the old Benioff seismometer which has given seismologists more knowledge about the cause of very deep earthquakes. Benioff noticed that earthquake hypocentres get deeper under the overriding tectonic plate proceeding away from the trench at a subduction zone. He realized that this spatially inclined cluster of earthquake sources indicate the position of the portion of the plate that has already been subducted. Therefore this pattern of earthquakes is known as a Wadati-Benioff zone. From the early 1930s, Benioff also worked on creating electric musical instruments; in particular a piano, violin and cello.

See also: https://en.wikipedia.org/wiki/Hugo_Benioff

Lenhardt – Biographies 99 Magnitude

Charles Francis Richter

(April 26, 1900 in Overpeck in Ohio/U.S.A – September 30, 1985 in Pasadena in California/U.S.A.) was an American seismologist and physicist. Richter is most famous as the creator of the Richter magnitude scale, which, until the development of the moment magnitude scale in 1979, quantified the size of earthquakes. The Seismology Lab at the California Institute of Technology wanted to begin publishing regular reports on earthquakes in southern California and had a pressing need for a system of measuring the strength of earthquakes for these reports. Together, Richter and Gutenberg devised the scale that would become known at the Richter scale to fill this need, based on measuring quantitatively the displacement of the earth by seismic waves, as Kiyoo Wadati had suggested in 1928. The pair designed a seismograph that measured this displacement and developed a logarithmic scale to measure intensity. By the way, the name “magnitude” for this measurement came from Richter's childhood interest in astronomy – as astronomers measure the brightness of stars in “magnitudes”. Gutenberg's contribution was substantial, but his aversion to interviews contributed to his name being left off the scale. After the publication of the proposed scale in 1935, seismologists quickly adopted it for use in measuring the energy of earthquakes. The quote “logarithmic plots are a device of the devil” is attributed to Richter. Richter is also known for having responded to the common question by journalists when finally earthquakes can be predicted: “All major earthquakes occur within three months of an equinox!“. The journalists went off satisfied, and stating, Richter can predict earthquakes…

See also: https://en.wikipedia.org/wiki/Charles_Francis_Richter Lenhardt – Biographies 100 More on Magnitude

Beno Gutenberg and Charles Francis Richter

The first magnitude scale was introduced by them in the early 1930s. Richter, together with Beno Gutenberg analysed the amplitudes of ground displacements which were recorded with a Wood-Anderson torsion seismometer (free period 0.8”, high frequency magnification 2,800, which was later corrected to ~ 2,080). He calculated the “size” or “strength” of a seismic event by relating it to a “master event” at a distance of 100 km which appeared on a Wood-Anderson seismograph with an amplitude of 1 mm. Such an event was addressed as an earthquake having a magnitude of “0” (zero). Beno Gutenberg Owing to the high sensitivity of modern seismometers, negative magnitudes are (1889 – 1960) frequently reported. The seismic energy is still positive, but much smaller than that of a magnitude 0 event (which equals a seismic energy of 63,000 Joules). Local magnitudes or seismic magnitudes in general are sometimes referred to as ‘Richter’-magnitudes, which is not correct. The magnitude is a logarithmic measure of the seismic energy released during an earthquake – however with a slope of 1.5 between seismic energy and magnitude. That leads to 1000-fold increase in released seismic energies between a e.g. magnitude 5 and 7 event – thus the dramatic difference in effects. Both seismologists are also known for their Gutenberg-Richter Law (GRL), which relates the number of seismic events to their magnitude.

Charles Francis Richter (1900 – 1985) See Gutenberg’s and Richter’s biographies for more details.

Lenhardt – Biographies 101 Deep Earthquakes Kiyoo Wadati

(和達 清夫, Wadachi Kiyoo, September 8, 1902 in Nagoya/Japan – January 5, 1995 in Tokyo/Japan) was an early seismologist at the Central Meteorological Observatory of Japan (now known as the Japan Meteorological Agency), researching deep (subduction zone) earthquakes. His name is attached to the Wadati-Benioff zone. It was Wadati's 1928 paper on shallow and deep earthquakes, comparing maximum below surface displacement against distance from the epicentre, which led Charles Richter to develop his earthquake magnitude scale in 1935. Kiyoo Wadati hypothesized that earthquakes in Japan were a result of plate motion. His early research compared time curve data for the arrival of P and S waves of two earthquakes with close epicenters. The calculations demonstrated that one earthquake occurred at a depth of 30 km, while the other occurred at a depth of greater than 300 km. Wadati compiled evidence of more than a dozen earthquakes between 1924 and 1927 in the Honshu region that occurred at the same depth range. Wadati plotted data that demonstrated an inclined intermediate and deep earthquake zone near the oceanic trench dipping toward the Asiatic continent northwestward and the Philippine Sea westward. The intermediate and deep earthquake zone was named the Wadati-Bennioff zone after Hugo Benioff demonstrated that the zone existed in each area in the circumpacific region. His observations, that deep earthquakes occurred, provided integral support for the theory of plate tectonics. Wadati is also well known for “Wadati diagram” in which absolute P-wave arrival times are plotted against the time difference of S- and P-wave arrivals. The slope of this graph can also be used to determine the dynamic Poisson’s ratio. Outliers from the slope indicate wrong phase readings, thus the graph assists in the quality control of phase readings.

See also: https://en.wikipedia.org/wiki/Kiyoo_Wadati Lenhardt – Biographies 102 Magnetic Memory

Émile Thellier

(February 11, 1904 at Mont-en-Ternois/France – May 11, 1987 in Paris/France) was a French physicist. Throughout his long scientific career, Thellier devoted his life to the study of rock magnetism and its applications in geophysics, geology and archaeology. In the early phase of his career he developed very sensitive and accurate instruments that allowed measurements to be made undisturbed by the presence of the earth’s magnetic field. Using magnetometers of his invention in a systematic study of the magnetisation of rocks, he discovered the laws of "magnetic memory", which were later confirmed theoretically by Louis Néel and are now known as the Thellier-Néel laws: they state that the baked clay retains a memory of the temperature, and of the direction and intensity of the field that was responsible for its thermo-remanent magnetization. His work led to the field of archeomagnetism. In close collaboration with his wife Odette (therefore the Thellier- Thellier paper on palaeointensity in 1959) the first method to study the earth's magnetic field in the recent past and used it on a large number of archeological sites in Europe and North Africa was developed. Their method is still used today worldwide. Together they recorded solar flares and noticed that abrupt solar storms do not follow a 27-day periodicity – opposed to solar storms with gradual onset.

See also: M. LeGoff, L. Daly, D. J. Dunlop, C. Papusoi 2006. Émile Thellier (1904-1987), a pioneer in studies of the “fossil” Earth’s magnetic field. Historical events and people in aeronomy, geomagnetism and solar-terrestrial physics, ISSN :1615-2824, W. Schröder editor. 2006, pp 98-112, and https://de.wikipedia.org/wiki/%C3%89mile_Thellier

Lenhardt – Biographies 103 Magnetic Properties

Louis Eugène Félix Néel

(November 22, 1904 in Lyon/France – November 17, 2000 in Brive-la- Gaillarde/France) was a French physicist. He was co-recipient (with the Swedish astrophysicist Hannes Alfvén) of the Nobel Prize for Physics in 1970 for his pioneering studies of the magnetic properties of solids. His contributions to solid state physics have found numerous useful applications, particularly in the development of improved computer memory units. About 1930 he suggested that a new form of magnetic behaviour might exist; called antiferromagnetism, as opposed to ferromagnetism. Above a certain temperature (the Néel temperature) this behaviour stops. Néel pointed out (1948) that materials could also exist showing ferrimagnetism. Néel has also given an explanation of the weak magnetism of certain rocks, making possible the study of the development of the Earth's magnetic field in “deep time”. Louis Néel tackled and solved a number of other problems and extended our knowledge of many aspects of magnetism. The most important of these are as follows: 1. theory of Rayleigh’s Laws, 2. magnetic properties of fine grains, 3. magnetic viscosity, 4. internal dispersion fields, 5. superantiferromagnetism, and 6. hysteresis.

See also: https://en.wikipedia.org/wiki/Louis_N%C3%A9el Lenhardt – Biographies 104 Ocean Ridges

Harry Hammond Hess

Born in New York/U.S.A. on May 24, 1906.

1932 Professor for Geology in Princeton WWII Sonic log surveys in the Atlantic 1962 Publication of History of Ocean Basins 1962 Chairman of the Space Science Board of N.A.S.A

Died on August 25, 1969 in Woods Hole/U.S.A.

Remark: First bathymetric profiles of the Northern Atlantic were already published by Maury in 1855. Echolot of a Guyot (atoll) See also: https://en.wikipedia.org/wiki/Harry_Hammond_Hess Lenhardt – Biographies 105 Subduction Zones

Zones, where oceanic plates subduct continental plates, are also referred to as “Wadati-Benioff“ zones.

Gravity Anomaly

Beno Kiyoo Wadati Gutenberg (1902 – 1995) (1889 – 1960)

?

Wadati, 1928 Charles Francis Gutenberg and Richter, 1941 Richter Hugo Benioff (1900 – 1985) (1899 – 1968)

Lenhardt – Biographies 106 Travel Time Tables

Keith Edward Bullen

(June 19, 1906 in Auckland/New Zealand – September 23, 1976 in Auckland/New Zealand) was a mathematician and geophysicist. He is noted for his seismological interpretation of the deep structure of the Earth's mantle and core. He was Professor of Applied Mathematics at the University of Sydney in from 1945 until 1971. Bullen's first paper with Jeffreys was a Nature letter on the subject of the Corrections to the travel times of P (compressional) waves from earthquakes. It was followed by two papers dealing with the method of hypocentral distance calculation. The Earth is an oblate spheroid, the polar and equatorial radii being 6356 and 6378 km respectively. In calculating the distance travelled by earthquake waves from a source to the observing station it is necessary to allow for the ellipticity of the Earth. It can be shown that the distance is more accurately determined if the positions of the source and the station are expressed in terms of geocentric latitude (the angle subtended at the centre of the Earth) rather than geographic latitude. This also facilitates model calculations which are carried out for the sphere of volume equal to that of the spheroid. This sphere has a radius of 6371.2 km. Travel time tables too are calculated for this sphere. The travel times on the spheroid differ from those on the sphere because of two other effects. The first is caused by the difference in the lengths of the ray path for the sphere and spheroid, and the second effect is caused by the ellipticity of the surfaces of equal velocity within the spheroid. The use of geocentric instead of geographic results in differences in P travel- times of the order of a few seconds and the two ellipticity effects mentioned to about 1 second. In 1940, he and Harold Jeffreys published the Jeffreys-Bullen Travel Time Tables.

See also: https://en.wikipedia.org/wiki/Keith_Edward_Bullen Lenhardt – Biographies 107 Gravimeter Lucien Jean Baptiste LaCoste

(August 25, 1907 in San Antonio/U.S.A. – March 8, 1995 in Austin/U.S.A.) was a prominent physicist and metrologist. He was co-inventor of the modern gravimeter and co-founder of a prominent company selling gravimetric instruments. LaCoste discovered the zero-length spring in 1932 while performing an assignment in Arnold Romberg's undergraduate physics course. During this period, LaCoste and his physics teacher Arnold Romberg invented the first modern seismographs and gravimeters, using steel and quartz (respectively) zero-length springs. While a graduate student, LaCoste decided to go into business together with Romberg, selling advanced gravimeters to oil-exploration companies. A zero-length spring is a spring supported in such a way that its exerted force is proportional to its length, rather than the distance it is compressed. Hence, over at least part of its movement, it does not conform to Hooke's Law of spring compression. The zero-length spring is extremely important to seismometers and gravimeters because it permits the design of vertical pendulums with (theoretically) infinite periods. In practice, periods of a thousand seconds are possible, a hundredfold increase from other forms of pendulums. Over a short period, starting in 1932, the design of these instruments was revolutionized, obsoleting all previous designs. LaCoste's most famous invention is the ship-, and aircraft-mounted gravimeter. These revolutionized exploration for minerals by allowing wide-ranging geological surveys. Since the accelerations from the vehicle typically are hundreds to thousands of times more forceful than the measured changes, this invention was considered impossible until LaCoste demonstrated it.

See also: https://en.wikipedia.org/wiki/Lucien_LaCoste, https://web2.ph.utexas.edu/utphysicshistory/LucienLaCoste.html Lenhardt – Biographies 108 Marine Geophysics

Edward “Teddy” Crisp Bullard

(September 21, 1907 in Norwich/U.K. – April 3, 1980 in La Jolla/U.S.A.) was a British geophysicist who is considered, along with Maurice Ewing, to have founded the discipline of marine geophysics. He developed the theory of the geodynamo, pioneered the use of seismology to study the sea floor, measured geothermal heat flow through the ocean crust, and found new evidence for the theory of continental. During World War II he was an experimental officer at HMS Vernon, and worked on the development of degaussing techniques to protect shipping from magnetic mines. Bullard became one of the most important geophysicists of his day. He also did studies of the ocean floor, even though he suffered from seasickness and could rarely take scientific trips on the ocean. He was important to dynamo theory, hence his most important work concerned the source of the Earth's magnetic field. Then during the early 1960s Bullard and his associates used a computer to try to fit all of the continents together. Instead of using the shorelines, as other geophysicists had done, he used a depth of 914 meters below sea level. This depth corresponds to about halfway between the shoreline and the ocean basins and represents the true edge of the continents. By doing this he discovered a near perfect fit among the continents put together. With this discovery he helped further the idea of a supercontinent that an earlier geophysicist, Alfred Wegener, had suggested calling Pangea. It turned out a posteriori that a very similar result had been published thirty years earlier by the French geologist Boris Choubert, but this work published in French in a francophone journal of low international influence had remained virtually unknown.

See also: https://en.wikipedia.org/wiki/Edward_Bullard Lenhardt – Biographies 109 Magnetic Storms

Hannes Olof Gösta Alfvén

(May 30, 1908 in Norrköping/Sweden – April 2, 1995 in Djursholm/Sweden) was a Swedish electrical engineer, plasma physicist and winner of the 1970 Nobel Prize in Physics for his work on magnetohydrodynamics (MHD). He was originally trained as an electrical power engineer and later moved to research and teaching in the fields of plasma physics and electrical engineering. Alfvén made many contributions to plasma physics, including theories describing the behaviour of aurorae, the Van Allen radiation belts, the effect of magnetic storms on the Earth's magnetic field (1939), the terrestrial magnetosphere, and the dynamics of plasmas in the Milky Way galaxy. Alfvén waves (low frequency hydromagnetic plasma oscillations, MHD) are named in his honour, and propagate at the Alfvén speed*. Many of his theories about the solar system were verified as late as the 1980s through external measurements of cometary and planetary magnetospheres. Alfvén and colleagues proposed the Alfvén–Klein model as an alternative cosmological theory to both the Big Bang and steady state theory cosmologies.

* Which depends on the ion number density and the ion mass.

See also: https://en.wikipedia.org/wiki/Hannes_Alfv%C3%A9n and https://en.wikipedia.org/wiki/Alfv%C3%A9n_wave Lenhardt – Biographies 110 Transform Faults and Hot Spots

John Tuzo Wilson (October 24, 1908 in Ottawa/Canada – April 15, 1993 in Toronto/Canada) was a Canadian geophysicist and geologist who achieved worldwide acclaim for his contributions to the theory of plate tectonics. In 1963 he developed the “Hotspot”-theory, and in 1965 he proposed the “Transform Fault”-concept. The “Wilson Cycle” – describing the “life cycle” of ocean basins – is named after him.

Hotspots can be used to determine velocities and directions of plate movements.

See also: https://en.wikipedia.org/wiki/John_Tuzo_Wilson Lenhardt – Biographies 111 Ocean Rifting

Marie Tharp

(July 30, 1920 in Ypsilanti/U.S.A. – August 23, 2006 Nyack/U.S.A.) was an American geologist and oceanographic cartographer who, in partnership with Bruce Heezen (see photograph), created the first scientific map of the Atlantic Ocean floor. In 1952, Tharp painstakingly aligned sounding profiles from Atlantis, acquired during 1946 – 1952, and one profile from the Naval ship Stewart acquired during 1921. She created a total of approximately six profiles stretching west-to-east across the North Atlantic. From these profiles, she was able to examine the bathymetry of the northern sections of the Mid-Atlantic Ridge. Tharp identified an aligned, v-shaped structure running continuously through the axis of the ridge and believed that it may be a rift valley. She believed that the rift valley formed when new material welled up to the surface, pushing either side of the ridge apart. Heezen soon hired Howard Foster to plot the location of earthquake epicenters in the oceans for a project relating large-scale turbidity currents to undersea earthquakes. The creation of this earthquake epicenter map proved to be a useful secondary dataset for examining the bathymetry of the Mid-Atlantic Ridge. When Foster's map of earthquake epicenters was overlain with Tharp's profile of the Mid-Atlantic Ridge it became clear that the location of these earthquakes aligned with Tharp's rift valley. After putting together these two datasets, Tharp became convinced that a rift valley did in fact exist within the crest of the Mid-Atlantic Ridge. It was only after seeing that the location of earthquake epicenters aligned with Tharp's rift valley that Heezen (who advocated the “expanding Earth hypothesis”) accepted her hypothesis and turned to the alternative theories of plate tectonics and continental drift. Tharp and Heezen published their first physiographic map of the North Atlantic in 1957. See also: https://en.wikipedia.org/wiki/Marie_Tharp Lenhardt – Biographies 112 Palaeomagnetism

(Stanley) Keith Runcorn

(November 19, 1922 in Southport/U.K. – December 5, 1995 in San Diego/U.S.A.) was a British physicist whose palaeomagnetic reconstruction of the relative motions of Europe and America revived the theory of continental drift and was a major contribution to plate tectonics. Runcorn's PhD led to his interest in palaeomagnetism, the study of the magnetism of rocks, which he pursued first at the Geophysics Department at the University of Cambridge and later at Newcastle University, where he was appointed to the Chair of Physics in 1956. At Newcastle, Runcorn developed a strong research group in geophysics, and made substantial contributions to various fields, including convection in the Earth and Moon, the shape and magnetic fields of the Moon and planets, magnetohydrodynamics (MHD) of the Earth's core, changes in the length of the day (!), polar wandering, continental drift and plate tectonics. He authored numerous publications (which is a bit unfair to quote these in respect to all the others) such as:

1960/1966 Methods and Techniques in Geophysics 1968 Mantles of the Earth and Terrestrial Planets 1967 Methods in Palaeomagnetism, together with by D.W. Collinson and K.M. Creer 1970 Palaeogeophysics 1973 Implications of Continental Drift to the Earth Sciences, together with D.H. Tarling 1980 Mechanisms of Continental Drift and Plate Tectonics, together with P. A. Davies 1985 Magnetism, planetary rotation, and convection in the solar system, together with W. O'Reilly 1988 The Physics of the Planets: Their origin, evolution and structure

See also: https://en.wikipedia.org/wiki/Keith_Runcorn Lenhardt – Biographies 113 Current Hot Spots

https://theextinctionprotocol.wordpress.com/2011/10/11/magma-plume-5-1-magnitude-earthquake-strikes

Lenhardt – Biographies 114 The “Heart”

Plumes originate at the Core-Mantle Boundary (CMB) and frequently daylight as hot spots.

https://serc.carleton.edu/NAGTWorkshops/deepearth/plumes.html

Lenhardt – Biographies 115 Other Noteworthy Developments

1910 Sergey Vasilievich Medvedev – Microseismic Zonation 1910 Nathan Mortimor Newmark – Earthquake Resistant Design (ERD) 1922 Bolton Seed – Soil Mechanics 1927 Nicolai Vissaronovich Shebalin – Earthquake Engineering 1933 Boris Kostrov – Source Dynamics 1964 Leon Knopoff – Q 1940 Norman Ricker – Seismic Pulse 1951 Ryutaro Takahoishi – Tsunami 1959 Vladimir Keilis-Borok – Stress Drop 1963 Norman Haskell – Amplitude Spectrum 1963 Frederick Vine & Drummond Mathews – Magnetic Reversal 1966 Keiiti Aki – Seismic Moment 1967 Dan McKenzie – Theory of Plate Tectonics 1988 Stuart Crampin – Shear Wave Splitting

Lenhardt – Biographies 116 Error 303, 404, …?

Not Found?

See also:

Benjamin F. Howell, 1990. An Introduction to Seismological Research – History and Development. Cambridge University Press Walter Kertz, 2002. Biographisches Lexikon zur Geschichte der Geophysik. Braunschweigische Wissenschaftliche Gesellschaft William H. K. Lee et al., 2003. International Handbook of Earthquake and Engineering Seismology, Vol. B Vincent Courtillot and Jean-Louis Le Mouël, 2007. The Study of Earth´s Magnetism (1269 – 1950): A Foundation by Peregrinus and Subsequent Development of Geomagnetism and Paleomagnetism. Rev. of Geophysics, 45, 1 – 31 Erhard Oeser, 2016. Historical Earthquake Theories: From Antiquity to the End of 19th Century. AV Akademikerverlag Wikipedia: https://en.m.wikipedia.org/wiki/List_of_geophysicists https://en.wikipedia.org/wiki/History_of_geophysics

Lenhardt – Biographies 117

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