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History of Seismology

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History of Seismology 1 History of Seismology Duncan Carr Agnew University of California at San Diego, La Jolla, California, USA 1. Introduction interest, and, quite often, social support for seismic studies. Table 1 lists some earthquakes (and one explosion) that have At present seismology is the study of seismic sources (mostly had an impact on seismology. earthquakes), the waves they produce, and the properties of the This article describes the history of seismology up to about media through which these waves travel. In its modern form the 1960, with a brief sketch of major themes since then. To cover subject is just over 100 years old, but attempts to understand this history in the space available requires a fair amount of earthquakes go back to the beginnings of science. The course of selection. Any reading of the older literature shows that a great seismology, more than that of many other sciences, has been many ideas were suggested long before they became generally affected by its object of study: From Lisbon in 1755 through accepted: For example, the ideas that shaking is a wave pro- Kobe in 1995, destructive earthquakes have provoked scienti®c pagated from a source, that some earthquakes (at least) are TABLE 1 Some Events of Significance to the History of Seismology Name Date Location Magnitude Importance 143 Gansu, China 7 Possibly first instrumental record of unfelt shock Lisbon 1755 Nov. 1 Azores-Cape St Vincent Ridge 8 Widespread seiching and tsunami: basis for theories of wave propagation Calabria 1783 Feb. 5 Southern Italy 7 First event studied by a scientific commission Basilicata (Neapolitan) 1857 Dec. 16 Southern Italy 7 Detailed investigation by Mallet Yokohama 1880Feb. 22 Near south coast of Honshu, Japan 5.8 Led to Seismological Society of Japan Casamicciola (Ischia) 1883 Jul. 28 Tyrrhenian Sea 6 Led to foundation of Italian seismological service Vyernyi (Alma-Alta) 1887 Jun. 9 Lake Issyk-Kul, Krygyzstan 7.3 Stimulated Russian study of earthquakes North Canterbury 1888 Aug. 31 South Island, New Zealand 7 First scientific observation of strike-slip faulting 1889 Apr. 18 Near south coast of Honshu, Japan? 7 ? First teleseismic recording Nobi (Mino-Owari) 1891 Oct. 28 Western Honshu, Japan 8.4 Large surface rupture; led to Imperial Earthquake Investigation Committee Assam 1897 Jun. 12 Northeastern India 8.7 Recognition of teleseismic primary and secondary phases San Francisco 1906 Apr. 18 Central California 7.7 Large surface rupture; geodetic detection of off-fault motions; led to Seismological Society of America Kulpa Valley 1909 Oct. 8 Northwestern Balkan region 6 Discovery of crustal phases Kanto (Kwanto) 1923 Sep. 1 Near south coast of Honshu, Japan 7.9 Led to foundation of Earthquake Research Institute (Tokyo) Buller (Murchison) 1929 Jun. 16 South Island, New Zealand 7.8 Stimulated local earthquake recording in New Zealand; inner-core phases in Europe 1946 Apr. 1 Unimak Island region 7.2 Led to tsunami warning system Ashkhabad 1948 Oct. 5 Turkmenistan±Iran border region 7.2 Stimulated Soviet earthquake program 1952 Nov. 4 Off east coast of Kamchatka 9.0First suggested observation of free oscillations RAINIER 1957 Sep. 19 Southern Nevada 4.0First underground nuclear explosion, helped stimulate VELA-UNIFORM program Chilean 1960May. 22 Off coast of Central Chile 9.5 First detection of free oscillations Alaskan 1964 Mar. 28 Southern Alaska 9.2 Stimulated US earthquake-hazards program Niigata 1964 Jun. 16 Near west coast of Honshu, Japan 7.5 Stimulus for modern Japanese earthquake programs Xintiang 1966 Mar. 22 Northeastern China 7.0Stimulated Chinese earthquake program INTERNATIONAL HANDBOOKOFEARTHQUAKE AND ENGINEERING SEISMOLOGY,VOLUME 81A ISBN: 0-12-440652-1 Copyright # 2002 by the Int'l Assoc. Seismol. & Phys. Earth's Interior Committee on Education. All rights of reproduction in any form reserved. 3 4 Agnew caused by faulting, and that the Earth contains a liquid core. 18th century the development of theories of electricity, and I have therefore focused less on the earliest occurrence of an especially their application to lightning, provoked several idea than the time when it became something seriously con- theories that related earthquakes to electrical discharges. In sidered within the seismological community. To make the England, much of this theorizing was stimulated by the narrative more readable, the sources for particular statements occurrence of several damaging earthquakes in the year 1750. are given in a separate set of notes, referenced through foot- However, the greatest stimulus to seismological thinking note numbers; these notes, the reference list, and a biblio- was undoubtedly the Lisbon earthquake of 1755, partly for its graphy of the history of seismology, are all included on the destructiveness, but even more for providing evidence of attached Handbook CD.1 motion at large distances: It caused seiches over much of Europe. At least two writers, J. Michell (1761) and (much more obscurely) J. Drijhout (1765), proposed that this distant 2. Early Ideas about Earthquakes motion was caused by a wave propagating from a speci®c location, thus more clearly than before separating the earth- The most common explanation given for earthquakes in early quake source from the effects it produced. The type of wave cultures was the same as for any other natural disaster: they envisaged was like a traveling wrinkle in a carpet; Michell were a manifestation of divine wrath. In European thought this also suggested that the vibrations close to the source were idea did not disappear from scienti®c discussion until well into related to waves propagated through the elasticity of the rocks, the 18th century. But two premodern cultures, the Chinese and as sound waves were known to propagate through the elasti- the Greek, also developed naturalistic explanations for seismic city of the air. The elasticity and pressure of gases, more shaking. Greek natural philosophers suggested a variety of speci®cally of high-temperature steam, also provided Michell's causes for earthquakes; the most in¯uential (and extensive) driving force for the earthquake itself, which he took to be treatment extant was by Aristotle (ca. 330 BCE), who attributed caused by water vaporized by sudden contact with under- earthquakes to winds (driven by an ``exhalation,'' the pneuma) ground ®res. (This steam also supported the propagation of blowing in underground caverns. The classical authors also waves to great distances.) Michell attempted to locate this attempted to classify earthquakes by different types of shaking: ``place of origin'' by comparing the times of the seiche- something that remained a mainstay of seismology for a long inducing wave and the observed sea wave, and also hazarded a time, and still survives in popular terminology.2 guess at the depth. While these ideas were not forgotten, they Chinese ideas about earthquakes were put forth by various did not lead to any additional research, and certainly did not thinkers at roughly the same time as the Greek ones, the replace older theories of earthquakes.4 dominant idea also being that shaking was caused by the blocking of a subtle essence (the qi). After the Han dynasty (200 BCE), Imperial state orthodoxy associated natural disas- 3. The Nineteenth Century to1880 ters with dynastic decline; this led to systematic preservation of accounts of earthquakes in the of®cial annals. China's The expansion and professionalization of science in the 19th technology also produced the ®rst seismoscope, invented in century meant that earthquake studies, like many other parts of AD 132 by Zhang Heng. This well-known device, which science, could become a specialization, at least for a few sci- reportedly signaled the direction of an earthquake as well as entists for part of their careers. One type of research that began the occurrence of shaking, is supposed on at least one occasion in this period was the accumulation of large volumes of data, to have responded to unfelt shaking; the mechanism of its with the aim of ®nding underlying patternsÐa style that has operation remains obscure.3 been called ``Humboldtean'' when applied to the Earth, but was The Aristotelian view of earthquakes (as of many other in fact much more general. For earthquake studies, this meant aspects of the world) remained the primary theory during the the ®rst systematic catalogs of shocks (as opposed to lists of medieval periods of both Islam and Europe. With the decline catastrophes); leaders in this were K.A. Von Hoff and A. Perrey, of Aristotelian thought in early modern Europe, other ideas the latter being a disciple of A. Quetelet, one of the founders of were put forward, though many of the writers were from statistics. Many of these compilations were used to look for northern Europe and so (unlike the Greeks) had little direct possible correlations between earthquake occurrence and experience of earthquakes. They did, however, know about astronomical cycles or meteorological events; this was one of gunpowder: This new technology of chemical explosives the main topics of 19th-century seismology. Along with these suggested that earthquakes might be explosions in the Earth catalogs came studies of individual shocks: Most European (or in the air); of the various chemical theories put forward, the earthquakes after about 1820stimulated some sort of special most popular involved the combustion of pyrites or a reaction study, by individuals (often local professors) or by commis- of iron with sulfur. Such theories also explained volcanic sions set up by governments or local scienti®c societies. action; that the most seismic part of Europe, namely Italy, The ®rst such commission was established after the was also volcanic helped to support this association. In the Calabrian earthquake of 1783; a century later, one earthquake History of Seismology 5 (in Andalusia, 25 December 1884) would bring forth three a map (Color Plate 1) that clearly delineates the seismic and commissions, one each from Spain, France, and Italy.
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