Consortium of Universities for Research in Earthquake Engineering CUREE 1301 S

Home , 1964 Alaska earthquake

Significant Earthquakes in the United States adapted from the 2001 CUREE Calendar illustrated essays by Robert Reitherman

Consortium of Universities for Research in Earthquake Engineering CUREE 1301 S. 46th Street, Richmond, CA 94804-4698 tel: 510-231-9557 fax: 510-231-5664 http://www.curee.org Significant United States Earthquakes

his year's CUREE Calendar offers brief, illustrated essays on a dozen significant United States earthquakes. The number is arbitrarily Tlimited by the number of months. While this is an arbitrary limit, it conveniently focuses our attention on especially significant events. Three key criteria have been used in the selection of these twelve earthquakes. irst, they are all important earthquakes as judged by the usual standards employed to compile short lists of earthquakes in reference Fbooks: They were of sizable magnitude, and they caused significant ground shaking and other effects, usually accompanied by large losses. "Large" is relative to American earthquake experience: We have been fortunate in never experiencing the huge fatality tolls that countries such as Japan, China, or Italy have experienced many times. Obscure earthquakes, the answers to trivia questions, won't be found on this select list, because they cannot pass this first threshold of importance in terms of seismological size and resulting impact.

econd, these twelve events have wielded an enduring influence on the earthquake engineering field. Newton taught us that if we give San object one nudge, it accelerates. But then, absent other forces, the object's velocity peaks, and with friction ever present in our daily experience, we will see the object quickly start to slow down and then come to a stop. Give the object a prolonged push, and it keeps on accelerating as long as a force is imparted to it. These dozen earthquakes, some occurring over a century ago, were not just brief nudges; they still impart forces to the earthquake engineering field to help keep it accelerating. These are not the twelve earthquakes in US history with the largest magnitudes, but the ones with the greatest long-term effects. Technical findings have been derived from these earthquakes on topics ranging from ground motion, tsunamis, and ground failures such as liquefaction, surface faulting, and landslides, as well as on the topics of buildings, bridges, and other kinds of construction. Other earthquakes have motivated governmental agencies, political leaders and the general public to adopt earthquake hazard reduction measures or to support the research and development of the earthquake field. Still others have demonstrated the earthquake hazard that exists in regions where earthquake hazard reduction measures (such as seismic codes, research efforts, or public interest in the earthquake subject) would have been much less had these earthquakes not occurred. One earthquake in the hand, one that has actually happened, is worth two in the bush that are only projected to occur. Fortunately, there is a positive aspect to disasters, and the earthquakes selected here illustrate that point.

hird, these earthquakes are distributed around the widespread geography of the United States. As the twentieth century closes, perhaps Tthe single most important fact about earthquake engineering in the USA is that it is national. The National Earthquake Hazards Reduction Act has been in operation for over two decades. Seismic code provisions are now developed through a national process. Though much is left to accomplish in implementing seismic design in regions of the country new to the subject, it is still true that today we have states and local jurisdictions adopting current regulations that never had such provisions in their building codes . Practicing engineers well beyond the West Coast routinely concern themselves with earthquakes in their design projects. And the academic earthquake engineering landscape has become the most national of all. In every region of the country there are engineering professors acknowledged as experts in their areas of specialty, major experimental labs are in place, research centers and programs have been established, and there are high quality educational programs at the undergraduate and graduate levels. ----Robert Reitherman, CUREE Executive Director

1 1949

1964 1959

1906 1989 1971 1811-1812 1994 1940 1933 1886

1946

1811-1812 New Madrid 1886 Charleston 1906 San Francisco 1933 Long Beach 1940 El Centro Location Map for Significant United States Earthquakes: 1946 Aleutian (Hawaii) 1949 Puget Sound 1959 Hebgen Lake 1964 Alaska 1971 San Fernando 1989 Loma Prieta 1994 Northridge

2 Fortunately for society, there were very few people or structures in the region at the time of the 1811-1812 New Madrid Earthquakes, only Largest Earthquakes a few years after the 1804 Louisiana Purchase. Only one fatality resulted from all of the New Madrid Earthquakes. (Steinbrugge, 1982, p. 293) Like the twentieth century’s largest earthquake in the USA, the 1964 Alaska Earthquake, these 1811-1812 earthquakes occurred In the 1811-1812 Sequence in a largely unpopulated area, and therefore damage was limited. Because of their location and also their early date in the history of earthquake studies, it wasn't until 100 years later that the first significant scientific report on the earthquakes (Fuller, 1912) was published. December 16, 1811 Ms 8.6

Coupled with the huge seismological scale of the sequence is the puzzling fact that the New Madrid Earthquakes were intraplate earthquakes. January 23, 1812 Ms 8.4

Almost all large earthquakes occur along plate boundaries. A high school science textbook can summarize the origin of most earthquakes February 7, 1812 Ms 8.7 in one sentence—they occur where tectonic plates, set in motion by seafloor spreading, collide and cause strain in the rock to accumulate, Algermissen, 1983, p. 40 which is occasionally released in the form of earthquakes as fault slippage occurs. Intraplate earthquakes are less elegantly explained and are less well understood. As stated by the late Professor Otto Nuttli of St. Louis University, “if one considered only the seismic activity in the Mississippi Valley during the twentieth century, he almost certainly would conclude that it is a minor seismic region. A study of global seismicity, from which it is found that the interiors of continents generally are stable, aseismic masses, would lead him to the same conclusion.” (Nuttli, 1973, p. 229)

5% in 50 yr. Most of the facts concerning the reported intensity of the shaking in 1811-1812 at particular sites have been obtained from newspaper accounts 2% in 50 yr. 10% in 50 yr. of what happened in the more populous East. For example, the largest New Madrid earthquakes were felt in Washington, DC, 1100 km (700 miles) away, but didn’t cause strong shaking at that distance. From reports of intensities at various locations, attenuation relationships can 10.00 be used to back-calculate what the intensity at the “bull’s eye,” the source, would have been and what the associated magnitude was. This line of thinking has been used for earthquakes such as the 1811-1812 sequence that predate seismological instrumentation. (The first seismographs in the USA were not installed until 1877.) (Rubey, 1969, p. viii) 1.00 Today, engineers and earth scientists do not use the same attenuation formulas for all areas of the United States. The New Madrid Earthquakes along with the 1886 Charleston Earthquake are the most notable US examples of this variation in attenuation. Rock that is hard and dense 0.10 transmits seismic waves more efficiently than softer rock. In the Pacific Coast states, the bedrock underlying soils tends to be softer than in the Central and Eastern USA. An earthquake of a given magnitude on the West coast is thus predicted to have a smaller felt area (region over which the vibrations can be felt).

0.2 sec. Spectral Acceleration, %g Acceleration, Spectral 0.2 sec. 0.1 0.01 0.001 0.0001 0.00001 In a high seismic area such as Los Angeles, earthquake shaking at the limits of probability for most seismic design purposes, a 2,500 Annual Frequency of Exceedance mean recurrence interval (2% probability of exceedance in 50 years), is only about 1.5 times more severe than the relatively probable Memphis Los Angeles level of shaking having a mean recurrence interval of about 475 years (10% probability of exceedance in 50 years). Because of source: NEHRP Provisions (BSSC, 1997, Part 2, Fig. B2) conservatism in structural design provisions, many buildings can withstand shaking 1.5 times their design ground motion level. For the largest city located near to the New Madrid source zone, Memphis,the rare 2,500-year earthquake shaking is similar in spectral accelerations to the comparable low-probability event for Los Angeles--but it is about five times greater than the more probable 475-year event in Memphis. To only design for the more probable event in the New Madrid region means risking collapse if the large one occurs; to design for the large one means using code provisions as strict, and as costly, as are required in the obviously more seismic city of Los Angeles. The 1997 NEHRP Provisions (BSSC, 1998) and supporting US Geological Survey seismic hazard mapping effort treated this complex issue more explicitly than ever before in the development of seismic codes in the USA. (Nordenson and Bell, 2000) 1811-1812 New Madrid Earthquakes The most spectacular release of seismic energy in North America in historic time is the sequence of earthquakes centered around New Madrid, Missouri, that occurred from December through January, 1811-1812. Magnitude 8 earthquakes usually have mean recurrence intervals of several centuries or several thousand years, but in that wintertime, earthquakes occurred at the rate of one magnitude 8 CUREE per month, not to mention the occurrence of five magnitude 7’s and ten 6’s in the sequence. 2001 CONSORTIUM of UNIVERSITIES for RESEARCH in EARTHQUAKE ENGINEERING

3 The August 31, 1886 Ms 7.7 earthquake (Algermissen, 1983, p. 37) that struck Charleston and the surrounding region in South Carolina was the subject of a document compiled by Clarence E. Dutton (Dutton, 1889) of the US Geological Survey, the most thorough report--one could say the first scientific report-- on an earthquake in the USA up to that time. In many ways, the Dutton report is similar to the documentation by Robert Mallet on the 1857 earthquake that struck the region near Naples, Italy (Mallet, 1862), in its use of engineering observations to try to decipher where the source of the earthquake was and how the waves traveled, as well as in the similar detail given to drawings of building damage to aid in this line of reasoning.

The timing of the 1886 earthquake allowed Dutton to include a fascinating illustration in his report of a model of a particle's motion as reconstructed by Professor Sekei Sekiya from the January 15, 1887 Yokohoma Earthquake. Numbers along the wire label the position of the particle at a given number of seconds into the earthquake record. The accuracy of this model, given the seismographs available at the time, may 1-20 seconds not be high, but it is a fascinating picture of the ultimate goal that underlies today's highly computational ground modeling techniques: to understand and predict exactly how the surface of the ground at a given point will move in an earthquake.

Diagram of Fall of Chimneys Liquefaction was common in this earthquake, though not recognized as such at the source: Dutton, 1889, p. 229 time. The "craterlets" mapped then, along with recent paleoseismology investigations that have pinpointed sites that liquefied in that earthquake or earlier ones, have been used to define the source zone for future earthquakes. This also illustrates a difference 20-40 seconds 100 miles in the approach to defining seismic hazard in the higher seismic West and moderate 0 100 200 km seismicity areas: In the former, there are often well-delineated faults and abundant historic (especially instrumentally measured) seismicity data. Seismic sources appear as neatly drawn line segments in plan view on the maps used to develop seismic zones for design. In the Central and Eastern USA, by contrast, the source of future earthquakes is often modeled in terms of polygons somewhere within which an earthquake may be released. Shown here is the source zone defined in the US Geological Survey seismic hazard mapping effort (Frankel et al., 1996) that supported 40-72 seconds the development of the 1997 NEHRP Provisions. Charleston Particle Motion Diagram, Sekei Sekiya, Building code maps highlight Charleston as the major city on the East Coast that faces 1887 Yokohama, Japan Earthquake the highest earthquake hazard and which also has such a high design wind speed. Source Zone For Seismic Code Purposes source: Dutton, 1889, Pl. XXXI Seismic Code Source Zone Combined with its severe hurricane storm surge threat because of its low elevation, source: Frankel et al., 1996 coastal site, Charleston takes the honor of being America's most multi-hazard city. 1886 Charleston Earthquake This earthquake is second only to the New Madrid sequence of 1811-1812 in “putting seismic risk on the map” in the eastern half of the United States. The fact that even today the location of possible sources of future such earthquakes is only vaguely known illustrates the fact that in the Central and Eastern United States, seismicity is more diffuse and sources are harder to pinpoint for purposes of CUREE estimating seismic hazard. 2001

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4 The cost of repairing the damage caused by the 1994 Northridge Earthquake, $44 billion (California Office of Emergency Services and EQE, 1997, p. 3-19), is the highest for any US earthquake (or other natural disaster), but the life loss in the April 18, 1906 San Francisco Earthquake, usually listed at 700 to 800 but estimated recently at several times more (Hansen, Condit, and Fowler, 1989), is by far the biggest for that important category of earthquake loss. Even when considered just in terms of property loss, the 1906 disaster is still in some ways at the top of the list of US earthquakes, because its proportional impact was so great. The impact on San Francisco, then the largest city in the Western US, including the losses from the devastating fire that burned for three days, was greater than in any other major city in any other US earthquake: Among the 28,188 buildings destroyed were the dwellings where about 200,000 to 250,000 people lived -- half to five eighths of the total population of the city. The property loss totalled about $7 billion in year 2000 dollars (Douty, 1977, p. 53, p. 81-84). Virtually all the major public and commercial buildings were destroyed. At Stanford University, 37% of the major structures suffered severe damage: collapse, or damage requiring replacement of more than half the walls. (Smith and Reitherman, 1984, p. 7) The town of Santa Rosa with a small population then of only 6,700, suffered the destruction of seven or eight downtown blocks by shaking and four or five blocks by fire, and there were 61 fatalities (Lawson, ed., 1908, p. 200)-- figures that are about equal today to what is expected in total losses distributed over an urban region of more than a million people from a magnitude 6 to 7 earthquake striking a modern California city.

In seismological terms, this was a Northern California rather than just a San

Francisco Earthquake. The San Andreas Fault that caused this Ms 8.3 Fire Damage in San Francisco earthquake (Algermissen, 1983, p. 68) had well-defined surface rupture for a source: Steinbrugge Collection, EERC-NISEE length of about 400 km (250 miles), none of which was within the City and County of San Francisco, because the fault runs slightly seaward of it. When geologists such as Andrew Lawson (UC Berkeley), J. C. Branner (Stanford University), and G. K. Gilbert (USGS) studied the fault, they made the same inference that today’s Earth scientists do: The build-up of strain in the rock was finally released by slippage along a weak plane, the fault, and vibrations resulted. By contrast, only a generation before, one of the most prominent geologists in the country, Josiah Whitney, looked at the impressive offsets from the 1872 Owens Valley Earthquake, another magnitude 8 event, and concluded that "the ground fractures, which are so carefully measured now after Barn at Skinner Ranch, Marin County, Located each earthquake, were of small importance, as they were the result, not the cause, of the earthquake. To him, when the earth shakes, on the Displacement of the San Andreas Fault the ground breaks; to modern theory, when the earth breaks, the ground shakes." (Hill, 1972, p. 53) The explanation of Hugo Fielding source: Steinbrugge Collection, EERC-NISEE Reid (Reid, 1908) of how strain accumlated and then suddenly was released is a classic theory of seismology. In later decades it was to be accompanied by an understanding of the planetary scale of this cycle of deformation and energy release--plate tectonics theory- -to give today’s Earth scientists their fundamental kit of concepts with which to understand the cause of earthquakes.

“In the years that followed the 1906 disaster, it became ‘proper’ to call it the 1906 fire and to omit any reference to the earthquake since eastern United States investment capital had a greater fear of earthquake than fire.” (Steinbrugge, 1982, p. 224) It was true that the majority of the damage in San Francisco was due to the fire, but there was obviously also a need to institute building code regulations for earthquake shaking. Due to political opposition and a lack of adequate engineering basis for such regulations, it was not until the much smaller 1933 Long Beach Earthquake that the seed that was to develop into seismic code provisions fell on favorable ground. (Geschwind, 1996, chapter 5; Joint Committee on Seismic Safety, 1974, App. B) 1906 San Francisco Earthquake The name of this earthquake reveals why it is so famous: Unlike its fellow magnitude 8 earthquakes that have occurred in the USA in historic time, this event happened in a time and place that exposed a relatively large population and amount of construction to the shaking, though the 1906 level of development and population was many times less than is exposed to San Francisco Bay Area CUREE earthquakes on the San Andreas or other faults today. 2001 CONSORTIUM of UNIVERSITIES for RESEARCH in EARTHQUAKE ENGINEERING

5 “While the lessons of the 1923 Tokyo disaster were known in the United States, it took the 1933 Long Beach, California earthquake to stimulate American action.” (Steinbrugge, 1982, p. 5) The Field Act took the enforcement of building codes out of the hands of local jurisdictions and gave that authority to the state (the agency now called the Division of the State Architect). As of 1933, only the city of Santa Barbara, following its 1925 earthquake, and the city of Palo Alto had any earthquake code requirements. (Joint Committee on Seismic Safety, 1974, p. 193) The Riley Act, with lesser enforcement “teeth” in its provisions, applied more broadly to other buildings, though it excluded dwellings. Effective statewide enforcement of seismic provisions in California was not to come until after World War II when the local jurisdictions of the San Francisco Bay Region adopted seismic code provisions. At the close of the twentieth century, due to the fact that it is only recently that seismic code provisions have been adopted in many areas of the country and are enforced, the USA cannot yet be said to have effective nationwide enforcement of seismic provisions.

The March 10, 1933 Ms 6.3 Long Beach Earthquake (Algermissen, 1983, p. 68) on the Newport-Inglewood Fault, which traverses the coastal edge of the Long Beach-Los Angeles area, caused a large life loss, 102, (Steinbrugge, 1982, p. 350, quoting Rube Binder), by American standards (though very small as compared with some earthquake disasters in other countries). This toll is the largest in any US earthquake other than the 1906 San Francisco disaster, except for three earthquakes in which most of the fatalities occurred because of tsunamis: 1918 Mona Passage, Puerto Rico (116 fatalities); 1946 Hawaii, from an Aleutian Earthquake (173); and the 1964 Alaska Earthquake (119 of 131 fatalities from the tsunami). The 1933 earthquake could be called the unreinforced masonry earthquake because it came at a time when not only did this class of building fare poorly in an earthquake—the 1886 Charleston, 1906 San Francisco, and 1925 Santa Barbara Earthquakes had already made this point—but furthermore the engineering and political worlds were ready to respond. Until the masonry industry could re-group and develop reinforced masonry, masonry lost its market footing in California. For brick, the solution devised was to build two wythes of brick a few inches apart, like two vertical slices of bread; the meat in this sandwich was then provided by what was Collapse of Unreinforced Masonry Walls source: Los Angeles Public Library essentially a reinforced concrete core. For hollow concrete block, code rules were also devised, requiring walls to be similarly filled with grout and a grid of rebar. Pure concrete frame construction without shearwalls was not common at this time and thus was largely untested by the earthquake, but became very popular in later decades. The 1967 Caracas and 1971 San Fernando Earthquakes caused collapses to non-ductile concrete frames and had an effect on code provisions for this class of construction that was similar to that of the 1933 disaster on masonry. A comparable impact on wood and steel construction did not occur until the 1994 Northridge Earthquake, but the pattern was the same: The earthquake provided engineering lessons while also serving as the well-publicized disaster that provided the political impetus for change. The effort led by John Freeman to have the Federal government develop and install strong motion seismographs bore fruit in 1932 when the first Coast and Geodetic instruments were installed, in time for three instruments in the area to trigger in the 1933 earthquake. (Freeman, 1932, p. 869 ff.) Loss estimates for a Newport-Inglewood Fault earthquake have been made several times in recent years and typically project the largest life and property losses of any scenario earthquake in the US. A1973 Federal study of scenario earthquakes in the Los Angeles region (Algermissen et al., Long Beach Accelerogram 1973), updated in 1981 (Steinbrugge et al., 1981), estimated over 20,000 fatalities and about $120 billion in property loss (year 2000 dollars), and a source: Heck et al., 1936, Fig. 16 1995 study (assuming a magnitude 7) estimated from 3,000 to 8,000 deaths and $175 to $220 billion in economic loss. (RMS, 1995, p. 3) 1933 Long Beach Earthquake It was only a magnitude 6.3 earthquake--the smallest of any of the dozen earthquakes written about here. However, it was the most influential of any of these, because it was the 1933 earthquake that caused the adoption of seismic code provisions in American building codes, a trend that has now extended almost nationwide. It was also the first significant US earthquake to be recorded by an CUREE accelerograph. 2001

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6 At a utilitarian building in El Centro, the Terminal Substation Building, an accelerograph recorded the motion of the May 19, 1940 earthquake. The shaking in that recording from the Ms 7.1 earthquake (Algermissen, 1983, p. 68) in the north-south direction was the most vigorous component. This record became the most commonly used strong-motion record in dynamic analyses and shake-table tests for the following two decades, having only the 1952 Taft record as a competitor in that era, and it is still used today. The instrument that recorded this famous accelerogram was attached to the building’s concrete floor and not in a free-field location, and because of soil-structure interaction of the massive foundation with the surrounding soft soil, the record may have under-represented the high frequency motions of the ground. (Brune and Anooshehpoor, 1991).

In the year following the earthquake, George Housner finished his thesis at Caltech that helped developed the response spectrum method of converting raw ground motion data into a form useful for structural analysis. (Housner, 1941). If structures were infinitely rigid, then as the base accelerated and moved a particular distance the same motion would be recorded at the same instant all the way up its height. The peak ground acceleration (PGA) would be the same as the peak structural response at any story. Buildings and other structures, however, are much more complex and difficult to analyze--and much more interesting from the standpoint of dynamics. A record with a lower PGA than another may cause more response in a given structure than one with a higher PGA, depending on frequency content. A pulse of acceleration with a long duration, (a high velocity and a large displacement), can be more damaging than a high frequency pulse with a much higher acceleration. As the analytical capability of engineers improved, and in the 1960s and 1970s when modern shake tables were created to play back these recorded motions, earthquake engineering developed an improved ability to put strong motion records to practical use and to extract more meaning from them. 1940 El Centro Accelerogram source: Housner and Jennings, 1982, p. 54 The peak acceleration of the 1940 recording is about 1/3 g. After this record had been used for many years to simulate an earthquake in analyses or in shake table research, many engineers as a matter of habit came to assume that this was near the upper bound of accelerations to expect from nearby earthquakes, and it was influential in setting calculation procedures for design loads. The 1952 Taft record was the next major accelerogram to be produced. As David Leeds has noted, who at the time was the technician who retrieved the record from that accelerograph, the town of Taft was not where the strongest shaking occurred in the 1952 Kern County Earthquakes.

It was located tens of miles from the origins of any of the major earthquakes in that series (three magnitude 6's and seven 5's, in addition to the July 21 Ms 7.7 earthquake). Of six unreinforced masonry schools in Taft, none was damaged more than moderately; in Bakersfield, this type of construction had severe damage. (Steinbrugge and Moran, 1954, p. 265, Table 7) It just happened that no strong motion instruments were located closer to the source where the motion was more severe, and so the Taft record came to represent the shaking of this large earthquake. Again, engineers tended to calibrate their ideas of how strong the ground could shake from an accelerogram that turned out to be only moderately intense.

When the 1971 San Fernando Earthquake occurred, there was considerable debate over the validity of the Pacoima Dam record, which had a PGA of 1 1/4 g. Engineers surveying the damage in the most heavily shaken corner of the San Fernando Valley in that earthquake, near the Pacoima Dam and where collapses occurred on the sites of the Veterans Administration and Olive View Hospitals, concluded that “the maximum horizontal ground acceleration at this site is estimated at approximately 40 percent of gravity,” (EERI, 1973, vol. I, part A, p. 44) Engineers of today, gazing at a collection of tilt-ups that had roof and wall collapses, would not cap their estimates of the maximum acceleration at such a relatively low level, because since 1940, many strong motion records have shown peak ground accelerations at or above the level of the El Centro record, and several records over 1 g have been recorded. As a result, engineers have had their concepts of ground motion severity re-calibrated upwardly in terms of instrumental values. John Blume was a pioneer in observing one reason why engineers were reluctant to accept the higher instrumental values: While the ground motions were more severe than engineers had assumed, their structures also had more capacity than they calculated. (Blume, 1979)

1940 El Centro Earthquake "North-South El Centro" is a phrase known to earthquake engineers around the world. By today's standards, that ground motion record obtained from the 1940 earthquake in California's Imperial Valley isn't remarkable, and in fact may be deceptively small, but for several decades it was one of the most often-used accelerograms in the USA and elsewhere to represent the effects of a large, nearby CUREE earthquake. 2001

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7 The April 1, 1946 earthquake in the Aleutian Trench near Unimak Island had a magnitude of "only" 7.4 (Ganse and Nelson, 1981, p. 53), unremarkable for this uninhabited portion of the Pacific Rim where a dozen earthquakes larger than this occurred between 1899 and 1979 (Algermissen, 1983, p. 88). However, the tsunami the earthquake generated was extremely devastating nearby--30 meters (100 feet) high--while in the distant Hawaiian Islands, the wave heights were from 10 to 15 meters (30 to 45 feet) in height, and "this is the only tsunami from a distant source known to have amounted to much on the California coast; it rose to 11 feet at Halfmoon Bay and 12 feet at Santa Cruz...." (Richter, 1958, p. 115, writing prior to the 1964 Alaska Earthquake, which caused similar waves at Half Moon Bay and Santa Cruz and considerable devastation at Crescent City)

Fortunately, the velocity of a tsunami (the square root of the product of gravitational acceleration and the water depth), which is about 800 km/ hr (500 mph) in the deep sea, diminishes rapidly in shallow water. Fast-moving tsunami waves may have a height of only a fraction of a meter and a wave length of 100 km (Bolt, 1978, p. 78), and such a small plateau superimposed on the ocean surface passes beneath a ship undetected. Just as seismologists early on used earthquake waves as a means to examine the interior of the earth, an early use of tsunami waves was to study the interior of the sea, or more precisely, to estimate the average depth of the Pacific Ocean based on tsunami travel times. Alexander Dallas Bache, a great-grandson of Benjamin Franklin and superintendent of the US Coast and Geodetic Survey, established the origin time of a Japanese earthquake in 1854, and then, via tidal records in California, found that the travel time was 12 hours. Using the relationship between velocity Scotch Cap US Coast Guard Light and depth stated above he found the average depth of the Pacific Ocean along that transect to be 3,600 meters, close to the more accurate figure House, Unimak Island, Alaska later found to be 4,280 meters. (Wilford, 1981, p. 280) As the wave nears land and travels through shallower water, the height increases to a maximum of usually 5 to 15 meters in susceptible areas, but the speed drops to that of ordinary waves. Ordinary waves are not very deep from Though constructed of reinforced con- front to back, whereas tsunamis at the shore may be separated by 5 to 15 minutes and be surges of water hundreds of meters long from front to crete and sited 13 m (40 ft) above sea back. The trough of the wave is associated with a withdrawal of water--a harbor can be drained dry in minutes--and the peaks can materialize level, a 30 m tsunami wave from the 1946 as a rapidly rising tide or as a bore with a distinct vertical face like a typical breaker, depending on the offshore topography. earthquake destroyed -- removed -- the structure down to its foundation. The 1946 tsunamis crossed the Pacific with a directional impetus that destined the Hawaiian Islands to receive the brunt of their effect, because of the orientation of the seafloor displacement in the Aleutians. (Tsunamis can also be generated by landslides along the shore that fall into the source: National Geophysical and Solar- Terrestrial Data Center water, by submarine landslides, or by volcanic explosions.) Waves as wide as entire islands and 15 meters (45 feet) high resulted at locations on the islands of Hawaii, Molokai, and Kaui. At Hilo on Hawaii, the harbor and downtown were flooded by strong waves. The death toll for the tsunami was 173. (Steinbrugge, 1982, p. 246)

As a result of the 1946 life loss in Hawaii, the Tsunami Warning Center was established in 1948 in Honolulu with the cooperation of other nations in the Pacific. The first success of the warning system came in 1952, when evacuations in Hawaii prevented any life loss from a tsunami caused by the Kamchatka Earthquake. Because the velocity of waves propagated through the Earth is so much higher than through the less dense ocean, a seismograph can detect the fact that a large earthquake has occurred offshore of Alaska well before the arrival of the tsunami itself. In the 1964 Alaskan Earthquake, it took 7 minutes for the ground waves to reach Hawaii while the tsunami waves arrived five hours later. For tsunamis generated off the coast of Chile, as in the 1960 Earthquake, tsunami arrival times in Hawaii are about 15 hours after the earthquake, and for sources in Japan about seven hours. Today's efforts at improving warnings include real-time tide gauge monitoring across the ocean and theoretical modeling of tsunamis for various specific coastline locations given a particular origin of the waves.

1946 Aleutian Earthquake (Hawaiian Tsunami) Other damaging tsunamis had occurred in the USA before-the 1918 Mona Passage tsunami killed 118 people in Puerto Rico--and losses from tsunamis elsewhere, e.g. the 1755 Lisbon tsunami or the 1896 or 1933 Sanriku tsunamis in Japan were far higher, but the 1946 Aleutian Earthquake, or rather the tsunami it caused, came at a time when its effects could be especially influential on emergency CUREE management practice and tsunami research. 2001 CONSORTIUM of UNIVERSITIES for RESEARCH in EARTHQUAKE ENGINEERING

8 The April 13, 1949 Puget Sound Earthquake had a moderately large surface wave magnitude of 7.1 (Algermissen, 1983, p. 80), though its loss totals of eight fatalities and $180 million in property damage (year 2000 dollars) do not make this earthquake especially large. Its 70 km (40 mile) depth was one reason damage was not greater. "The principal lesson learned from the 1949 earthquake was that the earthquake hazard truly exists in the Pacific Northwest. Building ordinances were strengthened as a result." (Steinbrugge, 1982, p.

315). In 1965, a Ms 6.5 earthquake located about 60 km (35 miles) deep between Seattle and Tacoma occurred, also causing significant damage. (Algermissen, 1983, p. 80) Today, there is probably no state organization of structural engineers outside California as active in the earthquake engineering field as the Structural Engineers Association of Washington. Earthquake-resistant construction is demonstrably a valid concern in Washington and Oregon: In a recent ranking of the projected average annual earthquake property loss of major US cities, there are two cities outside California that make the "top ten:" Seattle and Portland. (FEMA, 2000, p. 18)

The largest earthquake recorded to date by seismologists is the 1960 Chile Earthquake, which had a moment magnitude, Mw, of 9.5. Its energy release was about equal to the sum of a century's worth of earthquakes worldwide. Similar subduction of the Pacific seafloor beneath the North American plate offshore of Oregon, Washington, and Britsh Columbia is the cause behind the feared magnitude 9 Pacific Northwest earthquake in the class of the large Cascadia Subduction Earthquake that occurred January 26, 1700. That event in 1700 Library Damage after the Puget Sound Earthquake of 1949 source: Steinbrugge Collection, EERC-NISEE is not "historic" with reference to the United States, because it predates written records on the West Coast, but it was well chronicled in Japan, where it was observed in the form of a tsunami. The size and date of the 1700 Cascadia Earthquake was cleverly reconstructed by noting the arrival time and size of the tsunami in Japan, and then deducing the origin from where the tsunami must have come and the approximate size of the earthquake. Geologic studies have found corroborating evidence of a sudden change in elevation of the Washington coast at about that time. When the style of faulting causes vertical offset, as in a subduction earthquake, tsunamis are generated, whereas strike-slip movement as when the San Andreas ruptures (a portion of which extends offshore of California) does not vertically displace the water and cause a seismic sea wave. Horizontally shearing the floor under the water causes no significant wave, whereas lifting the floor, and lifting the relatively incompressible column of water resting on it, causes a bulge in the ocean's surface, and gravity charges that mass with tremendous energy as the bulge flattens out.

While a magnitude 8 or 9 earthquake is a frightening prospect and would cause significant ground motion and damage over a very wide area, as well as tsunami waves in the case of a Cascadia subduction zone earthquake, from an engineering standpoint the worst motion an individual structure will experience may be the smaller earthquake that is closer to the site. Another damage- reducing factor is that deep earthquakes do not usually have aftershocks. One analysis of the level of shaking that could be expected in the urbanized areas of the Puget Sound from a magnitude 8.5 Cascadia earthquake found that attenuation reduced this shaking to the point that it was not more severe than already assumed by the building code for smaller but closer earthquakes. "The fact that the UBC spectra are generally greater than the predicted spectra is somewhat reassuring from the standpoint of design. However, it should be noted that the long duration of strong shaking expected from these great earthquakes may also need to be considered in the seismic design, especially if the structure is susceptible to degradation over prolonged cyclic loading." (Krause, 1991, p. 230)

1949 Puget Sound Earthquake The Pacific Coast from Oregon north to Washington, British Columbia, and along Alaska's southern coast, is a major subduction zone where the seafloor collides in slow-motion with the continental plate and plunges beneath it. The often large magnitude of subduction earthquakes is somewhat offset by CUREE their large depth, which was about 70 km (40 miles) in the case of the 1949 Puget Sound Earthquake. 2001

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9 The August 17, 1959 Hebgen Lake Earthquake was not the first time Montana figured in the story of earthquake engineering developments in the United States. The first accelerograph in the country was installed there in 1932, and the first Coast and Geodetic Survey model of this instrument was called the "Montana seismograph."

We typically equate “earthquake disaster” with “urban earthquake disaster.” Property damage and injuries are the two main scales used to measure an earthquake’s destruction. We assume that unless we have a significant inventory of construction in the region affected by the shaking, an earthquake can’t have a significant effect.

The Hebgen Lake Earthquake (Ms 7.1, with four aftershocks over magnitude 6—Algermissen, 1983, p. 56) illustrates the environmental impact an earthquake can have, and also demonstrates that it is possible for an earthquake to be dangerous by its direct geologic impact even in the absence of vulnerable construction.

Landslides caused most of the 28 fatalities, 19 of which were caused by the Madison Canyon slide that had a volume of 33 million cubic meters (43 million cubic yards) and which instantly dammed the Madison River, creating a lake over 50 meters deep with a volume of 400 million cubic meters (324,000 acre feet). Ground motion, liquefaction, settlement, and surface rupture are aspects of the earthquake phenomenon that have often received more research attention than earthquake-induced landslides, but slides, as demonstrated by the 1959 earthquake, can be devastating on a huge scale. Other effects included surface displacement along the normal (vertical offset) fault -- instant cliffs -- almost 7 meters (21 feet) high, and forests were also extensively damaged. (Steinbrugge, 1982, p. 325)

Looking at the seismic hazard maps in the NEHRP Provisions (BSSC, 1998), the top of the scale for the violence of the shaking that can be expected with a given probability is attained only in a few areas of the United States, and the region where Montana, Idaho, and Wyoming are contiguous--the Yellowstone regon where the Hebgen Lake Earthquake occurred--is one of those few.

The 1959 earthquake is an early case where the vagaries of ground motion were pointed out. Log cabins with unreinforced masonry chimneys a few steps from the fault scarp that was 5 or 6 meters (15 or 20 feet) high were Hebgen Lake Earthquake Fault Scarp virtually unscathed. "It is not reasonable to conclude that all earthquakes will show similar damage patterns for similar earthquake magnitudes and similar geologic phenomena." (Steinbrugge, 1982, p. 325) After the Immediately after the August 17 earthquake, a family left their motel and next large earthquake in the interior of the West, the Ms 7.3 Borah Peak Earthquake, it was also noted that drove 500 feet on Highway 191, at which point they encountered a scarp standard attenuation relationships poorly predicted the severity of shaking at some locales. (Jackson and that wasn't there before. There were no serious injuries. Boatwright, 1985, p. 67) source: I. J. Witkind, National Geophysical Data Center Collection

In terms of expected annualized losses in the future, because of its low amount of construction exposed to the risk, Montana ranks 22nd among the states; but because of its high seismicity and small amount of development, when one considers the ratio of annualized loss to the value of the inventory at risk, Montana ranks eighth. (FEMA, 2000, p. 15) 1959 Hebgen Lake Earthquake The 1925 and 1935 Helena, Montana Earthquakes were well-known in their time and helped, along with the 1925 Santa Barbara and 1933 Long Beach Earthquakes in California, in generating support for the new earthquake engineering field. The large 1959 Hebgen Lake Earthquake that occurred in a largely unpopulated area of the state demonstrated the dramatic environmental effects an earth- CUREE quake can have. 2001

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10 The Prince William Sound Earthquake is an alternative seismological name for this earthquake, which indicates that the source was located offshore of the state’s southern coast. The size of the portion of the Earth’s crust (about 200,000 square kilometers), which displaced up to about six meters, makes this a truly great earthquake, and also generated the tsunami waves that accounted for 119 of the 131 fatalities caused by the earthquake . (Spaeth and Berkman, 1972, p. 39) Because the moment magnitude scale is computed from the product of the amount of displacement of the faulting and the surface area along that rupture plane, along with the rigidity of the rock, it is especially suited for measuring the impressive tectonic work done by such a huge earthquake. Whereas its magnitude computed from surface waves recorded by seismographs is 8.4 (Algermissen, 1983, p. 89), the Mw of the 1964 Alaska earthquake is 9.2. (Kanamori, 1977) It is true in earthquake disasters as in real estate that “location is everything.” While the largest of all earthquakes occur in subduction zones, fortunately they are often located beneath the seafloor far from human habitation. A case in point is the pair of earthquakes in Japan in 1923 (Tokyo) and the similar sized (M 8.3) 1933 Sanriku Earthquake: The 1923 Tokyo Earthquake was located closer to shore and the vibrations reached heavily urbanized sites with less attenuation, and the life loss was approximately 30 times greater than in the 1933 earthquake.

Like the great (Mw 9.3) 1960 Chile Earthquake, not a single strong motion record was retrieved from the March 28, 1964 Alaska Earthquake, due to the absence of strong motion seismographs. Year by year, the globe is being covered with an ever denser array of instruments that record strong, nearby ground motions as well as instruments designed to sensitively detect the faint motion from distant earthquakes, and new instrumentation technology is now producing devices that will accomplish both Elmendorf Air Force Base, near Anchorage tasks. source: Steinbrugge Collection, EERC-NISEE The multi-volume work by natural scientists, social scientists, and engineers published by the National Academy of Sciences (NAS, 1968-1973) was, as its foreword indicates, "perhaps the most comprehensive and detailed account of an earthquake yet compiled," including entire volumes devoted to subjects such as biology and human ecology, in addition to the Earth sciences and engineering subjects. Documentation of engineering aspects was the most thorough for a US earthquake up to that time, although it was not the first in-depth engineering study of a US earthquake along modern lines, for that honor goes to the report by Steinbrugge and Moran (1954) on the 1952 Mt. McKinley Building Kern County Earthquakes. Nonstructural damage was studied in detail for the first time in the 1964 earthquake. (Marx, Sun, and Brown, 1973) source: Steinbrugge Collection, EERC-NISE

The most lasting effect of the earthquake was on public policy. The Earth scientists were first to capitalize on the earthquake to scope out long-term multi-million-dollar research plans, followed by the engineers, (Wallace, 1999, p. 53 ff.) with the Press report (Press et al., 1965) and Housner report (Housner et al., 1969) respectively, being landmarks in those efforts. Integrated across disciplines and refined as policy initiatives, these earlier initiatives were given momentum by the Steinbrugge report (Steinbrugge et al., 1970) and then were given a further boost by the 1971 San Fernando Earthquake. The 1977 Earthquake Hazards Reduction Act thus traces its genealogy to developments that extend back to the 1964 Alaska Earthquake.

1964 Alaska Earthquake This was merely one of the dozen magnitude 8 or greater earthquakes to occur in Alaska in the twentieth century, though its proximity to Anchorage and nearby coastal towns caused this event to be the most damaging. Of wider impact was the fact that the 1964 earthquake was the subject of unusually comprehensive post-earthquake studies and also influenced the establishment of a CUREE national earthquake research and hazard reduction program in the United States. 2001

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11 The first major event in the history of American seismic codes was the 1933 Long Beach Earthquake. From then until the February 9, 1971 San Fernando Earthquake, there were significant developments, notably the increasing inclusion of dynamic considerations such as were introduced in 1951 in “Separate 66,” a special ASCE Transactions publication (ASCE, 1951) and in 1960 in the first SEAOC "Blue Book." (SEAOC, 1960) However, with the perspective of several decades of hindsight, 1971 stands out as the next major event after 1933.

It is no coincidence that California’s Hospital Seismic Safety Act (Senate Bill #519) was passed in 1972, shortly after this earthquake, or that the Veterans Administration, which suffered the collapse of two buildings at the Sylmar VA Hospital, enacted similar regulations, both of which aimed at protecting the functioning of a hospital after the earthquake as well as providing for occupant safety during an earthquake. The brand new Olive View Hospital main building owned by Los Angeles County was so badly damaged—three or its four exterior stair towers were completely leveled the way loggers fell trees, the lower story columns were spectacularly fractured, and there was up to about 750 mm (30 in) of permanent displacement—that it was subsequently demolished. By our contemporary standards, the 1970s post-earthquake analysis of the building still seems advanced: Accurate conclusions were drawn concerning: the need for ductility in column and joint reinforcement by means of improved confinement and bar splices; the hazards and operational consequences of nonstructural damage; the dangers of using a soft story (discontinuous shearwall configuration); the inadequacy of elastic analysis in explaining the structural failures and the desirability of inelastic analyses; and the need to pay special attention to near- fault ground motion: "Careful consideration should be given to the design of structures located close to potential earthquake faults, since severe, long- duration acceleration pulses may be associated with the faulting process." Analysis of Olive View Hospital (Mahin, Bertero, Chopra, and Collins, 1976, p. 119) source: Mahin et al., 1976, p.238

A steadily growing number of ground motion records had been compiled prior to 1971, but in most cases, these were literally records of the the motion of the ground. San Fernando was the first signficant earthquake that produced a number of records of structural response, Recorded (solid line) Vs. Calculated (dotted typically mid-height and roof records to complement basement or free-field data. By the 1970s, engineering analytical and computer line) Response, KB Valley Center capabilities had matured to allow efficient dynamic analyses to be run to compare observed and predicted response. Putting the newly source: William Gates, 1973, p. 462 available data collected from structures together with the ability to conduct dynamic analyses resulted in the ability to compare predicted and observed response, and now this type of research is routinely conducted after earthquakes to refine analytical methods and understanding the destructive content of motions.

Dam safety benefitted greatly from this earthquake. Liquefaction within the earthfill Lower San Fernando Dam caused the top to slump down about 10 meters, but because the reservoir was not full, the dam ended up about a meter short of overtopping and did not flood the urban area downstream where 80,000 people lived. San Fernando was the first US earthquake to cause bridge collapses. The reason is probably that earthquakes in earlier eras had tested shorter span highway bridges that had more conservative designs, especially with regard to their configuration. Since 1971, boosted by further damage in the 1989 Loma Prieta Earthquake, the state’s highway department, Caltrans, and the Federal Highway Administration, have devoted significant attention to bridge retrofit methods and new design procedures. 1971 San Fernando Earthquake This earthquake has personal meaning for many of the senior leaders of the earthquake engineering field in the USA: More than any other earthquake, this was the “textbook” from which they learned as they entered the earthquake engineering field. It is also remembered for making ductility a major theme in seismic codes, establishing hospital seismic safety as a mandatory goal, and for making dams and highway bridges major priorities, and as the first earthquake to generated a large number 2001 CUREE of structural response records. CONSORTIUM of UNIVERSITIES for RESEARCH in EARTHQUAKE ENGINEERING

12 The Loma Prieta Earthquake on October 17, 1989 featured damage to two major bridges: The San Francisco-Oakland Bay Bridge, and the double-decker Cypress Viaduct in Oakland. Scenario studies of even larger earthquakes in the Bay Area had previously concluded that the San Francisco-Oakland Bay Bridge would perform adequately but that perhaps approaches on the soft ground at either end might have damage. (Algermissen et al., 1972) The fall of a fifty-foot section of the upper deck of the bridge onto the lower deck thus came as an engineering surprise, and caused major transportation disruption for a month until emergency repairs could be made to re-open the bridge. Over a decade later, the bridge has been retrofitted to only a minor degree, and the replacement bridge for the eastern crossing of the Bay has just cleared the stage of political negotiations and environmental impact debate. The project is in its initial construction phase. The retrofit (or isolation-plus-retrofit) projects of several other major bridges in California are also at preliminary stages. Perhaps this progress has been too slow, but it has taken great efforts on the part of advocates of seismic safety to move these efforts up to this point.

The collapse of the Cypress Viaduct resulted in 41 fatalities, four fifths of the total for the earthquake, which helped maintain the momentum toward greater bridge safety that originated in the 1971 San Fernando Earthquake. (Governor's Board of Inquiry, 1990) State funding for bridge retrofits increased to $300 million per year and the research budget from $0.5 to $5 million, and in 1992 Federal law was revised to allow Federal highway bridge funds to be used for seismic retrofits. (Roberts, 1994, p. 165-167) The Northridge Earthquake six years later was to show that this pace was not sufficient to prevent further bridge collapses, because retrofits had not been implemented quickly enough, though the performance of new bridges and recent retrofits gave engineers confidence their solutions worked. (Seible, 1998, p. III-44). Knowing that bridges are vulnerable and how to fix them, and actually obtaining the funds and putting in place the needed construction projects, are two different things.

Seismologists advanced theories based on the cross-section of affected region to explain the bouncing or focusing of the vibrations of the Collapse of Bay Bridge upper deck span earthquake as they moved away from the source, under the Santa Cruz source: Caltrans Mountains, toward the heart of the urban region to the north. (Somerville and Yoshimura, 1990) Channeling of waves in particular azimuthal directions corresponding the "geologic grain" of the region was also suggested. (Campbell, 1991). At large distances from the source, Collapse of Struve Slough Bridge in the Marina district of San Francisco and where the Cypress structure collapsed in Oakland, local soils amplification effects were noted. source: Robert Reitherman (Benuska, ed., 1990, p. 65-66) The simple attenuation relationship that predicts a fall off of motion with distance would not predict the higher levels of motion at large distances in this earthquake.

The Loma Prieta Earthquake, like the more destructive Northridge Earthquake that occurred five years later, was generated from the fringe of an urbanized area, only more so. “Loma Prieta,” or “dark hill” in Spanish, is the name seismologists gave this earthquake on the San Andreas Fault because the epicenter was located near the promontory in the Santa Cruz Mountains with this name. The area is as scenic as it is sparsely populated. While a loss estimated at up to about $10 billion (Olson and Pantelic, 1990, p. 394) is not minor, on the scale of the value exposed to this earthquake of Mw 7 or Ms 7.1 (Hanks and Krawinkler, 1991, p. 1415) the loss was a small proportion.

1989 Loma Prieta Earthquake The San Francisco Bay Area hadn’t had a major earthquake since the 1906 disaster. (It also had never had both its major league baseball teams, the San Francisco Giants and the Oakland A’s, in the World Series.) The Loma Prieta Earthquake's damage to highway bridges was prominent. Also notable was the spotty pattern of ground motion: The severity of shaking did not uniformly attenuate with distance from the source. As important as CUREE distance were local soils and the particular travel paths of the seismc waves. 2001 CONSORTIUM of UNIVERSITIES for RESEARCH in EARTHQUAKE ENGINEERING

13 Earthquake engineers frequently generalized prior to the Northridge Earthquake of January 17, 1994 that of the four basic kinds of construction--concrete, masonry, steel, and wood--the first two had experienced major failures in earthquakes while the last two were almost inherently very earthquake-resistant because of their material properties and the types of systems employed. The masonry industry was delivered a blunt message by the Long Beach Eartquake of 1933 that an earthquake-resistant type of brick and block construction had to be developed. The concrete industry, especially after the 1971 San Fernando Earthquake, similarly had to react to negative performance and develop a stronger and more ductile kind of construction. Perhaps complacency had gradually developed with regard to steel and wood buildings, a condition that the Northridge Earthquake was to change.

"Starting in the 1960s, engineers began to regard welded steel moment-frame buildings as being among the most ductile systems contained in the building code. Many engineers believed that steel moment-frame buildings were essentially invulnerable to earthquake-induced structural damage and thought that should such damage occur, it would be limited to ductile yielding of members and connections....The Northridge earthquake of January 17, 1994 challenged this paradigm." (SAC, 2000, p. 1-3) The SAC Joint Venture was formed and received approximately $10 million in FEMA funding to quickly mount a focused testing and analysis effort. That six-year project was molded by practicing engineers and code officials and their needs for specific guidance on the evaluation of existing buildings and the design and construction of new ones.

The other kind of construction presumptively given a high grade on its "seismic report card" by engineers prior to the Northridge Earthquake was light woodframe ("two-by- four") construction, by far the most common construction type in the USA. In Los Angeles County, for example, 96% of all buildings are of woodframe construction, and the "general fraction of wood structures to total structures seems to be between 80% and 90% in all regions of the US, for example being 89% in Memphis, Tennessee and 87% in Wichita, One of 15 Hillside Houses Collapsed or Kansas." (Malik, 1995) In the Northridge Earthquake, about $20 billion, half the total That Were Severely Damaged and Immediately property loss in the disaster to all kinds of construction, was suffered by dwellings of Demolished After the Earthquake woodframe construction (Kircher et al., 1997, p. 714) Of the 10,193 buildings posted as source: Los Angeles Times red (unsafe) or yellow (limited entry) by building departments after the Northridge Earthquake, 91% were of woodframe construction. (Holmes and Somers, ed., 1996, p. 15) Of the 25 fatalities that occurred because of building damage in that earthquake, all but one were in damaged or collapsed woodframe buildings. ( In fairness to the wood buildings, it should be noted that they were not the only kinds of buildings to be damaged, for example some very large concrete parking structures completely collapsed.) The surprising amount of damage to woodframe buildings led to the formation of the FEMA-funded CUREE-Caltech Woodframe Project. Applied research (testing, analysis, investigations of Northridge Earthquake damage) has been mated with the involvement of practicing engineers to develop improved codes and design procedures. An economic aspects branch aims at improving loss estimation, cost-effectiveness analysis, and the risk assessment and perception basis of insurance. An extensive outreach effort has as its audience not only engineers but a broader spectrum including contractors and the general public. Collapsed Garage As occurred after the 1964 Alaska Earthquake (NAS, 1968-1973) and then the 1971 San Fernando Earthquake (NOAA, 1973) a comprehensive series source: Robert Reitherman of papers on the event was published, including social science, engineering, and Earth sciences aspects (CUREE, 1998) 1994 Northridge Earthquake Today's leaders of the earthquake engineering field in the United States began their careers when the 1971 San Fernando Earthquake was the key event that provided a comprehensive set of examples and data from which to learn. The generation of earthquake engineers who are now at early stages in their careers have a similar primer of more recent vintage to guide their studies: The 1994 CUREE Northridge Earthquake. 2001 CONSORTIUM of UNIVERSITIES for RESEARCH in EARTHQUAKE ENGINEERING

14 References Cited Algermissen, S. T. et al., 1972. A Study of Earthquake Losses in the San Francisco Bay Area. Frankel, Arthur, et al., 1996. National Seismic Hazard Maps, June 1996 Documentation. Washington, DC: National Oceanic and Atmospheric Administration. Denver, CO: US Geological Survey. Algermissen, S. T. et al., 1973. A Study of Earthquake Losses in the Los Angeles, California Freeman, John Ripley, 1932. Earthquake Damage and Earthquake Insurance. New York: Area. Washington, DC: National Oceanic and Atmospheric Administration. McGraw-Hill. Algermissen, S. T., 1983. An Introduction to the Seismicity of the United States. Oakland, Fuller, Myron L., 1912. The New Madrid Earthquake. USGS Bulletin 494. CA: Earthquake Engineering Research Institute. Gates, William, 1973. “KB Valley Center,” San Fernando, California, Earthquake of February Arnold, Christopher and Robert Reitherman, 1982. Building Configuration and Seismic 9, 1971, vol. IB. Washington, DC: National Oceanic and Atmospheric Administration. Design. New York: John Wiley and Sons. Ganse, Robert and John Nelson, 1981. Catalog of Significant Earthquakes, 2000 BC – 1979. ASCE, 1951. “Lateral Forces of Earthquake and Wind,” Transactions, vol. 77, April 1951, Boulder, Colorado: National Oceanic and Atmospheric Administration. later published as “Separate 66” as a separate booklet by ASCE. Geschwind, Carl-Henry, 1996. Earthquakes and Their Interpretation: The Campaign for Ayres, J. Marx, Tseng-Yao Sun, and Frederick R. Brown, “Nonstructural Damage to Buildings,” Seismic Safety in California, 1906-1933. Johns Hopkins University PhD thesis. Engineering volume in The Great Alaska Earthquake of 1964. Washington, DC: National Governor’s Board of Inquiry on the 1989 Loma Prieta Earthquake, 1990. Competing Against Academy of Sciences. Time. Panel chaired by George Housner; report edited by Charles Thiel. Sacramento, Benuska, Lee, ed., 1990. Loma Prieta Earthquake Reconnaissance Report. Spectra, California: Department of General Services. Supplement to Vol. 6, May 1990. Hanks, Thomas C. and Helmut Krawinkler, 1991. “The 1989 Loma Prieta Earthquake and its Blume, John, 1979. “On Instrumental Versus Effective Acceleration and Design Coefficients,” Effects: Introduction to the Special Issue,” Bulletin of the Seismological Society of Proc. of the Second US National Conference on Earthquake Engineering. America, vol. 81, no. 5, October 1991. Bolt, Bruce, 1978. Earthquakes: A Primer. San Francisco: W. H. Freeman. Hansen, Gladys, Emmet Condit, and David Fowler, 1989. Denial of Disaster. San Francisco: Brune, James N. and Abdolrasool Anooshehpoor, 1991. “Foam Rubber Modeling of the El Cameron and Co. Centro Terminal Substation Building,” Spectra, vol. 7, no. 1, February 1991. Heck, H. H., H. E. McComb, and F. P. Ulrich, 1936. “Strong-Motoin Program and Tiltmeters,” California Office of Emergency Services and EQE, 1997. 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Housner, George, 1941. “Calculating the Response of an Oscillator to Arbitrary Ground of the NEHRP Conference and Workshop on Research on the Northridge, California Motion,” Bulletin of the Seismological Society of America, vol. 31, 1941, p. 143-149. Earthquake of January 17, 1994. Richmond, California: CUREE (formerly California Housner, George, et al., 1969. Earthquake Engineering Research. Washington, DC: National Universities for Research in Earthquake Engineering). Academy of Science. Douty, Christopher Morris, 1977. The Economics of Local Disasters. New York: Arno Housner, George and Paul Jennings, 1982. Earthquake Design Criteria. Oakland, CA: Press. Earthquake Engineering Research Institute. Dutton, Clarence E., 1889. The Charleston Earthquake of August 31, 1886, in the Ninth Jackson, Suzette M. and John Boatwright, 1985. “The Borah Peak, Idaho Earthquake of Annual Report of the United States Geological Survey, 1887-’88. October 28, 1983 – Strong Ground Motion,” Spectra, vol. 2, no. 1, Nov.,1985. EERI Investigation Committee, 1973. “Sylmar Industrial Tract,” San Fernando, California, Joint Committee on Seismic Safety, 1974. Appendix B, “History of Earthquake Code Earthquake of February 9, 1971, vol. I, part A. Provisions,” Meeting the Earthquake Challenge: Final Report to the Legislature. FEMA (Federal Emergency Management Agency), 2000. HAZUS 99 Estimated Annualized Sacramento, CA: California Legislature. Earthquake Losses for the United States. FEMA Publication 366. Kanamori, H., 1977. “The Energy Release in Great Earthquakes.” Journal of Geophysical Research, vol. 82, p. 2981-2987.

15 Kircher, Charles et al., 1997. “Estimation of Earthquake Losses to Buildings,” Spectra, Rubey, William W., 1969. “Introduction,” 1969 reprint by Carnegie Institution, Washington, vol. 13, no. 4, November, 1997. DC, of A. C. Lawson, ed., 1908, The California Earthquake of April 18, 1906. Krause, C.B., 1991. “Ground-Motion Attenuation Equations for Earthquakes on the Cascadia SAC, 2000. Recommended Seismic Design Criteria for New Steel Moment-Frame Buildings.. Subduction Zone.” Spectra, vol. 7, no. 2, May 1991. FEMA 350. Washington, DC: Federal Emergency Management Agency. Companion volumes also published in 2000 by FEMA were Lawson, A. C., ed., 1908. The California Earthquake of April 18, 1906, vol. II, p. 16 ff. Recommended Seismic Evaluation and Washington, DC: Carnegie Institution; reprinted 1969. Upgrade Criteria for Existing Welded Steel Moment-Frame Buildings (FEMA 351), Recommended Post-earthquake Evaluation and Repair Criteria for Welded Steel Leyendecker, Edgar V., R. Joe Hunt, Arthur D. Frankel, and Kenneth S. Rukstales, 2000. Moment-Frame Buildings (FEMA 352), and Recommended Specifications and Quality “Development of Maximum Considered Earthquake Ground Motion Maps,” Spectra, Assurance Guidelines for Steel Moment-Frame Construction for Seismic Applications vol. 16, no. 1, February 2000. (FEMA 353). The SAC Joint Venture partners are Structural Engineers Association of Mahin, Stephen, V. V. Bertero, Anil Chopra, and R. G. Collins, 1976. Response of the Olive California, Applied Technology Council, and California (now “Consortium of”) View Hospital Main Building During the San Fernando Earthquake. University of Universities for Research in Earthquake Engineering. California at Berkeley Earthquake Engineering Research Center. SEAOC (Structural Engineers Association of California), 1960. Recommended Lateral Malik, A. M., 1995. Estimating Building Stocks for Earthquake Mitigation and Recovery Force Requirements and Commentary. San Francisco: SEAOC. Planning. Cornell Institute for Social and Economic Research. Seible, Frieder, 1992. “Research Overview: Highway Bridges and Transportation Systems,” Mallet, Robert, 1862. Great Neapolitan Earthquake of 1857: The First Principles of Proc. of the NEHRP Conference and Workshop on Research on the Northridge, Observational Seismology. London: Chapman and Hall. California Earthquake of January 17, 1994, vol. III-A. Richmond, CA: California (now Consortium of) Universities for Research in Earthquake Engineering. NAS (National Academy of Sciences), 1968-1973. The Great Alaska Earthquake of 1964. Volumes of the following titles with year of publication: Hydrology (1968), Human Smith, Gretchen, and Robert Reitherman, 1984. “Damage to Unreinforced Masonry Ecology (1970), Geology (1971), Biology (1971), Seismology and Geodesy (1972), Buildings at Stanford University in the 1906 San Francisco Earthquake.” Redwood Oceanography and Coastal Engineering (1972), Engineering (1973), and Summary City, CA: Scientific Service, Inc. and Recommendations (1973). Washington, DC: National Academy of Sciences. Somerville, Paul, and J. Yoshimura, 1990. “The influence of critical MOHO Reflections on NOAA (National Oceanic and Atmospheric Administration), 1973. San Fernando, strong ground motions recorded in San Francisco and Oakland during the 1989 Loma California, Earthquake of February 9, 1971. Washington, DC: NOAA, 4 volumes. Prieta Earthquake.” Geophysical Research Letters, vol. 17, p. 1203-1206. Nordenson, Guy J. and Glenn R. Bell, 2000. “Seismic Design Requirements for Regions in Spaeth, Mark G. and Saul C. Berkman, 1972. “The Tsunamis as Recorded at Tide Stations Moderate Seismicity,” Spectra, vol. 16, no. 1, February 2000. and the Seismic Sea Wave Warning System,” The Great Alaska Earthquake of 1964, Oceanography and Coastal Engineering vol.. Washington, DC: NAS. Nuttli, Otto W., 1973. “The Mississippi Valley Earthquakes of 1811 and 1812: Intensities, Ground Motion and Magnitudes,” Bulletin of the Seismological Society of America, Steinbrugge, Karl V. and Donald F. Moran, 1954. “An Engineering Study of the Southern vol. 63, no. 1, pp. 227-248, February 1973. California Earthquake of July 21, 1952 and Its Aftershocks.” Bulletin of the Seismological Society of America, vol. 44, no. 2B, April 1954. Olson, Robert and Jelena Pantelic, 1990. “Socioeconomic Impacts and Emergency Response,” Loma Prieta Earthquake Reconnaissance Report, supplement to vol. 6, Steinbrugge, Karl V. et al., Task Force on Earthquake Hazard Reduction, 1970. Earthquake Spectra, May, 1990. Hazard Reduction. Washington, DC: Executive Office of the President. Press, Frank et al., Ad Hoc Panel on Earthquake Prediction, 1965. Earthquake Prediction: Steinbrugge, Karl V., et al., 1981. Metropolitan San Francisco and Los Angeles Earthquake A Proposal for a Ten-Year Program of Research. Washington, DC: Office of Science Loss Studies: 1980 Assessment. USGS Open-File Report 81-113. and Technology. Steinbrugge, Karl V., 1982. Earthquakes, Volcanoes, and Tsunamis: An Anatomy of Hazards. Reid, Hugo Fielding, 1908. “Permanent Displacements of the Grounds,” in A. C. Lawson, New York: Skandia America Group. ed., The California Earthquake of April 18, 1906, vol. II, p. 16 ff. Washington, DC: Wallace, Robert E., 1999. Connections: Robert E. Wallace. Stanley Scott, interviewer. Carnegie Institution, 1908; reprinted 1969. Oakland, California: Earthquake Engineering Research Institute. RMS, Inc., 1995. What If A Major Earthquake Strikes the Los Angeles Area? Menlo Park, Wilford, John Noble, 1981. The Mapmakers. New York: Alfred A. Knopf. California: RMS, Inc. Roberts, James, 1994. “Highway Bridges.” Practical Lessons from the Loma Prieta Earthquake. Washington, DC: National Academy Press.