San Francisco Earthquake

April 18 — 24, 1906

The Huge 1906 California Earthquake Triggers a Major Scientific Project

April 18 marks the 100th anniversary of what is generally called the Great San Francisco Earthquake of 1906. Although most attention at the time focussed on the destruction in San Francisco, the earthquake's range was actually much wider, and caused more severe earthquake damage in other places. The devastation in San Francisco was compounded by the firestorms which resulted from broken gas and electric lines, and there was no city water to fight the fires because of ruptured water pipes.

In the wake of the disaster, San Francisco's elected officials were shunted aside by the city's banking and business interests, who formed the "Committee of 50" to handle relief and rebuilding. San Francisco's mayor chaired the committee, but had very little power. The Committee, anxious to attract investment and immigrants to San Francisco, downplayed the role of the earthquake and instead emphasized the fire damage.

Daniel Burnham, the architect of the Lincoln Memorial and of many civic improvements in Washington and Chicago, had been asked several years before to draw up a plan for the revitalization of San Francisco. Ironically, printed copies of the plan were ready for distribution the morning the earthquake hit. But even with half the city destroyed, the Committee rejected the opportunity to build a better and safer city, and quickly bulldozed the fallen buildings, with their human remains inside, and used them for landfill. The landfill areas of the old city had liquefied when the earthquake hit, dropping them five or six feet lower. The Marina district of today's San Francisco is built on the landfill of 1906.

Immediately after the earthquake, Gov. George C. Pardee, an eye, ear and nose specialist who had previously served as Mayor of Oakland, brought a large staff from Sacramento and based them in the current Oakland Mayor's office. One by one, the telegraph operators in San Francisco had been forced by the raging fires to abandon their posts, and finally only the naval wireless radio station at Yerba Buena Island was left to send out messages on military frequencies, which were picked up and forwarded over civilian telegraph cables.

Governor Pardee set up a system of messengers between Oakland and San Francisco, and became the relay point between the devastated city and the outside world. Pardee coordinated the flow of money, goods and materials into the city, determining what was needed and how it could be moved to the earthquake victims.

On the day after the earthquake, the Governor received a telegram from Andrew Lawson, the Chairman of the Department of Geology at the University of California at Berkeley. A decade before, Lawson had mapped a section of the San Andreas Fault, which at that time was only visible in a small area. The telegram read: "The appointment of a scientific commission to investigate the earthquake in this state would have a beneficial effect upon the public mind." Two days later, on April 21, Pardee announced the names of eight members, including Lawson, of a "Committee of Inquiry," which soon became known as the State Earthquake Investigation Commission.

The members of the Commission served without pay, but its expenses were supposed to be paid by the state. However, due to the chaos caused by the earthquake, Lawson contacted the Carnegie Institution, which wound up paying most of the costs plus supporting the printing of the final report. Lawson recruited a talented group of scientists to serve on the Commission, and hundreds of other geologists, astronomers, biologists, engineers, and civilian observers contributed to the report. This was no dry-as-dust commission—its members were field people who had surveyed and mapped most of the American West.

For example, there was Grove Karl Gilbert, a geologist who had volunteered as a young man on the geological survey of Ohio. In 1871, he was appointed a member of the U.S. government survey west of the 100th meridian, led by Lt. G.M. Wheeler. On that survey, he studied the Rocky Mountains, the Grand Canyon, and the extinct Lake Bonneville of Nevada and Utah. From 1889-1892 Gilbert served as the chief geologist of the U.S. Geological Survey. Later, he went on to study the history of the Niagara River, the earth movements in the Great Lakes Region, and the giant meteor impact crater near Flagstaff, Ariz.

Gilbert, along with another geologist named F.E. Matthes, headed north from San Francisco to trace the path of the now well-known San Andreas Fault. Others followed the fault southward, and still others travelled eastward by rail, horse and buggy, or on foot to determine how far the effects of the earthquake had been felt. The object of the project, coordinated by Lawson, was to determine the extent of the earthquake's effects, the kind of damage it caused, the exact time that the shocks arrived in various locations, and where the epicenter was located.

The Napa and Sonoma Valleys to the north of San Francisco had been hit harder than San Francisco, with the town of Santa Rosa almost completely destroyed. The winery workers reported that when the earthquake hit, the grape vines and their arbors rose and fell as if gigantic ocean waves were crashing down the slopes. At the town of Olema, Gilbert found the most serious displacements of all. One road had been moved to the right by 21 feet, and groves of trees, fences, and farm lanes had been moved far from their original positions.

This led Gilbert to assume that he had found the epicenter of the quake, which turned out not to be the case, because the amount of movement in an earthquake also depends on the amount of rock underpinning the soil, the characteristics of the soil itself, and the slope of the land. Olema had crumbling rocks, soft soil, and well-watered slopes, which led to the greater damage.

Almost all of the earthquake investigators carried cameras to record the damage, and in addition they talked to the local residents about when they had felt the series of earthquake shocks. When the material was gathered, Andrew Lawson plotted all the notations on maps, showing how large or small the shocks were, and from what direction they came. Hanging lamps with pendant glass prisms, which were popular at the time, provided many people with the chance to note their pendulum-like motions during the quake, which in turn provided the scientists with valuable information.

There had been some cool-headed scientists who, not threatened with the immediate collapse of the buildings they were sleeping in, had awakened to the early-morning earthquake and grabbed pen and paper to record when the shocks occurred. That had been the case with Gilbert himself, as well as the head of the San Francisco Weather Bureau, a retired British astronomer, and six astronomers manning a California observatory.

Professor T.J.J. See, the director of the Mare Island Naval Observatory on San Pablo Bay, was able to provide quite precise earthquake-timing information on the first shock because several of the observatory's pendulum clocks had stopped when the quake hit because the pendulums had been knocked too far sideways. Because so many homes and businesses had pendulum clocks, this was a convenient way to determine when an area was hit by the shock. It was important to determine times in different areas, because that was the way to pin down the epicenter of the quake—the earliest times meant that those locations were nearest to the epicenter.

From the massive effort at documentation, Lawson was able to determine that the most northerly place where the earthquake was felt was Coquille, Oregon., and the most southerly place was Anaheim, California. To the east, it was felt as far as Winnemucca, Nevada. This determined an approximate circle of some 400,000 square miles, but the area of heavy damage was lozenge-shaped, with the long axis following the San Andreas Fault. The fault itself ran for approximately 750 miles, plunging underground near southern California's Salton Sea, an area with active geysers, hot springs, and mud volcanoes.

This area contained the answer to why the worst damage was north of the epicenter—the southern part of the fault was pulling apart, allowing liquid magma to escape and thus take off some of the pressure. But in the north, the fault was narrow and rubbed together constantly, with the western edge moving north approximately one-and-a-half inches a year. When the buildup of tension was released, the shock waves travelled at 7,000 miles per hour.

The study of the San Andreas Fault yielded some surprising results. Up to that time, most geologists had thought that internal pressures moved soil and rocks up and down, such as during the formation of mountain ranges; but now it was obvious that pressure could also move the Earth's surface horizontally. The San Andreas Fault was labelled a right-lateral strike-slip fault because if you look across it from either side, everything has moved to the right. The fault was formed by the meeting of the North American Tectonic Plate, whose eastern edge runs down the center of Iceland, with the Pacific Tectonic Plate, whose western edge reaches to the South Island of New Zealand. The San Andreas is now recognized as one of the fastest-moving faults in the world, and geologists refer to it as the SAF.

Andrew Lawson was able to encourage and prod his far-flung staff enough to enable him to begin to analyze the data in early 1907. Even then, he had to send out other investigators to duplicate some observations when it was obvious they were incomplete or flawed. The final report of the Earthquake Commission appeared in 1908, and a second volume in 1910 contained the elastic rebound theory of earthquakes which had been developed by Commission member Harry Fielding Reid of Johns Hopkins University.

The Commission's findings generally fell upon deaf ears. Business leaders told a Stanford University seismologist not to investigate earthquakes nor publish reports. But Lawson pressed on, and, in April of 1907, published a proposal for a Seismological Institute. One hundred fifty-one scientists endorsed it, but no support was forthcoming. But the report did lead to the founding of the Seismological Society of America, and its first "Bulletin" appeared in March 1911. Geologic maps of California did not indicate the San Andreas Fault until 1938.

The Earthquake Commission Report was not reprinted until 1969, but it is still considered a primary reference tool for scientists. A paper written in 1999 for the Geological Society of America cited the fact that there was almost nothing in modern earthquake science that did not owe its origin to the hard-travelling California Earthquake Commission.