The 1906 San Francisco earthquake and subsequent four days of fire were shocking events that brought about revolutionary changes in earthquake science in the United States, which at the time lagged behind Europe and Japan.

Prior to 1906, state and city officials frequently dismissed calls from scientists who wished to conduct earthquake research, fearing that focusing on the potentially hazardous problem would be politically and economically damaging to the region.

After the Hayward Fault in central California slipped in 1868, there was wide destruction from San Francisco to San Jose. But a committee formed by the city to examine what caused the earthquake never amounted to anything.

"There is the allegation that it was suppressed by the business community in order to save the reputation of San Francisco as being an earthquake-prone place," said Stephen Tobriner, a professor of architectural history at the University of California at Berkeley.

That all changed when early in the morning on April 18, 1906, a 7.9 magnitude earthquake occurred.

The quake rocked the city for nearly a minute, and was felt from southern Oregon to south of Los Angeles and inland to parts of Nevada. Fires broke out and San Francisco was largely destroyed, with over 28,000 buildings in ruin. Over 3,000 people were killed, and about 225,000 people from a population of about 400,000 were left homeless.

With officials unprepared for such an event, rampant looting took place, and police issued a shoot-to-kill order. All accounts evidence a chaotic event much like the flooding of New Orleans following Hurricane Katrina in August and September 2005.

The scope of the disaster was quickly felt in political circles. Three days after the earthquake, Gov. George Pardee ordered an investigation into earthquakes in California to be run by a commission of geology experts. The commission was led by Andrew Lawson, chairman of the geology department at the University of California at Berkeley, and included professors from Stanford University, the Chabot Observatory in Oakland and Johns Hopkins University.

The resulting Lawson report, published in 1908, was the first integrated, government-commissioned earthquake investigation in the United States and perhaps the most significant and important study of earthquakes in the 20th century.

"To this day, the report remains a document of the highest regard among seismologists, geologists and engineers -- a benchmark for future, integrated investigations into the effects of earthquakes in the U.S.," wrote Paul Reasonberg of the U.S. Geological Survey.

Scientists who studied earthquakes in the 19th century knew that fault lines -- the lines between plates of the Earth's crust, or tectonic plates -- existed. But they failed to associate the fault lines with earthquakes.

A member of the Lawson Commission, Johns Hopkins professor H.F. Reid, made the crucial finding. Called the "theory of elastic rebound," the theory is still considered the underlying principle of earthquake science because it explains what causes earthquakes.

The elastic rebound theory says that plate motion in the Earth's crust accumulates energy just below the surface and elastically distorts the crust. When the crust can distort no more, it slips rapidly along a fault line and then returns to its undistorted state. This slip releases years of strain and generates seismic waves that produce shaking.

Making the connection between earthquakes and fault movements provided a blueprint for earthquake scientists for years to come.

"The elastic rebound hypothesis was one of the major contributions from the study of the 1906 earthquake," said Mary Lou Zoback, a senior research scientist at the U.S. Geological Survey. "It is still accepted today as a basis for seismic hazard assessment, despite that the basis for large-scale horizontal displacements wasn't established until the plate tectonic revolution six decades later."

The report also demonstrated the importance of observation. Before 1906, American scientists were aware of fault lines -- later discovered to be borders between tectonic plates. After 1906, the commission quickly went to work mapping the San Andreas Fault, which they suspected played a role in the disaster. Experts believe that this may have been the first time an entire fault line was mapped.

Researchers followed the fault south to San Bernadino, along hills of poison oak and small ponds, until the entire fault was mapped. As they tracked the fault, they noticed evidence of past movement, the result of 19th century earthquakes in Southern California.

"What was learned by scientists after 1906 really provides an underlying basis for modern earthquake study," Zoback said.

In the years following the earthquake, an academic movement grew out of the Lawson Commission's work.

Based in the bay area, the Seismological Society of America was founded in 1906 and by 1907 had, according to board minutes, "about 145 members."

There were also significant efforts to change the way the public thought about earthquakes. A written history of the organization posted on its Web site, noted that in a 1908 meeting "again the comments came up that newspapers try to suppress information on damage done by earthquakes as being 'unfavorable in a commercial way.'"

The historical account also mentions that "the point was made that the Society 'should strive in a dispassionate way to inform the public that the recurrence of earthquakes is inevitable but that with the observation of proper precautions (concerning which information should also be disseminated) except in very rare instances they need not greatly be feared.'"

By 1911, the Society had its own publication, the Bulletin, which was published by Stanford University Press. Lawson was one of the officers in change of publication.

The first course in seismology -- though its title was disguised -- appeared at the University of California at Berkeley in 1912.

"So many studies of earthquakes which were detrimental to the state's economic health had to be disguised or the people who undertook them were persuaded from doing it. And it took some time after 1906 for economic forces to be somewhat overthrown," said Phillip Fradkin, a journalist who has long covered earthquakes in California.

The gradual acceptance of uncontrollable forces of nature moved the architecture community in California to create some of the safest building standards in the world and enabled the scientific and health communities to explore innovative new forms of prediction and preparedness.

-- By James Yolles, Online NewsHour