Shortly after the quake in 1908, the exhaustive Lawson Report was released. Chaired by Andrew Lawson of the University of California-Berkeley, the report (The California Earthquake of April 18, 1906: Report of the State Earthquake Investigation Commission: Carnegie Institution of Washington Publication 87, 2 vols.) broke much new ground in seismology. In the report the elastic-rebound model described the horizontal nature of the faulting and the response of soft mud and landfill, as compared to sand/gravel, and bedrock bases was mapped. (see: http://earthquake.usgs.gov/regional/nca/1906/ )

Some with financial and political interests looked ahead from their 1906 vantage point with the fear that San Francisco would be forever tainted by the earthquake. For instance, after the great 1871 fire in Chicago, the city was rebuilt and fire-fighting capabilities improved. But what do you do with an earthquake threat? The region around San Francisco had major quakes in 1838 and 1868 and no one knew what was "under" the horizon. As a result, those with vested interests made the deliberate decision to put up a smokescreen and talk of the great San Francisco Fire as the primary event in 1906. For years it was called "the great fire" and the death count and destruction in dollars for the 1906 quake were underreported, at 700 dead and $250 million in damage. A century of growth and progress ensued?landfill replaced about half of the surface area of San Francisco Bay to create new real estate, building height restrictions were waved, and growth crawled across known fault zones.

Decades later, the region was hit by the Loma Prieta quake, just before the start of the third game of the 1989 Baseball World Series. At 5:04 p.m. (PDT), as the players warmed up and sportscasters exercised their voices, a magnitude 7.0 quake rocked the region and Candlestick Park. Areas of landfill around the bay, mapped in the 1908 Lawson Report, failed. The soft muds under a two kilometer portion of the Route 880 Cypress freeway structure collapsed killing fortytwo people and a section of the critical San Francisco-Oakland Bay Bridge fell, adding to the combined total damage of $8 billion across the region. Overall, sixty-seven people died in the region.

So what does the future hold for this most cosmopolitan of U.S. cities? With seven major fault lines across the San Francisco region, any quake forecast must consider the duration, strength, soil types, and building designs affected. In 2005 the USGS estimated for the Bay Area a 25% probability of a major quake, magnitude 7.0 or greater, in the next twenty years (see: http://quake.usgs.gov/research/seismology/wg02/ ).

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