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<\/a><\/p>\nSlippage along the San Andreas Fault in the Great 1906 earthquake:The total length is 296 miles. For comparison, the 1989 Loma Prieta earthquake had a rupture length of about 25 miles.<\/p>\n
The Great Earthquake<\/p>\n
120 years ago on April 18, 1906, the San Francisco earthquake (and subsequent fires) ranks as one of the most significant temblors of all time. At 5:12 a.m., a foreshock occurred with enough force to be felt widely throughout the San Francisco Bay Area. The great earthquake, measuring magnitude 7.9, came 20 seconds later and lasted 45 to 60 seconds.<\/p>\n
The earthquake of April 18, 1906, ranks as one of the most significant of all time. Today its importance comes more from the wealth of scientific knowledge derived from it than from its sheer size. Rupturing the northernmost 296 miles of the San Andreas Fault from northwest of San Juan Bautista to the triple junction at Cape Mendocino, the earthquake confounded contemporary geologists with its large, horizontal displacements and great rupture length. The significance of the fault and recognition of its large cumulative offset would not be fully appreciated until the advent of plate tectonics more than 50 years later.<\/p>\n
The initial jolt lasted about a minute, but the force released was powerful enough to buckle roadways and sidewalks, throw thousands of buildings off their foundations and break gas lines all over the city. The city\u2019s water mains broke too, making it even more difficult for San Francisco\u2019s 600 firefighters to save people and property.<\/p>\n
The fires burned most of Nob Hill where the railroad barons lived. They destroyed about 30 schools, City Hall, the opera house, the main library, police stations and a prison.<\/p>\n
Lessons in earthquake science<\/p>\n
The 1906 earthquake marked the dawn of modern scientific study of the San Andreas Fault system in California. Before 1906, earthquake research in the U.S. had advanced slowly compared to efforts in Japan and Europe. The first seismographs in the U.S. were installed in 1887 at the Lick Observatory on California\u2019s Mount Hamilton and at the University of California at Berkeley.<\/p>\n
Professor Andrew C. Lawson, chairman of the geology department at UC Berkeley, took the first steps that led to Gov. George C. Pardee\u2019s order, three days later, to appoint a State Earthquake Investigation Commission, which Professor Lawson headed. Scientists, including professors of geology and astronomy from Stanford University, the Lick Observatory, the Chabot Observatory in Oakland, the University of California, Johns Hopkins University and the U.S. Geological Survey served on the commission. It was the first integrated, government-commissioned scientific investigation into earthquakes in the U.S.<\/p>\n
Slippage along the San Andreas Fault in the Great 1906 earthquake:The total length is 296 miles. For comparison, the 1989 Loma Prieta earthquake had a rupture length of about 25 miles.<\/p>\n<\/a><\/p>\n