The California earthquake of April 18, 1906, ranks as one of the most significant earthquakes ever. Today, its importance comes more from the wealth of scientific knowledge derived from it than from its sheer size.
Two thousand people died right away, and forty thousand homes were destroyed. That caused rats to rush in, leading to an outbreak of Bubonic Plague. It took three years to eradicate the Plague.
Earthquake.USGS.Gov.
“At almost precisely 5:12 a.m., local time, a foreshock occurred with sufficient force to be felt widely throughout the San Francisco Bay area. The great earthquake broke loose some 20 to 25 seconds later, with an epicenter near San Francisco. Violent shocks punctuated the strong shaking, which lasted some 45 to 60 seconds.
“The earthquake was felt from southern Oregon to south of Los Angeles and inland as far as central Nevada. The highest Modified Mercalli Intensities (MMI’s) of VII to IX paralleled the length of the rupture, extending as far as 80 kilometers inland from the fault trace.
“One important characteristic of the shaking intensity noted in Lawson’s (1908) report was the clear correlation of intensity with underlying geologic conditions. Areas situated in sediment-filled valleys sustained stronger shaking than nearby bedrock sites, and the strongest shaking occurred in areas where ground reclaimed from San Francisco Bay failed in the earthquake.
“Modern seismic-zonation practice accounts for the differences in seismic hazard posed by varying geologic conditions.”
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