In the San Francisco Bay Area, scientists predict that history is bound to repeat itself soon. Only this time, California would not be revisited by a next "Big One" reminiscent to the Great San Francisco earthquake. Instead, a throng of the historic 7.0 magnitude temblor could take place.
This is what a new study found out after a team of researchers from the U.S. Geological Survey, California Geological Survey and University of Missouri in Kansas City, together with the URS Corporation and Lettis Consultants International, analyzed the past and recent earthquake records to predict the future of the state of California a century later after the notorious quake occurred.
The study, which is expected to come out in the June 2014 issue of the journal [pdf] Bulletin of the Seismological Society of America, observed a natural cycle of earthquakes between 1690 and 1776, the year when the city of Mission Dolores and Presidio of San Francisco were both founded. In the span of almost a hundred years, California experienced a cluster of tremors ranging from magnitudes of 6.6 to 7.8.
An earthquake usually forms when the accumulated stress from the friction between continental plates cannot be contained anymore; hence, it releases a tremendous force. The San Francisco Bay Area is located just between the Pacific and North American plates. Researchers discovered that after the 1906 earthquake, the area became quiet, which is fairly similar to what had happened before.
Anytime soon, the contained energy would be released along the faults of San Andreas, San Gregorio, Calaveras, and Greenville, as well as the creek of Hayward-Rodgers and the Concord-Green Valley, and it could not be a single "replica" of the Great San Francisco earthquake. It could be a worse series of "Big Ones" since there areas are more populous now and more lives are at risk.
"Everybody is still thinking about a repeat of the 1906 quake," said co-author David Schwartz, who is also a geologist at the U.S. Geological Survey. "It's one thing to have a 1906-like earthquake where seismic activity is shut off, and we slide through the next 110 years in relative quiet. But what happens if every five years we get a magnitude 6.8 or 7.2? That's not outside the realm of possibility."
To find out, the team dug trenches near the faults analyzed the surface ruptures formed by recent quakes in the area of California's major faults.
"What the cluster of earthquakes did in our calculations was to release an amount of energy somewhat comparable to the amount released in the crust by the 1906 quake," Schwartz said.
