Desert Quakes May Have Boosted Chances of ‘Big One’ Striking California

sciencehabit shares a report from Science Magazine: A pair of earthquakes that struck the remote California desert 1 year ago have raised the risk of ‘the big one’ hitting Southern California, according to a new study. The research finds that the 2019 Ridgecrest, California, quakes shifted underground stresses, making the San Andreas fault — the state’s longest and most dangerous fault — three times more likely to rupture. U.S. Geological Survey estimates for the annual probability of an earthquake on this part of the San Andreas are about one-third of a percent — equivalent to expecting a magnitude 7.8 every 300 years, on average. The new modeling triples that hazard to 1% per year — or a big one every century. And if the Garlock actually does rupture, then the hazard really rises on the San Andreas, by a factor of 150: The probability of a big one rises to 50% in the following year. In principle, a Garlock earthquake could lead to rupture on the San Andreas in a matter of hours or days, much as the two Ridgecrest events came within a day or two. USGS regional scenarios anticipate 1,800 deaths and 50,000 injuries in the event of a major San Andreas earthquake. More than 3 million homes could be damaged, at a reconstruction cost of $289 billion. The study has been published in the Bulletin of the Seismological Society of America.