California’s Bay Area is a complex mosaic of faults. Chances are one of them will experience a major quake in the coming decades. Photo: Chris Leipelt//Unsplash
As years pass without a major earthquake in Northern California’s Bay Area, scientists say the probability of a quake has gone up. The San Francisco Chronicle reported that it requested the U.S. Geological Survey to update decade-old estimates. After crunching the numbers, the USGS found the chance of a 6.7 earthquake or stronger in the next three decades went up by about two percent, to 74.1 percent.
The previous calculations in 2014 predicted the likelihood of a major quake along one of the Bay Area’s several faults — stretching from Santa Rosa to Monterey — at 72 percent. But since no such quake has struck since, the probability has increased.
The notorious San Andreas Fault, which runs through the Santa Cruz Mountains and heads offshore south of San Francisco, experienced the biggest jump in probability. USGS now gives it a 25.5 percent chance of a major quake, up from 21.9 percent.
San Andreas “is the longest fault in California and therefore capable of the biggest earthquakes,” Dr. Lucy Jones, USGS seismologist, told Bay Area news outlet ABC7. “It could go another hundred years; it could be tomorrow. It could be in the next minute.”
The most likely area to experience the next big quake is the Hayward-Rodgers Creek fault system, which runs along the east side of the bay. USGS gave it a 34.3 percent probability of rupturing.
Last month, the Chronicle also reported on geology research by San Jose State professor Kim Blisniuk showing the Santa Cruz Mountains are moving faster than believed, meaning a quake on the San Andreas Fault could come sooner than previous data indicated.
Further south on the San Andreas Fault in Southern California, a long earthquake drought also has scientists looking out for the next big slip. In June, scientists from the University of Hawaii found that a section of the fault near Los Angeles has reached its highest stress level in 1,000 years. It’s been more than 160 years since a major rupture along this portion of the fault at Cajon Pass.
