The United States Geological Service says there is a 1 in 100 chance of a major earthquake on California's San Andreas Fault in the next week—up from a 1 in 10,000 chance in a typical week. The raised risk is due to a swarm of small earthquakes detected along the fault this week, including a magnitude 4.6 quake under the Salton Sea Monday morning, the Los Angeles Times reports. The risk was raised to the same level during a similar swarm of earthquakes in 2016, one of only three other such swarms spotted in the last 88 years. Experts say that in a worst-case scenario, the fault could unleash a devastating magnitude 8.2 earthquake from the Mexican border through Los Angeles County and all the way north to Monterey County.
The swarm "does increase the chance of a big earthquake on the San Andreas somewhat," says USGS research geophysicist Morgan Page, per the Times. "So it's definitely something to watch." Similar swarms haven't resulted in bigger quakes so it's "not necessarily doom and gloom," Page says, "but every time it happens, we do worry that this could be the time that it triggers something." Google announced Tuesday that an earthquake alert system has been built into Android phones, and California users will receive a warning when they are near a quake of 4.5 magnitude or greater, the AP reports. The move will give "millions precious seconds to drop, cover, and hold on when the big one hits," Gov. Gavin Newsom said in a statement. (Read more San Andreas Fault stories.)