The past week has been a bit shaky for the Glen Avon and Fontana areas in the Inland Empire, thanks to a swarm of more than 430 earthquakes that have lightly jostled the region since May 25, according to the Caltech Seismology Laboratory.
The smallest of the quakes measured at magnitude 0.8, far too small to feel. Though residents did feel the larger ones, which were as big as 3.2 (still relatively small). Given that they were fairly shallow -- only a mile or two deep -- they were also more noticeable.
So what does that mean for earthquakes in our region? Could this trigger a Big One on the San Andreas?
"There's no reason for us to think that this current activity is leading up to a big or damaging earthquake," said Dr. Jen Andrews, staff seismologist at the Caltech Seismology Laboratory.
The area has seen clusters of quakes like these before, with records of them going back to the 1980s. Usually they result in magnitude 3.0 or 4.0, max.
Seismologist Dr. Lucy Jones detailed previous events on Twitter.
July 1992 and July 1994 had similar swarms. M3+ events in 1998, 2006, 2014. All within a few km of this location. These events are a little shallower so more people feel them, but that doesn't make them more significant. We've never seen a quake bigger than M4
— Dr. Lucy Jones (@DrLucyJones) June 3, 2019
Why is this swarm of quakes happening?
Massive pressure builds up deep in the earth as the North American and Pacific plates grind past each other. While release of that pressure can be felt as large bursts of energy on the main faults in the area, like the San Andreas, it's not just those areas that the pressure effects.
"It's all interconnected," said Andrews. "As [the plates] move, they load these blocks of earth adjacent to them. There's lots of strain building up. So we see these clusters of smaller events happening and they're relieving strain very locally."
Even though this swarm might not indicate an impending Big One, that doesn't mean a mega earthquake couldn't hit at any moment. Scientists say there's a roughly 92 percent chance that we'll see a 6.7 or larger quake some time in the next 30 years.
Today is as good a day as any to get prepared. Start by buying some water, food and emergency supplies, as well as by listening to our podcast, "The Big One: Your Survival Guide," which is all about what it'll be like for Southern California when it finally hits.
