A mid-sized earthquake hit the city of Santa Rosa on Sept. 13, 2022, registering as a 4.4 on the Moment Magnitude Scale. It was felt for miles around the Bay Area—as far south as San Jose and as far north as Clear Lake.

The quake only lasted for a few moments, and for most in Petaluma, there was hardly any indication of a tremor. However, it was more evident towards Santa Rosa. 

According to reports photo frames had been shaken off of walls, food had been knocked off shelves, a few water lines were cracked and in some buildings, elevators stopped working. However, no severe structural damage was reported in any of the buildings in Santa Rosa.

This certainly has not been the first time California has seen earthquakes. In 2014, a 7.0 magnitude earthquake struck the Bay Area in the middle of the night, leaving many residents shaken up, literally and figuratively. In 1989, a 6.9 magnitude earthquake caused severe structural damage all around the Bay Area and disrupted the World Series. And in 1906, the strongest of the bunch, a magnitude 7.9, rocked the city of San Francisco to the core, almost completely eviscerating it.

Due to California’s proximity to the San Andreas fault, a tectonic border between the North American Plate and the Pacific Plate, the state’s probability of having an earthquake is rather high—there is presently over a 99% chance that a magnitude 6.7 earthquake or greater will occur in the next 30 years.

One of the most interesting parts of the whole ordeal may not have even been the earthquake itself – a 4.4 is nothing jaw-dropping. Rather, it may have been the method by which people were alerted to the earthquake.

A few moments before the earthquake actually occurred, an emergency alert was sent out to every cell phone in the surrounding area. The alert read: “Earthquake Detected! Drop, Cover, Hold On. Protect Yourself.” –USGS ShakeAlert.

This early warning system is part of the USGS’ ShakeAlert program. First developed in 2006 by members of UC Berkeley and Caltech, the mission of the program was to be able to warn Californians of impending earthquakes at least a few seconds before they happened, allowing precious time for people to protect themselves and others.

Early development builds were used in early 2012 and 2013 with a few select test users and Bay Area companies, but this almost magical piece of technology wasn’t released to the public until 2017. Even then, it wasn’t fully completed. This year’s quake was the first “real deal” test of the equipment.

ShakeAlert uses a massive network of seismic sensors and data transmission devices that can predict the magnitude, location, and overall intensity of any earthquake a few seconds before shaking occurs. It does this by analyzing the S-waves and P-waves produced by seismic events that occur just a few moments before physical shaking begins.

This new system will be vital in the coming years for Californians to stay safe, especially with the risk of an earthquake always on the horizon.