Study reveals southern California is hit by small earthquakes every 3 minutes

WASHINGTON – A lot of things are happening in southern California – 10 times more than seismologists thought. But most of these earthquakes are so minimal that no one feels them.

Using a more accurate way to detect tiny earthquakes, scientists have counted 1.8 million earthquakes in Southern California from 2008 to 2017, according to a report published Thursday in the journal Science. The current catalog of earthquakes for the region has just under 180,000 for this decade.

Earthquakes occur when two blocks of the Earth suddenly slide one near the other. California is a seismic hot spot in the Lower 48 for earthquakes because of its many faults, including that of San Andreas.

The new report revealed on average that a minor earthquake occurred every three minutes or so. Most were below magnitude 1.

"This means that the Earth breaks down all the time," said senior author of the study, Zachary Ross, a seismologist at the California Institute of Technology in Pasadena, California.

Finding more of these micro-earthquakes, Ross and his colleagues hope to find patterns regarding shaking swarms and better information on faults to help understand and perhaps predict larger but more dangerous earthquakes.

"At the moment, we do not really understand the fundamental things about earthquakes," Ross said. "Everything would be of great help."

Paul Earle, chief of operations at the US Geological Survey's National Earthquake Information Center, which is not part of the study, said the research was giving the experts "a new set of glasses to look inside the Earth ".

The researchers used an older method based on the principle that earthquakes from certain locations have unique wave types. "A lot like fingerprints," said Susan Hough, USGS seismologist. She was not part of the study but called her "pretty cool".

The researchers looked for earthquake fingerprints that would not normally be visible unless you were looking for them. Apparatuses looking to tremble are so sensitive that they can even detect the traffic, construction, waves and big earthquakes on the planet, Ross said.

While computing power limited this type of work in the past, the use of a supercomputer and new algorithms allowed the Ross team to do the work necessary to find the earthquakes in Southern California.