U.S. Geological Survey map shows swarm of quakes over the past seven days.

The big one will not be triggered by an earthquake swarm that struck in Riverside and San Bernardino counties over the past eight days, according to scientists at Caltech and the U.S. Geological Survey.

The so-called Glen Avon Earthquake Swarm began on May 25 and continued through Monday, the largest a magnitude 3.2 on Sunday about 3 miles north-northwest of Glen Avon. There were a total of 430 quakes as of Monday morning, 23 of them between magnitude 2 and magnitude 3, according to the USGS.

In addition to the one Sunday morning, one other quake topped magnitude 3, a magnitude 3.1 that struck on May 25, according to Caltech and the USGS.

Despite their small magnitude, some of the quakes were felt because of their relatively shallow depth of about 1.6 miles.

“Based on past historic recordings, this swarm is only expected to generate events of magnitude less than 4.0,” according to a Caltech-USGS statement.

Quakes in the area between Chino and Riverside are common, according to Caltech and the USGS.

“Earthquake swarms are characterized as clusters of events in space and time that have no obvious mainshock,” according to the Caltech-USGS statement.

— City News Service

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Chris Jennewein

Chris Jennewein is Editor & Publisher of Times of San Diego.