The seismic storm that unleashed more than 1,000 small earthquakes in San Bernardino and Riverside counties these last three weeks elicited what has become a typical reaction in quake country.

To some, the “swarmageddon” 40 miles east of downtown Los Angeles brought fear that a bigger threat was coming. To others, as long as they didn’t feel a shake, it was easy to just put it out of their minds.

View Comments (8)

California has small quakes all the time — a magnitude 3 every other day, on average. But not all of them act the same, and some bring more danger than others.

As officials install more seismic sensors as part of the state’s early warning system, experts are getting an increasingly better look at California’s smaller earthquakes.

There is general agreement that the recent swarm probably isn’t a precursor to a catastrophic quake. But other small quakes — especially ones near major fault lines like the San Andreas — are potential warnings.

“I would redefine normal as: You should still be prepared for a large earthquake,” U.S. Geological Survey research geophysicist Andrea Llenos said. “We do know a big earthquake is going to happen” — just not when and where….

On Sept. 26, 2016, a rapid succession of small earthquakes — the strongest a trio measuring above magnitude 4.0 — began rupturing under the Salton Sea close to the San Andreas fault. Scientists worried those quakes could set off a domino effect, reawakening the southern San Andreas from its long slumber. That fault is capable of producing a magnitude 8.2 quake.

Their worst fears didn’t materialize.

But “any time you have an increase in the number of small earthquakes,” Llenos said, “you’re likely to increase the likelihood of a slightly larger earthquake happening.”… (Excerpts fron The LA Times article by Rong-Gong Lin II)