6.4-magnitude earthquake hits Northern California

A 6.4-magnitude earthquake rocked the Northern California region earlier Tuesday, with more than three dozen smaller quakes reported, the U.S. Geological Survey reported.

These smaller movements are called aftershocks. As the region continues to assess the damage, here’s what to know about them.

What are aftershocks? Aftershocks are smaller earthquakes that occur in the same general area as the larger event, according to the United States Geological Survey (UGS). The U.S. Geological Survey said on its website that the smaller quakes were caused by realignment of faults caused by the larger quake.

UC Berkeley’s Seismology Laboratory put it this way:

“Imagine that you and a friend slide a large wooden dresser into a new position on a wood or tile floor. After it’s in place, you may hear a slight pop or squeak as it secures ,” it explains on its website, referring to and how plates settle into new positions after being shaken by a main earthquake — producing aftershocks. “

The frequency of these aftershocks decreases over time, the USGS said.

What is the difference between an aftershock and a “swarm”? What happened in Northern California on Tuesday was defined as an earthquake and aftershocks because of a larger, identifiable “mainshock,” or main shock.

“Earthquake swarms, on the other hand, are sequences of mostly small earthquakes with no identifiable mainshock. Swarms are usually short-lived, but they can last for days, weeks, and sometimes months. They often occur in the Repeat occurrences at the same sites. Most swarms are associated with geothermal activity,” the USGS said.

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