More than 130 quakes after M4.6 NE of Gonzales, California

More than 130 quakes after M4.6 NE of Gonzales, California

Following a M4.6 earthquake that hit just NE of Gonzales, California on November 13, 2017, the USGS has registered more than 130 aftershocks within the 5 km (3.1 miles) of the epicenter. Although most of those aftershocks weren't felt by the Central Coast, the aftershock sequence is raising fears a large earthquake is about to strike the region.

This one has been a quite productive aftershock sequence, but only 17 were stronger than M2.5 and six were greater than 3.0,  USGS seismologist Ole Kaven said. "We suspect there will be aftershocks in the 2 to 3 magnitude range for at least a few more weeks, but smaller shakers could continue for even longer."

"Last Monday's quake occurred on a "creeping section" of the San Andreas Fault, so seismic activity in the area is normal," Kaven said.  "It's a reminder that we are living in earthquake country."

M4.6 earthquake Pinnacles, California November 13, 2017

Similarly sized earthquakes were recorded in the same spot in 2001, 2004 and 2011. In each case, the USGS observed a pattern of aftershocks like the region is seeing now.

"The San Andreas fault in southern California last had a major quake in 1857 (M7.9)," Robert Graves, a research geophysicist at USGS, recently said.

"Studies that have dated previous major offsets along the fault trace show that there have been about 10 major quakes over the past 1 000 - 2 000 years, with the average time between these quakes about 100 - 150 years."

This suggests the region is overdue for another major earthquake by 10 years.

Featured image credit: Google, USGS

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