The University of Nevada Seismological Lab has recorded hundreds of aftershocks since last Friday's magnitude 4.5 earthquake centered near Carson City.
The main earthquake occurred at a depth of five miles beneath the surface of northern Carson Valley, near the southwest flank of Prison Hill.
UNR says aftershocks can occur for weeks to months following this type of event. By definition, aftershocks are smaller than the main shock of an earthquake sequence; however, past observations of earthquake sequences worldwide indicate that there is an approximate 5% chance that the March 20 earthquake could be a foreshock to a larger event.
“Both the rate of aftershocks and the chance of a larger event are expected to decrease in the days and weeks following last week’s earthquake,” Seismic Network Manager Ken Smith said.
The magnitude 4.5 earthquake produced moderate shaking near the epicenter in Carson City and Minden. Residents in the surrounding Carson Valley, Reno, Sparks and Tahoe/Truckee regions reported light to weak shaking. Minor damage was reported in south Carson Valley, and people as far away as Fallon, Susanville, Sacramento, the San Francisco Bay Area and Fresno who reported feeling the event via the U.S. Geological Survey “Did You Feel It?” website.
In June 2013, there was a swarm of 122 small earthquakes in Carson City, culminating in one magnitude 2.9 and two magnitude 2.8 shakers. In 2018, the Carson City area saw more than 100 earthquakes that began Dec. 8, with the two largest coming in at magnitude 3.1 and 3.6 on Dec. 20.
Between 1850 and 1960, historical records indicate that the Reno, Carson City and Tahoe/Truckee areas experienced about 15 magnitude 6-plus earthquakes. The most recent significant event to occur near Carson City is the 1994 magnitude 5.9 Double Springs Flat earthquake that occurred between southern Carson Valley and Antelope Valley.
Several active faults that cut through the Carson Valley have the potential to produce magnitude 6.5-7.5 earthquakes. Last summer, Nevada Seismological Lab researchers Ian Pierce and Steve Wesnousky opened trenches across the Carson City and Indian Hills faults to study the past earthquake history. (above photo)
