The United States Geological Survey recorded a Magnitude 4.9 Earthquake at a depth of 8.2 km about 7.9 km to the east of Chalis in Custer County, Idaho, slightly before 10.45 am local time (slightly before 5.45 pm GMT) on Saturday 3 January 2015. There are no reports of any serious damage or injuries associated with this event, but it was felt across much of Idaho and southeastern Montana, and the area has been shaken by several large Earthquakes since the main event.
The approximate location of the 3 January 2014 Custer County Earthquake. Google Maps.
The quake took part in an area known as the Central Idaho Seismic Zone, which is bisected by six active faults, the Madison, Centennial, Beaverhead, Lemhi, Lost River, and Sawtooth. These faults are associated with the Yellowstone Magma Chamber in the northeast of Wyoming, an area that suffers more-or-less constant small tremors due to the movement of magma beneath the surface, but which seldom experiences larger quakes. The constant small movements around Yellowstone can lead to stress building up in rocks further away, leading to Earthquakes as the rocks release the strain by readjusting their positions, which can affect Wyoming as well as neighbouring Idaho and Montana. The same faults also suffer stress due to more distant rock movements, notably on the subduction zone on the American west coast.
Witness accounts of Earthquakes can help geologists to understand these events and the underlying structures that cause them. If you felt this quake (or if you were in the area but did not, which is also useful information) then you can report it to the United States Geological Survey here.
See also...
The United States Geological Survey recorded a Magnitude 4.9 Earthquake at a depth of 5.0 km, roughly 15 km north of Chalis City in Custer County, Idaho...
Two cars travelling in opposite directions were swallowed by a sinkhole that opened up to the north of...
The United States Geological Survey recorded a Magnitude 3.1 Earthquake at a depth of 4.4 km beneath the city of Driggs in Teton County in eastern Idaho, slightly before 5.05 pm local time on...
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