Utah Has Been Hit by Over 700 Earthquakes Since the Magnitude 5.7 Quake on March 18

Utah was rocked by 728 earthquakes in the two weeks following the 5.7 magnitude mainshock that struck on March 18, the University of Utah Seismograph Stations (UUSS) has said.

The two largest aftershocks reached 4.6 on the moment magnitude scale, occurring at at 8:02 am and 1:12 pm on Wednesday, March 18. There were a further 33 earthquakes of a magnitude 3 or higher.

The UUSS said there were no foreshocks, which means none of the 728 recorded anticipated a larger earthquake in the same location. According to the United States Geological Survey (USGS), an earthquake can only be identified as a foreshock after a larger earthquake has been recorded at the same site.

Salt Lake City, Utah, was struck by a 5.7 magnitude earthquake in mid-March. The epicenter was a site 2.5 miles (4 kilometers) north-northeast of Magna, Utah.

According to UP Seis, a quake with a magnitude between 5 and 5.9 is considered moderate. One of 5.7 will cause "slight damage to buildings and other structures."

According to Earthquake Track, the 5.7 magnitude earthquake was the strongest quake to hit the state in the last year. Over the past 365 days, 887 earthquakes with a magnitude of 1.5 or higher have been recorded in Utah—351 of which have taken place over the last 30 days.

More recently, Boise, Idaho was rattled by a strong earthquake with a magnitude of 6.5, which was felt at around 5:52 p.m. on Tuesday, March 31. It was the first earthquake with a magnitude greater than 5 to strike Idaho in more than 50 years.

Geologists have been quick to assure residents there is no link between this recent seismic activity and Yellowstone, which lies approximately 300 miles east of Boise.

"Based on current scientific knowledge, there is no obvious relationship between the earthquake in Idaho and the Magna earthquake or large events on the Wasatch Fault," said the UUSS. "The earthquake in Idaho was not related to Yellowstone, nor did it have any impact on the volcano."

According to the Yellowstone volcano observatory monthly update, the current volcano alert level is normal. The USGS explained the earthquakes in Utah and Idaho were not related to Yellowstone. Neither are they likely to significantly impact the Yellowstone system.

"Some strong earthquakes in the region, like the 1983 M6.9 Borah Peak, ID, and 1959 M7.3 Hebgen Lake, MT, earthquakes, have impacted geyser behavior, but that is due to the response of the shallow and fragile geyser conduits to shaking," said USGS.

"It is not yet clear if the M6.5 in central Idaho will have a similar impact; observations of geyser activity over the coming days to weeks will answer that question."

According to the Utah Geological Survey, there have been 16 earthquakes of a magnitude 5.5 or stronger since 1847, when the Mormon pioneers entered Salt Lake Valley. Utah has a history of larger earthquakes of magnitude 6.5 or greater.

The cause of Utah's seismic activity is not that it lies on a boundary between tectonic plates, like California and Japan. The state sits on the western part of the North American plate. Instead, earthquakes are triggered by the Pacific plate's interactions along the plate margin on the U.S. west coast and by underground coal mining.

Building damaged by earthquake on March 18, 2020 in Magna, Utah
Bricks and debris lay at the base of a building damaged by an earthquake on March 18, 2020 in Magna, Utah. The UUSS recorded more than 700 quakes in the two weeks that followed. George Frey/Getty