California may be primed for a major earthquake to hit this week.
The U.S. Geological Survey stated in an earthquake forecast on August 10 that an earthquake swarm beneath the Salton Sea in California that began on August 10 has a “significantly greater” probability of larger earthquakes than usual.
A 4.6-magnitude quake at 8:56 a.m. on August 10 was the largest of a seismic cluster located about 13 kilometres (eight miles) away from the southern end of the San Andreas Fault.
Although the U.S. Geological Survey initially assessed it as a 4.0-magnitude quake based upon preliminary measurements, it later upgraded it to a 4.6-magnitude seismic event.
At a depth of 10 kilometres (six miles), it was located 13 kilometres (8 miles) southeast of Bombay Beach, 33 kilometres (20 miles) northwest of Brawley, 101 kilometres (63 miles) southeast of Palm Springs, and 145 kilometres (90 miles) northeast of San Diego.
The U.S. Geological Survey stated that there are three scenarios that could occur over the coming week (up until about August 18).
The most likely scenario (80 percent chance) is that the swarm will continue on but none of the temblors will exceed magnitude 5.4, and the frequency of quakes will likely decrease.
While small quakes (3.0-magnitude or above) may be felt by those close to epicentres, moderate quakes (from about 4.5- to 5.4-magnitude) may occur, and could cause local damage to structures.
However, there is an approximately 19 percent chance that a larger earthquake from 5.5- to 6.9-magnitude could hit within the coming days. Quakes of this size could cause damage in the Salton Sea area, followed by aftershocks.
There also remains a one-percent chance that a 7.0-magnitude or larger quake could occur. Although this is the least likely scenario, if it does happen, it would cause serious damage to nearby communities, with aftershocks increasing the frequency of small earthquakes.
The last earthquake in the area over 7.0-magnitude took place over 300 years ago.
The region has previously experienced swarms in 2001, 2009, and 2016.