A swarm of minor earthquakes near California’s Salton Sea is raising concern about the potential for a larger temblor at the state’s San Andreas Fault.
According to the U.S. Geological Survey, the dozens of tremors began in the early morning on Monday, ranging in size from a 2.6 magnitude quake to a 4.6 magnitude quake northwest of Palm Springs and the Salton Sea.
The swarm marks only the fourth time in almost 90 years of modern seismology records that such an incident has occurred in that part of the Golden State
The area is overdue for a “Big One.” Larger-scale quakes on the San Andreas Fault are expected every 200 years on average, and the southern area has not seen action since 1680 to 1690.
According to The Los Angeles Times, there is generally a 20% chance of a magnitude 7 or higher earthquake on the fault over the next 30 years.
Salton Sea earthquake swarm update: So far there's been 90+ quakes since 8:56am PT with three quakes >M4. Largest in the sequence so far is still the M4.6 quake. These swarms can generate 100s of quakes, but typically they settle down after a few days. pic.twitter.com/nixsdcD8tr
— Brian OLSON (@mrbrianolson) August 10, 2020
During this earthquake swarm, the probability of larger earthquakes in this region is significantly greater than usual. The southernmost section of the San Andreas Fault is capable of rupturing in large-magnitude earthquakes (magnitude 7+), but the last earthquake that strong was more than 300 years ago,” the Geological Survey said in a Monday statement.
“In a typical week, there is approximately a 1-in-10,000 chance of a magnitude 7+ earthquake on the southernmost San Andreas Fault. That probability is significantly elevated while swarm activity remains high,” they wrote.
A calculated 1-in-100 chance of a high-magnitude quake in the next week is a worrying rise from the normal 1-in-10,000 odds.
The last time a similar swarm happened was almost four years ago, prompting San Bernardino officials to close City Hall for two days, though no bigger quake occurred.
This time, the smaller quakes are notably farther away from the San Andreas fault than the 2016 swarm.
That said, the San Andreas Fault is dangerous enough to inspire a 2015 blockbuster disaster movie featuring Dwayne “The Rock” Johnson, as well as numerous references in similar films.
And in the worst-case scenario, it has the ability to unleash a devastating 8.2 magnitude quake that would rip through the state.
While large earthquakes can easily happen with no detectable warning at all, California has a history of smaller earthquakes preceding “Mega Quakes.”
In 1857, the San Andreas Fault saw a 7.8 magnitude temblor preceded by two smaller-scale quakes farther north and, in 1992, a 6.1 magnitude quake in Joshua Tree National Park kicked off a series of strengthening quakes.
A 7.1 magnitude earthquake in July 2019 was the most powerful quake to hit the state in two decades.
Author : Julia Musto
Source : Fox News : San Andreas Fault earthquake swarm sparks fears of ‘Big One