(TMU) — In early July, two major earthquakes—measuring 6.4 and 7.1 on the Richter scale—hit Ridgecrest, California and left a 30-mile long scar across the surface of the Mojave Desert. A staggering number of earthquakes have been recorded in the aftermath of what were two of the strongest quakes to hit California in decades.
While the rate of aftershocks is finally beginning to slow, the U.S. Geological Survey says the chance of a magnitude 7 or higher earthquake happening as a result of the Ridgecrest event is 1 in 300—“possible, but with a low probability.” In comparison, there is a 1 in 10,000 chance that a magnitude 7.8 or higher quake will strike the southern San Andreas fault any given day.
According to Zachary Ross, Caltech assistant professor of geophysics, seismic activity is common in areas of the earth that experience a high heat flow.
Ridgecrest sits near the Coso Volcanic Field that lies within the borders of the Naval Air Weapons Station in China Lake—2.5 miles north of Ridgecrest. As it turns out, Coso is one of the largest producers of geothermal power in the United States.
Despite the slowdown in aftershocks, their continued existence is both interesting and concerning to some seismologists and observers. According to officials, the tremors are moving and they’re getting closer to two major earthquake faults—the Owens Valley fault to the northwest and the Garlock fault to the southeast.
Back in 1872, the Owens Valley fault triggered a magnitude 7.8-7.9 earthquake—one of the strongest in California’s modern record. The Garlock fault, while it may be lesser known, is capable of producing a magnitude 8.0 or higher quake.
U.S. Geological Survey research geophysicist Morgan Page stresses the significance:
“Little earthquakes are telling us where big earthquakes are more likely.”
While it is impossible to predict when and where the next big quake will occur, scientists continue to urge the public to be prepared with a plan. Not all big earthquakes trigger seismic activity on nearby faults, but some do.
According to the Los Angeles Times:
“Perhaps the most famous example of triggered earthquakes in California occurred in 1992. An April 22 magnitude 6.1 earthquake in Joshua Tree National Park began a quake sequence that migrated north in the coming months.
Then on June 28, an earthquake 63 times stronger ruptured—the magnitude 7.3 Landers earthquake with an epicenter more than 25 miles northeast of Palm Springs. A sleeping 3-year-old toddler died after being struck by a collapsing chimney during a sleepover.
Three hours later, a magnitude 6.3 quake struck about 20 miles west, just a few miles away from Big Bear.”
“We always worry when seismicity picks up very close to a major fault or if it’s at the end of a major fault,” Caltech seismologist Egill Hauksson said.
As it turns out, an earthquake doesn’t reduce the risk of a future earthquake—it actually increases it. And the spread is modeled a lot like a disease epidemic.
“It’s based on the idea on how a contagion spreads to a population,” Page said.
“Every earthquake actually increases the probability of more earthquakes.”
The latest large aftershock occurred on Thursday at 5:42 p.m. just 16 miles from Ridgecrest, according to the U.S. Geological Survey. In the last 10 days, 68 earthquakes of a magnitude 3.0 or higher have occurred in the area.