A recently discovered deep creep could be responsible for the mysterious earthquakes happening in California.
For more than three decades, unusual earthquakes have been recorded by geoscientists in California. The cause of these earthquakes that exhibit surprising deformation patterns had baffled scientists over the years. However, a newly discovered deep creep near California’s fault line could potentially solve the mystery.
According to researchers from the University of Massachusetts Amherst, the unusual seismic activity normally occurs in about a third of the hundreds of small earthquakes that happen in between the larger ones recorded in the area.
Apparently, the small vibrations are from an ongoing deep creep found six miles below the ground of the San Bernardino Basin near the San Andreas and the San Jacinto fault lines. The findings from this new study published in the journal Geophysical Research Letters could support more refined analyses of the earthquake rupture risk and fault loading within the region.
The San Bernardino basin lies in between the two fault lines of San Andreas and San Jacinto. The San Andreas is a major fault line that cuts through much of the length of California. The San Jacinto is a smaller fault line that sits parallel to a portion of San Andreas to the south of California.
The boundaries of the two fault lines slide past each other in what is known as a “strike-slip” movement. However, data gathered from these seismic activities show that there’s another movement that extends the fault.
“Within this basin, many earthquakes below 10‐km depth show deformation that does not match what we expect for this region during the current period between large damaging earthquakes along the San Jacinto and San Andreas faults. Rather than showing expected horizontal slip, many of these earthquakes show vertical movement,” the researchers explained in their paper.
The researchers believe that studies of the tremors and energy building up in the basin are compromised and should not be used to predict the “loading of the nearby San Andreas and San Jacinto faults.” The phenomenon is also not a feature of the dreaded “Big One” earthquake but could still help geoscientists better understand the seismic activity within the area where the “Big One” is expected to strike.