A NASA-led study of a 2014 magnitude-5.1 earthquake centered in La Habra revealed that the temblor deformed the Earth’s crust across a wider swath of the northern Los Angeles Basin and northern Orange County than was expected and strain remains in deeper area faults that could produce future quakes.
A team of researchers led by Andrea Donnellan, a geophysicist at NASA’s Jet Propulsion Laboratory in Pasadena, measured surface deformation from the March 28, 2014, earthquake using GPS and NASA airborne radar data, according to the study released Tuesday.
The quake did more than $12 million in damage, largely due to its shallow depth of 3.6 miles and the dense population of the affected area, and was felt across seven counties, according to JPL.
While the surface deformation occurred over a wide area, much of it was located south of the main rupture and that’s where most of the quake’s damage occurred, according to JPL.
“Most of the damage occurred within a 3.7-mile radius of the epicenter, with a substantial amount of damage south of the main rupture,” according to JPL.
Donnellan’s team measured 3.1 inches of northward horizontal motion and two- to four-tenths of an inch of upward motion, JPL reported.
The study shows “that even moderate earthquakes near Los Angeles can produce ground deformation and damage to water mains away from their epicenters,” JPL reported.
“The earthquake faults in this region are part of a system of faults,” Donnellan said. “They can move together in an earthquake and produce measurable surface deformation, even during moderate magnitude earthquakes.”
A future quake that would release strain on the fault system — including one like the Northridge earthquake of 1994 — could occur on any one or several of the fault structures, Donnellan said.
It’s possible that such a quake could occur on a fault or faults that have not been mapped at the surface, she said.
“Identifying specific fault structures most likely to be responsible for future earthquakes for this system of many active faults is often very difficult,” Donnellan said.
Lisa Grant of UC Irvine, a study co-author, said the study findings could be helpful in assessing earthquake risk and disaster planning.
“The study builds upon more than two decades of NASA-led research to develop new methods to better measure and monitor movements of the solid Earth using satellite and airborne data and advanced computer modeling,” Donnellan said.
“It also provides a means of using these technologies to identify which faults moved during earthquakes, to measure exactly how much Earth’s surface deformed during earthquakes and to use these measurements to estimate future earthquake potential.”
— City News Service
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