How radar mapping helps scientists study earthquakes.
The magnitude-7.2 earthquake that struck near Calexico on Easter Sunday shifted the Earth's crust near the epicenter about 10 feet, according to radar images and data collected by researchers at NASA's Jet Propulsion Laboratory, all of which was released Wednesday.
"This is a normal slip for this size earthquake," said JPL geophysicist Andrea Donnellan. "It's a lot of motion."
Airborne radar images of the area taken by the JPL-developed Uninhabited Aerial Vehicle Synthetic Aperture Radar were posted online by NASA for the first time Wednesday.
"Our next concern is this bigger system of faults that could continue to break," Donnellan said.
That's where computer models, GPS and the flyovers might be able to tell us what to expect in the years and months to come.
Researchers used data collected by the airborne radar to detect changes in the distance between the aircraft and the ground over repeated GPS-guided flights. According to JPL, they combined data from flights on Oct. 21 and April 13 to determine the deformities in the Earth's crust.
"With the seismometers, we can measure the earthquakes themselves," said Donnellan. "With these techniques we can actually see what's happening quietly. If you think of Silly Putty, it can stretch -- we can measure that. If you pull it hard enough it'll break. That's the earthquake and that's what the seismometers measure."
The UAVSAR has been mapping the San Andreas and other faults from north of San Francisco to the Mexican border every six months since spring 2009, looking for ground motion and increased strain along faults, according to NASA.
"The goal of the ongoing study is to understand the relative hazard of the San Andreas and other faults to its west like the Elsinore and San Jacinto faults, and capture ground displacements from larger quakes,'' said Donnellan.