It is almost a certainty that at least one, possibly more, earthquakes have shaken California today. They may not have been large, but they were all significant because these small quakes release pressure from faults.
According to the U.S. Geological Survey, a fault is a three-dimensional surface within Earth where rocks have broken. The rocks on one side of the fault have moved past the other side. A fault line is where the fault cuts the Earth's surface.
With the help of an airborne radar system, scientists at NASA/Jet Propulsion Laboratory in La Cañada Flintridge are studying these faults throughout the state to create a type of earthquake map that will allow them to get a better understanding of which faults are most active and which are more likely to have large earthquakes in the future.
The program is called the Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR), and it took its first earthquake study flight in February.
The program allows scientists to study a fault as it progresses with built up pressure, then release. The radar is housed in a pod under an aircraft that flies out of NASA's Dryden Flight Research Center in Edwards, Calif. It flies at an altitude of 45,000 feet and the radar collects data over a designated region.
“The key thing is it shoots images at two different times,” said Eric Fielding, a geophysicist at JPL.
The UAVSAR can shoot images minutes to months apart. By looking at how the surface of the Earth deforms between earthquakes, scientists will have a better understanding of that particular fault line, Fielding added.
The best data will be derived after larger earthquakes occur. “We will look at how the strain is building on the fault,” Fielding said.
Currently, the UAVSAR is being used to study faults in California only.
“We use satellites to look at earthquake [faults] around the world,” Fielding said. “The first [UAVSAR] flight to [study earthquakes in California] was in February 2009. We are waiting for it to come by next month with the second flight.”
Fielding said the program is not promising a way to predict the exact time of an earthquake.
“As far as we know now, that would be impossible,” he said.
The data would determine the likelihood of a large — magnitude of 5 or above — earthquake striking a particular fault line within the next 30 years.
All faults across the state are being studied with a particular emphasis on the 800-mile-long San Andreas fault. “Some faults are locked, building stress and pressure, while others are creeping or slipping all the time,” Fielding said. “We will map which are locked and which are creeping.”
Fielding will be studying the Hayward fault along the east side of San Francisco Bay, south of Berkeley.
The Hayward fault creeps in some parts but ruptured in a magnitude 6.8 to 7.0 earthquake in 1868.
Fielding will also be studying the landslides along Hayward.
“The Berkeley landslides are moving all the time,” he said. “We hope to understand what causes these landslides to move, the physics of how it works after an earthquake.”
The information gathered will be shared with scientists around the world and will be released on JPL's website at www.jpl.nasa.gov.