Mexico quake deformed earth – NASA
June 24, 2010 8:42am
The magnitude 7.2 temblor that rocked Baja California and Southern California on April 4 deformed the Earth so much that it can be seen in the first-ever airborne radar images of deformation in the Earth's surface caused by a major earthquake.
The quake moved the Calexico region in a downward and southerly direction by up to 31 inches, according to the data released Thursday by the National Aeronautics and Space Administration.
The radar was used at an altitude of 41,000 feet on a Gulfstream-III aircraft from NASA's Dryden Flight Research Center at Edwards in Kern County.
A science team from NASA's Jet Propulsion Laboratory in Pasadena used a technique that detects minute changes in the distance between the aircraft and the ground over repeated, GPS-guided flights. The team combined data from flights on Oct. 21, 2009, and April 13, 2010. The resulting maps are called interferograms.
The April 4 El Mayor-Cucapah quake was centered 32 miles south-southeast of Calexico along a geologically complex segment of the boundary between the North American and Pacific tectonic plates. The quake, the region's largest in nearly 120 years, was felt in southern California and parts of Nevada and Arizona. It killed two, injured hundreds and caused substantial damage. There have been thousands of aftershocks, extending from near the northern tip of the Gulf of California to a few miles northwest of the U.S. border.
The area northwest of the main rupture, along the trend of California's Elsinore fault, has been especially active, and was the site of a large, magnitude 5.7 aftershock on June 14.
NASA has mapped California's San Andreas and other faults along the plate boundary from north of San Francisco to the Mexican border every six months since spring 2009, looking for ground motion and increased strain along faults.
"The goal of the ongoing study is to understand the relative hazard of the San Andreas and faults to its west like the Elsinore and San Jacinto faults, and capture ground displacements from larger quakes," says JPL geophysicist Andrea Donnellan, principal investigator of the UAVSAR project to map and assess seismic hazard in Southern California.
Data from the Baja quake are being integrated into JPL's QuakeSim advanced computer models to better understand the fault systems that ruptured and potential impacts to nearby faults, such as the San Andreas, Elsinore and San Jacinto faults.
The maps can be seen at: http://www.nasa.gov/topics/earth/features/UAVSARimage20100623.html