Earthquake Ground Deformation

Remote sensing and GPS studies of the Magnitude 7.2 El Mayor-Cucapha Earthquake

Republished from a December, 2010 press release by NASA.

Earthquake Ground Deformation Data

New technologies developed by NASA and other agencies are revealing surprising insights into a major earthquake that rocked parts of the American Southwest and Mexico in April, 2010 including increased potential for more large earthquakes in Southern California.

At the fall, 2010 meeting of the American Geophysical Union in San Francisco, scientists from NASA and other agencies presented the latest research on the magnitude 7.2 El Mayor-Cucapah earthquake, that region's largest in nearly 120 years. Scientists have studied the earthquake's effects in unprecedented detail using data from GPS, advanced simulation tools and new remote sensing and image analysis techniques, including airborne light detection and ranging (LiDAR), satellite synthetic aperture radar and NASA's airborne Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR).

Siginificant Findings:

• The earthquake is among the most complex ever documented along the Pacific/North American tectonic plate boundary. The main shock activated segments of at least six faults, some unnamed or previously unrecognized. It triggered slip along faults north of the border as far as 165 kilometers (about 100 miles) away, including the San Andreas, San Jacinto, Imperial and Superstition Hills Faults, and many faults in California's Yuha Desert, some not previously mapped. Some of this slip was quiet, without detectable earthquakes. Activity was observed on several northwest-trending faults due for potentially large earthquakes.
• The rupture's northern end in Southern California resembles the frayed end of a rope. The complex, 32-kilometer (20-mile) network of faults that slipped there during and after the earthquake -- many unnamed or previously unrecognized -- reveals how the earthquake distributed strain.
• Satellite radar, UAVSAR and GPS station data show additional slip along some of the Yuha Desert faults in the months after the main earthquake. Recent data from UAVSAR and satellite radar show this slip slowed and probably stopped in late summer or early fall.
• Mexico's Sierra Cucapah mountains were, surprisingly, lowered, not raised, by the earthquake.
• The main rupture jumped an 11-kilometer (7-mile) fault gap-more than twice that ever observed before.
• UAVSAR and satellite radar reveal deep faulting that may be a buried continuation of Mexico's Laguna Salada Fault that largely fills the gap to California's Elsinore Fault. This could mean the fault system is capable of larger earthquakes. A connection had only been inferred before.
• Analyses show a northward advance of strain after the main shock, including a pattern of triggered fault slip and increased seismicity. The July 7, 2010 magnitude 5.4 Collins Valley earthquake on the San Jacinto Fault may have been triggered by the main earthquake.
• Forecasting methods in development suggest earthquakes triggered by the main shock changed hazard patterns, while experimental virtual reality scenarios show a substantial chance of a damaging earthquake north of Baja within three  to 30 years of a Baja quake like the one in April.