High-Flying Radar Uncovers Hidden Faults After Napa Earthquake

Major Cleanup Begins in Napa Amid Series of Aftershocks 2:29

The Aug. 24 Napa earthquake woke several small, previously unrecognized Napa Valley faults, according to the first results from a high-flying NASA radar instrument. The magnitude-6.0 Napa earthquake, the biggest to shake northern California in 25 years, injured 170 people and killed one woman. Most of the damage was centered on the West Napa Fault. The U.S. Geological Survey (USGS) found that the West Napa Fault moved a total of 18 inches (46 centimeters) along a 9.3-mile-long (15 kilometers) length, USGS scientist Dan Ponti said Sept. 4 at a USGS earthquake seminar. New radar images of Napa Valley also confirm that the West Napa Fault caused the deadly earthquake.

But the images also reveal a handful of smaller faults running roughly northwest to southeast, parallel to the West Napa Fault. "These really tiny ones are probably not big enough faults to have a significant earthquake, but it's a good thing to have people go out and check whether they are part of a larger fault system," said Eric Fielding, a geophysicist at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California. The radar images were created from UAVSAR (uninhabited aerial vehicle synthetic aperture radar) data collected during flights on May 29, 2014, and on Aug. 29, 2014.

Image: Ground deformation from the Aug. 24 earthquake in Napa, California
Ground deformation from the Aug. 24 earthquake in Napa, California. Each color fringe corresponds to deformation of 4.7 inches (12 centimeters). NASA / JPL-Caltech / ASI / Google Earth
— Becky Oskin, LiveScience

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