NASA Reveals the Scars Left by the California Earthquakes That Can Be Seen From Space

Scars left on the surface of Earth by the strong earthquakes that hit California last week can be seen from space, with NASA images revealing how the ground was displaced during the events.

On July 4 and 5, Southern California was hit by magnitude 6.4 and 7.1 earthquakes, respectively. This was followed by over 1,000 aftershocks around the epicenter, near the city of Ridgecrest. The 7.1 quake was the biggest to hit the area in over 40 years.

Scientists at NASA's Jet Propulsion Laboratory (JPL) have now produced a map showing the surface displacement before and after the two earthquakes. The first image was taken on April 8 last year and the next on July 8, 2019. "Each color cycle represents 4.8 inches of ground displacement in the radar line-of-sight," a statement from NASA said. The image covers an area of 31 by 78 miles, and each pixel measures about 98 yards across.

"No filter was applied during the processing. The linear features across which the color fringes break indicate likely locations of surface rupture caused by the earthquakes, and the 'noisy' areas may indicate locations where ground surface was disturbed by the earthquakes."

California earthquake
Map showing ground deformation after the recent earthquakes in California. NASA/JPL-Caltech

A month before the two earthquakes, the USGS said a swarm of over 400 small earthquakes had been recorded in Southern California's Inland Empire, NDT reported. The swarm started on May 25, with at least 432 quakes measuring between magnitude 0.8 and 3.2 recorded in Riverside County.

The cause of the earthquake swarm was not identified, but Robert Graves, from the USGS, said this sort of event was not uncommon because of the geology of the region: "We live in an earthquake country, so these earthquakes in and of themselves are not going to cause any damage, but it's certainly a chance for people to take a look at their emergency supplies," he was quoted as saying.

The latest earthquakes have raised fears of when the next "big one" will hit California. Many towns and cities sit along fault lines, including the San Andreas Fault, which spans 800 miles and marks a boundary between the Pacific Plate and the North American Plate. This fault is of particular concern because three major cities—San Francisco, San Diego and Los Angeles—are all in its vicinity. A strong or major earthquake near one of these spots could cause a huge amount of damage, experts say.

A statement from the California Volcano Observatory, which monitors seismic activity in California and Nevada, on Wednesday said the seismic activity that began on July 5 has continued "at a rate of about 600 magnitude 1.0 or greater earthquakes per day."

The intensity of activity in the region is "gradually declining" and that they "continue to monitor the situation," it said.

This article has been updated to include the latest statement from the California Volcano Observatory.