What to do when an earthquake hits
Just a few days after two earthquakes rocked the Ridgecrest area in Southern California, scientists at NASA’s Jet Propulsion Laboratory put together a colorful map showing just how much the ground moved.
The colors work similarly to the contour lines on a topographical map, according to Eric Fielding, a geophysicist at NASA’s JPL who has worked on these kinds of maps for 22 years.
The JPL used synthetic aperture radar data — provided by the Japanese Aerospace Exploration Agency from the ALOS-2 satellite — to produce the map.
Each color represents a difference of 4.8 inches in ground movement either toward or away from the satellite, Fielding said.
In addition to the tie-dye-like colors on the map, there’s a line of color “noise” that extends from the upper left area of the map to the lower right.
That’s the 30-mile-long crack in the Earth that ruptured as a result of the magnitude 7.1 quake on July 5, Fielding said.
“That’s pretty typical for a magnitude 7 earthquake,” Fielding said. “We saw that in the Landers earthquake in 1992 and Hector Mine in 1999. It’s definitely similar to these earlier events.” (The Landers earthquake happened near the town of Landers and had a magnitude of 7.3, while the Hector Mine earthquake occurred in the Mojave Desert and had a magnitude of 7.1.)
There’s also a smaller line on the map that heads southwest toward the town of Ridgecrest. That’s the fault that ruptured in the magnitude 6.4 earthquake on July 4, Fielding said.
The map doesn’t show specific numbers detailing how much the ground moved, but Fielding said a National Science Foundation GPS station east of Ridgecrest moved more than 2 feet during the magnitude 7.1 earthquake on Friday.
A map like this is typically the first map NASA releases after an event like an earthquake, Fielding said. An easier-to-understand map is usually released later, and in this case scientists are still working on it.
“We released it (the map) right away on Tuesday to get it to the geologists out in the field,” Fielding said. State and federal scientists use the map to help assess damages and map the faults that happened during the two earthquakes and the more than 1,000 aftershocks, according to the JPL.
This map shows that much of the cracks in the Earth’s surface happened inside the China Lake Naval Air Weapons Station, Fielding said.
“It’s going to take them a long time to map all of that on the ground,” Fielding said. “Especially if they have to get permission from the Navy.”