NASA / JPL-Caltech
Curious how much the soil has shifted after the two major earthquakes in Southern California last week? NASA has just the right map for this question – and it looks like beautiful, psychedelic art.
On July 4, a magnitude 6.4 earthquake hit the town of Ridgecrest north of Los Angeles. The next evening, the area was shaken again when a magnitude 7.1 earthquake hit. Luckily, there were no serious injuries or major infrastructure damage.
The map was produced by the Advanced Rapid Imaging and Analysis team at NASA's Jet Propulsion Laboratory. It shows rippling rainbows forming a circular pattern around the faults of the two quakes.
Each rainbow strip means that the ground has been moved there by about 4.8 inches. It's the same logic as a topographic map, where lines that are closer together indicate steeper slopes. The closer the rainbow stripes are together, the more the ground has been moved by the Temblor.
Eric Fielding, geophysicist at JPL, says that the parts of the map along the flaw in which the colors appear confused, even more suggest dramatic ground motion.
He explains how they mapped the changes.
"We took a radar picture before the earthquake and another picture after the earthquake," Fielding tells NPR. Then they compare the changes of the individual points between the two pictures. "It allows us to measure the amounts by which the ground has moved toward or away from the satellite."
The scientists used data captured by the radar of the Japanese ALOS-2 satellite. According to Fielding, the radar can detect movements up to half an inch.
Here's another map created by NASA that displays the same information differently:
In this case, the difference in color makes it easier to see that the Earth's surface moved in different directions along the fault. "We can clearly see that the two sides of the error are moving in opposite directions," he said.
The long line of green circles on the map that runs from northwest to southeast is the error that occurred during the larger earthquake on July 5th. According to Fields, the error is about 48 km long. The line of green circles that cuts into this fault almost at right angles is the fraction of the smaller earthquake on July 4th.
"The 6.4 has a warp that is almost exactly perpendicular to the 7.1," he said.
The blue area west of the largest fault moved 2.7 feet northwest during the greatest shock, while the red area moved up to 2 feet southeast, according to NASA.