Laser scans of Earth's land surface taken from aircraft have now yielded the most comprehensive before-and-after picture of an earthquake yet, scientists revealed today (Feb. 9).
These kinds of scans before and after large quakes may help reveal where exactly the quakes ruptured the Earth down to a scale of just a few inches, which may help experts prepare for the hazards of such quakes, researchers said.
Scientists from the United States, Mexico and Chinaworking with the National Center for Airborne Laser Mapping flew over the area struck by the magnitude-7.2 El Mayor-Cucapah earthquake in northern Mexico on April 4, 2010. The quake produced a 74-mile-long (120 kilometer) rupture through Baja California, Mexico.
This earthquake did not happen on a major fault, like the San Andreas, but ran through a series of smaller faults in the Earth's crust. Over the past century, most of the damaging earthquakes on continents have arisen from such multiple-fault ruptures.
"We can recognize their activity from how they disrupt the landscape, but we don't have a good way of assessing the potential size of earthquakes they produce, because they tend to rupture together with other, nearby faults in a complicated way," said researcher Michael Oskin, a geologist at the University of California, Davis. "These types of earthquakes can be especially dangerous if they occur near an urban area that is not well prepared."
Before and after
The research team scanned the area with LIDAR, or Light Detection and Ranging, which bounces a stream of laser pulses off the ground. New, airborne LIDAR equipment can measure surface features to within a few inches.
The scientists finished a detailed scan over about 140 square miles (360 square km) in less than three days. With this data they were able to discover and map the several faults, including a previously unknown one. Since the Mexican government scanned this area with LIDAR back in 2006, they were also able to compare the old and new data to identify just how the many faults in the area reacted.