Lasers Shine New Light on Quakes

Lasers fired from low-flying planes could help researchers identify previously unknown fault zones after a quake, a new study shows. Soon after the magnitude-7.2 temblor that struck northern Baja California, Mexico, on 4 April 2010, scientists used aircraft-mounted laser altimeters, which are typically used to map terrain at high-resolution, to scan the swath of landscape including the numerous fault zones believed to have generated the quake. Then, they compared that high-resolution view of the terrain with data fortuitously collected during similar scans when the region was mapped in 2006. Differences between the two sets of data reveal fault zone slippage that occurred during the quake, the researchers report online today in Science. Besides showing ground movements (a portion of the Borrego fault runs diagonally from lower left to upper right, with yellow tones depicting vertical motion of up to 1 meter and blue tones revealing subsidence of as much as 4 meters in the image shown; ground-level image shown in inset), data collected at the southern end of the quake's 120-kilometer-long rupture zone revealed a previously unknown set of faults that had been masked by the thick sediments of the Colorado River Delta. Repeated scans of quake-prone areas could therefore help scientists better assess a region's seismic hazard, the researchers contend.