Analyses by NASA's UAVSAR after the Bayou Corne, La., sinkhole formed show it detected precursory ground movement of up to 10.2 inches (260 millimeters) more than a month before the sinkhole collapsed. Colors represent surface displacement; one full color wrap equals 4.7 inches (120 millimeters).
Findings suggest that radar data, if collected routinely from airborne systems or satellites, could in some cases foresee sinkholes before they happen, decreasing danger to people and property.
New analyses of NASA airborne radar data collected in 2012 reveal the radar detected indications of a huge sinkhole before it collapsed and forced evacuations near Bayou Corne, La., that year. Sinkholes are depressions in the ground formed when Earth surface layers collapse into caverns below. They usually form without warning. The data were collected as part of an ongoing NASA campaign to monitor sinking of the ground along the Louisiana Gulf Coast.
Researchers Cathleen Jones and Ron Blom of NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, Calif., analyzed interferometric synthetic aperture radar (InSAR) imagery of the area acquired during flights of the agency’s Uninhabited Airborne Vehicle Synthetic Aperture Radar (UAVSAR), which uses a C-20A jet, in June 2011 and July 2012. InSAR detects and measures subtle deformations in Earth's surface.
Their analyses showed the ground surface layer deformed significantly at least a month before the collapse, moving mostly horizontally up to 10.2 inches (260 millimeters) toward where the sinkhole would later form. These precursory surface movements covered a much larger area”about 1,640 by 1,640 feet (500 by 500 meters)”than that of the initial sinkhole, which measured about 2 acres (1 hectare).
Image courtesy of NASA/JPL-Caltech.
