NASA announced Friday that it may have found a way to predict sinkholes up to a month before they occur. The warning would be provided by interferometric synthetic aperture radar (iSAR), which could be placed on satellites or planes to scan areas prone to sinkholes.
iSAR scans the ground several times in several different wavelengths to put together interferograms, which can show small movements of the Earth such as the effect of flooding on riverbanks, the ripples of earthquakes and where the ground is sinking.
Sinkholes are depressions in the ground formed when layers of the earth's surface fall into underground caverns. Usually they form without warning.
"While horizontal surface deformations had not previously been considered a signature of sinkholes, the new study shows they can precede a sinkhole formation well in advance," said researcher Cathleen Jones of NASA's Jet Propulsion Laboratory in Pasadena, California. "This kind of movement may be more common than previously thought, particularly in areas with loose soil near the surface."
As part of their research into iSAR, researchers at NASA's Jet Propulsion Laboratory have been monitoring changing ground conditions along the U.S. Gulf Coast. After a sinkhole formed in Bayou Corne, Louisiana in 2012, researchers looked at radar scans in the same area one month and one year prior to the event. They found that the ground surface layer had shifted as much as 10 inches toward the center of the sinkhole.
The data, published in last month's issue of the journal Geology, demonstrates that once the technology is used more widely, including on satellite platforms, it will be able to be used to determine when a sinkhole is about to form, the researchers said. The U.S. is collaborating with India to launch an iSAR-equipped satellite at some point in the next seven years.
"Our work shows radar remote sensing could offer a monitoring technique for identifying at least some sinkholes before their surface collapse, and could be of particular use to the petroleum industry for monitoring operations in salt domes," NASA researcher Ron Blom said. "Salt domes are dome-shaped structures in sedimentary rocks that form where large masses of salt are forced upward. By measuring strain on Earth's surface, this capability can reduce risks and provide quantitative information that can be used to predict a sinkhole's size and growth rate."
NASA uses a variety of satellites and other mechanisms to monitor the Earth's condition from air, land and space.