Assessing collapse risk in evaporite sinkhole-prone areas using gravimetry and radar interferometry

摘要

We are applying geophysical and remote-sensing methods to better understand sinkhole precursor movement and assess the potential for sinkhole development in evaporitic areas. The approach is illustrated with two examples over bedded salt deposits and a salt dome in Texas, USA. Large sinkholes (50 to 200 m in diameter) formed over Permian bedded salt near Wink in western Texas in June 1980 and May 2002 and on the flank of a coastal-plain salt dome in Daisetta in May 2008. Residents, government officials, and industry representatives wish to better understand the potential for sinkhole formation and growth. At Wink, limited data on vertical ground movement from standard surveying has been greatly extended by satellite-based radar interferometry, which we are using to delineate areas having recent movement and determine rates of movement. Results from interferometry guide site-specific investigations that include acquisition of high-resolution gravity data, which has identified shallow-source mass deficits that indicate potential for continued subsidence or sinkhole formation. At Daisetta, we used interferometry to determine that no detectable subsidence preceded sinkhole collapse and used gravimetry to identify areas where shallow mass deficits exist across the salt dome. Data from both areas can be used to construct risk maps, design comprehensive subsurface investigations, and develop monitoring programs based on repeat radar interferometry and geodetic GPS measurements.