Assessing Collapse Risk in Evaporite Sinkhole-prone Areas Using Microgravimetry and Radar Interferometry

Abstract

Geophysical and remote-sensing methods were applied 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 (90 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 in both areas. At Wink, limited spatial and temporal data on vertical ground movement from standard surveying has been greatly extended by satellite-based radar interferometry, which was used to delineate areas having recent movement and determine rates of movement. Results from interferometry guided site-specific investigations that included acquisition of high-resolution gravity data, which identified shallow-source mass deficits that indicate potential for continued subsidence or sinkhole formation. At Daisetta, interferometry was used to determine that no detectable subsidence preceded sinkhole collapse (indicating sudden collapse once the upward-migrating void reached a depth that allowed the cohesiveness of overlying semiconsolidated sediments to be overcome), and gravimetry was used to identify other 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.