SOME QUICK, HELPFUL, AND LOW-RISK THINGS THAT CAN BE DONE WHEN A MAJOR SINKHOLE FORMS: GROUND AND AIRBORNE SURVEYS AFTER THE APRIL 2023 DAISETTA SINKHOLE COLLAPSE, SOUTHEASTERN TEXAS

On April 2, 2023, a sinkhole formed on the northwestern flank of the Hull salt dome in the city of Daisetta, Texas. This nearly circular sinkhole is located adjacent to the southwestern edge of a larger sinkhole that collapsed in 2008. At the request of local emergency officials, we visited the sinkhole six days after collapse to map concentric fissures and scarps around the new sinkhole; conduct a drone-based, structure-from-motion survey to obtain high-resolution images and construct a post-collapse topographic map of the sinkhole area; measure water depth in both sinkholes; acquire differential GPS elevations to georeference drone imagery and detect elevation change; and use a passive seismic method to estimate the depth to cap rock or salt near the sinkhole. Preliminary analysis of data acquired during the initial site visit provided useful information about the sinkhole (including affected area, water depth, and expansion potential) to emergency responders and the concerned public.

Drone imagery, differential GPS measurements, and related field studies of the 2008 and 2023 Daisetta sinkholes revealed that the newer sinkhole has a smaller areal extent (70 m vs. 170 m diameter), shallower maximum water depth (9 m vs. 23 m), and a similar halo of concentric scarps, fissures, and cracks compared with the 2008 sinkhole. Pre-collapse evidence of potential sinkhole formation, important for early warning of future sinkhole collapse, included (1) ground movement and related structural damage noted about 16 months before collapse, and (2) elevation loss sufficient to create a water-filled low near the center of the 2023 sinkhole outline that is evident on aerial imagery acquired seven months before collapse. We interpret that additional collapse is possible to the edge of the currently fissured halo and perhaps beyond, but the collapsed area could also not expand much beyond its current extent (similar to the limited growth of the 2008 sinkhole). Future rapid collapse similar to that observed in 2008 and 2023 is possible in adjacent areas along the steep flank of the salt dome. Beyond these useful initial studies at newly formed sinkholes such as those at Daisetta, we recommend in-depth investigations to better understand the cause and mechanism of collapse to minimize risk associated with possible future events.