LIDAR STUDIES OF NEOTECTONIC PROCESSES IN TEXAS GULF COAST

Houston, the fourth largest city of United States, lies within the wide coastal shelf margin of the Gulf of Mexico. Sediment deposition has resulted in the progradation of a continental margin sedimentary wedge into the Gulf of Mexico basin throughout the Latest Jurassic, Cretaceous and Cenozoic. Regions of active growth faulting typically occur near shelf margins and represent a significant societal hazard. Houston lies near the Oligocene prograding shelf margin, but faults associated with this paleo-margin remain active today. Our ongoing research addresses this anomalous behavior and is designed to determine the mechanisms most responsible for driving faults above a fossilized continental margin. A broader goal is to investigate the interplay between sedimentation and lithospheric deformation by integrating measurement of present day processes with knowledge of the underlying stratigraphy and plate dynamics. We used GPS data, acquired during the period between 1995 and 2005. GPS data were obtained from the Houston-Galveston Coastal Subsidence District. We found evidence of ongoing subsidence in northwestern Houston and of possible horizontal surface movement towards the Gulf of Mexico.

However none of the sites for which the GPS data are acquired are close to either faults or salt domes. They have been chosen to avoid such local structures in order to better monitor regional subsidence. InSAR too has numerous disadvantages in application to the Houston area because of atmospheric contamination. Our efforts for several months failed to find images with good coherence primarily because of considerable variability in the atmosphere. In general remote sensing techniques are not very useful in very dense urban areas with tall buildings. However, LiDAR is highly suitable over faults and salt domes in this region. We used LiDAR data collected in 1996, 2001, and 2008 to estimate the surface deformation in this region. Our preliminary data suggest association between active faults and rising salt domes. The faults are considered to reactivate on growth faults that sole out in a detachment surface. The idea that rising salt domes are driving normal faulting and subsidence will be further tested by multiple Terrestrial Laser Scanner scans of faults and salt dome surfaces and shallow geophysical surveys.