MULTIDISCIPLINARY INVESTIGATION OF SURFACE DEFORMATION IN HOUSTON, TEXAS

Sedimentation and deformation toward the Gulf of Mexico Basin cause faulting in the coastal regions. In particular, hundreds of active faults to surface are known in the Houston Metropolitan area, where surface deformation has been an ongoing problem. Most of the previous studies attributed the causes of the surface deformation to anthropogenic activities, mainly the subsurface withdrawals of oil, gas, and groundwater. However, the majority of the studies done have not accounted for the vast amount of salt underneath the Houston area and its role in the surface deformation. This work assessed the surface deformation in the greater Houston area and their possible relationship with subsurface salt movements, using GPS, Lidar, geophysical and inSAR data. GPS rates for the last seventeen years show a change in surface deformation patterns. High rates of subsidence in the northwestern areas (~4 cm/yr) and signs of uplift in the southeast are observed (up to 2 mm/yr). High rates of subsidence appear to be decreasing. Contrary to previous studies in which the location of subsidence appeared to be expanding towards the northwest, current results show that the area of subsidence is shrinking and migrating towards the northeast. Two different LiDAR datasets (from 2001 and 2008), provide time-lapse images and suggest elevation changes across the major fault systems and also show changes between salt domes and their surrounding areas. To help illuminate the subsurface character of the faults and salt domes, we undertook geophysical surveys [Ground Penetrating Radar (GPR), seismic reflection, and gravity] across some of the faults and salt domes.

This study found that although groundwater withdrawal may be a large influence in the surface deformation of the Houston area, but salt withdrawal and salt diapirism may also be playing a significant role in the surface deformation of southeast Texas.