ACTIVE SURFACE FAULTS, A MANIFESTATION OF HOUSTON AREA NEOTECTONICS

Over 300 active faults intersect the earth's surface in the Houston Metropolitan area on the northern edge of the Gulf of Mexico basin. These surface faults have caused damage to roads, pipelines and buildings. The faults in southeast Houston are generally associated with salt domes, whereas the faults in northwest Houston define a southwest-northeast regional trend. We used LiDAR data to better map faults in the Houston area. We developed a grid refinement algorithm for processing the raw data to generate a 1.5 meter resolution DEM. The refined grids allowed for better spatial resolution of the scarps and in some cases revealed features that were not noticed on the original DEM. Hill-shading proved the best method for identifying faults that were then examined in the field. Our analysis of the LiDAR data confirmed the locations of many previously mapped faults and found several candidate scarps which may be faults. Field visits to locations of scarps identified by the LiDAR in some cases show a clearly visible scarp whereas in others the elevation changes detected by the LiDAR are subtle and unlikely to be readily noticed on the ground. Photographs of the sites were taken to record their character.

We used GPR and high resolution seismic data on a few scarps to image them in the near-surface and help determine whether these scarps are faults or related to some other natural or anthropogenic surface features. These data provide indications of faulting at two known fault locations and suggest that one of the candidate locations does not appear to be faulted. It may correspond to the cut bank of an old stream channel.

These are growth faults originating from deposition prograding into the Gulf of Mexico basin. Faulting commenced in the Oligocene when the prograding shelf margin was in the Houston area. These faults remain active. The faults may be reactivated by subsidence due to shallow water withdrawal, but may also result from Holocene salt tectonics, both diapiric and salt withdrawal. Our ongoing studies include using InSAR and GPS to measure subsidence and fault slip rates and aim to lend further insights into Houston area neotectonics.