Characterizing Houston Surface Faults with DEMs and Other GIS Data

Over 300 active faults intersect the Earth's surface in the Houston Metropolitan area. These surface faults have caused damage to roads, pipelines and buildings. Most of these faults form part of a regional down to the basin fault system along the northern coast of the Gulf of Mexico. In this study several kinds of information were used to improve characterization of the fault systems: lidar data, Ground Penetrating Radar, (iii) shallow seismic data, and GPS data. Lidar data acquired in 2001 were used to remap the active faults of the area. A grid refinement algorithm for processing the raw lidar data to generate a 1.5 meter resolution DEM was developed. Spatial resolution of the scarps on the refined grids was improved and in some cases revealed features that were not observed on the unrefined DEM. Throw and throw differences were computed using different generations of lidar DEMs to provide a measure of the change in faults over time. Hill-shading proved the best method for selecting faults for examination in the field. Shallow seismic data indicated disturbed ground in the vicinity of the faults, while GPR data showed near-surface structure which aided in determining whether topographic features that resemble scarps are faults or related to some other natural or anthropogenic surface features. GPS data for the period from 1995 to 2005 showed ongoing subsidence in northwestern Houston and horizontal displacement towards the Gulf of Mexico.