IMPEDIMENTS TO UNDERSTANDING ACTIVE FAULTING ALONG THE NORTHERN GULF OF MEXICO BASIN

It is well known that south Louisiana and south Texas are cut by active, generally down-to-the-south normal faults. Surface ruptures along these faults are known hazards and are responsible for substantial damage to the built environment. Study of these faults has been difficult because of poor exposure and the dense vegetative cover of coastal Louisiana and Texas. Traditional tectonic geomorphology-based methodologies developed in arid to semiarid environments are less effective in this semitropical environment. For example, the combination of generally continuous fault motion, weak surface materials cut by the faults, and high rates of weathering have promoted rapid degradation of fault-related landforms. Faults, therefore, are generally not exposed, but are instead marked by fault-line scarps whose associated topographic contours are linear and sub-parallel to fault strands. This is in contrast to the highly fractal patterns of topographic contours typically produced in this low relief, erosion-dominated landscape. New approaches and tools are needed for effective detection, mapping and measurement of active faults of the region. Studies are needed to document these methods and tools and to provide users with specific information relating to: 1) the efficacy of these methods and tools in specific geological settings and under a range of environmental conditions; 2) the effective range of spatial and temporal resolution of observations and measurements, and 3) the limitations of the methods and tools.