Use of Integrated MASTER Multispectral Imagery and LiDAR DEM for Active Fault Detection and Evaluation

Displacement caused by surface fault rupture associated with large earthquakes not only disrupts infrastructure and damages natural and built environments, but also constitutes a life safety hazard. The California Geological Survey (CGS) has the authority and responsibility, under the Alquist-Priolo Earthquake Fault Zoning Act, to identify and map active faults in California for the purpose of surface rupture hazard identification and mitigation through regulatory zoning. Mapping and evaluation of active faults is generally accomplished through conventional aerial photo interpretation and field mapping, which rely on recognizing fault-related geomorphic features and juxtaposition of contrasting rocks, soil, and geologic structure. Faults covered by vegetation or concealed by young alluvium will most likely not be detected by this method. Furthermore, spatial accuracy of photo-interpreted fault traces is limited to the accuracy, scale, and method of transfer to conventional topographic base maps, which generally lack the spatial accuracy of geolocated imagery. The inherent limitations of conventional active fault mapping are expected to be overcome by using integrated MASTER and LiDAR data. MASTER is a multispectral imagery with 50 spectral bands ranging from visible to thermal region of the electromagnetic spectrum. LiDAR on the other hand is a laser-based technology with very high positional accuracy, sub-meter resolution and capability to filter out vegetation. MASTER and LiDAR are integrated via data transformation/fusion and the resulting fused imagery are utilized to interpret active faults through recognition of fault features associated with different distinctive properties related to geology, drainage, vegetation, hydrology, thermal, anthropogenic, and topography. The completeness and accuracy of the fault interpretation is gauged by overlaying it to a baseline data of previously mapped fault traces. The research study, supported by a NASA grant, evaluated a well-mapped, 26-km reach of the southern San Andreas Fault Zone in the Antelope Valley near Palmdale.