Detection of Previously Unmapped Faults by Remote Sensing Mapping of a San Andreas Fault Zone transect, in the San Bernardino Mountains

SMSU Event Center BC

This study evaluated a transect across the San Andreas and San Jacinto Fault zones and compared multiple geologic maps along with LIDAR and historic aerial photography to develop our own interpretation of faults and related landscape features. Both the San Andreas and the San Jacinto Faults are seismogenic and capable of producing large earthquakes with fault ground surface rupture which are both significant hazards to the Southern California population (Schulz and Wallace, 2016). However, recently the Southern California Earthquake Center (SCEC) has stated that previously unrecognized small faults in this and other fault zones may pose seismic hazards, but such faults may have been overlooked during prior investigations. Thus, this study focused on: assuring that older faults were properly mapped, as most of the mapping predates the advent of GIS databases; and mapping smaller lineaments that may indicate the location of previously unmapped faults. This project’s methodology used historic photogrammetry, existing LIDAR imagery, and published maps. We created a lineament map along the 10-km long by 1-km wide study transect. We recognized 20 significant linear features or possible smaller faults that appear to have been overlooked in the San Andreas Fault Zone as well as the Cleghorn Fault zone in the San Bernardino Mountains. As we have identified these various potential fault-related linear features, each one should be investigated further in more detailed studies to clarify if they are faults and if they pose a potential seismic hazard.