On the California coastline, active earthquake faults are numerous, and construction or modification of structures often requires a geologic hazards investigation to determine the risks associated with any proximal fault features.
Often used in conjunction, a preliminary magnetic investigation and subsequent refraction seismic and/or electrical resistivity surveys are the methods of choice for determining the subsurface location of a fault of ancient landslide. These remote sensing methods can then be verified or given “ground truth” through subsequent borings and/or trenches. Once the exact location of such features has been determined, appropriate setback distances and building foundation parameters can be determined.
In some cases, GPR may also be helpful to determine the location of a buried fault, however, there are many limitations to the method, including limited depth of investigation, and soil type dependency (clay soil may limit the depth of investigation).