Abstract

The Seismo-Lineament Analysis Method (SLAM) integrates data from earthquakes, geomorphology, and geological fieldwork to facilitate recognition of seismogenic faults. SLAM is a set of procedures that can spatially correlate a nodal plane from an earthquake focal-mechanism solution with faults observed at the ground surface. The intersection of the ground surface with the uncertainty volume of a given nodal plane defines a seismo-lineament. The surface trace of the fault that produced the earthquake is likely to be located within the seismo-lineament (1) if the nodal plane is coincident with the fault, (2) if the fault is emergent, and (3) if the fault is approximately planar at the scale of the analysis. As an example, SLAM was applied to a M2.9 earthquake with a strike-slip focal-mechanism solution and an epicenter near Point Dume in the Santa Monica Mountains, southern California. Geomorphic lineaments and several faults with low pressure-temperature (PT) gouge zones and sub-horizontal shear striae were observed within and parallel to the seismo-lineament of a nodal plane oriented 095 75SW associated with left-lateral strike slip. This zone of strike-slip faults is not included on published maps and will require additional fieldwork to characterize. Extending >20 km, this may be an important (perhaps newly emergent) structure in the Santa Monica Mountains. Under appropriate circumstances, SLAM can generate spatial hypotheses relating earthquakes to faults observed at the ground surface, even in cases when lack of Holocene cover may constrain trench studies.

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