Estimating slip distribution along the southernmost ∼80 km of the San Andreas Fault by examining tectonically offset features

Abstract

We measured tectonically offset geomorphic features along approximately 80 km of the southernmost San Andreas Fault (sSAF) between Bombay Beach and Indio Hills in the Salton Trough to obtain a better estimate for slip distribution and slip-per-event for the past several large, surface rupturing earthquakes along this segment of the fault. In addition to gathering aerial imagery from previously published B4 light detection and ranging (LiDAR) and uncrewed aerial vehicle (UAV) imagery, we constructed new high-resolution orthomosaic images and digital surface models (DSMs) generated from Structure-from-Motion-Multiview Stereo (SfM-MVS) techniques from UAV imagery at multiple localities along the San Andreas fault in the Salton Trough region of California, which include study areas at Durmid Hill, Salt Creek, Ferrum, Mecca Hills, and Indio Hills. The aerial imagery, along with field mapping, were used to identify and measure a total of 146 offset features with lateral displacement measurements ranging between 1.5 and 23 m, with all measurements below 2.5 m found along multi-stranded sections of fault. Investigation of offset features suggests that the last several large, surface rupturing events produced average displacements of 3.0–4.4 m per event, with lower overall lateral slip values where multiple fault strands are present. Offset features along sections of the fault with multiple active strands with only partial displacement measured were not considered in our final slip distribution.