Reconstruction of Late Quaternary Offsets Along the Southernmost Elsinore Fault Zone Using High Resolution SfM Imagery
Our study is focused on the tectonic geomorphology along the southernmost Elsinore Fault, located along the southwestern range front of the Coyote Mountains, Imperial County, California. This investigation expands on earlier work (Rockwell, 1990; Fletcher et al. 2011; Rockwell et al 2018) in determining surficial expression of the tectonic geomorphology in this region. In this study an Unmanned Aerial Vehicle (UAV) was deployed and collected very high-resolution imagery along the fault, to identify and resolve displacements of offset Holocene alluvial bars and channels. We identified evidence for three late Holocene surface ruptures in Alverson Canyon, and we compare our results to those interpreted from previously collected total station survey, tripod-based LiDAR survey, and field-based tape measure estimates. The average displacement of the offsets were measured with a maximum offset of 5.6m ± 0.5m and a minimum offset of 4.6m ± 0.5m. Combined with the Rockwell (1990) estimate age of the Q4 bar at 2-3 ka, we resolved a short term slip rate of about 1.5 – 2 mm/yr, consistent with Fletcher et al. (2011) estimate for this section of the fault. The rapidly increasing technological advances of UAV surveys allow us to accurately identify the surficial expression of past surface ruptures.