REFINING THE ESTIMATE OF SLIP RATE ON THE OWL LAKE FAULT (EASTERN CALIFORNIA) AND IMPLICATIONS FOR THE TECTONICS OF THE GARLOCK FAULT

The Owl Lake Fault is an active, 25-km-long, left-lateral strike-slip fault that divaricates NE from the Garlock Fault toward Death Valley in eastern California and transfers regional strain to the fault systems in Death Valley. As an active fault, the Owl Lake Fault is a poorly understood link between the extension of Death Valley and other active faults within Mojave Desert. In addition to the larger tectonic framework, improved understanding of the Owl Lake fault as a seismogenic structure has direct implication for the assessment of the earthquake hazard in Eastern California. A significant limitation on the understanding of the Owl Lake Fault’s role is the wide range of estimates on its slip rate, which range from 0.5 to 7.8 mm/yr. The project aims to constrain the slip rate and understand kinematics of the Owl Lake Fault. For this project, I have used recent airborne LiDAR data (approximately 10 points/m²) to map the fault and precisely measure horizontally offset landforms along the Owl Lake fault. Subsequent to LiDAR mapping, field work facilitated the ground-truth verification of initial mapping as well as more precise measurements of small fault offsets using kinematic GPS and low-altitude photogrammetry. Initial efforts at refining the slip rate use scarp degradation models to infer the ages of alluvial fans and stream terraces that are offset by faulting. Additionally, sample material has been collected for dating faulted landforms using terrestrial cosmogenic nuclide concentrations. The detailed, local ‘microtopography’ permits assessing the smallest offsets (75-100 cm) which are interpreted as reflecting the last coseismic offset. The final step for this project involves analyzing offset measurement data and estimating slip rates. Histograms of offsets will be constructed from LiDAR and field measurements. Based on the distributions shown, this analysis will test whether the Owl Lake Fault has characteristic earthquake behaviors. A better slip rate on the Owl Lake fault is key to understanding how the Garlock fault changes along strike – the Owl Lake Fault may ‘leak’ slip from the western and central Garlock Fault, which has a slip rate of 5-7 mm/yr, as its strike changes eastward and terminates in the Avawatz Mountains.