DETERMINING AGES OF FAULTED SURFACES ALONG INACCESSIBLE PORTIONS OF THE EASTERN GARLOCK FAULT USING RADIOMETRIC ASSESSMENTS OF SURFACE CHARACTER: APPLICATIONS FOR SLIP RATE STUDIES

The Garlock fault plays a major, but uncertain, role in the diffuse inboard portion of the Pacific - North American plate boundary. While prior neotectonic and paleoseismic investigations indicate that the Garlock fault is very active on a millennial time scale, seismological and geodetic investigations show little activity on shorter time scales. Various models for the role of the Garlock fault rely upon changes in slip rate magnitude from west to east, where both the overall gradient and spatial location of abrupt changes in slip rate have considerable implications for how the Garlock fault interacts with surrounding faults. The 2019 Ridgecrest earthquake sequence has highlighted the extent to which the Garlock fault may interact with surrounding faults and the need for refined slip rate measurements, particularly on the eastern Garlock fault. A significant portion of the eastern Garlock fault lies within inaccessible portions of Naval Air Warfare Station China Lake and Fort Irwin, with unexploded ordinance constituting a major hazard. To better constrain ages, and thus slip rates in the region, we are examining the use of various radiometric observations from several previously dated sites to quantify the change in surface roughness and reflectance. This includes surface roughness from aerial LiDAR and radar backscatter, as well as surface composition from multispectral reflectivity. We find that two main processes likely affect the radiometric signature of the faulted surfaces: the development of desert pavement and desert varnish. We intend to use these relationships to establish age estimates for inaccessible sites along the eastern Garlock and develop more accurate slip rate estimates.