Application of UAV Photography to Refining the Slip Rate on the Pyramid Lake Fault Zone, Nevada

Abstract

The Pyramid Lake fault zone (PLFZ) is a 50‐km‐long, active northwest‐trending right‐lateral fault in the northern Walker Lane, located ∼30 km east of Reno, Nevada. Previous paleoearthquake and slip‐rate studies report that the Pyramid Lake fault has produced four surface‐rupturing paleoearthquakes since 15,475±720 cal B.P., three of which occurred after 8980±260 cal B.P., and has had an average minimum slip rate of 2.6±0.3 mm/yr since the late Pleistocene. These observations imply that coseismic offset for each paleoearthquake averaged 7–9 m, larger than expected from empirical scaling relationships for a strike‐slip fault of its length. To reconcile this discrepancy, we used a small camera‐mounted unmanned aerial vehicle to develop high‐resolution digital elevation models and interpret previously unreported right‐laterally offset geomorphic features along the northern section of the PLFZ. Offset measurements at seven sites range from 8 to 21 m. The ages of displaced features are interpreted from previous lake level and mapping studies of Lake Lahontan. From these observations, slip‐rate estimates at the sites range between 0.5 and 1.6 mm/yr. These lower values of slip rate require that coseismic displacements associated with previously reported paleoearthquakes average only 3–5 m, within the range that would be predicted from empirical scaling relationships of rupture length and coseismic displacement.