Afterslip From the 2020 M 6.5 Monte Cristo Range, Nevada Earthquake

Abstract

Measurements of surface deformation after an earthquake can be used to probe the frictional properties of the earthquake fault and the rheological properties of the crust and upper mantle. Large magnitude earthquakes (approximately M > 7) can stress deeper parts of the Earth's crust and upper mantle; their postseismic motions likely reflect a range of processes and properties, including afterslip, viscous relaxation of the lower crust and/or upper mantle, and poroelastic effects. In contrast, stress changes associated with smaller magnitude events may only affect the upper and middle crust and may exhibit a more limited range of postseismic phenomena. Whether a deformation process is active or not likely depends in part on stress change magnitude. Studying postseismic responses for a range of earthquake magnitudes is therefore important.Until recently, studies of the postseismic response of smaller magnitude earthquakes were challenged by low signal to noise ratios. However, improvement in geodetic techniques, such as GPS and InSAR, now permits such studies. Here, we present geodetic and seismic data covering the first 7 months after the 15 May 2020, M w 6.5 Monte Cristo Range (MCR), Nevada, earthquake. Combined seismic and geodetic data suggest that aseismic afterslip on the main fault plane dominates the postseismic response. We focus on three questions:1. What is the ratio of seismic to aseismic afterslip? 2. How is postseismic slip distribution related to coseismic slip and surface rupture? 3. Does afterslip reduce the shallow slip deficit (difference between surface slip and slip at depth)?