Using InSight Data to Calibrate Seismicity From Remote Observations of Surface Faulting

Abstract

AbstractWe use a scaling relationship between fault length and scalar moment to predict seismicity from the Cerberus Fossae graben using shear modulus and fault lengths. Cerberus Fossae is 20–40° (1,200–2,300 km) from the InSight lander and matches the location of 21 recorded seismic events withMw ≥ 3. These unique seismic observations make an ideal laboratory to test our method of predicting seismicity on another planet using surface fault observations. Terrestrial faults have observed patterns of rupture depth distributions and segmentation. We use these patterns and magnitudes of detected marsquakes to predict moment release of events in Cerberus Fossae over a range of plausible Martian rupture vertical slip extents (VSEs) of 2, 20, and 40 km, which are rooted in estimates of crustal thickness, elastic thickness, and seismicity depth. We sum individual events for each case to determine cumulative moment release and use deformation duration to determine annual moment release. Predicted seismicity rates are dependent on the duration of deformation, which in this case is well constrained to 2–10 Ma. We compare our results to events recorded at Cerberus Fossae by InSight and find that seismicity rates for the cases with a 40 km maximum VSE or no limit on VSE are within an order of magnitude of observed seismicity. Faults with maximum VSEs of 2 km best match observed magnitudes. Our approach, using only observed fault lengths, segmentation, seismogenic thickness estimates, and deformation duration, produces seismicity estimates that are as accurate as methods that take rupture offset into account.