Figure 3. Stress transferred by the Aug. 14, 2021, magnitude-7.2 mainshock to surrounding faults. In (a), we calculate stress on faults with the same geometry as the mainshock, based on a preliminary finite fault model (USGS, 2021). Lobes of stress increase (red) extend in four directions. (b) Here we use the focal mechanisms of past earthquakes to infer the geometry of surrounding faults, which indicates that the faults that ruptured in 2010 aftershocks were re-stressed by the 2021 earthquake (red beachballs). (c) Because the density of focal mechanisms is very sparse, here we interpolate between focal mechanisms for a smooth grid. Credit: Temblor Inc.