Focal mechanism determined by moment tensor analysis on an M4.4 event in Yellowstone National Park in 2017

Focal mechanism determined by moment tensor analysis, which uses a model to fit the long-period (~10 s period or greater) ground motion records recorded at multiple locations. This example is for a M4.4 event that occurred during the 2017 Maple Creek earthquake swarm.  Left-hand plots show the fit between recorded ground motions at different seismic stations (black lines) and modeled ground motions (red dashed lines). The associated focal mechanism beachball diagram is shown at the right, with labels showing the directions to stations used in the model.  Above the mechanism, various parameters of the model solution are listed.  Depth indicates the earthquake depth.  Strike indicates the horizontal directions of the two possible fault planes.  Rake indicates the angle of modeled slip on those fault planes. Dip indicates the steepness angle of the fault plane from vertical.  M₀ indicates seismic moment of different components of the mechanism.  M_w indicates moment magnitude.  Percent DC is the percentage of the modeled source that represents simple faulting, while CLVD and ISO indicate deviations from simple faulting.  Variance, Var. Red., and RES/Pdc indicate parameters associated with how well the model explains the data.  Source: Jamie Farrell, University of Utah Seismograph Stations (https://quake.utah.edu/special-events/ongoing-yellowstone-earthquake-sw…).