Figure 2. Average slip along strike of different existing coseismic models. Solid lines show the average coseismic slip along strike of published models, dashed line show the average coseismic slip along strike of our preferred coseismic model with 120km fault width.
Stress-driven afterslip provides a physically based model for post-seismic afterslip (Wang and Fialko, 2018). In this kind of model, the slip distribution and time history of afterslip is determined by the coseismic slip and the frictional properties of the fault plane. Under the assumption of frictional homogeneity on the plane, the spatial pattern of the stress-driven afterslip is determined by the coseismic slip distribution, while the frictional parameters control the time evolution of slip and displacement.
In this study, we first compare the stress-driven afterslip predictions for three published slip models (Elliottet al., 2022; Liu et al., 2022; Ye et al., 2022), and find that most of the models show significant misfit to the postseismic displacements (section 4.1). We find that the azimuthal misfits in some models result from the peak afterslip being located too close to the coastline; the location of the peak afterslip is determined mainly by the downdip end of the slip distribution. Using the insights gained from these comparisons, we then systematically vary the coseismic slip inversion to identify how the slip model must change to best predict the afterslip, considering a range of models for the contribution of viscoelastic relaxation. Finally, as an additional test of our conclusions about the slip model, we compare the model predictions to the data from GPS campaign measurements collected three weeks after the earthquake, which contain both coseismic and postseismic signal.
2 Data