Characterization of Slip on Fault in Shallow Zone Above Seismogenic Zone for Inland Crustal Earthquakes with Surface Ruptures

To update the recipe for predicting broadband strong ground motions with permanent displacement in the vicinity of surface ruptures, we examined slip characteristics in the shallow zone above the seismogenic zone using source inversion results, observed fault displacements, and models of long-period motion generation area. We compiled the waveform inversion results of heterogeneous slip models for eight inland crustal earthquakes with surface ruptures in Japan and outside with magnitudes of approximately M _w 6.5 or greater. The average slip in the rupture area agreed with the three-stage source scaling relationship. The average slip in the shallow zone at depths of approximately 3 km or less was comparable to or slightly greater than the average slip in the rupture area. Meanwhile, the average fault displacement was almost equal to the average slip in the rupture area. Furthermore, by extracting the shallow large slip area with a slip 1.5 times or more the average slip in the rupture area, we confirmed that the average slip in the shallow large slip area was nearly equivalent to the average slip in the asperity area and the slip in the long-period motion generation area. The maximum slip in the shallow large slip area was almost equal to the maximum fault displacement. This study results in confirming a proportional relationship between geomorphological data such as the fault displacement on the surface during the earthquake and seismological data such as the average slip estimated from source inversion analysis.