Differences in Earthquake source and ground motion characteristics between surface and buried faulting earthquakes

Previous work has shown that the ground motions from earthquakes that break the ground surface are weaker than those from buried faulting earthquakes. In this paper, we describe differences in kinematic and dynamic source parameters that may give rise to these differences in ground motion levels. From kinematic rupture models, we show that the slip velocity of surface faulting earthquakes is less that the slip velocity of buried faulting earthquakes. From dynamic rupture models, we infer that rupture in the shallow part of fault (upper few km) is controlled by velocity strengthening, with larger slip weakening distance Dc, larger fracture energy, larger energy absorption from the crack tip, lower rupture velocity, and lower slip velocity than at greater depths on the fault. Dynamic rupture modeling using these properties results in lower ground motions for surface faulting than for buried faulting events, consistent with the observations.