Abstract
AbstractInland earthquake activity in and around the Kinki region, southwest Japan, increases in the period from several decades before to about a decade after the occurrence of great interplate earthquakes along the Nankai Trough. To quantitatively investigate this relationship, we calculated long‐term changes in the Coulomb failure function (ΔCFF) on inland active faults in this region with viscoelastic slip response functions. As sources for the change in CFF, we investigated east‐west compression within the Niigata‐Kobe Tectonic Zone (NKTZ), historical interplate earthquakes and interseismic locking along the Nankai Trough subduction zone, and historical inland earthquakes in this region. Among these sources, the NKTZ east‐west compression is the primary cause of the long‐term changes in CFF. The changes in CFF due to interplate earthquakes are mostly negative on reverse faults and positive on strike‐slip faults. This result suggests that the inland reverse faulting activity mostly increases before interplate earthquakes and decreases after the earthquakes, whereas strike‐slip activity is mostly suppressed before interplate earthquakes and increases thereafter. This suggestion is supported by spatiotemporal pattern of historical inland earthquakes if focal mechanisms of historical earthquakes correspond to fault geometries in the region. The calculated changes in CFF are usually consistent with the occurrence of historical inland earthquakes. If we use the change in shear stress instead of the change in CFF, this consistency is enhanced, which suggests low apparent coefficients of friction in this region.
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