2009 Volume 63 Issue 6 Pages 343-354
Ground motion over a loosely coupled swaying faultblock is shown through three-dimensional non-lineardynamic simulations to be strengthened near the peripheral bounding faults. The model is considered the Rokko fault block in West Japan, which has been identified as such a swaying fault block. One of the peripheral faults bounding this block was activated during the 1995 South Hyogo Prefecture Earthquake (M7.3) in Kobe, and high seismicity along the fault appears to have impeded complete cohesion among the blocks in the area. The Rokko fault block rose as a horst structure in the late Pliocene to middle Pleistocene, and is bounded by a steep inward-dipping fracture. Crushed zones associated with other peripheral active faults of the Rokko massif have similar depth and high seismicity, confirming the Rokko block to be a swaying fault block. The strong peripheral ground motion simulated by assuming a vibrating cube adhered loosely to the host rock is in accordance with the prediction of seimic risk for the plain, where fault blocks are similarly embedded with loose adhesion.
