Future Earthquakes and Their Strong Ground Motions in the Tokyo Metropolitan Area

概要

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The Tokyo Metropolitan Area (TMA) is located close to the triple junction of the Pacific, Philippine Sea, and continental plates. Various earthquakes occur in this complex plate system. Those generated by active faults might be candidates for future earthquakes beneath TMA, but their occurrence probabilities are not high. A deeper part of the Philippine Sea slab is also located beneath TMA. This part can generate a large earthquake with a high probability, so a prediction of strong shaking has been carried out following the recipe for strong ground motions. The occurrence probability of a subduction-zone earthquake along the Sagami trough is low because the 1923 Kanto earthquake occurred only 80 years ago. The probabilities of earthquakes along the Nankai trough are high. In particular, the Tokai earthquake has a probability as high as 86%. The Dai-DaiToku project has made models of the Philippine Sea slab shape and the Kanto basin structure, and a 250 m-mesh geomorphological site classification map, which will enhance the accuracy of strong ground motion prediction.