Tsunami generation near Japan by earthquakes in Along-strike Single Segmentation and Along-dip Double Segmentation

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  • 日本付近の一重と二重の地震セグメント帯で発生した地震が励起した津波
  • ニホン フキン ノ ヒトエ ト ニジュウ ノ ジシン セグメントタイ デ ハッセイ シタ ジシン ガ レイオコシタ ツナミ

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After the 2011 Tohoku-oki megathrust earthquake, we have proposed a hypothesis on the earthquake activity characterizing the distribution of earthquakes into Along-dip Double Segmentation (ADDS) and Along-strike Single Segmentation (ASSS): The apparent absence of earthquakes in the trench-ward segments as opposed to the Japan Island-ward segments that generate repeated smaller earthquakes (ADDS), where the 2011 Tohoku-oki megathrust occurred. In the mean time, a young and buoyant plate is subducting rapidly under the overriding plate where there is weak seismic activity before the main event all over the plate interface of the subduction zone (ASSS). The 1960 and 2010 Chile megathrusts occurred in ASSS. In and near Japan, ADDS earthquake activity is restrictively found along the Pacific side of Hokkaido and Tohoku regions and the Hyuganada, Kyushu. The rest of seismic activity near Japan is classified into ASSS. We found a distinct difference in tsunami excitations between earthquakes in ADDS and ASSS, comparing tsunami magnitude m from local tsunami heights and seismic moment Mo from long-period surface-waves. Tsunami wave heights of ASSS earthquakes are almost two times larger than those of ADDS's. This is also confirmed by studying tsunami magnitude Mt calculated from teleseismic tsunami wave heights. The reason of this different excitation of tsunamis is also considered.

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