南海トラフから沈み込むプレートの形と中央構造線  [in Japanese] Frontal shape of subducting plate along the Nankai Trough and recent activity of the Median Tectonic Line  [in Japanese]

沈み込むプレートの熱的同化という概念を導入して, 西南日本弧の地殻底地震の分布域は沈み込むプレートのseismic slabの形を表すと再解釈した。このseismic slabの形は沈み込むプレート(四国海盆)の年齢を考慮すると定量的に説明できる。物質的な意味でのプレートは長くのびていたとしても力学的にはseismic slabの部分だけが西南日本弧のテクトニクスに影響を与えるので, 中央構造線ぞいの横ずれ断層活動に対する以前の解釈(Shiono, 1974, 1980)は大きく変更する必要はない。ただし, このseismic slabの先端の前進速度は沈み込み速度の約1/10であると予想されるので, 断層運動の歴史を議論するときには注意しなければならない。

Based on an idea of thermal assimilation of the subducting plate, hypocentral distribution of subcrustal earthquakes beneath Southwest Japan is re-interpreted to represent a seismic slab of the Philippine Sea plate subducting along the Nankai Trough. The shape of the seismic slab can be explained in terms of a subduction of the young Shikoku Basin which was formed along nearly N-S trending spreading axis. Considering that only seismic and brittle parts of the subducting plate have the mechanical influence on the arc, the previously presented decoupling model (Shiono, 1974, 1980) is useful to explain the recent strike-slip movements along the Median Tectonic Line (MTL) without serious modification; where the seismic slab does not reach the MTL and remains with in the outer block, strike slip movements occur to release horizontal shear due to oblique plate convergence because the outer block is decoupled from the inner one along the MTL.