Nakamura Yasuyuki, Fujiwara Toshiya, Kodaira Shuichi, Miura Seiichi, Obana Koichiro
Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 3173-25 Showa-machi, Kanazawa-ku, Yokohama, Kanagawa, 236-0001, Japan.
Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 2-15 Natsushima-cho, Yokosuka, Kanagawa, 237-0061, Japan.
Sci Rep. 2020 Jul 14;10(1):11607. doi: 10.1038/s41598-020-68449-6.
Since the giant 2011 Tohoku earthquake and tsunami, much research has focused on the distribution of coseismic slip at shallow depths during this subduction megathrust event. Here we present seismic images obtained in the immediate vicinity of the trench axis, that show thrust faults and fold-and-thrust type deformation structures near the epicenter of the 2011 Tohoku earthquake where the large coseismic slip has been inferred, and chaotic structure and the absence of thrust faults in northern and southern source areas. Seismic profiles show evidence of slope failures of the trench inner wall in a proposed tsunami source region around 39°-40° N, where the slips estimated from previous studies are in disagreement. Our results show that structural characteristics in the trench axis may be related to the occurrence of shallow megathrust slip and tsunamigenesis in the Japan Trench.
自2011年日本东北大地震及海啸以来，许多研究聚焦于此次俯冲型巨大逆冲事件中浅部同震滑动的分布情况。在此，我们展示了在海沟轴附近获取的地震图像，这些图像显示在2011年日本东北地震震中附近存在逆冲断层以及褶皱 - 逆冲型变形构造，据推断该区域发生了大规模同震滑动，而在南北源区则呈现出混乱的构造且不存在逆冲断层。地震剖面显示，在北纬39° - 40°附近一个假定的海啸源区，海沟内壁存在斜坡失稳的迹象，此前研究估算的滑动情况与此处并不一致。我们的结果表明，海沟轴的构造特征可能与日本海沟浅部巨大逆冲滑动及海啸的发生有关。
