Kochi Institute for Core Sample Research, Japan Agency for Marine-Earth Science and Technology, Nankoku, Japan.
Science. 2013 Feb 8;339(6120):687-90. doi: 10.1126/science.1229379.
The 2011 moment magnitude 9.0 Tohoku-Oki earthquake produced a maximum coseismic slip of more than 50 meters near the Japan trench, which could result in a completely reduced stress state in the region. We tested this hypothesis by determining the in situ stress state of the frontal prism from boreholes drilled by the Integrated Ocean Drilling Program approximately 1 year after the earthquake and by inferring the pre-earthquake stress state. On the basis of the horizontal stress orientations and magnitudes estimated from borehole breakouts and the increase in coseismic displacement during propagation of the rupture to the trench axis, in situ horizontal stress decreased during the earthquake. The stress change suggests an active slip of the frontal plate interface, which is consistent with coseismic fault weakening and a nearly total stress drop.
2011 年矩震级 9.0 的东日本大地震在日本海沟附近产生了超过 50 米的最大同震滑移，这可能导致该地区的应力状态完全降低。我们通过综合大洋钻探计划在地震后大约 1 年钻取的钻孔来确定前缘棱柱体的原地应力状态，并推断出震前的应力状态，从而验证了这一假设。根据从钻孔破裂中估计的水平应力方向和大小，以及在破裂传播到海沟轴的过程中同震位移的增加，原地水平应力在地震期间减小。这种应力变化表明前缘板块界面的积极滑动，这与同震断层弱化和几乎完全的应力降一致。
