Stress measurements in the Scientific Drilling Projectof 2008 Wenchuan Earthquake Fault, China

为研究大地震断层破裂与应力变化的关系，对汶川地震断层科学钻探工程（WFSD）和日本海沟快速钻探工程（JFAST）穿越2011年9级东北冲地震断层的地应力状态进行了测定。我们发现，在东北冲地震断层附近的原地水平应力在地震期间明显下降。应力变化表明，与同震断层弱化和几乎总的应力下降一致的前缘板块界面的活动滑动。

To investigate relations of fault rupturing during a great earthquake and stress change, we tried to determine in situ stress state both in Wenchuan Earthquake Fault Scientific Drilling Project (WFSD) and in Japan Trench Fast Drilling Project (JFAST) penetrating through the fault ruptured during 2011 M9 Tohoku-Oki earthquake. We found that in-situ horizontal stress in the vicinity of the Tohoku-Oki earthquake fault decreased during the earthquake distinctly. The stress change suggests an active slip of the frontal plate-interface consistent with coseismic fault weakening and a nearly total stress drop.