2011年日本东大地震的震源断层力学环境及地震成因研究

日本2011年3月11日东日本Ms9.0级大地震是太平洋板块在日本海沟向Okhotsk板块下俯冲过程中发生的一次板间逆冲地震。这次地震是日本有地震记录以来最大的地震。惊人的海底位移（最大达60余米）、相对短的断层破裂长度、频繁的大地震活动背景，大大出乎地震学家的预料。有关这次大地震成因，目前看法不一，有人认为是由于慢滑动事件引发；有人认为是在地震断层顶部存在高强度的障碍体所导致，这些看法大抵基于震源运动学反演，缺少震源动力学分析。本项目结合这次地震观测到的GPS、海底变形和应力钻孔等资料，拟研究直接反演震源断层应力降的动力学方法，利用这个方法得到的断层应力降，构建一个非线性规划问题,研究这次大地震断层的力学环境（主应力大小和方向、孔隙压力、摩擦系数等）。通过这些结果，探讨这次大地震的可能动力学成因。 项目所提出的反演方法和非线性规划思想可用于一般断层动力学问题的研究。

The Tohuku-oki earthquake occurred on March 11, 2011, Japan, between the Pacific and Okhotsk plates.It was a largest event in the recorded earthquake events in Japan and unexpected to geoscientists for suprising seafloor displacement (larger than 60m), relatively smaller faulting distance and frequensly big earthquake activitiy in this region.About the origin of the earthquake, there are different points of views. Slowly sliping events and high strength asperities are main considerations. This project plan to propose a method to inverse fault stress drops by using GPS on land and deformation data of safloor, and then to study the mechanic environment of the earthquake fault，such as principal stresses in magnitudes and directions,pore pressure, friction coefficient and so on by using nonlinear programming method on the basis of the stress drops.From these results, we try to probe the possible dynamic reasion of the Tohoku-oki earthquake. We expect that the methods to be put forword can be used to general fault mechanics problems.