利用断层应力积累探讨大地震发生的地点--以日本2011年东北9级大地震为例  

Exploring the location of large earthquakes using fault stress accumulation-A case study upon M_(W)9.0 Tohoku-Oki earthquake in Japan

作　　者：谢周敏 蔡永恩 吉岡祥一 阿部大毅 XIE ZhouMin;CAI YongEn;Shoichi Yoshioka;Daiki Abe(National Institute of Natural Hazards,Beijing 100085,China;Institute of Theoretical and Applied Geophysics,School of Earth and Space Sciences,Peking University,Beijing 100871,China;Research Center for Urban Safety and Security,Kobe University,Kobe 657-8501,Japan;Department of Planetology,Graduate School of Science,Kobe University,Kobe 657-8501,Japan)

机构地区：[1]国家自然灾害防治院,北京100085 [2]北京大学地球与空间科学学院理论与应用地球物理研究所,北京100871 [3]日本神戸大学都市安全研究中心,神戸657-8501 [4]日本神户大学研究生院行星科学系,神户657-8501

出　　处：《地球物理学报》2022年第1期1-11,共11页Chinese Journal of Geophysics

基　　金：国家自然科学基金项目(41674054和41474080)资助.

摘　　要：大地震在哪里发生是地震预报首先要解决的问题.利用反演GNSS观测数据得到的2011年日本东北9级大地震前7年(2004—2010年)断层上的应力变化,我们发现了这次地震断层的孕震区.为了进一步研究该孕震区的演化过程,本文继续反演这次大地震在1997—2003年间的断层应力变化过程.通过这两期的反演工作,我们看到,在这14年中,断层应力的年变化图案的主要特征基本是稳定的,并存在明显的应力增加区和降低区.前者与地震的破裂区吻合,后者与前震、重复小地震和无震滑动的区域一致.显著的剪切应力增加区不但与主震,而且还与大余震的破裂区相符合.我们发现断层面上高应力积累区的零剪应力和零正应力变化的等值线不重合,前者在断层面上的深度大于后者,这意味着在剪应力增加区存在着正应力降低区或剪切强度降低区(由于剪切强度与正应力成正比).断层初始破裂点似乎更偏好零正应力等值线附近的位置,这是因为该处不但靠近剪切强度降低区,而且位于剪应力积累最显著的地方.研究结果表明,正应力变化对大地震的初始破裂有影响;本文所使用的断层应力变化反演方法,可以用来作为预测大地震发生位置的一种手段.Where a large earthquake will occur is the first problem to be solved in earthquake prediction.Using the fault stress changes obtained from inversion for the GNSS observation data in the 7 years(2004—2010)before the 2011 M 9.0 Tohoku-Oki earthquake,we have found the seismogenic zone of the earthquake.In order to further study its evolution process,we investigate the fault stress changes from 1997 to 2003 in this paper.Through the two phases of inversion work,we see that the main characteristics of the annual change pattern of the fault stress changes are basically stable during the 14 years,the stress in the seismogenic zone increases year by year,and there exist obvious stress increase and decrease areas.The former is consistent with the rupture zone of the earthquake,and the latter is consistent with the foreshocks,small repeated earthquakes and aseismic sliding zones.The areas of significant shear stress increase are not only consistent with the main shock,but also with the rupture areas of the large aftershocks.We found that the contours of zero-shear and zero-normal stress change on the fault plane do not coincide,the former has a greater depth than the latter,which means that there exists a normal stress reduction zone or a shear strength reduction zone in the shear stress increase zone because the shear strength is proportional to the normal stress.The initial rupture point of the fault seems to be more preferred the location close to the contour of zero-normal stress change,because it is not only close to the area of shear strength reduction,but also located in the most significant area of shear stress accumulation.The results obtained show that normal stress changes have an impact on the initial rupture of a large earthquake,and the inversion method of fault stress change can be used to predict the location of large earthquakes.

关 键 词：俯冲带地震 地震应力模型 断层应力变化反演 大地震位置预测 

分 类 号：P315[天文地球—地震学]