本州M_W9.1地震前破裂区内地震与地球自转之间的相关现象  

Relationship between the Earth′s rotation rate and earthquakes occurring prior to the 2011 M_W9.1 Tohoku-Oki Japan earthquake

作　　者：陈学忠[1] 李艳娥[1] 隗永刚[1] 郭祥云[1] 陈丽娟 CHEN XueZhong;LI YanE;WEI YongGang;GUO XiangYun;CHEN LiJuan(Institute of Geophysics,China Earthquake Administration,Beijing 100081,China;Chongqing Earthquake Administration,Chongqing 401147,China)

机构地区：[1]中国地震局地球物理研究所,北京100081 [2]重庆市地震局,重庆401147

出　　处：《地球物理学报》2020年第2期440-444,共5页Chinese Journal of Geophysics

基　　金：国家重点研发计划(2018YFC1503405)资助

摘　　要：强震发生前震源系统可能处于不稳定状态,在这种情况下,震中附近地区的地震活动或许会对微小的应力变化敏感.地球自转会在震源断层面上引起应力,地球自转速率变化也会在震源断层面上引起应力变化.由于地球自转速率变化非常微小,在震源断层面上引起应力变化也非常微弱,如果震源区处于极不稳定状态,这种微弱的应力变化或许会激发一些地震活动.这些被激发的地震活动将会表现出与地球自转速率变化的显著相关性.为了考察2011年3月11日日本本州9.1地震发生前震中附近地区是否存在与地球自转速率变化显著相关的地震活动,选取2000年1月-2011年2月M≥5.0地震集中活动区域为研究区域,根据USGS发布的1991年1月-2011年2月的地震目录,利用舒斯特(Schuster)统计检验方法,研究了地球自转与本州M_W9.1地震前发生的地震活动之间的相关性.检验结果用P值来评估,P值越低表示相关性越显著.结果如下:在研究区内5.4≤M≤6.9地震的P值的时间变化显示本州M_W9.1地震前从2009年6月-2010年1月存在低于0.5%的P值.当P值达最低值时,约82%的5.4≤M≤6.9地震发生在地球自转速率季节性变化的加速期,显示出了地震活动与地球自转速率加速之间的显著相关性.取3°×3°的空间窗,以0.1°的步长沿经度和纬度滑动对P值进行空间扫描,可以得到P值的空间分布.扫描区域远大于研究区,经纬度范围为(33°N-43°N,138°E-147°E).在P值的空间分布图上,可发现在P值处于最低值期间,低于0.5%的P值集中分布在研究区的北部,本州M_W9.1地震震中位于这个低P值区的边缘.因此,本州M_W9.1地震前在其破裂区内存在显著的与地球自转相关的地震活动现象,说明破裂区内存在非常不稳定的地区.When a strong earthquake is approaching,its focal region may become extremely unstable and small to moderate earthquakes around it could be susceptible to tiny stress changes.It is known that weak stress changes on the focal fault plane can be caused by variations in the Earth′s rotation rate.Therefore,when a focal region becomes extremely unstable,variations in the Earth′s rotation rate could trigger earthquakes resulting in a significant correlation between the triggered earthquakes and the variations in the Earth′s rotation rate.We used the data of the M_W9.1 Tohoku-Oki mainshock(on March 11,2011)to investigate the correlation between variations in the Earth′s rotation rate and occurrences of earthquakes near the focal region prior to this great event.In the analysis,we used earthquakes in the USGS catalog that occurred from January 1991 to February 2011 within a region where earthquakes of M≥5.0 occurred frequently from January2000 to February 2011.We statistically analyzed whether they have a significant correlation with the Earth′s rotation rate using the Schuster′s test.The results were evaluated based on the Pvalue,where a smaller P-value corresponds to a higher correlation between the occurrence of earthquakes and Earth′s rotation rate.The results show that within the study region,for earthquakes of 5.4≤M ≤6.9,lower P-values(<0.5%)appeared from June 2009 to January2010.When the P-value reached its minimum,approximately 82% of the earthquakes(5.4≤M≤6.9)occurred during an acceleration of the Earth′s rotation,revealing a significant correlation between the occurrence of earthquakes and the Earth′s rotation rate.Furthermore,by moving a spatial window of 3°×3°by 0.1°intervals in both the latitudinal and longitudinal directions,we resolved the spatial distribution of the P-value within a large region(33°N-43°N,138°E-147°E).LowP-values(below 0.5%)are observed in the northern part of the study region.The epicenter of the M_W9.1 Tohoku-Oki mainshock is located at the edge of th

关 键 词：本州MW9.1地震 地球自转 舒斯特检验 P值 

分 类 号：P315[天文地球—地震学]