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陈学忠1,,
李艳娥1,
隗永刚1,
郭祥云1,
陈丽娟2
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

基金项目: 国家重点研发计划(2018YFC1503405)资助


详细信息
作者简介: 陈学忠, 男, 1963年生, 研究员, 主要从事地震学研究.E-mail:cxz8675@163.com
中图分类号: P315

收稿日期:2018-09-20
修回日期:2019-12-06
上线日期:2020-02-05



Relationship between the Earth's rotation rate and earthquakes occurring prior to the 2011 MW9.1 Tohoku-Oki Japan earthquake

CHEN XueZhong1,,
LI YanE1,
WEI YongGang1,
GUO XiangYun1,
CHEN LiJuan2
1. Institute of Geophysics, China Earthquake Administration, Beijing 100081, China
2. Chongqing Earthquake Administration, Chongqing 401147, China


MSC: P315

--> Received Date: 20 September 2018
Revised Date: 06 December 2019
Available Online: 05 February 2020


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MW9.1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MW9.1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MW9.1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MW9.1地震震中位于这个低P值区的边缘.因此,本州MW9.1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.
本州MW9.1地震/
地球自转/
舒斯特检验/
P

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 MW9.1 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 January 2000 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 P-value, 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 January 2010. 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). Low-P-values (below 0.5%) are observed in the northern part of the study region. The epicenter of the MW9.1 Tohoku-Oki mainshock is located at the edge of the low-P-value region. Therefore, there exists a significant correlation between the occurrence of earthquakes and the Earth's rotation rate in the rupture zone prior to the MW9.1 Tohoku-Oki mainshock, implying a remarkably unstable region within the rupture zone.
MW9.1 Tohoku-Oki earthquake/
Earth's rotation rate/
Schuster's test/
P-value



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