王同利^1,,
崔博闻¹,
叶青²,
李菊珍¹,
王丽红¹,
童琼³
1. 北京市地震局, 北京 100081
2. 中国地震台网中心, 北京 100045
3. 湖南省地震局长沙地震台, 长沙 410012

基金项目: 中国地震局震情跟踪面上项目(2020020403), 中国地震实验场项目(2019CSES0113)及冬奥会保障晋冀蒙监测能力提升项目资助


详细信息

作者简介: 王同利, 女, 高级工程师, 主要从事地震电磁研究和小震定位工作.E-mail:416991552@qq.com

中图分类号: P319

收稿日期:2019-12-31
修回日期:2020-03-31
上线日期:2020-06-05

Temporal-spatial distribution of apparent resistivity before and after the Jiuzhaigou M_S7.0 earthquake

WANG TongLi^1,,
CUI BoWen¹,
YE Qing²,
LI JuZhen¹,
WANG LiHong¹,
TONG Qiong³
1. Beijing Earthquake Agency, Beijing 100080, China
2. China Earthquake Networks Center, China Earthquake Administration, Beijing 100045, China
3. Hunan Earthquake Agency, Changsha 410012, China


MSC: P319

--> Received Date: 31 December 2019
Revised Date: 31 March 2020
Available Online: 05 June 2020


摘要
摘要:本文应用归一化变化速率（NVRM）方法，研究了2017年九寨沟M_S7.0地震周边800 km范围内25个地电阻率台站2012—2018年的连续观测数据，分析了震中区周围的地电阻率时、空演化过程.结果显示：（1）25个台站中共有14个台站在震前出现了地电阻率变化，结合本次地震震源机制等分析其时空变化，认为邻近地震破裂带的临夏、通渭、武都和宝鸡台地电阻率在震前出现了下降—折返回升型的变化，符合前人已总结的强地震前地电阻率的变化过程.（2）地震发生前震中区周围大区域内出现了地电阻率负异常变化，且以震中区为中心呈条带分布，异常区的长轴方向与地震断裂带走向或地震烈度分布的长轴方向几乎垂直，与地震主压应力轴方向吻合.本文认为九寨沟M_S7.0强震发生之前，震中区周围出现的区域性地电阻率异常空间丛集现象是很好的中期和短临前兆；地电阻率震前异常动态演化、各向异性等特征对认识本次强震发震断层活动以及震源区应力场分布有启示意义.
关键词: 九寨沟地震/
地电阻率/
时空分布/
异常变化/
震源机制

Abstract:The Jiuzhaigou M_S7.0 earthquake occurred in Sichuan Province on August 8, 2017. In this paper, data collected from a total of 25 stations distributed within ~800 km of the epicenter of the Jiuzhaigou M_S7.0 earthquake from 2012 to 2018, were used to investigate the temporal-spatial evolution of apparent resistivity by applying the Normalized Variation Rate Method (NVRM). The results are as follows: (1) Apparent resistivity anomalies were observed at 14 stations around the epicenter before the earthquake. Combining with the focal mechanism analysis, we suggested that the temporal spatial variation of apparent resistivity observed at Linxia, Tongwei, Wudu and Baoji stations adjacent to the earthquake rupture zone was consistent with the development of apparent resistivity anomaly associated with the mechanism of earthquake. (2) Negative abnormal changes of apparent resistivity occurred in a large area and were featured with a two-quadrant distribution pattern around the epicenter before the earthquake. The long axis direction of the area with apparent resistivity anomaly was nearly perpendicular to the direction of the earthquake rupture, the fault strike, and the long axis direction of the earthquake intensity distribution, and was also consistent with the direction of the maximum principal stress. Our results obtained in this paper showed that the apparent resistivity anomaly observed near the epicenter before the mainshock could be served as seismic precursory for short-term earthquake prediction, therefore the dynamic evolution of the apparent resistivity anomaly is of great significance for understanding the mechanism of earthquake and the distribution of stress field.
Key words:Jiuzhaigou earthquake/
Apparent resistivity/
Temporal-spatial distribution/
Variations of apparent resistivity anomaly/
Focal mechanism



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