2021—2022年川滇地区4次MS≥6.0地震前井下地电阻率观测的异常变化

doi:10.3969/j.issn.0253-4967.2023.06.007

摘要/Abstract

摘要：

2021—2022年川滇地区先后发生了云南漾濞 M_S6.4、四川芦山 M_S6.1、马尔康 M_S6.0 和泸定 M_S6.8 4次M_S≥6.0地震。距这些地震震中400km的范围内布设有红格、冕宁、甘孜井下地电阻率观测站, 其观测数据在这4次地震前出现了不同程度和形态的中短期异常变化。红格站EW和NS测道自2020年12月开始出现同步下降变化, 2021年漾濞 M_S6.4 地震后NS测道的异常恢复, 但EW测道仍然持续下降, 截至2022年9月5日泸定 M_S6.8 地震发生, EW测道的异常持续时间约为21个月。甘孜站N10°E测道的下降异常变化始于2022年4月, 6月底开始出现转折回升, 10月异常恢复, 其间先后发生芦山 M_S6.1、马尔康 M_S6.0、泸定 M_S6.8 地震。2022年9—11月, 甘孜站 N60°W测道出现年变畸变异常, 2023年1月26日泸定再次发生 M_S5.6 地震。冕宁站EW、 NS、 N45°W测道自2022年6月下旬开始出现同步上升变化, 于泸定 M_S6.8 地震后异常恢复。依据这些异常变化, 在周、月会商中对2021年漾濞 M_S6.4、 2022年泸定 M_S6.8、 2023年泸定 M_S5.6 地震做出了短期预测。

关键词: 地电阻率, 井下观测, 川滇地区, 地震, 异常变化

Abstract:

There have been four M_S≥6.0 earthquakes, i.e. the Yangbi M_S6.4, Lushan M_S6.1, Maerkang M_S6.0 and Luding M_S6.8, occurred in Sichuan-Yunnan area from 2021 to 2022. Three borehole apparent resistivity monitoring stations of Hongge, Mianning and Garzê, normally operated within 400km away from these earthquakes. These stations recorded different types of middle-short abnormal changes before the four earthquakes. The EW and NS arrays at Hongge station began to display synchronous decline change since December 2020. According to the empirical relationship between the duration of the anomaly and the magnitude, it is predicted that there is a possibility of a magnitude 6.0 earthquake in the Sichuan-Yunnan border area. But there had been no short-term abnormal changes that can give a forecast opinion on a time scale. Short-term abnormal changes appeared at Hongge station in March 2021. The maximum decline magnitudes of the NS and EW arrays were 2.1% and 1.4%, respectively. We believed that the risk of a strong earthquake has further increased. The distance from the Yangbi earthquake to Hongge station is 232km. Data of NS array recovered to normal status after the Yangbi M_S6.4 earthquake in 2021, but the data of EW array continued to decline. In the fault virtual dislocation(FVD)model, the coseismic slips are loaded in a way of equal in magnitude but opposite in direction, which provides the relative deformation around the epicenter. In a compressive tectonic region, compressive areas from the FVD model can be formed as the areas with compression enhancement. The dilatant areas cannot be distinguished between absolutely dilatant areas and compressive areas. However, they can be regarded as relatively dilatant areas where the original extensive stress is enhanced, or the original compressive stress is released to some extent. It is found that Hongge station is located in the relative expansion region generated by the Yangbi earthquake. Abnormal changes at Hongge station are not only affected by the seismogenic process of the Yangbi earthquake, but also possibly indicating the existence of another strong earthquake. The anomaly duration of the EW array was about 21 months long and the decline magnitude was 2.8%up to September 5, 2023, when the Luding M_S6.8 earthquake occurred, which is about 340km far away from Hongge station. The N10°E array of Garzê station began to show abnormal decline change since April 2022 with the maximum decline magnitude of about 0.5%. Apparent resistivity curve changed to rise change since late June, and the anomaly recovered to the normal status in October. Three earthquakes of Lushan M_S6.1, Maerkang M_S6.0 and Luding M_S6.8 occurred during the period of anomaly evolution, with a distance of 306km, 183km and 293km from the Garzê station, respectively. The regional deformation before Lushan and Maerkang earthquakes from the fault virtual dislocation model show that the seismogenic process of these two earthquakes has little influence on the abnormal changes detected from Garzê station. The abnormal changes are probably related to the preparation of another big earthquake. At the earthquake situation consultation meeting on August 26, the Electromagnetism Laboratory predicted that a magnitude 6.0 earthquake would occur in the northwest of Sichuan in the short term. After the Luding M_S6.8 earthquake, the observation data of the N10°E array returned to the normal status. The N60°W array showed distortion in annual variation pattern from September to November 2022. Another M_S5.6 earthquake occurred in Luding on January 26, 2023. The EW, NS and N45°W arrays of Mianning station showed synchronous rise changes since late June 2022, and anomalies recovered after the Luding M_S6.8 earthquake. After the Luding earthquake, the regional deformation characteristics before the earthquake are also analyzed by the fault virtual dislocation model. The Garzê station is located in the area of compression enhancement, while Mianning station is located in the area of relative expansion. Results from petrophysical experiments have demonstrated the decline changes when water-bearing rock and soil samples are under compression, and the rise changes as samples are undergoing stress unloading. Resistivity does not recover to the initial status when the compression stress is completely released, suggesting the existence of irreversible change in the samples. Therefore, the patterns of anomalies recorded at Garzê and Mianning stations are consistent with the area deformation where the stations were located. In summary, according to the abnormal changes of three borehole apparent resistivity observation in Hongge, Mianning and Garzê station from 2020 to 2022, we have made short-term prediction for the Yangbi M_S6.4 in 2021, Luding M_S6.8 in 2022 and Luding M_S5.6 in 2023, at the regular weekly and monthly earthquake situation consultation meetings.

Key words: Apparent resistivity, borehole observation, Sichuan-Yunnan area, earthquake, anomaly

解滔, 韩盈, 于晨. 2021—2022年川滇地区4次M_S≥6.0地震前井下地电阻率观测的异常变化[J]. 地震地质, 2023, 45(6): 1370-1384.

XIE Tao, HAN Ying, YU Chen. APPARENT RESISTIVITY ABNORMAL CHANGES OF BOREHOLE MONITORING BEFORE FOUR M_S≥6.0 EARTHQUAKES IN SICHUAN-YUNNAN AREA FROM 2021 TO 2022[J]. SEISMOLOGY AND GEOLOGY, 2023, 45(6): 1370-1384.

图/表 7

图1 川滇地区地电阻率观测站和2021—2022年4次MS≥6.0地震的空间分布

Fig. 1 The locations of apparent resistivity stations and the four MS≥6.0 earthquakes in Sichuan-Yunnan area from 2021 to 2022.

表1 四川地区3个井下地电阻率观测站装置的参数

Table1 Configuration parameters of the three borehole apparent resistivity stations in Sichuan province

序号	观测站	测道	启用年月	AB/m	MN/m	H/m
1	红格	NS	2014-07	422	152	90
		EW	2014-07	345	118	90
2	甘孜	N10°E	2018-01	400	120	60
		N60°W	2018-01	400	120	60
3	冕宁	NS	2020-01	600	200	120
		EW	2020-01	600	200	120
		N45°W	2020-01	600	200	120

图2 观测站电测深曲线 a 甘孜站; b 冕宁站; c 红格站

Fig. 2 The electrical sounding curve of the three stations.

Fig. 3 地表观测和井下观测时各层介质影响系数的分布(虚线为负值) The sensitivity coefficients of the ground and borehole monitoring for the three stations (dashed lines denote the negative coefficients).a 甘孜站地表观测; b 甘孜站井下观测; c 冕宁站地表观测; d 冕宁站井下观测; e 红格站地表观测; f 红格站井下观测

图4 2016—2023年红格站井下地电阻率的观测数据 a NS测道的日均值; b NS测道的日均值年度对比; c EW测道的日均值; d EW测道的日均值年度对比

Fig. 4 Apparent resistivity of borehole monitoring data at Hongge station from 2016 to 2023.

图5 2018—2023年甘孜站井下地电阻率的观测数据 a N10°E测道的日均值; b N10°E测道的日均值年度对比; c N60°W测道的日均值; d N60°W测道的日均值年度对比

Fig. 5 Apparent resistivity of borehole monitoring data at Garzê station from 2018 to 2023.

图6 2020—2023年冕宁站井下地电阻率的观测数据 a NS测道的日均值; b NS测道的日均值年度对比; c EW测道的日均值; d EW测道的日均值年度对比; e N45°W测道的日均值; f N45°W测道的日均值年度对比

Fig. 6 Apparent resistivity of borehole monitoring data at Mianning station from 2020 to 2023.

参考文献 31

[1]	杜学彬. 2010. 在地震预报中的2类视电阻率变化[J]. 中国科学(地球科学), 40(10): 1321—1330.
	DU Xue-bin. 2010. Two types of changes in apparent resistivity in earthquake prediction[J]. Scientia Sinica(Terrae), 40(10): 1321—1330 (in Chinese).
[2]	杜学彬, 叶青, 马占虎, 等. 2008. 强地震附近电阻率对称四极观测的探测深度[J]. 地球物理学报, 51(6): 1943—1949.
	DU Xue-bin, YE Qing, MA Zhan-hu, et al. 2008. The detection depth of symmetric four-electrode resistivity observation in/near the epicentral region of strong earthquakes[J]. Chinese Journal of Geophysics, 51(6): 1943—1949 (in Chinese).
[3]	高曙德. 2016. 深井地电观测技术在地震监测中的应用探讨[J]. 地球物理学进展, 31(5): 2078—2088.
	GAO Shu-de. 2016. Discussion on the deep well geoelectric observation technique applied in earthquake monitoring[J]. Progress in Geophysics, 31(5): 2078—2088 (in Chinese).
[4]	高曙德. 2020. 四川九寨沟7.0级地震前震情跟踪概述及震后总结[J]. 地球物理学进展, 35(4): 1250—1260.
	GAO Shu-de. 2020. Overview of tracking of Sichuan Jiuzhaigou M_S7.0 earthquake in 2017 and its post earthquake precursor anomaly summery[J]. Progress in Geophysics, 35(4): 1250—1260 (in Chinese).
[5]	康云生, 安海静, 马可兴, 等. 2013. 天水地电阻率地表与井下多种观测方式的试验分析[J]. 地震工程学报, 35(1): 190—195.
	KANG Yun-sheng, AN Hai-jing, MA Ke-xing, et al. 2013. Test analysis on geoelectrical resistivity observation combining the surface and deep-well methods at Tianshui seismic station in Gansu Province[J]. China Earthquake Engineering Journal, 35(1): 190—195 (in Chinese).
[6]	马小溪, 王兰炜, 朱涛, 等. 2023. 地电阻率交流观测中的电感性耦合效应特征模拟和分析[J]. 地球物理学报, 66(1): 289—300.
	MA Xiao-xi, WANG Lan-wei, ZHU Tao, et al. 2023. Study on inductive coupling effect in AC geoelectrical resistivity observation[J]. Chinese Journal of Geophysics, 66(1): 289—300 (in Chinese).
[7]	毛先进, 段炜, 杨玲英, 等. 2021. 分层均匀结构地电阻率影响系数一个重要特性普适性的证明[J]. 地震研究, 44(1): 129—132.
	MAO Xian-jin, DUAN Wei, YANG Ling-ying, et al. 2021. General proof of an important property of the apparent resistivity sensitivity coefficients of stratified uniform structures[J]. Journal of Seismological Research, 44(1): 129—132 (in Chinese).
[8]	聂永安, 姚兰予. 2009. 成层半空间深埋电极产生的电位分布[J]. 中国地震, 25(3): 246—255.
	NIE Yong-an, YAO Lan-yu. 2009. Study on electrical potential by buried source electrode within horizontally layered half-space model[J]. Earthquake Research in China, 25(3): 246—255 (in Chinese).
[9]	钱复业, 卢振业, 丁鉴海. 1998. 电磁学分析预报方法[M]. 北京: 地震出版社.
	QIAN Fu-ye, LU Zhen-ye, DING Jian-hai. 1998. Electromagnetic Analysis and Prediction Methods[M]. Seismological Press, Beijing (in Chinese).
[10]	钱复业, 赵玉林, 于谋明, 等. 1982. 地震前地电阻率的异常变化[J]. 中国科学(B辑), 12(9): 831—839.
	QIAN Fu-ye, ZHAO Yu-lin, YU Mou-ming, et al. 1982. The anomalous changes of georesistivity before earthquakes[J]. Science in China(Ser B), 12(9): 831—839 (in Chinese).
[11]	钱家栋, 陈有发, 金安忠. 1985. 地电阻率法在地震预报中的应用[M]. 北京: 地震出版社.
	QIAN Jiao-dong, CHEN You-fa, JIN An-zhong. 1985. The Geo-resistivity Method Used in Earthquake Prediction[M]. Seismological Press, Beijing (in Chinese).
[12]	王兰炜, 张宇, 张世中, 等. 2015. 我国井下地电阻率观测技术现状分析[J]. 地震地磁观测与研究, 36(2): 95—102.
	WANG Lan-wei, ZHANG Yu, ZHANG Shi-zhong, et al. 2015. The status of deep-well geo-electrical resistivity observation in China[J]. Seismological and Geomagnetic Observation and Research, 36(2): 95—102 (in Chinese).
[13]	汪志亮, 郑大林, 余素荣. 2002. 地震地电阻率前兆异常现象[M]. 北京: 地震出版社.
	WANG Zhi-liang, ZHENG Da-lin, YU Su-rong. 2002. Geoelectric Resistivity Precursor Anomalies of Earthquake[M]. Seismological Press, Beijing (in Chinese).
[14]	肖武军, 解滔, 张尧. 2019. 晋冀蒙交界及附近地区小极距井下地电阻率观测装置设计[J]. 中国地震, 35(1): 134—143.
	XIAO Wu-jun, XIE Tao, ZHANG Yao. 2019. Observation scheme for short electrode spacing well apparent resistivity at the vicinity of Shanxi-Hebei-Inner Mongolia area[J]. Earthquake Research in China, 35(1): 134—143 (in Chinese).
[15]	解滔, 杜学彬, 卢军. 2016a. 井下视电阻率观测影响系数分析[J]. 中国地震, 32(1): 40—53.
	XIE Tao, DU Xue-bin, LU Jun. 2016a. Sensitivity coefficients analysis of deep-well apparent resistivity measurement[J]. Earthquake Research in China, 32(1): 40—53 (in Chinese).
[16]	解滔, 李飞, 沈红会, 等. 2013. 新沂地震台地电阻率反向年变分析[J]. 地震学报, 35(6): 856—864.
	XIE Tao, LI Fei, SHEN Hong-hui, et al. 2013. Reverse annual variation of georesistivity at Xinyi seismic station, Jiangsu Province[J]. Acta Seismologica Sinica, 35(6): 856—864 (in Chinese).
[17]	解滔, 卢军. 2016b. 地表固定干扰源影响下地电阻率观测随时间变化特征分析[J]. 地震地质, 38(4): 922—936. doi: 10.3969/j.issn.0253-4967.2016.04.010.
	XIE Tao, LU Jun. 2016b. Apparent resistivity temporal variation characteristics affected by the fixed disturbance source on surface of measurement area[J]. Seismology and Geology, 38(4): 922—936 (in Chinese).
[18]	解滔, 卢军. 2023a. 地电阻率观测常见变化形态及其可能原因分析[J]. 中国地震, 39(1): 128—142.
	XIE Tao, LU Jun. 2023a. Usual variations of apparent resistivity and its possible causes[J]. Earthquake Research in China, 39(1): 128—142 (in Chinese).
[19]	解滔, 卢军, 杜学彬. 2022a. 自适应变化幅度方法提取直流视电阻率中短期异常[J]. 中国地震, 38(1): 52—60.
	XIE Tao, LU Jun, DU Xue-bin, 2022a. An adaptive variation amplitude method for extracting medium and short-term anomalies of apparent resistivity[J]. Earthquake Research in China, 38(1): 52—60 (in Chinese).
[20]	解滔, 任越霞, 廖晓峰, 等. 2023b. 2022年四川泸定 M_S6.8 地震前地下介质视电阻率变化特征及其机理分析[J]. 地球物理学报, 66(4): 1428—1437.
	XIE Tao, REN Yue-xia, LIAO Xiao-feng, et al. 2023b. Changes in apparent resistivity and its possible mechanisms before the Luding M_S6.8 earthquake on September 5, 2022, Sichuan Province, China[J]. Chinese Journal of Geophysics, 66(4): 1428—1437 (in Chinese).
[21]	解滔, 王洪岐, 刘立波, 等. 2014. 四平台地电阻率相反年变有限元数值分析[J]. 地球物理学进展, 29(2): 588—594.
	XIE Tao, WANG Hong-qi, LIU Li-bo, et al. 2014. Inverse annual variations of apparent resistivity at Siping earthquake station by using finite element method[J]. Progress in Geophysics, 29(2): 588—594 (in Chinese).
[22]	解滔, 薛艳, 卢军. 2022b. 中国M_S≥7.0地震前视电阻率变化及其可能原因[J]. 地球物理学报, 65(8): 3064—3077.
	XIE Tao, XUE Yan, LU Jun. 2022b. Changes in apparent resistivity and its possible reasons before earthquakes of M_S≥7.0 in China[J]. Chinese Journal of Geophysics, 65(8): 3064—3077 (in Chinese).
[23]	解滔, 于晨, 卢军. 2019. 开展小极距井下地电阻率观测的可行性分析[J]. 中国地震, 35(1): 14—24.
	XIE Tao, YU Chen, LU Jun. 2019. Feasibility analysis on short-electrode spacing well apparent resistivity observation[J]. Earthquake Research in China, 35(1): 14—24 (in Chinese).
[24]	薛顺章, 温新民, 董永德, 等. 1994. 地电阻率预报地震新方法的研究[J]. 地震学报, 16(2): 227—234.
	XUE Shun-zhang, WEN Xin-min, DONG Yong-de, et al. 1994. A new method for earthquake prediction by earth-resistivity measurements[J]. Acta Seismologica Sinica, 16(2): 227—234 (in Chinese).
[25]	叶青, 王晓, 杜学彬, 等. 2022. 中国地震井下地电阻率研究进展[J]. 吉林大学学报(地球科学版), 52(3): 669—683.
	YE Qing, WANG Xiao, DU Xue-bin, et al. 2022. Research progress of seismic underground geo-resistivity in China[J]. Journal of Jilin University(Earth Science Edition), 52(3): 669—683 (in Chinese).
[26]	赵和云, 钱家栋. 1982. 地电阻率法中勘探深度和探测范围的理论讨论和计算[J]. 西北地震学报, 4(1): 40—56.
	ZHAO He-yun, QIAN Jia-dong. 1982. Theoretical discussion and calculation about detective depth and detective range in earth resistivity method[J]. Northwestern Seismological Journal, 4(1): 40—56 (in Chinese).
[27]	赵和云, 钱家栋. 1987. 郫县台多极距观测资料的反演和分析[J]. 中国地震, 3(S1): 73—78.
	ZHAO He-yun, QIAN Jia-dong. 1987. Inversion and analysis of data of temporal changes in apparent resistivity with multi-separations in Pixian stations, Sichuan Province[J]. Earthquake Research in China, 3(S1): 73—78 (in Chinese).
[28]	赵玉林, 钱复业, 杨体成, 等. 1983. 原地电阻率变化的实验[J]. 地震学报, 5(2): 217—225.
	ZHAO Yu-lin, QIAN Fu-ye, YANG Ti-cheng, et al. 1983. Experiments in situ of electrical resistivity changes[J]. Acta Seismologica Sinica, 5(2): 217—225 (in Chinese).
[29]	Park S K, Van G P. 1991. Inversion of pole-pole data for 3-D resistivity structure beneath arrays of electrodes[J]. Geophysics, 56(7): 951—960. DOI URL
[30]	Roy A, Poddar M. 1981. A simple derivation of Seigel’s time domain induced polarization formula[J]. Geophysical Prospect, 29(1): 432—437. DOI URL
[31]	Yamazaki Y. 1966. Electrical conductivity of strained rocks(the second paper), further experiments on sedimentary rocks[J]. Bulletin of Earthquake Research Institute, Tokyo Imperial University, 44(4): 1553—1570.