ANALYSIS ON FORMATION MECHANISM OF TYPICAL VARIATIONS OF GEO-RESISTIVITY AT BAOCHANG STATION

doi:10.3969/j.issn.0253-4967.2021.03.011

Abstract

Abstract: Fixed-electrode quasi-Schlumberger arrays are mainly used in geo-electric observation of China earthquake networks. The distance between power supply poles is generally about 1km. The detection depth is estimated to be within 0.705km by conventional geophysical and electrical methods in homogeneous medium. The resistivity at seismic station for precursor information monitoring reflects the overall electrical characteristics within the detection range below the polar distribution area, which is also known as apparent resistivity or geo-resistivity. Due to the small distance between power supply poles, small detection depth and great influence from shallow layer, there are usually annual, diurnal and step variations in geo-resistivity curves. Because of the above variations, the characteristics of abnormal variations before earthquakes are usually not obvious, or even annihilated. In this paper, taking Baochang station as an example, the causes of long-term, annual, diurnal and step variations are analyzed by inversion and numerical simulation. Baochang station is located in Baochang Town, Taipusi Banner, Xilin Gol League, Inner Mongolia. Its geographical coordinates are 41.9°N and 115.3°E. The regional geological structure is the eastern segment of Inner Mongolia axis, the fourth-order structural unit. The nearest fault structure is the Chifeng-Kaiyuan Fault, which is the northern boundary fault of North China fault-block region. The resistivity of geo-electric survey area at Baochang station basically presents horizontal distribution characteristics, and the type of electric sounding curve is KH. The inversion results show that the vertical profile of the survey area is divided into four layers: the first layer is frozen soil layer with depth from 0m to 1m, the second layer is sand gravel layer with depth from 1m to 6.5m, the third layer is aquifer with depth from 6.5m to 71.5m, and the fourth layer is quartz porphyry layer with depth greater than 71.5m. When power supply electrode distance AB is 560m and measuring electrode distance MN is 80m, the one dimensional influence coefficients of NS and EW direction in the third layer are all over 0.9, which is one order of magnitude larger than those in the other three layers. This indicates that the variation of resistivity in the range of 7m to 71m can effectively reflect the variation of geo-resistivity. Since 1993, the geo-resistivity at Baochang station has been declining for a long time in NS and EW direction, and the variation rate shows obvious anisotropic characteristics, which is mainly the result of the continuous effect of regional stress on the resistivity of the third layer. There is a normal annual variation pattern of “high in winter and spring, low in summer and autumn” in both directions of geo-resistivity at Baochang station, resulting mainly from the seasonal variation of temperature and rainfall on the resistivity of the first layer. The normal diurnal variation of geo-resistivity at Baochang station is characterized by “high in the morning, low in the afternoon and night”, which is mainly caused by the influence of temperature on surface resistivity. Similar diurnal variation also exists in the hourly value curves of geo-resistivity at the stations of Xiaomiao, Ganzi, Wujiahe, Qingguang and Baodixintai. The geo-resistivity step variation of Baochang station has the characteristics of “low frequency in winter and spring, high frequency in summer and autumn”, and most of them coincide with rainfall, pumping, embedding steel strand, etc. The results of experiments and numerical simulation show that the above factors are the main interference sources of the geo-resistivity step variations.

Key words: geo-resistivity, influence coefficient, variation characteristics, formation mechanism

摘要： 中国地震台网地电观测以对称四极装置的地电阻率观测为主, 其观测曲线通常存在长期变化、年变、日变和阶跃等, 文中以宝昌台为例, 通过反演、数值模拟等方法分析上述变化成因。宝昌台地电布极区地下的电阻率基本呈现水平分布, 电测深曲线类型属于KH型。该台NS、 EW测向的地电阻率自1993年至今一直存在长期下降变化, 且变化速率存在显著的各向异性, 主要是台站所在区域的应力对第3层电阻率持续作用的结果。该台NS、 EW测向的地电阻率均存在冬春高、夏秋低的正向年变形态和凌晨及上午高、下午及晚间低的正向日变形态。其中, 年变主要是温度、降雨量季节性变化对第1层电阻率作用的结果, 日变主要是温度日变对第1层电阻率作用的结果。该台地电阻率阶跃存在冬春频次低、夏秋频次高的特点, 且多与降雨、抽水和埋设钢绞线等在时间上吻合, 实验、数值模拟等结果证实上述因素是引起地电阻率阶跃的主要干扰源。

关键词: 地电阻率, 影响系数, 变化特征, 机理

CLC Number:

P315.72⁺2

DAI Yong, GAO Li-xin, YANG Yan-ming, WEI Jian-min, Ge-gen. ANALYSIS ON FORMATION MECHANISM OF TYPICAL VARIATIONS OF GEO-RESISTIVITY AT BAOCHANG STATION[J]. SEISMOLOGY AND GEOLOGY, 2021, 43(3): 647-662.

戴勇, 高立新, 杨彦明, 魏建民, 格根. 地电阻率变化成因分析——以宝昌台为例[J]. 地震地质, 2021, 43(3): 647-662.

References

[1] 戴勇, 高立新, 高昌志, 等. 2013. 宝昌台地电阻率变化特征[J]. 地震研究, 36(3): 358—363.
DAI Yong, GAO Li-xin, GAO Chang-zhi, et al. 2013. Variation characteristic of earth resistivity at Baochang station[J]. Journal Seismological Research, 36(3): 358—363(in Chinese).
[2] 杜学彬. 2010. 在地震预报中的2类视电阻率变化[J]. 中国科学(D辑), 40(10): 1321—1330.
DU Xue-bin. 2010. Two types of changes in apparent resistivity in earthquake prediction[J]. Science China(Ser D), 40(10): 1321—1330(in Chinese).
[3] 杜学彬, 李宁, 叶青, 等. 2007. 强地震附近视电阻率各向异性变化的原因[J]. 地球物理学报, 50(6): 1802—1810.
DU Xue-bin, LI Ning, YE Qing, et al. 2007. A possible reason for the anisotropic changes in apparent resistivity near the focal region of strong earthquake[J]. Chinese Journal of Geophysics, 50(6): 1802—1810(in Chinese).
[4] 杜学彬, 阮爱国, 范世宏, 等. 2001. 强震近震中区地电阻率变化速率的各向异性[J]. 地震学报, 23(3): 289—297.
DU Xue-bin, RUAN Ai-guo, FAN Shi-hong, et al. 2001. Anisotropy of the variation rate of apparent resistivity near the epicentral region of strong earthquakes[J]. Acta Seismologica Sinica, 23(3): 289—297(in Chinese).
[5] 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).
[6] 高立新, 黄根喜, 阎海滨. 1999. 张北-尚义6.2级地震(1998-01-10)前倾斜与地电阻率前兆异常[J]. 地壳形变与地震, 19(4): 88—90.
GAO Li-xin, HUANG Gen-xi, YAN Hai-bin. 1999. The dependable precursory anomaly before Zhangbei-Shangyi M_S6.2 earthquake occurred on January 10, 1998[J]. Crustal Deformation and Earthquake, 19(4): 88—90(in Chinese).
[7] 高立新, 戴勇, 杨彦明. 2019. 视电阻率典型变化成因分析[J]. 国际地震动态, (8): 138—139.
GAO Li-xin, DAI Yong, YANG Yan-ming. 2019. Analysis on the cause of typical variation of apparent resistivity[J]. Recent Developments in World Seismology, (8): 138—139(in Chinese).
[8] 孔珑. 2014. 工程流体力学(第4版)[M]. 北京: 中国电力出版社.
KONG Long. 2014. Engineering Fluid Dynamics(4th Edition)[M]. China Electric Power Press, Beijing(in Chinese).
[9] 李丹, 钱连红. 2016. 2015年度内蒙古地区地下水位变化评估[J]. 内蒙古水利, (5): 3—4.
LI Dan, QIAN Lian-hong. 2016. Evaluation of groundwater level change in Inner Mongolia in 2015[J]. Inner Mongolia Water Resources, (5): 3—4(in Chinese).
[10] 刘刚, 邓春林. 2011. 防雷与接地技术概论 [M]. 广州: 华南理工大学出版社.
LIU Gang, DENG Chun-lin. 2011. Introduction to Lightning Protection and Grounding Technology [M]. South China University of Technology Press, Guangzhou(in Chinese).
[11] 内蒙古自治区地震局. 2006. 内蒙古自治区地震监测志 [M]. 呼和浩特: 内蒙古人民出版出版社.
Earthquake Agency of Inner Mongolia Autonomous Region. 2006. Seismological Monitoring Records of Inner Mongolia Autonomous Region [M]. Inner Mongolia People's Publishing House, Hohhot(in Chinese).
[12] 钱复业, 赵玉林. 1980. 地震前地电阻率变化十例[J]. 地震学报, 2(2): 78—89.
QIAN Fu-ye, ZHAO Yu-lin. 1980. Ten examples of changes in earth-resistivity prior to earthquakes[J]. Acta Seismologica Sinica, 2(2): 78—89(in Chinese).
[13] 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 Jia-dong, CHEN You-fa, JIN An-zhong. 1985. Application of Resistivity Method in Earthquake Prediction [M]. Seismological Press, Beijing(in Chinese).
[14] 石富强, 张国强, 方炜, 等. 2014. 陕西周至地电台地电阻率年变特征分析[J]. 地震学报, 36(6): 1113—1123.
SHI Fu-qiang, ZHANG Guo-qiang, FANG Wei, et al. 2014. Annual variation characteristics of georesistivity at Zhouzhi geoelectric station, Shaanxi Province[J]. Acta Seismologica Sinica, 36(6): 1113—1123.
[15] 汤吉, 赵国泽. 1998. 张北-尚义地震前后电阻率的变化及分析[J]. 地震地质, 20(2): 164—171.
TANG Ji, ZHAO Guo-ze. 1998. Variation and analysis of resistivity before and after the Zhangbei-Shangyi earthquake[J]. Seismology and Geology, 20(2): 164—171(in Chinese).
[16] 王家映. 1998. 地球物理反演理论 [M]. 武汉: 中国地质大学出版社.
WANG Jia-ying. 1998. Geophysical Inversion Theory [M]. China University of Geosciences Press, Wuhan(in Chinese).
[17] 王兰炜, 朱旭, 朱涛, 等. 2011. 地电阻率多极距观测系统及试验研究[J]. 地震, 31(1): 20—31.
WANG Lan-wei, ZHU Xu, ZHU Tao, et al. 2011. Multi-separation array geo-electrical resistivity observation and its experimental system[J]. Earthquake, 31(1): 20—31(in Chinese).
[18] 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. Precursory Anomalies of Seismic Ground Resistivity [M]. Seismological Press, Beijing(in Chinese).
[19] 魏建民, 戴勇, 刘芳, 等. 2019. 宝昌地震台地电阻率电性结构特征[J]. 地震地磁观测与研究, 40(3): 56—63.
WEI Jian-min, DAI Yong, LIU Fang, et al. 2019. Structural characteristics of electricity of ground resistivity at Baochang seismic station[J]. Seismological and Geomagnetic Observation and Research, 40(3): 56—63(in Chinese).
[20] 西安交通大学物理教研组. 1974. 物理学(第3册)[M]. 西安: 西安交通大学出版社.
School of Physics, Xi'an Jiaotong University. 1974. Physics(Volume 3)[M]. Xi'an Jiaotong University Press, Xi'an(in Chinese).
[21] 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).
[22] 解滔, 卢军. 2015. 地电阻率三维影响系数及其应用[J]. 地震地质, 37(4): 1125—1135.
XIE Tao, LU Jun. 2015. Three-dimensional sensitivity coefficients of apparent resistivity and preliminary application[J]. Seismology and Geology, 37(4): 1125—1135(in Chinese).
[23] 解滔, 卢军. 2016. 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.
XIE Tao, LU Jun. 2016. Apparent resistivity temporal variation characteristics affected by the fixed disturbance source on surface of measuring area[J]. Seismology and Geology, 38(4): 922—936(in Chinese).
[24] 熊仲华. 2006. 地震观测技术 [M]. 北京: 地震出版社.
XIONG Zhong-hua. 2006. Earthquake Observation Technology [M]. Seismological Press, Beijing(in Chinese).
[25] 徐菊生, 袁金荣, 高士钧, 等. 1999. 利用GPS观测结果研究华北地区现今构造应力场[J]. 地壳形变与地震, 19(2): 81—89.
XU Ju-sheng, YUAN Jin-rong, GAO Shi-jun, et al. 1999. Research on the precent tectonic stress field in North China with GPS observations[J]. Crustal Deformation and Earthquake, 19(2): 81—89(in Chinese).
[26] 徐锡泉, 高昌志, 王亮. 2014. 内蒙古宝昌台地电阻率长期观测数据研究[J]. 地震工程学报, 36(2): 405—412.
XU Xi-quan, GAO Chang-zhi, WANG Liang. 2014. Study on long-term observation data of earth resistivity at Baochang station in Inner Mongolia[J]. China Earthquake Engineering Journal, 36(2): 405—412(in Chinese).
[27] 鄢泰宁. 2014. 岩土钻掘工艺学 [M]. 长沙: 中南大学出版社.
YAN Tai-ning. 2014. Geotechnical Drilling Technology [M]. Central South University Press, Changsha(in Chinese).
[28] 姚文斌. 1989. 电测深数值计算和解释入门 [M]. 北京: 地震出版社.
YAO Wen-bin. 1989. Introduction to Numerical Calculation and Interpretation of Electrical Sounding [M]. Seismological Press, Beijing(in Chinese).
[29] 张国苓, 乔子云, 贾立峰, 等. 2015. 河北阳原台地电阻率变化分析[J]. 震灾防御技术, 10(2): 464—471.
ZHANG Guo-ling, QIAO Zi-yun, JIA Li-feng, et al. 2015. Analysis on the anomaly of resistivity at Yangyuan station, Hebei Province[J]. Technology for Earthquake Disaster Prevention, 10(2): 464—471(in Chinese).
[30] 张国民, 傅征祥, 桂燮泰. 2001. 地震预报引论 [M]. 北京: 科学出版社.
ZHANG Guo-min, FU Zheng-xiang, GUI Xie-tai. 2001. Introduction to Earthquake Prediction [M]. Science Press, Beijing(in Chinese).
[31] 张学民, 李美, 关华平. 2009. 汶川8.0级地震前的地电阻率异常分析[J]. 地震, 29(1): 108—115.
ZHANG Xue-min, LI Mei, GUAN Hua-ping. 2009. Anomaly analysis of earth resistivity observations before the Wenchuan earthquake[J]. Earthquake, 29(1): 108—115(in Chinese).
[32] 赵和云. 1994. 地电阻率趋势变化的形态特征与地震[J]. 地震学报, 16(3): 368—375.
ZHAO He-yun. 1994. The relationship between morphological characteristics of the trend of georesistivity and earthquakes[J]. Acta Seismologica Sinica, 16(3): 368—375(in Chinese).
[33] 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 of exploration depth and exploration range in georesistivity method[J]. Journal of Northwest Seismology, 4(1): 40—56(in Chinese).
[34] 中国地震局. 2001. 地震及前兆数字观测技术规范: 电磁观测(试行)[M]. 北京: 地震出版社.
China Earthquake Administration. 2001. Technical Specification for Digital Observation of Earthquakes and Precursors: Electromagnetic Observation(Trial)[M]. Seismological Press, Beijing(in Chinese).
[35] 中国地震局监测预报司. 2010. 地震电磁学理论基础与观测技术(试用本)[M]. 北京: 地震出版社.
Department of Monitoring and Prediction, China Earthquake Administration. 2010. Theoretic Basis and Observation Technology of Seismology and Electromagnetics(Probationary Version)[M]. Seismological Press, Beijing(in Chinese).
[36] Lu J, Xie T, Li M, et al. 2016. Monitoring shallow resistivity changes prior to the 12 May 2008 M8.0 Wenchuan earthquake on the Longmen Shan tectonic zone, China[J]. Tectonophysics, (675): 244—257.
[37] Lu J, Xue S Z, Qian F Y, et al. 2004. Unexpected changes in resistivity monitoring for earthquakes of the Longmen Shan in Sichuan, China, with a fixed Schlumberger sounding array[J]. Physics of the Earth and Planetary Interiors, 145(1): 87—97.
[38] O'Neill D J, Merrick N P. 1984. A digital linear filter for resistivity sounding with a generalized electrode array[J]. Geophysical Prospecting, 32(1): 105—123.
[39] Zhao J L, Wang L W, Qian J D, et al. 2011. Research on geo-electrical resistivity observation system specially used for earthquake monitoring in China[J]. Earthquake Science, 24(6): 497—511.
[40] Zhao Y L, Lu J, Li Z N, et al. 1996. Strain-geoelectric resistivity precursor and the virtual dislocation model to the Tangshan earthquake[J]. Acta Seismologica Sinica, 9(1): 103—108.