ANALYSIS ON THE 2013 BADONG M5.1 EARTHQUAKE SEQUENCE AND THE SEISMOGENIC STRUCTURE

doi:10.3969/j.issn.0253-4967.2016.03.019

Abstract

Abstract:

On 16^th September 2013, an M5.1 earthquake occurred in Badong County, Hubei Province, which is the biggest one since the first water impounding in 2003 in the head region of the Three Gorges Reservoir area. The crustal velocity information is needed to determine the earthquake location and focal mechanism. By comparison, the 1-D velocity structure model from Zhao was adopted in this study. Double difference location method was applied to determine the precise locations of the M5.1 earthquake sequence. Relocation results show that the dominant distribution of this sequence is along NEE direction. In order to understand its seismogenic structure, focal depth profiles were made. Profile AA' was along the sequence distribution, and the earthquake sequence extended about 12km. Focal depth of mainshock is deeper than that of aftershocks, and earthquake rupture propagated laterally southwestward. The seismic profile BB' and CC' were perpendicular to profile AA', which represent the dip direction. Both profiles show that the focal depth becomes deeper toward southeast, and dip angle is about 50°. It means that the possible seismogenic fault strikes NEE and dips southeast. Focal mechanism could provide more information for judging the seismogenic structures. Many methods could obtain the focal mechanism, such as P-wave first motion method, CAP method, and some other moment tensor methods. In this paper, moment tensor inversion program made by Yagi Y is adopted. 12 regional seismic stations ranging from 100~400km are picked up, and before the inversion, we removed the mean and trend. The seismic waveforms were band pass filtered between 0.05 and 0.2Hz, and then integrated into displacement. Green's functions were calculated using the discrete wavenumber method developed by Kohketsu. The focal mechanism of the M5.1 mainshock manifests that the NEE-striking fault plane probably is the possible seismogenic fault, which is consistent with the analysis of focal depth profiles. The focal mechanisms of the M_L≥2.0 aftershocks are retrieved by P-wave first motion method, and the nodal plane I is in accordance with the earthquake sequence distribution and the fault plane of the mainshock. FMSI program was adopted to inverse the stress field in the earthquake area, and the results show that the earthquake sequence is under the control of the regional stress field. The earthquake sequence occurred on the stage of slow water unloading, and ETAS model was introduced to testify the influences of water level fluctuations on earthquakes. The results denote that the reservoir played a triggering role in the earthquake, however, the NEE-striking seismogenic fault is the controlling factor.

Key words: double-difference location method, focal depth profile, focal mechanism, tectonic stress field, ETAS model

摘要：

2013年12月16日湖北省巴东县发生M5.1地震，该地震是三峡库首区自2003年蓄水以来震级最大的1次。双差地震精定位结果显示，巴东地震序列呈NEE向线性展布，主震震源较深，余震震源深度逐渐变浅。垂直余震优势展布的震源深度剖面均显示出向SE变深的特征；倾角约50°左右，向深部变缓，揭示可能的发震断层走向NEE，倾向SE，倾角约为50°。利用矩张量反演得到了主震的震源机制解，与地震序列定位分析比较吻合的是NEE向节面，综合判断该节面可能为发震断层，倾向SE，倾角50°左右，性质以走滑为主兼逆冲分量。利用P波初动方法求解了M_L2.0以上余震的震源机制，并采用FMSI程序反演得到了震源区的构造应力场，结果显示其方向与区域现代构造应力场方向一致，说明该地震序列受区域应力场的控制。地震序列发生在175m高水位运行期的水位缓慢降落阶段，基于ETAS模型对流体触发作用进行了定量检测，显示库水对地震序列的触发作用占17％，余震自激发占83％。综合分析认为，巴东M5.1地震为库水触发的构造型地震，NEE向断裂构造为可能的发震构造。

关键词: 双差定位, 震源深度剖面, 震源机制, 构造应力场, ETAS模型

CLC Number:

P315.2

ZHANG Li-fen, LIAO Wu-lin, LI Jing-gang, WEI Gui-chun, SHEN Xue-lin. ANALYSIS ON THE 2013 BADONG M5.1 EARTHQUAKE SEQUENCE AND THE SEISMOGENIC STRUCTURE[J]. SEISMOLOGY AND GEOLOGY, 2016, 38(3): 747-759.

张丽芬, 廖武林, 李井冈, 魏贵春, 申学林. 2013年12月16日巴东M5.1地震序列及发震构造分析[J]. 地震地质, 2016, 38(3): 747-759.

References

陈学波. 1994. 长江三峡工程坝区及外围深部构造特征研究［M］. 北京:地震出版社.
CHEN Xue-bo. 1994. Study on the Characteristics of Deep Structure in and around the Damsite of the Yangtze River Three Gorges Project［M］. Seismological Press, Beijing(in Chinese).
蒋海昆, 宋金, 吴琼, 等. 2012. 基于ETAS模型对三峡库区流体触发微震活动的定量检测［J］. 地球物理学报, 55(7):2341-2352.
JIANG Hai-kun, SONG Jin, WU Qiong, et al. 2012. Quantitative investigation of fluid triggering on seismicity in the Three Gorges reservoir area based on ETAS model［J］. Chinese J Geophys, 55(7):2341-2352(in Chinese).
蒋海昆, 杨马陵, 孙学军, 等. 2011. 暴雨触发局部地震活动的一个典型例子:2010年6月广西凌云-凤山交界3级震群活动［J］. 地球物理学报, 54(10):2606-2619.
JIANG Hai-kun, YANG Ma-ling, SUN Xue-jun, et al. 2011. A typical example of locally triggered seismicity in the boundary area of Lingyun and Fengshan following the large rainfall event of June 2010［J］. Chinese J Geophys, 54(10):2606-2619(in Chinese).
兰从欣, 邢成起, 苗春兰, 等. 2005. 近年首都圈地区中小地震震源机制解及其特征分析［J］. 华北地震科学, 23(4):21-25.
LAN Cong-xin, XIN Cheng-qi, MIAO Chun-lan, et al. 2005. Analysis of small earthquake focal mechanisms and characteristics in the capital circle area of China［J］. North China Earthquake Science, 23(4):21-25(in Chinese).
李强, 赵旭, 蔡晋安, 等. 2009. 三峡水库坝址及邻区中上地壳P波速度结构［J］. 中国科学(D辑), 39(4):427-436.
LI Qiang, ZHAO Xu, CAI Jin-an, et al. 2009. P wave velocity structure of upper and middle crust beneath the Three Gorges reservoir dam and adjacent region［J］. Science in China(Ser D), 39(4):427-436(in Chinese).
龙锋, 杜方, 阮祥, 等. 2010. 用ETAS模型分析自贡矿井注水触发地震［J］. 中国地震, 26(2):164-171.
LONG Feng, DU Fang, RUAN Xiang, et al. 2010. Water injection triggered earthquakes in the Zigong mineral wells in ETAS model［J］. Earthquake Research in China, 26(2):164-171(in Chinese).
苏恺之, 李方全, 张伯崇, 等. 1996. 长江三峡地区地壳应力与孔隙水压力综合研究［M］. 北京:地震出版社.
SU Kai-zhi, LI Fang-quan, ZHANG Bo-chong, et al. 1996. Integrated Research on the Stress Field and Pore Pressure at the Three Gorges Site［M］. Seismological Press, Beijing(in Chinese).
夏金梧, 周乐群, 刘世凯. 1996. 鄂西秭归盆地及外缘主要断裂特征及活动性研究［J］. 水文地质工程地质, (1):10-14.
XIA Jin-wu, ZHOU Le-qun, LIU Shi-kai. 1996. Study on the characteristics and activities of the main faults in the Zigui Basin and outer margin in the western Hubei［J］. Hydrogeology and Engineering Geology, (1):10-14(in Chinese).
易桂喜, 龙锋, 闻学泽, 等. 2015. 2014年11月22日康定M6.3地震序列发震构造分析［J］. 地球物理学报, 58(4):1205-1219.
YI Gui-xi, LONG Feng, WEN Xue-ze, et al. 2015. Seismogenic structure of the M6.3 Kangding earthquake sequence on 22 Nov. 2014, southwestern China［J］. Chinese J Geophys, 58(4):1205-1219(in Chinese).
张丽芬, 姚运生, 廖武林. 2013. 2011年M_S4.6瑞昌-阳新地震的震源机制及发震构造探讨［J］. 地震地质, 35(2):290-297.
ZHANG Li-fen, YAO Yun-sheng, LIAO Wu-lin. 2013. Focal mechanisms and seismogenic structures of the M_S4.6 Ruichang-Yangxin earthquake of 2011.［J］. Seismology and Geology, 35(2):290-297(in Chinese).
赵旭, 李强, 蔡晋安. 2007. 三峡库首区最小一维速度模型研究［J］. 大地测量与地球动力学, 27(专刊):1-7.
ZHAO Xu, LI Qiang, CAI Jin-an. 2007. On minimum 1D velocity structure model applied in Three Gorges reservoir area［J］. Geodesy and Geodynamics, 27(Spec):1-7(in Chinese).
Dziewonski A M, Chou T A, Woodhouse J H. 1981. Determination of earthquake source parameters from waveform data for studies of global and regional seismicity［J］. J Geophys Res, 86:2825-2852.
Gephart J W, Forsyth D W. 1984. An improved method for determining the regional stress tensor using earthquake focal mechanism data:Application to the San Ferando earthquake sequence［J］. J Geophys Res, 89(B11):9305-9320.
Gephart J W. 1990. Stress and the direction of slip on fault planes［J］. Tectonics, 9(4):845-858.
Hainzl S, Ogata Y. 2005. Detecting fluid signals in seismicity data through statistical earthquake modeling［J］. J Geophys Res, 110:B05S07.
Kisslinger C. 1980. Evaluation of S to P amplitude ratio for determining focal mechanism from regional network observations［J］. Bull Seism Soc Am, 70:999-1014.
Kohketsu K. 1985. The extended reflectivity method for synthetic near field seismograms［J］. J Phys Earth, 33:121-131.
Lei X L, Yu G Z, Ma S L, et al. 2008. Earthquake induced by water injection at-3km depth within the Rongchang gas field, Chongqing, China［J］. J Geophys Res, 113:B10310.
Ogata Y. 1988. Statistical models for earthquake occurrences and residual analysis for point processes［J］. J Am Stat Assoc, 83(401):9-27.
Ogata Y. 1989. Statistical models for standard seismicity and detection of anomalies by residual analysis［J］. Tectonophysics, 169(1-3):159-174.
Ogata Y. 1992. Detection of relative quiescence before great earthquakes, through a statistical model［J］. J Geophys Res, 97:19845-19871.
Reasenberg P, Oppenheimer D. 1985. FPFIT, FPPLOT and FPPAGE:Fortran computer programs for calculating and displaying earthquake fault plane solutions［J］. US Geol Surv Open-File Rept:85-739, 25.
Waldhauser F, Ellsworth W L. 2000. A double-difference earthquake location algorithm:Method and application to the Northern Hayward Fault, California［J］. Bull Seism Soc Am, 90(6):1353-1368.
Zhu L P, Helmgerger D V. 1996. Advancement in source estimation techniques using broadband regional seismograms［J］. Bull Seism Soc Am, 86(5):1634-1641.

[1]	FAN Wen-jie. CHARACTERISTICS OF TECTONIC STRESS FIELD AROUND THE YANGBI M_S6.4 EARTHQUAKE AND ITS SURROUNDING AREAS ON MAY 21, 2021 AND ITS GEODYNAMIC IMPLICATION [J]. SEISMOLOGY AND GEOLOGY, 2023, 45(1): 208-230.
[2]	ZHANG Ke, WANG Xin, YANG Hong-ying, WANG Yue, XU Yan, LI Jing. THE CHARACTERISTICS AND SEISMOGENIC STRUCTURE ANALYSIS OF THE 2021 YANGBI M_S6.4 EARTHQUAKE SEQUENCE, YUNNAN [J]. SEISMOLOGY AND GEOLOGY, 2023, 45(1): 231-251.
[3]	DENG Wen-ze, LIU Jie, YANG Zhi-gao, SUN Li, ZHANG Xue-mei. PRELIMINARY ANALYSIS FOR RUPTURE PROCESS OF THE MAY 22TH, 2021, MADOI(QINGHAI) M_S7.4 EARTHQUAKE [J]. SEISMOLOGY AND GEOLOGY, 2022, 44(4): 1059-1070.
[4]	LI Zong-xu, HE Ri-zheng, JI Zhan-bo, LI Yu-lan, NIU Xiao. THE FOCAL MECHANISM AND TECTONIC SIGNIFICANCE OF THE M_S5.6 EARTHQUAKE ON JULY 24, 2009 IN NIMA, TIBET [J]. SEISMOLOGY AND GEOLOGY, 2022, 44(4): 992-1010.
[5]	WANG Yu-qing, FENG Wan-peng, ZHANG Pei-zhen. PRESENT DEFORMATION OF~90° INTERSECTING CONJUGATE FAULTS AND MECHANICAL IMPLICATION TO REGIONAL TECTONICS: A CASE STUDY OF 2019 M_W≥6.4 PHILIPPINES EARTHQUAKE SEQUENCE [J]. SEISMOLOGY AND GEOLOGY, 2022, 44(2): 313-332.
[6]	WANG Xiao-shan, WAN Yong-ge. CHARACTERISTICS OF THE CRUSTAL STRESS FIELD AND ITS DIRECTION CONVERGENCE BEFORE THE WENCHUAN EARTHQUAKE [J]. SEISMOLOGY AND GEOLOGY, 2022, 44(2): 363-377.
[7]	YU Zhan-yang, SHEN Xu-zhang, LIANG Hao, ZHENG Wen-jun, LIU Xu-zhou. THE CHARACTERISTICS OF MAJOR FAULTS AND STRESS FIELD IN WEIHE-YUNCHENG BASIN CONSTRAINED BY SEISMIC ACTIVITY AND FOCAL MECHANISM SOLUTIONS [J]. SEISMOLOGY AND GEOLOGY, 2022, 44(2): 395-413.
[8]	ZHANG Zhi-wei, LONG Feng, ZHAO Xiao-yan, WANG Di. STUDY ON FOCAL MECHANISM SOLUTION AND STRESS FIELD CHARACTERISTICS IN SICHUAN AND YUNNAN AREA [J]. SEISMOLOGY AND GEOLOGY, 2022, 44(1): 170-187.
[9]	XUE Yan, XIE Meng-yu, LIU Jie, ZHUANG Jian-cang. STUDY ON FORESHOCK SEQUENCES OF THE GLOBA L GREAT SHALLOW-FOCUS EARTHQUAKES WITH M_W≥8.0 [J]. SEISMOLOGY AND EGOLOGY, 2021, 43(5): 1233-1249.
[10]	ZHAO Tao, WANG Ying, MA Ji, SHAO Ruo-tong, XU Yi-fei, HU Jing. RELOCATION AND FOCAL MECHANISM SOLUTIONS OF THE 2021 MADUO, QINGHAI M_S7.4 EARTHQUAKE SEQUENCE [J]. SEISMOLOGY AND EGOLOGY, 2021, 43(4): 790-805.
[11]	WANG Ying, ZHAO Tao, HU Jing, LIU Chun. RELOCATION AND FOCAL MECHANISM SOLUTIONS OF THE 2021 YANGBI, YUNNAN M_S6.4 EARTHQUAKE SEQUENCE [J]. SEISMOLOGY AND EGOLOGY, 2021, 43(4): 847-863.
[12]	ZHANG Sheng-feng, ZHANG Yong-xian, FAN Xiao-yi. ANALYSIS ON BACKGROUND AND TRIGGERED SEISMICITY OF JIASHI, XINJIANG, CHINA BASED ON SPATIAL-TEMPORAL ETAS MODEL [J]. SEISMOLOGY AND GEOLOGY, 2021, 43(2): 297-310.
[13]	CUI Ren-sheng, ZHAO Cui-ping, ZHOU Lian-qing, CHEN Yang. SEISMICITY FEATURE AND SEISMOGENIC FAULT OF THE M_S6.4 EARTHQUAKE SEQUENCE ON JANUARY 19, 2020 IN JIASHI, XINJIANG [J]. SEISMOLOGY AND GEOLOGY, 2021, 43(2): 329-344.
[14]	LI Jin, JIANG Hai-kun, WEI Yun-yun, SUN Zhao-jie. PRELIMINARY STUDY FOR SEISMOGENIC STRUCTURE OF THE M_S6.4 JIASHI EARTHQUAKE ON JANUARY 19, 2020 [J]. SEISMOLOGY AND GEOLOGY, 2021, 43(2): 357-376.
[15]	ZHANG Wen-ting, JI Ling-yun, ZHU Liang-yu, JIANG Feng-yun, XU Xiao-xue. A TYPICAL THRUST RUPTURE EVENT OCCURRING IN THE FORELAND BASIN OF THE SOUTHERN TIANSHAN: THE 2020 XINJIANG JIASHI M_S6.4 EARTHQUAKE [J]. SEISMOLOGY AND GEOLOGY, 2021, 43(2): 394-409.