利用小震分布和区域应力场确定龙滩库区地震断层面参数

doi:10.3969/j.issn.0253-4967.2020.03.002

摘要/Abstract

摘要： 文中基于2006-2016年龙滩水库数字地震台网记录的地震波形和震相资料, 采用结合波形互相关技术的双差定位方法对4 017次地震进行重新定位, 求解得到库区126个中小地震的震源机制解, 并反演各地震丛所在区域的应力场。将库区地震划分为11个地震密集带, 依据成丛小地震发生在活动断裂面及其附近的原则, 结合模拟退火算法和高斯-牛顿算法反演了11个地震密集带相应的断层及断层面参数, 包括断层面的走向、倾向、倾角、长度、深度和地理位置, 并依据局部区域应力场参数计算了各断层面的滑动角。结果显示: 11条断层的走向、倾向、倾角及运动性质与地质调查给出的穿过各地震丛所在区域的主要断裂信息基本一致, 研究成果可作为龙滩库区主要断裂带资料的重要补充。龙滩库区最大主应力优势方向为NW-SE或NWW-SEE, 最大和最小主应力轴倾角近水平, 中间主应力轴倾角很陡, 蓄水前、后区域应力场主压应力方向未发生明显变化, 与华南块体的构造应力场方向基本一致。蓄水后库区的R值逐渐增大, 且不同地震丛所在区域的R值变化存在差异。八茂、拉浪和布柳河地震丛所在区域R值增幅显著, 表明中间应力轴压应力状态减弱并逐渐转为张应力状态。精定位和断层面参数计算结果显示, 地震丛集活动与穿过地震丛的主要断裂带密切相关。这些断裂的倾角普遍很陡, 均与库区主要河流交会, 利于流体向断层深部渗透。推测库区蓄水主要影响库区应力场主应力的相对大小, 对主应力方向的影响有限。水对库区介质的润滑作用及附加应力场与原地应力的叠加可能是导致库区主应力相对大小发生变化的主要因素。龙滩库区蓄水后的张剪性应力环境有利于库区断层失稳滑动, 可较好地解释蓄水后库区地震密集活跃现象。量化的断裂信息可为龙滩库区地震危险性分析、地震成因的数值模拟、地震预测等方面的深入研究提供支持。

关键词: 断层面解, 小震丛集, 震源机制解, 应力场, 龙滩水库

Abstract: The Longtan reservoir is located in Tian'e County, Guangxi Zhuang Autonomous Region, southwestern China on the upper reaches of Hongshui River, the main stream of the Pearl River. The dam of the reservoir is 200m high, and the maximum water depth can be up to 194m as the water level reaches 400m. The reservoir storage capacity is 27.3 billion cubic meters, so it is a typical high-dam reservoir with large storage capacity. Terrain of the reservoir is high in the west and low in the east. The reservoir is located at the confluence of the Hongshui River, Buliu River, Nanpan River, Beipan River, Mengjiang River and Caodu River. The construction of Longtan hydropower station officially started in July 2001, and the reservoir impoundment was on September 30, 2006. The power station is equipped with 9 sets of 700 000kW water turbine generator units, with a total installed capacity of 6.3 million kW and an average annual generating capacity of 18.7 billion kW·h. So its storage and hydropower capacity rank third only to the world-famous Three Gorges hydropower project and the ultra-large hydropower project in Xiluodu of Jinsha River in China. Seismicity enhanced rapidly in the reservoir area after the impoundment. More the 5 000 earthquakes have been recorded so far, with the maximum magnitude of M_L4.8, which occurred on September 18, 2010. The earthquakes are mainly concentrated in the deep water area where fault zones run through. Assuming the seismogenic fault can be simulated by a plane and most small earthquakes occur nearby the fault plane, the information of seismogenic fault can be obtained by the hypocenter location parameters of small earthquakes.

Key words: fault plane solution, small earthquake clustering, focal mechanism, stress field, Longtan reservoir

中图分类号:

P315.2

阎春恒, 周斌, 李莎, 向巍, 郭培兰. 利用小震分布和区域应力场确定龙滩库区地震断层面参数[J]. 地震地质, 2020, 42(3): 562-580.

YAN Chun-heng, ZHOU Bin, LI Sha, XIANG Wei, GUO Pei-lan. DETERMINATION OF FAULT PLANE PARAMETERS IN THE LONGTAN RESERVOIR BY USING PRECISELY LOCATED SMALL EARTHQUAKE DATA AND REGIONAL STRESS FIELD[J]. SEISMOLOGY AND GEOLOGY, 2020, 42(3): 562-580.

参考文献

[1] 陈翰林, 赵翠萍, 修济刚, 等. 2009a. 龙滩水库地震精定位及活动特征研究[J]. 地球物理学报, 52(8): 2035-2043.
CHEN Han-lin, ZHAO Cui-ping, XIU Ji-gang, et al.2009a. Study on precise relocation of Longtan reservoir earthquakes and its seismic activity[J]. Chinese Journal of Geophysics, 52(8): 2035-2043(in Chinese).
[2] 陈翰林, 赵翠萍, 修济刚, 等. 2009b. 龙滩库区水库地震震源机制及应力场特征[J]. 地震地质, 31(4): 686-698. doi: 10.3969/j.issn.0253-4967.2009.04.01.
CHEN Han-lin, ZHAO Cui-ping, XIU Ji-gang, et al.2009b. Study on the characteristics of focal mechanisms of reservoir induced earthquakes and stress field in the Longtan reservoir area[J]. Seismology and Geology, 31(4): 686-698(in Chinese).
[3] 陈益明. 1989. 龙滩水库区诱发地震危险性估计[J]. 西北地震学报, 11(3): 69-77.
CHEN Yi-ming.1989. The estimation of induced earthquake danger in the Longtan reservoir region[J]. Northwestern Seismological Journal, 11(3): 69-77(in Chinese).
[4] 刁桂苓, 徐锡伟, 陈于高, 等. 2011. 汶川M_W7.9和集集M_W7.6地震前应力场转换现象及其可能的前兆意义[J]. 地球物理学报, 54(1): 128-136.DIAO Gui-ling, XU Xi-wei, CHEN Yu-gao, et al. 2011. The precursory significance of tectonic stress field transformation before the Wenchuan M_W7.9 earthquake and the Chi-Chi M_W7.6 earthquake [J]. Chinese Journal of Geophysics, 54(1): 128-136(in Chinese).
[5] 广西壮族自治区地质局. 1968. 南丹幅地质图[CM]. 北京: 地质出版社.
Geological Bureau of Guangxi Zhuang Autonomous Region. 1968. Geological Map of Nandan County[CM]. Geological Publishing House, Beijing(in Chinese).
[6] 广西壮族自治区地质局. 1972. 乐业幅地质图[CM]. 北京: 地质出版社.
Geological Bureau of Guangxi Zhuang Autonomous Region. 1972. Geological Map of Leye County[CM]. Geological Publishing House, Beijing(in Chinese).
[7] 郭培兰, 姚宏, 袁媛. 2006. 龙滩水库地震危险性分析[J]. 高原地震, 18(4): 17-23.
GUO Pei-lan, YAO Hong, YUAN Yuan.2006. Analysis on potential seismic risk in Longtan reservoir[J]. Plateau Earthquake Research, 18(4): 17-23(in Chinese).
[8] 韩晓明, 张帆, 陈立峰, 等. 2018. 2013年通辽5.3级地震及余震的破裂特征讨论[J]. 地震地质, 40(3): 685-697. doi: 10.3969/j.issn.0253-4967.2018.03.013.
HAN Xiao-ming, ZHANG Fan, CHEN Li-feng, et al.2018. Discussion on rupture characteristics of the 2013 Tongliao M5.3 earthquake and its aftershocks[J]. Seismology and Geology, 40(3): 685-697(in Chinese).
[9] 华卫, 陈章立, 郑斯华, 等. 2012. 水库诱发地震与构造地震震源参数特征差异性研究: 以龙滩水库为例[J]. 地球物理学进展, 27(3): 924-935.
HUA Wei, CHEN Zhang-li, ZHENG Si-hua, et al.2012. Differences existing in characteristics of source parameters between reservoir induced seismicity and tectonic earthquake: A case study of Longtan reservoir[J]. Progress in Geophysics, 27(3): 924-935(in Chinese).
[10] 黄浩, 付虹. 2019. 小湾水库库区蓄水前后构造应力场的变化特征[J]. 地震地质, 41(6): 1413-1428. doi: 10.3969/j.issn.0253-4967.2019.06.007.
HUANG Hao, FU Hong.2019. Characteristics of tectonic stress field of the Xiaowan reservoir before and after the impoundment[J]. Seismology and Geology, 41(6): 1413-1428(in Chinese).
[11] 蒋海昆, 张晓东, 单新建, 等. 2014. 中国大陆水库地震统计特征及预测方法研究 [M]. 北京: 地震出版社: 132-135.
JIANG Hai-kun, ZHANG Xiao-dong, SHAN Xin-jian, et al.2014. Research on Statistical Characteristics and Prediction of Reservoir-induced Earthquake in China's Mainland [M]. Seismological Press, Beijing: 132-135(in Chinese).
[12] 李峰, 张效亮, 贾启超, 等. 2017. 利用精定位小震资料反演1933年叠溪M71/2地震震源断层面参数[J]. 震灾防御技术, 12(3): 565-573.
LI Feng, ZHANG Xiao-liang, JIA Qi-chao, et al.2017. The seismogenic fault plane parameters inversion of the 1933 M71/2 Diexi earthquake using precisely located small earthquakes[J]. Technology for Earthquake Disaster Prevention, 12(3): 565-573(in Chinese).
[13] 李伟琦. 1989. 广西新构造分区特征及其与地震的关系[J]. 华南地震, 9(4): 22-26.
LI Wei-qi.1989. The relationship between the characteristics of neotectonic regionalization and earthquakes in Guangxi[J]. South China Journal of Seismology, 9(4): 22-26(in Chinese).
[14] 李祖武. 1981. 水库地震与地质构造的关系[J]. 地震地质, 3(2): 61-69.LI Zu-wu. 1981. The relation between the reservoir-induced earthquakes and geologic structures [J]. Seismology and Geology, 3(2): 61-69(in Chinese).
[15] 刘白云, 袁道阳, 张波, 等. 2012. 1879年武都南8级大地震断层面参数和滑动性质的厘定[J]. 地震地质, 34(3): 415-424. doi: 10.3969/j.issn.0253-4967.2012.03.003.
LIU Bai-yun, YUAN Dao-yang, ZHANG Bo, et al.2012. Determination of fault parameters and sliding behavior of the 1879 southern Wudu M8.0 earthquake[J]. Seismology and Geology, 34(3): 415-424(in Chinese).
[16] 刘杰, 郑斯华, 康英, 等. 2004. 利用P波和S波的初动和振幅比计算中小地震的震源机制解[J]. 地震, 24(1): 19-26.
LIU Jie, ZHENG Si-hua, KANG Ying, et al.2004. The focal mechanism determinations of moderate-small earthquakes using the first motion and amplitude ratio of P and S wave[J]. Earthquake, 24(1): 19-26(in Chinese).
[17] 刘特培, 邵叶, 杨选, 等. 2017 利用高精度小震资料确定新丰江水库大坝区NW向发震断层[J]. 地震学报, 39(1): 23-33.LIU Te-pei, SHAO Ye, YANG Xuan, et al. 2017. Determination of the NW-trending faults in Xinfengjiang reservoir dam by using high-precision small earthquakes data [J]. Acta Seismologica Sinica, 39(1): 23-33(in Chinese).
[18] 刘锡大, 侯建军, 游象照. 1987. 右江断裂带的新构造活动[J]. 地震研究, 10(2): 175-183.
LIU Xi-da, HOU Jian-jun, YOU Xiang-zhao.1987. Neotectonic motion of Youjiang fault zone[J]. Journal of Seismological Research, 10(2): 175-183(in Chinese).
[19] 刘耀炜, 许丽卿, 杨多兴. 2011. 龙滩水库诱发地震的孔隙压力扩散特征[J]. 地球物理学报, 54(4): 1028-1037.
LIU Yao-wei, XU Li-qing, YANG Duo-xing.2011. Pore pressure diffusion characteristics of Longtan reservoir-induced earthquake[J]. Chinese Journal of Geophysics, 54(4): 1028-1037(in Chinese).
[20] 潘建雄. 1989. 红水河龙滩水库诱发地震地质条件的探讨[J]. 地震地质, 11(4): 91-99.
PAN Jian-xiong.1989. The geological environment for induced earthquake in Longtan reservoir of Hongshui River[J]. Seismology and Geology, 11(4): 91-99(in Chinese).
[21] 齐玉妍, 吕国军, 孙丽娜, 等. 2017. 1303年山西洪洞8级地震震源断层研究[J]. 地震, 37(1): 148-157.
QI Yu-yan, LÜ Guo-jun, SUN Li-na, et al.2017. Seismogenic fault of the 1303 Hongtong M8 earthquake in Shanxi Province[J]. Earthquake, 37(1): 148-157(in Chinese).
[22] 盛书中, 万永革, 王未来, 等. 2014. 2010年玉树M_S7.1地震发震断层面参数的确定[J]. 地球物理学进展, 29(4): 1555-1562.
SHENG Shu-zhong, WAN Yong-ge, WANG Wei-lai, et al.2014. The fault plane parameter determination of the 2010 Yushu M_S7.1 earthquake[J]. Progress in Geophysics, 29(4): 1555-1562(in Chinese).
[23] 史海霞, 赵翠萍. 2010. 广西龙滩库区地震剪切波分裂研究[J]. 地震地质, 32(4): 595-606. doi: 10.3969/j.issn.0253-4967.2010.04.007.
SHI Hai-xia, ZHAO Cui-ping.2010. Study on the S-wave splitting characteristics in Longtan reservoir area, Guangxi, China[J]. Seismology and Geology, 32(4): 595-606(in Chinese).
[24] 史水平, 陆炳情, 龙政强, 等. 2009. 龙滩库区蓄水初期水库诱发地震活动分析[J]. 地震地磁观测与研究, 30(6): 6-11.
SHI Shui-ping, LU Bing-qing, LONG Zheng-qiang, et al.2009. Analysis on seismic activity in Longtan reservoir region during initial stage of filling[J]. Seismological and Geomagnetic Observation and Research, 30(6): 6-11(in Chinese).
[25] 史水平, 于学庆, 龙政强, 等. 2010. 龙滩库区蓄水后地震性质分析[J]. 地震地磁观测与研究, 31(3): 40-45.
SHI Shui-ping, YU Xue-qing, LONG Zheng-qiang, et al.2010. Analysis on the nature of earthquake in Longtan area after the reservoir storage water[J]. Seismological and Geomagnetic Observation and Research, 31(3): 40-45(in Chinese).
[26] 万永革. 2015. 联合采用定性和定量断层资料的应力张量反演方法及在乌鲁木齐地区的应用[J]. 地球物理学报, 58(9): 3144-3156.
WAN Yong-ge.2015. A grid search method for determination of tectonic stress tensor using qualitative and quantitative data of active faults and its application to the Urumqi area[J]. Chinese Journal of Geophysics, 58(9): 3144-3156(in Chinese).
[27] 万永革. 2016. 地震学导论 [M]. 北京: 科学出版社: 469.
WAN Yong-ge.2016. Introduction to Seismology [M]. Science Press, Beijing: 469(in Chinese).
[28] 万永革. 2020. 震源机制与应力体系关系模拟研究[J]. 地球物理学报, 63(6): 2281-2296.
WAN Yong-ge.2020. Simulation on relationship between stress regimes and focal mechanism of earthquakes[J]. Chinese Journal of Geophysics, 63(6): 2281-2296(in Chinese).
[29] 万永革, 沈正康, 刁桂苓, 等. 2008. 利用小震分布和区域应力场确定大震断层面参数方法及其在唐山地震序列中的应用[J]. 地球物理学报, 51(3): 793-804.
WAN Yong-ge, SHEN Zheng-kang, DIAO Gui-ling, et al.2008. An algorithm of fault parameter determination using distribution of small earthquakes and parameters of regional stress field and its application to Tangshan earthquake sequence[J]. Chinese Journal of Geophysics, 51(3): 793-804(in Chinese).
[30] 万永革, 盛书中, 许雅儒, 等. 2011. 不同应力状态和摩擦系数对综合P波辐射花样影响的模拟研究[J]. 地球物理学报, 54(4): 994-1001.
WAN Yong-ge, SHENG Shu-zhong, XU Ya-ru, et al.2011. Effect of stress ratio and friction coefficient on composite P wave radiation patterns[J]. Chinese Journal of Geophysics, 54(4): 994-1001(in Chinese).
[31] 万永革, 吴忠良, 周公威, 等. 2000. 根据震源的2个节面的走向角和倾角求滑动角[J]. 地震地磁观测技术, 21(5): 26-30.
WAN Yong-ge, WU Zhong-liang, ZHOU Gong-wei, et al.2000. How to get rake angle of the earthquake fault from known strike and dip of the two nodal planes[J]. Seismological and Geomagnetic Observation and Research, 21(5): 26-30(in Chinese).
[32] 王福昌, 万永革, 钱小仕, 等. 2013. 由地震分布丛集性给出断层参数的一种新方法[J]. 地球物理学报, 56(2): 522-530.
WANG Fu-chang, WAN Yong-ge, QIAN Xiao-shi, et al.2013. A new method for determining fault planes parameters according to earthquake clustering[J]. Chinese Journal of Geophysics, 56(2): 522-530(in Chinese).
[33] 王立凤, 詹艳, 赵国泽, 等. 2010. 广西龙滩库区库水加卸载过程中地下电阻率的变化[J]. 地震地质, 32(4): 586-594. doi: 10.3969/j.issn.0253-4967.2010.04.006.
WANG Li-feng, ZHAN Yan, ZHAO Guo-ze, et al.2010. The resistivity variation in water loading of Longtan reservoir in Guangxi, China[J]. Seismology and Geology, 32(4): 586-594(in Chinese).
[34] 王鸣, 王培德. 1992. 1989年10月18日大同-阳高地震的震源机制和发震构造[J]. 地震学报, 14(4): 407-415.
WANG Ming, WANG Pei-de.1992. The mechanism and seismogenic structure of Datong-Yanggao earthquake which occurred on Oct. 18, 1989[J]. Acta Seismologica Sinica, 14(4): 407-415(in Chinese).
[35] 夏宏良. 2004. 浅析岩体及其结构面力学强度参数选取[J]. 水力发电, 30(6): 50-52.
XIA Hong-liang.2004. Analysis for the selection of mechanical strength parameters of rock mass and its structural planes[J]. Water Power, 30(6): 50-52(in Chinese).
[36] 向宏发, 周庆. 2006. 广西红水河龙滩水电站工程场地地震动参数复核 [R]. 北京: 中国地震局地质研究所.
XIANG Hong-fa, ZHOU Qing.2006. Review report of ground motion parameters of Red River Longtan Hydropower Station in Guangxi [R]. Institute of Geology, China Seismological Bureau, Beijing(in Chinese).
[37] 徐宗学, 黄乃安, 常宝琦. 1989. 广西龙滩水库诱发地震环境影响评价[J]. 华南地震, 9(2): 84-91.
XU Zong-xue, HUANG Nai-an, CHANG Bao-qi.1989. The evaluation of Guangxi Longtan reservoir induced earthquake environmental impact[J]. South China Journal of Seismology, 9(2): 84-91(in Chinese).
[38] 阎春恒, 周斌, 郭培兰, 等. 2016. 结合波形互相关技术的龙滩水库地震双差定位[J]. 地震研究, 39(3): 427-435.
YAN Chun-heng, ZHOU Bin, GUO Pei-lan, et al.2016. Double-difference relocation of earthquake in Longtan reservoir combined with waveform cross-correlation technique[J]. Journal of Seismological Research, 39(3): 427-435(in Chinese).
[39] 阎春恒, 周斌, 陆丽娟, 等. 2015. 龙滩水库蓄水后库区中小地震震源机制[J]. 地球物理学报, 58(11): 4207-4222.
YAN Chun-heng, ZHOU Bin, LU Li-juan, et al.2015. Focal mechanisms of moderate and small earthquakes occurred after reservoir recharge in the Longtan reservoir region[J]. Chinese Journal of Geophysics, 58(11): 4207-4222(in Chinese).
[40] 杨超群, 孟凡顺, 万永革. 2013. 采用精确定位小震资料反演伽师地震断层面[J]. 地球物理学进展, 28(6): 2865-2871.
YANG Chao-qun, MENG Fan-shun, WAN Yong-ge.2013. Calculating the parameters of fault plane for Jiashi earthquake by the data of small earthquakes accurately located[J]. Progress in Geophysics, 28(6): 2865-2871(in Chinese).
[41] 叶庆东, 阎春恒, 王生文, 等. 2018. 广西龙滩水库地壳Q_S二维成像[J]. 地震学报, 40(6): 689-700.
YE Qing-dong, YAN Chun-heng, WANG Sheng-wen, et al.2018. Crustal 2-D Q_S tomography in Longtan reservoir, Guangxi region[J]. Acta Seismologica Sinica, 40(6): 689-700(in Chinese).
[42] 游象照. 1982. 广西活动性断裂的特征及其与地震关系[J]. 华南地震, 2(3): 7-14.
YOU Xiang-zhao.1982. Characteristics of active faults in Guangxi and its relation to earthquake[J]. South China Journal of Seismology, 2(3): 7-14(in Chinese).
[43] 游象照. 1988. 广西地震活动与地震地质特征[J]. 广西地质, (1): 63-73.
YOU Xiang-zhao.1988. Earthquakes in Guangxi and their geological characteristics[J]. Geology of Guangxi, (1): 63-73(in Chinese).
[44] 于品清, 孔凡健. 1983. 水库地震地质构造条件的讨论[J]. 地壳形变与地震, (3): 71-81.
YU Pin-qing, KONG Fan-jian.1983. Discussion on geological tectonic conditions of reservoir induced earthquake[J]. Crustal Deformation and Earthquake, (3): 71-81(in Chinese).
[45] 詹艳, 王立凤, 王继军, 等. 2012a. 广西龙滩库区深部孕震结构大地电磁探测研究[J]. 地球物理学报, 55(4): 1400-1410.
ZHAN Yan, WANG Li-feng, WANG Ji-jun, et al.2012a. Electromagnetic survey of the seismogenic structures beneath the Longtan reservoir, Guangxi Province[J]. Chinese Journal of Geophysics, 55(4): 1400-1410(in Chinese).
[46] 詹艳, 王立凤, 肖骑彬, 等. 2012b. 龙滩库区库水加卸载过程深部电阻率变化与水库地震[J]. 地球物理学报, 55(8): 2625-2635.
ZHAN Yan, WANG Li-feng, XIAO Qi-bin, et al.2012b. The deep resistivity variation during water loading and unloading and induced earthquake in the Longtan reservoir, Guangxi[J]. Chinese Journal of Geophysics, 55(8): 2625-2635(in Chinese).
[47] 张培震, 沈正康, 王敏, 等. 2004. 青藏高原及周边现今构造变形的运动学[J]. 地震地质, 26(3): 367-377.
ZHANG Pei-zhen, SHEN Zheng-kang, WANG Min, et al.2004. Kinematics of present-day tectonic deformation of the Tibetan plateau and its vicinities[J]. Seismology and Geology, 26(3): 367-377(in Chinese).
[48] 张培震, 王祺, 马宗晋. 2002. 青藏高原现今构造变形特征与GPS速度场[J]. 地学前缘, 9(2): 442-450.
ZHANG Pei-zhen, WANG Qi, MA Zong-jin.2002. GPS velocity field and active crustal deformation in and around the Qinghai-Tibet Plateau[J]. Earth Science Frontiers, 9(2): 442-450(in Chinese).
[49] 张有天. 2005. 岩石水力学与工程 [M]. 北京: 中国水利水电出版社.
ZHANG You-tian.2005. Rock Hydraulics and Engineering [M]. China Water Power Press, Beijing(in Chinese).
[50] 周斌, 孙峰, 阎春恒, 等. 2014. 龙滩水库诱发地震三维孔隙弹性有限元数值模拟[J]. 地球物理学报, 57(9): 2846-2868.
ZHOU Bin, SUN Feng, YAN Chun-heng, et al.2014. 3D-poreelastic finite element numerical simulation of Longtan reservoir-induced seismicity[J]. Chinese Journal of Geophysics, 57(9): 2846-2868(in Chinese).
[51] Hardebeck J L, Michael A J.2006. Damped regional-scale stress inversions: Methodology and examples for southern California and the Coalinga aftershock sequence[J]. Journal of Geophysical Research, 111(B11): B11310.
[52] Hauksson E, Shearer P.2005. Southern California hypocenter relocation with waveform cross-correlation, Part 1: Results using the double-difference method[J]. Bul1etin of the Seismological Society of America, 95(3): 896-903.
[53] Reasenberg P A, Oppenheimer D.1985. FPFIT, FPPLOT, andFPPAGE: Fortran computer programs for calculating and displaying earthquake fault-plane solutions [R]. US Geological Survey Open-File Report: 85-739.
[54] Snoke J A.1989. Earthquake mechanism[C]∥ James D E. Encyclopedia of Geophysics. Van Nostrand Reinhold Company, New York: 239-245.
[55] Waldhauser F, Ellsworth W L.2000. A double difference earthquake location algorithm: Method and application to the Northern Hayward Fault, California[J]. Bul1etin of the Seismological Society of America, 90(6): 1353-1368.
[56] Wan Y G.2010. Contemporary tectonic stress field in China[J]. Earthquake Science, 23:377-386.
[57] Wan Y G, Sheng S Z, Huang J C, et al.2016. The grid search algorithm of tectonic stress tensor based on focal mechanism data and its application in the boundary zone of China, Vietnam and Laos[J]. Journal of Earth Science, 27(5): 777-785.