基于加密地震观测讨论红河断裂带北段维西-乔后断层的地震活动性特征

doi:10.3969/j.issn.0253-4967.2021.06.010

摘要/Abstract

摘要：

文中基于滇西北地区临时加密台站和区域固定台站地震观测资料, 利用波形相关方法对2018年2月25日—2019年7月31日记录的连续波形进行高分辨率地震检测和高精度地震定位, 据此分析红河断裂带北段维西-乔后断层的地震活动性特征。研究表明, 目前维西-乔后断层除了一些特殊的断层部位(交会区、阶区等)外, 地震活动微弱, 但在其西侧可能存在一条隐伏的陡倾角右旋走滑断层, 沿该断层小地震活动活跃。地震频度、能量释放率、 b值等统计参数及其随时间的变化表明, 维西-乔后断层及其附近地区的地震活动相对稳定, 区域应力增强不明显; 空间上大部分区域的b值较高, 低b值区主要分布在一些特殊的断层部位(如断层交会区、阶区等), 但尺度一般较小。ETAS模型统计结果表明, 40%以上的地震活动受外部因素触发, 包括深层流体扰动和远程强地震触发等。由此我们认为, 维西-乔后断层主断层目前的地震活动性较弱, 但其西侧的隐伏分支断层小地震活动丛集且有增强趋势, 需要综合分析主断层及其西侧隐伏分支断层的活动性, 以评估其地震危险性。

关键词: 地震活动性, 维西-乔后断层, 分支断层

Abstract:

Based on the seismic data from temporary stations and regional stations in the northwestern area of Yunnan, the paper performs high-resolution detection and high-precision location on continuous waveforms recorded from February 25, 2018 to July 31, 2019 using waveform correlation methods and analyzes the seismicity characteristics of the Weixi-Qiaohou Fault in the northern section of the Red River fault zone. Studies have shown that the Weixi-Qiaohou Fault exhibits weak seismic activity currently, except for some special fault locations(such as terraces, intersections, etc.), but there may be a hidden steep-dip right-lateral strike-slip fault along the west side of the fault. Small earthquakes are frequent along the fault. The distribution of seismic activity and focal mechanism solutions indicate that this fault is a right-lateral strike-slip fault with a steep dip. Statistical parameters, such as seismic frequency, energy release rate and b-value, indicate that the seismic activity in the Weixi-Qiaohou Fault and its surrounding areas is relatively stable, and the regional stress enhancement is not obvious. The b-value is relatively high in most areas, and low b-value areas are mainly distributed in some special fault locations(such as terraces, intersections, etc.), but the scale is generally small. The statistical results of the ETAS model show that more than 40% of seismic activity may be affected by external factors such as deep fluid disturbance and remote strong earthquake triggering. This shows that the role of external trigger mechanisms in seismic activity cannot be ignored. The external triggering seismic activity factors are related to the disturbance of deep fluid activity and the dynamic triggering of long-distance strong earthquakes. Therefore, we believe that the Weixi-Qiaohou Fault is currently not active, but on the hidden branch fault to its west, small earthquake activity is clustering and has a tendency to increase. So, when assessing the seismic risk of the fault, comprehensive analysis shall be made on the activity of the main fault and the branch fault to its west.

Key words: seismicity, Weixi-Qiaohou Fault, branch fault

中图分类号:

P315.2

王志伟, 马胜利, 雷兴林, 王凯英. 基于加密地震观测讨论红河断裂带北段维西-乔后断层的地震活动性特征[J]. 地震地质, 2021, 43(6): 1524-1536.

WANG Zhi-wei, MA Sheng-li, LEI Xing-lin, WANG Kai-ying. DISCUSSION ON SEISMICITY CHARACTERISTICS OF WEIXI-QIAOHOU FAULT IN THE NORTHERN SECTION OF RED RIVER FAULT ZONE BASED ON THE DENSE SEISMIC ARRAY OBSERVATION[J]. SEISMOLOGY AND EGOLOGY, 2021, 43(6): 1524-1536.

图/表 7

图 1 滇西北地区活断层与2006—2018年期间地震活动分布图 DL 大理; EY 洱源; LJ 丽江; YS 永胜; F1 维西-乔后断层; F2 澜沧江断层; F3 怒江断层; F4 龙蟠-乔后断层; F5 丽江断层; F6 鹤庆断层; F7 永胜断层; F8 红河断层。断层数据从数字“中国活动构造图”中导入, 地震目录数据由中国地震数据中心①(①http://data.earthquake.cn。)提供

Fig. 1 Map view of active faults and seismic activity from 2006 to 2018 in the northwestern area of Yunnan.

图 2 a 模板地震与检测到的小地震随时间的变化; b地震震级-频度关系 a 红色为模板地震, 绿色为检测到的小地震, 负震级表示S波或Lg震相的最大振幅小于零级地震;b MC为完整的地震目录的震级下限, 最大似然b值和最小二乘法b值分别用bml和bls表示, SE表示标准误差

Fig. 2 Template events and detected microearthquakes changing over time(a), and magnitude-frequency relationship(b)

图 3 滇西北地区活断层与2018年2月25日—2019年7月31日期间的地震活动分布图详细的城市地名和断层名见图 1 ; 蓝色实线表示AA'—CC' 3个深度剖面; 红色虚线表示可能存在的分支断层;2019年11月25日发生的M4.4地震使用震源机制解下半球的投影表示

Fig. 3 Map view of active faults and seismic activity from February 25, 2018 to July 31, 2019 in the northwestern area of Yunnan.

图 4 从AA'到CC'的震源深度剖面分布图, 对应于图 3 中的剖面红色实线表示维西-乔后断层, 断层各段的倾角根据地质断层产状测量和震源机制解结果获得(王晓山等, 2015; 尹凤玲等, 2018); 红色虚线表示可能存在的分支断层。2019年11月25日发生的M4.4地震使用震源机制解垂直于深度剖面的投影表示

Fig. 4 The focal depth distribution from section AA' to CC'.

图 5 地震活动主要统计参数分布图 a 地震震级随时间变化图; b 地震日频度和能量释放率随时间变化图;c b值随时间变化图, b值通过最小二乘法进行计算, 统计参数为固定事件数(100)扫描, 步长为20个事件数

Fig. 5 Distribution of main statistical parameters of seismic activity.

图 6 滇西北区域添加小地震后的b值空间分布图 S1—S6表示相对低b值区域, F1—F8所代表的断层详见图 1

Fig. 6 Spatial distribution characteristics of b-value after adding micro-earthquakes in the northwest area of Yunnan.

图 7 ETAS模型建模统计分析 a ETAS模型统计结果。灰色虚线表示理论地震累计数随时间变化, 蓝色实线表示拟合后地震累计数随时间变化;b 将实际观测地震活动转化为预测地震活动, 其震级随转化时间的变化图, 转化时间即为转化地震数

Fig. 7 ETAS model statistical analysis.

参考文献 34

[1]	常祖峰, 常昊, 李鉴林, 等. 2016. 维西-乔后断裂南段正断层活动特征[J]. 地震研究, 39(4): 579-586.
	CHANG Zu-feng, CHANG Hao, LI Jian-lin, et al. 2016. The characteristic of active normal faulting of the southern segment of Weixi-Qiaohou Fault[J]. Journal of Seismological Research, 39(4): 579-586(in Chinese).
[2]	付虹, 赵小艳. 2013. 汶川 M_S8.0 地震前云南地区显著前兆观测异常分析[J]. 地震学报, 35(4): 477-484.
	FU Hong, ZHAO Xiao-yan. 2013. Analysis on remarkable precursory anomalies observed in Yunnan area before Wenchuan M_S8.0 earthquake[J]. Acta Seismologica Sinica, 35(4): 477-484(in Chinese).
[3]	虢顺民, 向宏发, 计凤桔, 等. 1996. 红河断裂带第四纪右旋走滑与尾端拉张转换关系研究[J]. 地震地质, 18(4): 301-309.
	GUO Shun-min, XIANG Hong-fa, JI Feng-ju, et al. 1996. A study on the relation between Quaternary right-lateral slip and tip extension along the Honghe Fault[J]. Seismology and Geology, 18(4): 301-309(in Chinese).
[4]	虢顺民, 张靖, 李祥根, 等. 1984. 云南红河断裂带北段断裂位错与地震重复发生的时间间隔[J]. 地震地质, 6(1): 1-12.
	GUO Shun-min, ZHANG Jing, LI Xiang-gen, et al. 1984. Time interval between fault dislocation and earthquake repetition in the northern section of Yunnan Honghe fault zone[J]. Seismology and Geology, 6(1): 1-12(in Chinese).
[5]	刘耀炜, 任宏微, 张磊, 等. 2015. 鲁甸6.5级地震地下流体典型异常与前兆机理分析[J]. 地震地质, 37(1): 307-318.
	LIU Yao-wei, REN Hong-wei, ZHANG Lei, et al. 2015. Underground fluid anomalies and the precursor mechanisms of the Ludian M_S6.5 earthquake[J]. Seismology and Geology, 37(1): 307-318(in Chinese).
[6]	鲁小飞, 谭凯, 赵斌, 等. 2019. 汶川地震前后红河断裂闭锁程度和滑动亏损研究[J]. 大地测量与地球动力学, 39(5): 464-468.
	LU Xiao-fei, TAN Kai, ZHAO Bin, et al. 2019. Study on the degree of locking and sliding loss of Honghe Fault before and after Wenchuan earthquake[J]. Geodesy and Geodynamics, 39(5): 464-468(in Chinese).
[7]	王晓山, 吕坚, 谢祖军, 等. 2015. 南北地震带震源机制解与构造应力场特征[J]. 地球物理学报, 58(11): 4149-4162.
	WANG Xiao-shan, LÜ Jian, XIE Zu-jun, et al. 2015. Focal mechanism solution and tectonic stress field characteristics of the south-north seismic zone[J]. Chinese Journal of Geophysics, 58(11): 4149-4162(in Chinese).
[8]	向宏发, 韩竹军, 虢顺民, 等. 2004. 红河断裂带大型右旋走滑运动与伴生构造地貌变形[J]. 地震地质, 26(4): 43-56.
	XIANG Hong-fa, HAN Zhu-jun, GUO Shun-min, et al. 2004. Large dextral strike-slip movement and associated structural geomorphic deformation in the Honghe fault zone[J]. Seismology and Geology, 26(4): 43-56(in Chinese).
[9]	杨竹转, 邓志辉, 杨跃文, 等. 2018. 2014年鲁甸 M_S6.5 地震前云南丽江地下流体的异常变化[J]. 地震地质, 40(2): 480-498.
	YANG Zhu-zhuan, DENG Zhi-hui, YANG Yue-wen, et al. 2018. Abnormal changes of underground fluid in Lijiang, Yunnan before the Ludian M_S6.5 earthquake in 2014[J]. Seismology and Geology, 40(2): 480-498(in Chinese).
[10]	易桂喜, 闻学泽, 苏有锦. 2008. 川滇活动地块东边界强震危险性研究[J]. 地球物理学报, 51(6): 1719-1725.
	YI Gui-xi, WEN Xue-ze, SU You-jin. 2008. Study on the risk of strong earthquakes at the eastern boundary of the Sichuan-Yunnan active block[J]. Chinese Journal of Geophysics, 51(6): 1719-1725(in Chinese).
[11]	易桂喜, 闻学泽, 辛华, 等. 2013. 龙门山断裂带南段应力状态与强震危险性研究[J]. 地球物理学报, 56(4): 1112-1120.
	YI Gui-xi, WEN Xue-ze, XIN Hua, et al. 2013. Stress state and strong earthquake risk of the southern Longmenshan fault zone[J]. Chinese Journal of Geophysics, 56(4): 1112-1120(in Chinese).
[12]	尹凤玲, 蒋长胜, 韩立波, 等. 2018. 红河断裂带库仑应力演化及未来地震危险性估计[J]. 地球物理学报, 61(1): 183-198.
	YIN Feng-ling, JIANG Chang-sheng, HAN Li-bo, et al. 2018. Coulomb stress evolution and future seismic hazard estimation in Honghe fault zone[J]. Chinese Journal of Geophysics, 61(1): 183-198(in Chinese).
[13]	云南省地震局. 1988. 云南省地震资料汇编[M]. 北京: 地震出版社.
	Yunnan Earthquake Agency. 1988. Compilation of Earthquake Data in Yunnan Province[M]. Seismological Press, Beijing(in Chinese).
[14]	张建国. 2009. 中越红河断裂活动性研究[D]. 合肥: 中国科学技术大学.
	ZHANG Jian-guo. 2009. Research on the activity of Honghe Fault in China and Vietnam[D]. University of Science and Technology of China, Hefei(in Chinese).
[15]	赵小艳, 付虹. 2014. 2013年洱源 M_S5.5 和 M_S5.0 地震发震构造识别[J]. 地震学报, 36(4): 640-650.
	ZHAO Xiao-yan, FU Hong. 2014. Seismic structure identification of M_S5.5 and M_S5.0 earthquakes in Eryuan in 2013[J]. Acta Seismologica Sinica, 36(4): 640-650(in Chinese).
[16]	Hainzl S, Fischer T. 2002. Indications for a successively triggered rupture growth underlying the 2000 earthquake swarm in Vogtland/NW-Bohemia[J]. Journal of Geophysical Research: Solid Earth, 107(B12): ESE5-1-ESE5-9.
[17]	Hainzl S, Ogata Y. 2005. Detecting fluid signals in seismicity data through statistical earthquake modeling[J]. Journal of Geophysical Research: Solid Earth, 110(B5): B05S07. doi: 10.1029/2004JB003247. DOI
[18]	Helmstetter A, Sornette D. 2003. Mainshocks are aftershocks of conditional foreshocks: How do foreshock statistical properties emerge from aftershock laws[J]. Journal of Geophysical Research: Solid Earth, 108(B1): ESE20-1-ESE20-24.
[19]	Hua Y, Zhang S, Li M, et al. 2018. A new geodynamic model related to seismicity beneath the southeastern margin of the Tibetan plateau revealed by regional tomography[J]. Geophysical Journal International, 214(2): 933-951. doi: 10.1093/gji/ggy183. DOI URL
[20]	Lei X L, Ma S, Chen W, et al. 2013. A detailed view of the injection-induced seismicity in a natural gas reservoir in Zigong, southwestern Sichuan Basin, China[J]. Journal of Geophysical Research: Solid Earth, 118(8): 4296-4311. DOI URL
[21]	Lei X L, Satoh T. 2007. Indicators of critical point behavior prior to rock failure inferred from pre-failure damage[J]. Tectonophysics, 431(1): 97-111. DOI URL
[22]	Lei X L, Xie C, Fu B. 2011. Remotely triggered seismicity in Yunnan, southwestern China, following the 2004 M_W9.3 Sumatra earthquake[J]. Journal of Geophysical Research, 116: B08303.
[23]	Lei X L, Yu G, Ma S, et al. 2008. Earthquakes induced by water injection at-3km depth within the Rongchang gas field, Chongqing, China[J]. Journal of Geophysical Research: Solid Earth, 113(B10): B10310.
[24]	Ogata Y. 1992. Detection of precursory relative quiescence before great earthquakes through a statistical model[J]. Journal of Geophysical Research, 97(B13): ESE 20-1-ESE 20-24.
[25]	Ogata Y. 2005. Synchronous seismicity changes in and around the northern Japan preceding the 2003 Tokachi-Oki earthquake of M8.0[J]. Journal of Geophysical Research, 110: B08305. doi: 10.1029/2004JB003323. DOI
[26]	Ogata Y, JonesL M, Toda S. 2003. When and where the aftershock activity was depressed: Contrasting decay patterns of the proximate large earthquakes in southern California[J]. Journal of Geophysical Research, 108, ESE 20-1-ESE 20-24. doi: 10.1029/2002JB002009.s. DOI
[27]	Peng Z, Zhao P. 2009. Migration of early aftershocks following the 2004 Parkfield earthquake[J]. Nature Geoscience, 2(12): 877-881. doi: 10.1038/ngeo697. DOI URL
[28]	Scholz C H. 1968. The frequency-magnitude relation of microcracking in rock and its relation to earthquakes[J]. Bulletin of Seismological Society of America, 58:399-415. DOI URL
[29]	Schorlemmer D, Wiemer S, Wyss M. 2005. Variations in earthquake-size distribution across different stress regimes[J]. Nature, 437:539-542. DOI URL
[30]	Sornette A, Sornette D. 1999. Renormalization of earthquake aftershocks[J]. Geophysical Research Letters, 26(13): 1981-1984. DOI URL
[31]	Waldhauser F, Ellsworth W L. 2000. A double-difference earthquake location algorithm: Method and application to the northern Hayward Fault, California[J]. Bulletin of the Seismological Society of America, 90(6): 1353-1368. DOI URL
[32]	Zhang M, Wen L. 2015. An effective method for small event detection: Match and locate(M&L)[J]. Geophysical Journal International, 200(3): 1523-1537. doi: 10.1093/gji/ggu466. DOI URL
[33]	Zhu L, Ben-Zion Y. 2013. Parametrization of general seismic potency and moment tensors for source inversion of seismic waveform data[J]. Geophysical Journal International, 194(2): 839-843. DOI URL
[34]	Zhuang J, Ogata Y, Vere-Jones D. 2002. Stochastic declustering of space-time earthquake occurrences[J]. Journal of the American Statistical Association, 97(458): 369-380. DOI URL