FOCAL MECHANISM SOLUTION AND TECTONIC STRESS FIELD CHARACTERISTICS OF THE MIDDLE TIANSHAN MOUNTAINS, XINJIANG

doi:10.3969/j.issn.0253-4967.2020.03.004

Abstract

Abstract: The middle part of the Tianshan Mountains in Xinjiang is located in the north-central part of the Tianshan orogenic belt, between the rigid Tarim Basin and Junggar Basin. It is one of the regions with frequent deformation and strong earthquake activities. In this paper, 492 M_S>2.5 earthquake events recorded by Xinjiang seismograph network from 2009 to 2018 were collected. The M_S3.5 earthquake was taken as the boundary, the focal mechanism solutions of the earthquake events in this region were calculated by CAP method and FOCEMEC method respectively. At the same time the focal mechanism solutions of GCMT recorded historical earthquake events in this region were also collected. According to the global stress map classification standard, the moderate-strong earthquakes in the region are mainly dominated by thrust with a certain slip component, which are distributed near the combined belts of the Tarim Basin, Junggar Basin, Turpan Basin and Yili Basin with Tianshan Mountains. The thrust component decreases from south to north, while the strike-slip component increases. The spatial distribution characteristics of the tectonic stress field in the middle section of the Tianshan Mountains in Xinjiang are obtained by using the damped regional-scale stress field inversion method. The maximum principal compressive stress in axis the study area rotated in a fan shape from west to east, the NW direction in the western section gradually shifted to NE direction, its elevation angle is nearly horizontal, in the state of near horizontal compression. The minimum principal compressive stress axis is nearly EW, and the elevation angle is nearly vertical. Influenced by large fault zones such as Kashi River, Bolhinur, Nalati, Fukang, the southern margin of the Junggar and the north Beiluntai, the local regional stress field presents complex diversity. Under the influence of the northward extrusion of Pamir and Tarim blocks, the whole Tianshan is shortened by compression, but its shortening rate decreases from south to north and from west to east, the stress shape factor increases gradually from west to east, the intermediate principal compressive stress axis exhibits a change in compression to extension. There are some differences in the characteristics of tectonic stress field between the north and south of Tianshan Mountains. The regional maximum principal compressive stress axis is 15° north by east on the south side, while it is nearly NS on the north side. The deformation of the Tianshan Mountains and the two basins on both sides is obviously larger than that in the inside of the mountain. Changes in the crustal shortening rate caused by the rotation of the rigid Tarim block and Junggar block to the relatively soft Tianshan block, as well as the uplifts of Borokonu and Bogda Mountains, the comprehensive influence of the material westward expansion constitute the stress field distribution characteristics of the north and south sides of the middle section of Tianshan Mountains. The recent two M_S6.6 earthquakes in the region caused the regional stress field to rotate counterclockwise. The post-earthquake stress field and the main source focal mechanism solution tend to be consistent. The seismic activity in the study area is week in the south and strong in the north. The focal depth is about 20km. Most strike-slip earthquakes occur near the junction belt of the Tianshan and Junggar Basin.

Key words: middle section of Tianshan Mountains, focal mechanism solution, tectonic stress field, basin-range junction belt

摘要： 文中收集了新疆测震台网2009-2018年记录的492个M_S2.5以上的地震事件, 以M_S=3.5为界, 分别用CAP方法和FOCEMEC程序计算其震源机制解, 并收集了GCMT记录的该区域历史地震事件的震源机制解结果。按照全球应力图分类标准对计算得到的震源机制解数据进行分类, 发现区域内中强地震主要以逆冲型为主, 兼有一定的走滑分量。采用阻尼区域应力场反演方法获取新疆天山中段的构造应力场空间分布特征, 结果表明研究区内最大主压应力轴由西向东呈扇形旋转, 自西段的NW向逐渐转为NE向, 仰角近水平, 最大主张应力轴近EW向, 仰角近直立。受喀什河断裂、那拉提断裂、博阿断裂、准噶尔南缘断裂和北轮台断裂等大型断裂带的影响, 局部区域应力场呈现出复杂的多样性。在帕米尔和塔里木块体持续向N挤压的影响下, 天山整体被挤压缩短, 但由南向北、由西向东缩短速率逐渐降低, 应力形因子自西向东逐渐增大, 且中间主压应力轴由偏压缩成分转为偏拉张成分。研究区南侧最大主压应力轴方向为N15°E, 而北侧则为近SN向, 这与塔里木块体的顺时针旋转有直接关联。区内近期发生的2次M_S6.6地震均造成区域应力场的逆时针旋转, 震后应力场与主震震源机制解趋于一致。

关键词: 新疆天山中段, 震源机制解, 构造应力场, 盆山结合带

CLC Number:

P315.2

ZHANG Zhi-bin ZHAO Xiao-cheng REN Lin. FOCAL MECHANISM SOLUTION AND TECTONIC STRESS FIELD CHARACTERISTICS OF THE MIDDLE TIANSHAN MOUNTAINS, XINJIANG[J]. SEISMOLOGY AND GEOLOGY, 2020, 42(3): 595-611.

张志斌, 赵晓成, 任林. 新疆天山中段的震源机制解与构造应力场特征分析[J]. 地震地质, 2020, 42(3): 595-611.

References

[1] 崔华伟, 万永革, 黄骥超, 等. 2019. 帕米尔-兴都库什地区构造应力场反演及拆离板片应力形因子特征研究[J]. 地球物理学报, 62(5): 1633-1649.
CUI Hua-wei, WAN Yong-ge, HUANG Ji-chao, et al.2019. Inversion for the tectonic stress field and the characteristic of the stress shape factor of the detachment slab in the Pamir-Hindu Kush area[J]. Chinese Journal of Geophysic, 62(5): 1633-1649(in Chinese).
[2] 崔子健, 陈章立, 王勤彩, 等. 2019. 南北地震带区域构造应力场反演[J]. 地震学报, 41(2): 219-229.
CUI Zi-jian, CHEN Zhang-li, WANG Qin-cai, et al.2019. Inversion for regional tectonic stress field in the North-South Seismic Belt of China[J]. Acta Seismologica Sinica, 41(2): 219-229(in Chinese).
[3] 高国英, 聂晓红, 龙海英. 2010. 2003-2008年新疆区域构造应力场特征探讨[J]. 地震地质, 32(1): 70-79. doi: 10.3969/j.issn.0253-4967.2010.01.007.GAO Guo-ying, NIE Xiao-hong, LONG Hai-ying. 2010. Discussion on the characteristics of regional stress field of Xinjiang from 2003 to 2008 [J]. Seismology and Geology, 32(1): 70-79(in Chinese).
[4] 黄骥超, 万永革, 崔华伟. 2015. 鲁甸M_S6.5地震前后区域应力偏转现象的初步讨论[J]. 国际地震动态, (9): 30.
HUANG Ji-chao, WAN Yong-ge, CUI Hua-wei.2015. Preliminary discussion on regional stress deflection before and after of the Ludian M_S6.5 earthquake[J]. Recent Developments in World Seismology, (9): 30(in Chinese).
[5] 李杰, 陈刚, 魏文薪, 等. 2016. 基于GPS观测的北天山主要断裂现今构造运动特征研究[J]. 地震学报, 38(5): 751-760.
LI Jie, CHEN Gang, WEI Wen-xin, et al.2016. Characteristics of present-day tectonics movement of typical faults in northern Tianshan mountain deduced from GPS observation[J]. Acta Seismologica Sinica, 38(5): 751-760(in Chinese).
[6] 李金, 周龙泉, 龙海英, 等. 2015. 天山地震带(中国境内)震源机制一致性参数的时空特征[J]. 地震地质, 37(3): 792-803. doi: 10.3969/j.issn.0253-4967.2015.03.010.
LI Jin, ZHOU Long-quan, LONG Hai-ying, et al.2015. Spatial-temporal characteristics of the focal mechanism consistency parameter in Tianshan(within Chinese territory)seismic zone[J]. Seismology and Geology, 37(3): 792-803(in Chinese).
[7] 李天觉, 陈棋福. 2019. 西北太平洋俯冲带日本本州至中国东北段应力场反演[J]. 地球物理学报, 62(2): 520-533.
LI Tian-jue, CHEN Qi-fu.2019. Stress regime inversion in the northwest Pacific subduction zone, the segment from northern Honshu, Japan to Northeast China[J]. Chinese Journal of Geophysic, 62(2): 520-533(in Chinese).
[8] 李艳永, 王成虎, 杨佳佳. 2018. 呼图壁地区震源机制解及构造应力场特征分析[J]. 大地测量与地球动力学, 38(2): 1246-1250.
LI Yan-yong, WANG Cheng-hu, YANG Jia-jia.2018. The focal mechanism solution and stress field inversion of earthquake along Hutubi[J]. Journal of Geodesy and Geodynamics, 38(2): 1246-1250(in Chinese).
[9] 林向东, 袁怀玉, 徐平, 等. 2017. 华北地区地震震源机制分区特征[J]. 地球物理学报, 60(12): 4589-4622.
LIN Xiang-dong, YUAN Huai-yu, XU Ping, et al.2017. Zonational characteristics of earthquake focal mechanism solutions in North China[J]. Chinese Journal of Geophysics, 60(12): 4589-4622(in Chinese).
[10] 刘泽民, 倪红玉, 张炳, 等. 2015. 基于FOCMEC方法反演震源机制解的交互式程序研制与使用[J]. 华北地震科学, 33(1): 19-24.
LIU Ze-min, NI Hong-yu, ZHANG Bing, et al.2015. The development and manual of interactive program inversing focal mechanism with interactive FOCMEC method[J]. North China Earthquake Sciences, 33(1): 19-24(in Chinese).
[11] 刘兆才, 万永革, 黄骥超, 等. 2019. 2017年精河M_S6.6地震邻区构造应力场特征与发震断层性质厘定[J]. 地球物理学报, 62(4): 1336-1348.
LIU Zhao-cai, WAN Yong-ge, HUANG Ji-chao, et al.2019. The tectonic stress field adjacent to the source of the 2017 Jinghe M_S6.6 earthquake and slip property of its seismogenic fault[J]. Chinese Journal of Geophysic, 62(4): 1336-1348(in Chinese).
[12] 卢华复, 王胜利, 罗俊成, 等. 2006. 塔里木盆地东部断裂系统及其构造演化[J]. 石油与天然气地质, 27(4): 433-441.
LU Hua-fu, WANG Sheng-li, LUO Jun-cheng, et al.2006. Fault systems and their tectonic evolution in the eastern Tarim Basin[J]. Oil & Gas Geology, 27(4): 433-441(in Chinese).
[13] 祁玉萍, 龙锋, 肖本夫, 等. 2018. 2017年九寨沟7.0级地震序列震源机制解和构造应力场特征[J]. 地球学报, 39(5): 622-634.
QI Yu-ping, LONG Feng, XIAO Ben-fu, et al.2018. Focal mechanism solutions and tectonic stress field characteristics of the 2017 M_S7.0 Jiuzhaigou earthquake sequence[J]. Acta Geoscientica Sinica, 39(5): 622-634(in Chinese).
[14] 沈军, 汪一鹏, 李莹甄, 等. 2003. 中国新疆天山博阿断裂晚第四纪右旋走滑运动特征[J]. 地震地质, 25(2): 183-194.
SHEN Jun, WANG Yi-peng, LI Ying-zhen, et al.2003. Late Quaternary right-lateral strike-slip faulting along the Bolokenu-Aqikekuduke Fault in Chinese Tianshan[J]. Seismology and Geology, 25(2): 183-194(in Chinese).
[15] 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).
[16] 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).
[17] 王琪, 张培震, 牛之俊, 等. 2001. 中国大陆现今地壳运动和构造变形[J]. 中国科学(D辑), 31(7): 529-536.
WANG Qi, ZHANG Pei-zhen, NIU Zhi-jun, et al.2001. Present-day crustal movement and tectonic deformation in China continent[J]. Science in China (Ser D), 31(7): 529-536(in Chinese).
[18] 吴传勇, 吴国栋, 沈军, 等. 2014. 那拉提断裂晚第四纪活动及其反映的天山内部构造变形[J]. 第四纪研究, 34(2): 269-280.
WU Chuan-yong, WU Guo-dong, SHEN Jun, et al.2014. The Late-Quaternary activity of the Nalati Fault and its implications for the crustal deformation in the interior of the Tianshan Mountains[J]. Quaternary Sciences, 34(2): 269-280(in Chinese).
[19] 谢富仁, 陈群策. 1999. 地壳应力观测与研究[J]. 国际地震动态, (2): 2-8.
XIE Fu-ren, CHEN Qun-ce.1999. Observations and researches of crustal stress[J]. Recent Developments in World Seismology, (2): 2-8(in Chinese).
[20] 谢富仁, 崔效锋, 赵建涛, 等. 2004. 中国大陆及邻区现代构造应力场分布[J]. 地球物理学报, 47(4): 654-662.
[21] XIE Fu-ren, CUI Xiao-feng
ZHAO Jian-tao, et al.2004. Regional division of the recent tectonic stress field in China and adjacent areas[J]. Chinese Journal of Geophysics, 47(4): 654-662(in Chinese).
[22] 杨佳佳, 张永庆, 谢富仁. 2018. 日本海沟俯冲带M_W9.0地震震源区应力场演化分析[J]. 地球物理学报, 61(4): 1307-1324.
YANG Jia-jia, ZHANG Yong-qing, XIE Fu-ren.2018. The evolutionary analysis of the stress field in the seismic focal zone of the great Tohoku-Oki earthquake(M_W=9.0)in the Japan Trench subduction zone[J]. Chinese Journal of Geophysics, 61(4): 1307-1324(in Chinese).
[23] 杨少敏, 李杰, 王琪. 2008. GPS研究天山现今变形与断层活动[J]. 中国科学(D辑), 38(7): 872-880.
YANG Shao-min, LI Jie, WANG Qi.2008. The deformation pattern and fault rate in the Tianshan Mountains inferred from GPS observations[J]. Science in China (Ser D), 38(7): 872-880(in Chinese).
[24] 杨晓平, 邓起东, 张培震, 等. 2008. 天山山前主要推覆构造区的地壳缩短[J]. 地震地质, 30(1): 112-131.
YANG Xiao-ping, DENG Qi-dong, ZHANG Pei-zhen, et al.2008. Crustal shortening of major nappe structures on the front margins of the Tianshan[J]. Seismology and Geology, 30(1): 112-131(in Chinese).
[25] 杨主恩, 张先康, 赵瑞斌, 等. 2005. 天山中段的深浅构造特征[J]. 地震地质, 27(1): 11-19.
YANG Zhu-en, ZHANG Xian-kang, ZHAO Rui-bin, et al.2005. Characteristics of shallow and deep structures of the middle segment of the Tianshan Mountains, China[J]. Seismology and Geology, 27(1): 11-19(in Chinese).
[26] 姚远, 宋和平, 陈建波, 等. 2018. 新疆天山南部北轮台断裂带晚第四纪活动速率[J]. 地震地质, 40(1): 71-86. doi: 10.3969/j.issn.0253-4967.2018.01.006.
YAO Yuan, SONG He-ping, CHEN Jian-bo, et al.2018. Late Quaternary crustal shortening rate of the Beiluntai Fault in southern Tian Shan, Xinjiang[J]. Seismology and Geology, 40(1): 71-86(in Chinese).
[27] 尹光华, 蒋靖祥, 张勇. 2003. 新疆伊犁喀什河断裂带及其活动性研究[J]. 内陆地震, 17(2): 109-116.
YIN Guang-hua, JIANG Jing-xiang, ZHANG Yong.2003. Research on Kashi River Fault in Yili, Xinjiang and its activity[J]. Inland Earthquake, 17(2): 109-116(in Chinese).
[28] 游新兆, 杜瑞林, 王琪, 等. 2001. 中国大陆地壳现今运动的GPS测量结果与初步分析[J]. 地壳形变与地震, 21(3): 1-8.
YOU Xin-zhao, DU Rui-lin, WANG Qi, et al.2001. GPS results of current crustal movement of China continent and primary analysis[J]. Crustal Deformation and Earthquake, 21(3): 1-8(in Chinese).
[29] 张红艳, 谢富仁, 崔效锋, 等. 2014. 北天山中东段活动断层滑动与现代构造应力场[J]. 中国地震, 30(1): 13-22.
ZHANG Hong-yan, XIE Fu-ren, CUI Xiao-feng, et al.2014. Active fault sliding and recent tectonic stress field in the northern Tianshan Mountains[J]. Earthquake Research in China, 30(1): 13-22(in Chinese).
[30] 张志斌, 冉慧敏, 金花. 2019. 2016年12月8日新疆呼图壁M_S6.2地震发震构造初步研究[J]. 地震工程学报, 41(4): 962-969.
ZHANG Zhi-bin, RAN Hui-min, JIN Hua.2019. A preliminary study of seismogenic structure for the Hutubi, Xinjiang M_S6.2 earthquake on December 8, 2016[J]. China Earthquake Engineering Journal, 41(4): 962-969(in Chinese).
[31] 郑勇, 马洪生, 吕坚, 等. 2009. 汶川地震强余震(M_S≥5.6)的震源机制解及其发震构造关系[J]. 中国科学(D辑), 39(4): 413-426.
ZHENG Yong, MA Hong-sheng, LÜ Jian, et al.2009. Focal mechanism solution and seismogenic tectonic relationship of strong aftershocks(M_S≥5.6)in Wenchuan earthquake[J]. Science in China (Ser D), 39(4): 413-426(in Chinese).
[32] Abdrakhmatov K Y, Aldazhanov S A, Hager B H, et al.1996. Relatively recent construction of the Tien Shan inferred from GPS measurements of present-day crustal deformation rates[J]. Nature, 384(6608): 450-453.
[33] Aki K, Richards P G.1980. Quantitative Seismology: Theory and Methods[M]. W H Freeman and Company, New York, USA.
[34] Avouac J P, Tapponnier P, Bai M, et al.1993. Active thrusting and folding along the northern Tien Shan and Late Cenozoic rotation of the Tarim relative to Dzungaria and Kazakhstan[J]. Journal of Geophysical Research: Solid Earth, 98(B4): 6755-6804.
[35] Chang Y, Warren L M, Zhu L, et al.2019. Earthquake focal mechanisms and stress field for the intermediate-depth Cauca cluster, Colombia[J]. Journal of Geophysical Research: Solid Earth, 124(1): 822-836.
[36] Chen Y, Cogne J, Courtillot V, et al.1991. Paleomagnetic study of Mesozoic continental sediments along the northern Tien Shan(China)and heterogeneous strain in central Asia[J]. Journal of Geophysical Research: Solid Earth, 96(B3): 4065-4082.
[37] 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 Fernando earthquake sequence[J]. Journal of Geophysical Research: Solid Earth, 89(B11): 9305-9320.
[38] Guiraud M, Laborde O, Philip H.1989. Characterization of various types of deformation and their corresponding deviatoric stress tensors using microfault analysis[J]. Tectonophysics, 170(3-4): 289-316.
[39] 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: Solid Earth, 111(B11): 1-11.
[40] Maury J, Cornet F H, Dorbath L.2013. A review of methods for determining stress fields from earthquakes focal mechanisms: Application to the Sierentz 1980 seismic crisis(Upper Rhine graben)[J]. Bulletin de la Société Géologique de France, 184(4-5): 319-334.
[41] Snoke J A.1989. Earthquake Mechanism, Encyclopedia of Geophysics[M]. Van Nostrand Reinhold Company,New York, USA: 239-245.
[42] Snoke J A, Munsey J W, Teague A G, et al.1984. A program for focal mechanism determination by combined use of polarity and SV-P amplitude ration data[J]. Earthquake Notes, 55(3): 15-20.
[43] Wu W N, Kao H, Hsu S K, et al.2010. Spatial variation of the crustal stress field along the Ryukyu-Taiwan-Luzon convergent boundary[J]. Journal of Geophysical Research: Solid Earth, 115: B11401. doi: 10.1029/2009JB007080.
[44] Zhao L S, Helmberger D V.1994. Source estimation from broadband regional seismograms[J]. Bulletin of the Seismological Society of America, 84(1): 91-104.
[45] Zhu L P, Helmberger D V.1996. Advancement in source estimation techniques using broadband regional seismograms[J]. Bulletin of the Seismological Society of America, 86(5): 1634-1641.
[46] Zoback M L.1992. First- and second-order patterns of stress in the lithosphere: The World Stress Map Project[J]. Journal of Geophysical Research: Solid Earth, 97(B8): 11703-11728.