Deformation Pattern of the 23 August 1985 Wuqia Mw 6.9 Earthquake Surface Rupture (Xinjiang Province): Control from Inherited Folding-Related Structures
-
摘要: 1985年8月23日发生在新疆维吾尔自治区乌恰县境内的Mw6.9地震，是有地震仪器记录以来，帕米尔-南天山会聚带内发生的最强地震事件之一，也是碰撞造山带前陆地区少数形成显著地表破裂的强震事件之一. 在前人研究工作基础上，我们通过对震后Worldview卫星影像、无人机影像、野外调查获得的天然断层露头和人工探槽断层剖面的综合分析，对乌恰地震地表破裂的几何形态、变形样式、下伏断层结构进行了约束. 研究表明，地表破裂东段呈弧形展布，其走向、运动性质和下伏断层倾角变化显著；相比较而言，西段虽因后期地表过程改造而非常不连续，其运动性质、走向和下伏断层倾角却更为稳定. 由于地表破裂东、西两段分别位于明尧勒背斜南翼向形枢纽的南、北两侧，我们推测这种变形特征的显著差异，可能与向形枢纽两侧先存构造（先存的明尧勒背斜褶皱变形过程中形成的弯滑断层）的发育情况不同有关.Abstract: The 23 August 1985 Wuqia Mw 6.9 earthquake in Xinjiang Province, represents one of the strongest events in the Pamir-Southern Tian Shan convergence zone during the instrumental period. It was also one of the few events that produced clear coseismic surface rupture in the mountain ousforeland region. Based on previous studies of
Feng et al. (1986 ,1988) andAinscoe (2018) , in this study, we investigate map-view geometry, deformation patterns, and subsurface fault geometry of the Wuqia coseismic surface rupture, through a combining analysis of post-seismic Worldview satellite images, drone images, as well as fault outcrops from natural and artificial trench exposures. Our study documents that the eastern segment of the surface rupture exhibits an arcuate shape overall, and its strike, slip sense, and underlying fault dip have a significant variation along the fault. Comparatively, the western segment has more constant trending, slip sense, and underlying fault dip along the fault, even though it is quite discontinuous due to erosion of post-seismic surface process. Given that the eastern and western segments of the surface rupture lies at the southern and northern sidesof a synclinal hinge at Mingyaole southern limb, respectively, we suggest that such contrasting deformation pattern is dominantly controlled by the inherited folding-related structures of the Mingyaole fold (i.e., flexural-slip faults formed during the Mingyaole folding deformation).-
Key words:
- thrust fault /
- earthquake surface rupture /
- inherited structure /
- Pamir /
- Southern Tian Shan
-
图 1 1985年乌恰Mw6.9地震构造背景和发震断层（改自Li et al., 2019）
a. 帕米尔-南天山汇聚带构造位置图；b. 帕米尔前缘断层带（PFT）、南天山前陆冲断带及其与1985年乌恰地震和其它历史强震的关系（构造位置见图a）；1985年乌恰地震震源机制解据GlobalCMT catalog（
http://www.globalcmt.org/CMTsearch.html ）；1968年前的地震资料据全球地震危险性评估计划（Global Seismic Hazard Assessment Program；http://www.seismo.ethz.ch/static/GSHAP ）与中国历史强震目录（国家地震局震害防御司，1995），1968年—2018年的地震资料据美国地质调查局地震目录（http://earthquake.usgs.gov/earthquakes/ ）；STST. 南天山逆断层；Bai. 伯什克然木河；Bie. 别尔托阔依河；GZ. 盖孜河；Ke. 克孜勒苏河；Ka. 喀帕卡河；Kang. 康苏河；c. 横切托姆洛安断层和明尧勒背斜的构造横剖面，1985年乌恰地震使托姆洛安上断坡发生破裂（剖面位置见图b）Fig. 1. Seismotectonic setting and seismogenic fault geometry of 1985 Wuqia Mw6.9 earthquake (modified from Li et al., 2019)
图 2 1985年乌恰Mw6.9地震地表破裂分布图
地震地表破裂据冯先岳等（1988）和Ainscoe（2018）；下伏断层倾角据冯先岳等(1987, 1988)和冯先岳（1994）
Fig. 2. Spatial distribution of the 1985 Wuqia Mw 6.9 earthquake surface rupture
图 3 乌恰地震地表破裂（东段）平面展布、位移分布和下伏断层结构
a. 地表破裂平面展布、位移分布与下伏断层倾角，据冯先岳等(1987, 1988)、Ainscoe（2018）和Li et al.（2015a，2019）；b. 沿断层走向的同震位移分布；c~e.为天然断层露头和人工探槽剖面照片（左）与解译结果（右），剖面位置见图a
Fig. 3. Spatial extent, slip distribution, and subsurface fault geometry of the Wuqia coeismic surface rupture (eastern segment)
图 4 乌恰地震地表破裂（西段）平面展布、位移分布和下伏断层结构
a，b. 地表破裂平面展布、位移分布与下伏断层倾角，据冯先岳等(1987, 1988)、Ainscoe（2018）和Li et al.（2015a，2019）；c，d. 乌恰地震断层与明尧勒背斜迁移枢纽和弯滑断层的关系，剖面位置见图a；e. 天然断层露头照片（上）与解译结果（下），剖面位置见图b
Fig. 4. Spatial extent, slip distribution, and subsurface fault geometry of the Wuqia coeismic surface rupture (western segment)
图 6 先存构造对地震地表破裂几何形态和变形样式的控制作用
迁移枢纽的活动会使地层从右侧的缓倾域迁移至左侧的陡倾域，并形成褶皱陡坎和平行层滑动的弯滑断层；a.当地震断层切割缓倾域时，由于不发育弯滑断层，会形成低倾角、切割地层的断层面；相应的地表破裂迹线较为弯曲；b.相反，当地震断层切割迁移枢纽及其左侧的陡倾域时，会沿弯滑断层形成的先存软弱面发生破裂，从而在地表形成具有平行层滑动特征的、平直的逆断层陡坎
Fig. 6. The control of inherited structures to the coseismic surface deformation pattern
-
Ainscoe, E., 2018. Earthquakes and Active Faults in Central Asia. University of Oxford, Oxford. Berberian, M., 1979. Earthquake Faulting and Bedding Thrust Associated with the Tabas-E-Golshan (Iran) Earthquake of September 16, 1978. Bulletin of the Seismological Society of America, 69(6): 1861-1887. https://doi.org/10.1785/bssa0690061861 Burtman, V. S., Molnar, P., 1993. Geological and Geophysical Evidence for Deep Subduction of Continental Crust beneath the Pamir. Geological Society of America Special Papers, 281: 1-76. https://doi.org/10.1130/spe281-p1 Chen, J., Scharer, K. M., Burbank, D. W., et al., 2005. Kinematic Models of Fluvial Terraces over Active Fault-Related Folds: Constraints on the Growth Mechanism and Kinematics. Seismology and Geology, 27(4): 513-529 (in Chinese with English abstract). Department of Earthquake Disaster Prevention, State Seismological Bureau, 1995. Catalogue of Historical Strong Earthquakes in China (23rd Century B. C. to 1911). Seismological Press, Beijing (in Chinese with English abstract). Fan, G. W., Ni, J. F., Wallace, T. C., 1994. Active Tectonics of the Pamirs and Karakorum. Journal of Geophysical Research: Solid Earth, 99(B4): 7131-7160. https://doi.org/10.1029/93jb02970 Feng, X. Y., Luan, C. Q., Li, J., et al., 1988. The Deformation Zone of Wuqia Earthquake of M=7.4 in 1985. Seismology and Geology, 10(2): 39-45 (in Chinese with English abstract). Feng, X. Y, Yang Z., Luan C. Q., 1986. The Wuqia Earthquake of Xinjiang. Earthquake Research in China, 2(1): 62-66 (in Chinese with English abstract). Feng, X. Y., Luan C. Q., Li J., et al., 1987. Study on the Paleoearthquakes along the Kazikearte Fault. Inland Earthquake, 1(3): 231-239 (in Chinese with English abstract). Feng, X. Y., 1994. Surface Rupture Associated with the 1985 Wuqia Earthquake, in Xinjiang. Research on Active Fault (3). Seismological Press, Beijing, 45-55 (in Chinese with English abstract). Fossen, H., 2016. Structural Geology. Second Edition. Cambridge University Press, Cambridge. Lee, J. C., Chu, H. T., Angelier, J., et al., 2002. Geometry and Structure of Northern Surface Ruptures of the 1999 Mw=7.6 Chi-Chi, Taiwan Earthquake: Influence from Inherited Fold Belt structures. Journal of Structural Geology, 24(1): 173-192. doi: 10.1016/S0191-8141(01)00056-6 Li, T., Chen, J., Thompson, J. A., et al., 2012. Equivalency of Geologic and Geodetic Rates in Contractional Orogens: New Insights from the Pamir Frontal Thrust. Geophysical Research Letters, 39(15): 1-10. https://doi.org/10.1029/2012gl051782 Li, T., Chen, J., Thompson, J. A., et al., 2015a. Hinge-Migrated Fold-Scarp Model Based on an Analysis of Bed Geometry: aStudy from the Mingyaole Anticline, Southern Foreland of Chinese Tian Shan. Journal of Geophysical Research: Solid Earth, 120(9): 6592-6613. https://doi.org/10.1002/2015jb012102 Li, T., Chen, J., Thompson, J. A., et al., 2015b. Active Flexural-Slip Faulting: a Study from the Pamir-Tian Shan Convergent Zone, NW China. Journal of Geophysical Research: Solid Earth, 120(6): 4359-4378. https://doi.org/10.1002/2014jb011632 Li, T., Chen, J., Thompson Jobe, J. A., etal., 2017. Active Flexural-Slip Faulting: Controls Exerted by Stratigraphy, Geometry, and Fold Kinematics. Journal of Geophysical Research: Solid Earth, 122(10): 8538-8565. https://doi.org/10.1002/2017jb013966 Li, T., Chen, J., Thompson Jobe, J. A., et al., 2018. Active Bending-Moment Faulting: Geomorphic Expression, Controlling Conditions, Accommodation of Fold Deformation. Tectonics, 37(8): 2278-2306. https://doi.org/10.1029/2018tc004982 Li, T., Chen, Z. X., Chen, J., et al., 2019. Along-Strike and Downdip Segmentation of the Pamir Frontal Thrust and Its Association with the 1985 Mw 6.9 Wuqia Earthquake. Journal of Geophysical Research: Solid Earth, 124(9): 9890-9919. https://doi.org/10.1029/2019jb017319 Li, Z. F., Xu, X. W., Ren, J. J., et al., 2022. Vertical Slip Distribution along Immature Active Thrust and Its Implications for Fault Evolution: A Case Study from Linze Thrust, Hexi Corridor. Earth Science, 47(3): 831-843 (in Chinese with English abstract). Philip, H., Meghraoui, M., 1983. Structural Analysis and Interpretation of the Surface Deformations of the El Asnam Earthquake of October 10, 1980. Tectonics, 2(1): 17-49. https://doi.org/10.1029/tc002i001p00017 Philip, H., Rogozhin, E., Cisternas, A., et al., 1992. The Armenian Earthquake of 1988 December 7: Faulting and Folding, Neotectonics and Palaeoseismicity. Geophysical Journal International, 110(1): 141-158. https://doi.org/10.1111/j.1365-246x.1992.tb00718.x Sharp, R. V., 1975. Displacement on Tectonic Ruptures. California Division Mines and Geology Bulletin, 196: 187-194. Scharer, K. M., Burbank, D. W., Chen, J., et al., 2004. Detachment Folding in the Southwestern Tian Shan-Tarim Foreland, China: Shortening Estimates and Rates. Journal of Structural Geology, 26(11): 2119-2137. https://doi.org/10.1016/j.jsg.2004.02.016 Thompson, J. A., Li, T., Chen, J., et al., 2017. Quaternary Tectonic Evolution of the Pamir‐Tian Shan Convergence Zone, Northwest China. Tectonics, 36(12): 2748-2776. https://doi.org/10.1002/2017TC004541 Wu, D. Y., Ren, Z. K., Lü H. H., et al., 2023. Geomorphic Constraints on Listric Thrust Faulting: Implications for Active Deformation of Bayan Anticline in Youludusi Basin, East Tianshan, China. Earth Science, 48(4): 1389-1404 (in Chinese with English abstract). Xu, X. W., Wen, X. Z., Ye, J. Q., et al., 2008. The Ms8.0 Wenchuan Earthquake Surface Ruptures and Its Seismogenic Structure. Seismology and Geology, 30(3): 597-629 (in Chinese with English abstract). Xu, X. W., 2009. Album of 5.12 Wenchuan 8.0 Earthquake Surface Ruptures, China. Seismological Press, Beijing (in Chinese with English abstrac). Yeats, R. S., Sieh, K., Allen, C. R. 1997. The Geology of Earthquakes. Oxford University Press, Oxford, Oxford. Zhu, H. Z., 1986. An Investigation on Wuqia Earthquake(M=7.4), Xinjiang. Journal of Seismology. 19(3): 36-42 (in Chinese with English abstract). 陈杰, Scharer K. M., Burbank D. W., 等, 2005. 西南天山明尧勒背斜的第四纪滑脱褶皱作用. 地震地质, (4): 530-547. https://www.cnki.com.cn/Article/CJFDTOTAL-DZDZ200504001.htm 冯先岳, 杨章, 栾超群, 等, 1986. 新疆乌恰地震. 中国地震, 2(1): 62-66. https://www.cnki.com.cn/Article/CJFDTOTAL-ZGZD198601008.htm 冯先岳, 栾超群, 李军, 等, 1987. 卡兹克阿尔特断裂古地震研究. 内陆地震. 1(3): 231-239. https://www.cnki.com.cn/Article/CJFDTOTAL-LLDZ198703000.htm 冯先岳, 栾超群, 李军, 等, 1988. 1985年乌恰7.4级地震形变带. 地震地质, 10(2): 39-45. https://www.cnki.com.cn/Article/CJFDTOTAL-DZDZ198802004.htm 冯先岳, 1994. 新疆乌恰地震破裂带. 活动断裂研究3. 北京: 地震出版社, 45-55. 国家地震局震害防御司, 1995. 中国历史强震目录(公元前23世纪-公元1911年). 北京: 地震出版社. 李占飞, 徐锡伟, 任俊杰, 等, 2022. 新生逆冲断裂地表垂直位错分布与断层活动性关系: 以河西走廊临泽断裂为例. 地球科学, 47(03): 831-843. doi: 10.3799/dqkx.2021.238 武登云, 任治坤, 吕红华, 等, 2023. 铲式逆冲断层的地貌约束: 以东天山尤路都斯盆地巴音背斜构造为例. 地球科学, 48(4): 1389-1404. doi: 10.3799/dqkx.2022.169 徐锡伟, 闻学泽, 叶建青, 等, 2008. 汶川M_S8.0地震地表破裂带及其发震构造. 地震地质, (3): 597-629. https://www.cnki.com.cn/Article/CJFDTOTAL-DZDZ200803003.htm 徐锡伟, 2009. 5.12汶川8.0级地震地表破裂图集. 北京: 地震出版社. 朱海之, 1986. 新疆乌恰7.4级地震考察纪实. 地震学刊, 19(3): 36-42. https://www.cnki.com.cn/Article/CJFDTOTAL-DZXK198603004.htm -
下载:
点击查看大图
计量
- 文章访问数: 210
- HTML全文浏览量: 273
- PDF下载量: 47
- 被引次数: 0
