青藏高原东北缘地壳应变与应力特征研究

doi:10.12196/j.issn.1000-3274.2022.04.001

摘要/Abstract

摘要： 青藏高原东北缘是青藏高原隆升和变形的前缘, 地壳变形剧烈, 研究其地壳运动和变形对理解该区的构造活动特征和动力学机制具有重要的意义。本研究收集1991—2016年的GNSS速度场数据, 采用多尺度球面小波方法计算应变率张量, 分析主应变率、面应变率和最大剪应变率的空间分布特征。面应变率结果显示青藏高原东北缘大部分区域具有轻微的压缩, 平均压缩率小于15 nstrain/a, 压缩率较高的区域集中在青藏高原东北缘的边缘地区, 其中祁连山断裂带和海原断裂带区域的面压缩率大于20 nstrain/a。东昆仑断裂带、祁连山断裂带、海原断裂带和六盘山断裂带具有较高的剪应变率, 最大约为40 nstrain/a。研究还收集青藏高原东北缘1904—2021年2.0级以上地震的震源机制解, 通过区域阻尼应力反演方法得到该区域的应力场, 最大主应力方向显示青藏高原东北缘35°N以南的区域表现为近EW向的挤压, 而35°N以北的区域表现为NE向的挤压。根据最大、最小主应力的倾角把研究区划分为正断、逆冲和走滑3类区域, 发现青藏高原东北缘内部的大部分区域和六盘山断裂的北部区域表现出走滑的运动特征, 而祁连山断裂带、海原断裂带和西秦岭断裂带以南的区域表现出明显的挤压逆冲特点, 与面压缩率的高值区域较为重合。对比主应力轴方向和主应变率轴方向发现青藏高原东北缘内部区域中上地壳变形是垂直连贯的, 而与塔里木盆地、阿拉善地块和华南地块相接区域主应力和主应变率方向差异较大, 可能与壳内软弱带和复杂的地表局部构造有关, 这些区域岩石圈复杂的变形和较强的地震活动性是青藏高原的NE向扩张变形受到较为坚硬的塔里木盆地、阿拉善地块、鄂尔多斯地块和华南地块阻挡的结果。

关键词: 青藏高原东北缘, 应变率场, 应力场, 多尺度球面小波, 区域阻尼应力反演

Abstract: The northeastern Qinghai-Xizang Plateau is the most distant area of the uplift and deformation of the Qinghai-Xizang Plateau, with intense crustal deformation. The study of the crustal tectonic movement and deformation of this area is of great significance to understand its characteristics of tectonics and dynamic mechanism. In this study, the GNSS velocity field from 1991 to 2016 is collected, the multi-scale spherical wavelet method is used to calculate the strain rate tensors, and the spatial distribution characteristics of principal strain rate, surface strain rate and maximum shear strain rate are analyzed. The strain rates show that most areas in the northeast edge of the Qinghai-Xizang Plateau are characterized by slight surface compression, less than 15 nstrain/a. The areas with high surface compression rate are concentrated in the northeast edge of the Qinghai-Xizang Plateau, among which the surface compression in the Qilian Mountain Fault Zone and Haiyuan fault zone is greater than 20 nstrain/a. There are high shear strain rates in the eastern Kunlun fault zone, Qilian Mountain Fault Zone, Haiyuan fault zone and the southern section of Liupanshan fault zone, with a maximum of about 40 nstrain/a. The focal mechanism solutions from 1904 to 2021 on the northeast edge of the Qinghai-Xizang Plateau are also collected. The stress field in the region is obtained by the method of regional damping stress inversion. The direction of the maximum principal stress is basically consistent with the direction of the principal strain rate, showing that the area at the south of 35°N is featured by EW compression, and the area at the north of 35°N is characterized by NE compression. The study also classifies the studied area as normal, thrust and strike slip zones according to the dip angles of the maximum and minimum principal stress. It shows that most zones within the Qinghai-Xizang Plateau and the northern section of Liupanshan fault are characterized by strike slip, while the Qilian Mountain Fault zone, Haiyuan fault zone and the south of West Qinling fault zone present compressive thrust movement, coinciding with the areas of high value in surface compression. Comparing the directions of principal stress axes and principal strain rate axes, we find that the deformation of the upper and middle crust in the northeast margin of the Qinghai-Xizang Plateau is vertically coherent, while the directions of principal stress and principal strain rates in the areas around the Tarim Basin, Alxa block and South China block are pretty different, likely related to the weak zones in the crust and local surface structures. The intense deformation and strong seismicity in these areas are possibly ascribed to the northeastward expansion of the Qinghai-Xizang Plateau impeded by the relatively rigid the Alxa block, Ordos block and South China block.

Key words: Northeastern Qinghai-Xizang Plateau, Strain rate field, Stress field, Multiscale spherical wavelet, Inversion of regional damping stress

中图分类号:

P315.7

杨业鑫, 孟国杰, 吴伟伟, 赵国强. 青藏高原东北缘地壳应变与应力特征研究[J]. 地震, 2022, 42(4): 1-13.

YANG Ye-xin, MENG Guo-jie, WU Wei-wei, ZHAO Guo-qiang. Characteristics of Crustal Strain and Stress in the Northeastern Qinghai-Xizang Plateau[J]. EARTHQUAKE, 2022, 42(4): 1-13.

参考文献

[1] Tapponnier P, Xu Z Q, Roger F. Oblique stepwise rise and growth of the Tibet Plateau[J]. Science, 2001, 294(5547): 1671-1677.
[2] Gan W J, Zhang P Z, Shen Z K, et al. Present-day crustal motion within the Tibetan plateau inferred from GPS measurements[J]. Journal of Geophysical Research, 2007, 112(B8): B08416.
[3] Meng G J, Ren J W, Wang M, et al. Crustal deformation in western Sichuan region and implications for 12 May 2008 M_S8.0 earthquake[J]. Geochemistry, Geophysics, Geosystems, 2008, 9(11): 1-9.
[4] Liang S M, Gan W J, Shen C Z, et al. Three-dimensional velocity field of present-day crustal motion of the Tibetan Plateau derived from GNSS measurements[J]. Journal of Geophysical Research, 2013, 118(10): 5722-5732.
[5] Wang M, Shen Z K. Present-day crustal deformation of continental China derived from GNSS and its tectonic implications[J]. Journal of Geophysical Research, 2020, 125(2): e2019JB018774.
[6] 江在森, 马宗晋, 张希, 等. GNSS初步结果揭示的中国大陆水平应变场与构造变形[J]. 地球物理学报, 2003, 46(3): 352-358.
JIANG Zai-seng, MA Zong-jin, ZHANG Xi, et al. Horizontal strain field and tectonic deformation of China mainland revealed by preliminary GPS result[J]. Chinese Journal of Geophysics, 2003, 46(3): 352-358 (in Chinese).
[7] 沈正康, 王敏, 甘卫军, 等. 中国大陆现今构造应变率场及其动力学成因研究[J]. 地学前缘, 2003, 10(S1): 93-100.
SHEN Zheng-kang, WANG Min, GAN Wei-jun, et al. Contemporary tectonic strain rate field of Chinese continent and its geodynamic implications[J]. Earth Science Frontiers, 2003, 10(S1): 93-100 (in Chinese).
[8] Shen Z K, Lü J N, Wang M, et al. Contemporary crustal deformation around the southeast borderland of the Tibetan Plateau[J]. Journal of Geophysical Research: Solid Earth, 2005, 110: B11409.
[9] 朱爽, 杨博. 青藏高原东北缘近期水平形变场分析[J]. 大地测量与地球动力学, 2014, 34(3): 81-85.
ZHU Shuang, YANG Bo. Analysis of recent horizontal deformation in the northeastern margin of the Qinghai-Tibetan Plateau[J]. Journal of Geodesy and Geodynamics, 2014, 34(3): 81-85 (in Chinese).
[10] 瞿伟, 高源, 陈海禄, 等. 利用GPS高精度监测数据开展青藏高原现今地壳运动与形变特征研究进展[J]. 地球科学与环境学报, 2021, 43(1): 182-204.
QU Wei, GAO Yuan, CHEN Hai-lu, et al. Review on Characteristics of present crustal tectonic movement and deformation in Qinghai-Tibet Plateau, China using GPS high precision monitoring data[J]. Journal of Earth Sciences and Environment, 2021, 43(1): 182-204 (in Chinese).
[11] 林向东, 徐平, 葛洪魁, 等. 小江断裂中段及其邻近地区应力场时间变化分析[J]. 地震学报, 2011, 33(6): 755-762.
LIN Xiang-dong, XU Ping, GE Hong-kui, et al. Possible crustal stress change in middle section of Xiaojiang fault and its adjacent area[J]. Acta Seismologica Sinica, 2011, 33(6): 755-762 (in Chinese).
[12] 王强. 基于震源机制解反演研究云南现今构造应力场特征[D]. 云南: 云南大学, 2015.
WANG Qiang. Study on the characteristics of current tectonic stress field in Yunnan based on focal mechanism solution inversion[D]. Yunnan: Yunnan University, 2015 (in Chinese).
[13] 田建慧, 罗艳. 中国大陆及其周边地区应力场特征[J]. 地震, 2019, 39(2): 110-121.
TIAN Jian-hui, LUO Yan. Characteristics of stress field in China's mainland and surrounding areas[J]. Earthquake, 2019, 39(2): 110-121 (in Chinese).
[14] 徐纪人, 赵志新, 石川有三. 中国大陆地壳应力场与构造运动区域特征研究[J]. 地球物理学报, 2008, 51(3): 770-781.
XU Ji-ren, ZHAO Zhi-xin, Ishikawa Yuzo. Regional characteristics of crustal stress field and tectonic motions in and around Chinese mainland[J]. Chinese Journal of Geophysics, 2008, 51(3): 770-781 (in Chinese).
[15] Tape C, Musé P, Simons M, et al. Multiscale estimation of GNSS velocity fields[J]. Geophysical Journal International, 2009, 179(2): 945-971.
[16] 苏小宁, 孟国杰, 王振. 基于多尺度球面小波解算GNSS应变场的方法及应用[J]. 地球物理学报, 2016, 59(5): 1585-1595.
SU Xiao-ning, MENG Guo-jie, WANG Zhen. Methodology and application of GPS strain field estimation based on multi-scale spherical wavelet[J]. Chinese Journal of Geophysics, 2016, 59(5): 1585-1595 (in Chinese).
[17] Martínez-Garzón P, Kwiatek G, Ickrath M, et al. MSATSI: A MATLAB package for stress inversion combining solid classic methodology, a new simplified user‐handling, and a visualization tool[J]. Seismological Research Letters, 2014, 85(4): 896-904.
[18] Bogdanova I, Vandergheynst P, Antoine J P, et al. Stereographic wavelet frames on the sphere[J]. Applied and Computational Harmonic Analysis, 2005, 19(2): 223-252.
[19] Zhang P Z, Shen Z K, Wang M, et al. Continuous deformation of the Tibetan Plateau from global positioning system data[J]. Geology, 2004, 32(9): 809-812.
[20] 郑文俊, 张培震, 袁道阳, 等. GPS观测及断裂晚第四纪滑动速率所反映的青藏高原北部变形[J]. 地球物理学报, 2009, 52(10): 2491-2508.
DENG Wen-jun, ZHANG Pei-zhen, YUAN Dao-yang, et al. Deformation on the northern of the Tibetan plateau from GPS measurement and geologic rates of late quaternary along the major fault[J]. Chinese Journal of Geophysics, 2009, 52(10): 2491-2508 (in Chinese).
[21] Han C R, Huang Z C, Xu M J, et al. Focal mechanism and stress field in the northeastern Tibetan Plateau: insight into layered crustal deformations[J]. Geophysical Journal International, 2019, 218(3): 2066-2078.
[22] Pan Z Y, He J K, Shao Z G. Spatial variation in the present-day stress field and tectonic regime of northeast Tibet from moment tensor solutions of local earthquake data[J]. Geophysical Journal International, 2020, 221(1): 478-491.
[23] Michael A J. Determination of stress from slip data: Faults and folds[J]. Journal of Geophysical Research, 1984, 89(B13): 11517-11526.
[24] Hardebeck J L, Michael A J. Damped regional-scale stress inversions: Methodology and examples for southern California and the Coalinga aftershock sequence[J]. Journal of Geophysical Research, 2006, 111(B11): B11310.
[25] Zhang P Z, Shen Z K, Wang M, et al. Continuous deformation of the Tibetan Plateau from globle positioning system data[J]. Geology, 2004, 32(9): 809-812.
[26] 杨晓松, 马瑾. 大陆岩石圈解耦及块体运动讨论以青藏高原—川滇地区为例[J]. 地学前缘, 2003(S1): 240-247.
YANG Xiao-song, MA Jin. Continental lithosphere decoupling implication for block movement[J]. Earth Science Frontiers, 2003(S1): 240-247 (in Chinese).
[27] 韩存瑞. 青藏高原东缘地壳各向异性与应力应变场[D]. 南京: 南京大学, 2021.
HAN Cun-rui. Crustal anisotropy and stress/strain field in the eastern margin of the Tibetan plateau[D]. Nanjing: Nanjing University, 2021 (in Chinese).
[28] Klemperer S L. Crustal flow in Tibet: geophysical evidence for the physical state of Tibetan lithosphere, and inferred patterns of active flow[J]. Geological Society, London, Special Publications, 2006, 268: 39-70.
[29] Huang Z C, Tilmann F, Xu M J, et al. Insight into NE Tibetan Plateau expansion from crustal and upper mantle anisotropy revealed by shear-wave splitting[J]. Earth and Planetary Science Letters, 2017, 478: 66-75.
[30] Huang J L, Zhao D P. High-resolution mantle tomography of China and surrounding regions[J]. Journal of Geophysical Research, 2006, 111: B09305.
[31] 潘宇航, 蒲举, 程建武, 等. 青藏高原东北缘SKS波分裂研究[J]. 地震工程学报, 2017, 39(1): 168-176.
PAN Yu-hang, PU Ju, CHENG Jian-wu, et al. SKS wave splitting of the northeastern maigin of the Qinghai Tibet Plateau[J]. China Earthquake Engineering Journal, 2017, 39(1): 168-176 (in Chinese).
[32] 张辉, 高原, 石玉涛, 等. 基于地壳介质各向异性分析青藏高原东北缘构造应力特征[J]. 地球物理学报, 2012, 55(1): 95-104.
ZHANG Hui, GAO Yuan, SHI Yu-tao, et al. Tectonic stress analysis based on the crustal seismic anisotropy in the northeastern margin of Tibetan plateau[J]. Chinese Journal of Geophysics, 2012, 55(1): 95-104 (in Chinese).
[33] Clark M K, Royden L H. Topographic ooze: Building the eastern margin of Tibet by lower crustal flow[J]. Geology, 2000, 28(8): 703-706.
[34] Wang C Y, Han W B, Wu J P, et al. Crustal structure beneath the eastern margin of the Tibetan Plateau and its tectonic implications[J]. Journal of Geophysical Research: Solid Earth, 2007, 112(B7): B07307.
[35] 常利军, 王椿镛, 丁志峰, 等. 青藏高原东北缘上地幔各向异性研究[J]. 地球物理学报, 2008, 51(2): 431-438.
CHANG Li-jun, WANG Chun-yong, DING Zhi-feng, et al. Seismic anisotropy of upper mantle in the northeastern margin of the Tibetan plateau[J]. Chinese Journal of Geophysics, 2008, 51(2): 431-438 (in Chinese).