Focal Depth and Mechanism of Intraplate Earthquakes in the Qinghai-Tibet Plateau
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摘要: 青藏高原板内地震以浅源地震为主, 下地壳基本上没有地震, 地震震源多集中在15~40 km的深度范围, 主要在中地壳内, 呈似层状弥散分布.其中30~33 km深度是一个优势层, 与壳内分层有关.总体上青藏高原南、北部的震源面略呈相向倾斜特征.70~100 km深度区间出现了比较集中的震级较小的地震, 可能与壳幔过渡带的拆离作用有关.高原内部的正断层系与板内地震密切相关, 是板内浅源地震的主控构造.总之, 青藏高原地震震源沿着活动的上地壳脆性层与软弱层之间的脆-韧性过渡带分布.这些板内地震活动属于大陆动力学过程, 与板块碰撞和板块俯冲无关.初步认为青藏高原浅层到深层多震层的成因分别是韧性基底与脆性盖层、韧性下地壳与脆性上地壳、韧性下地壳与脆性上地幔的韧-脆性转换、拆离和解耦的产物.Abstract: The Qinghai-Tibet plateau intraplate earthquakes are mainly shallow earthquakes, and basically no earthquakes happens in the lower crust. Earthquakes mostly distribute in the range of 15-40 km in depth, basically within the middle crust and concentrate at the depth of 30-33 km as an advantage layer related to the crustal stratification. On the South and North of the plateau, the focal surfaces slightly dip to the center. Some earthquakes concentrate within the range of 70-100 km depth, which may be associated with the detachment between crust and mantle. The intraplate earthquakes in the central Qinghai-Tibet are closely related to the normal faults which are dominant earthquake faults. In short, the Qinghai-Tibet plateau seismic activity distributes along the brittle-ductile transition zone between the brittle upper crust layer and the ductile lower crust. Intraplate seismic activity is a continental dynamic process, irrelevant to plate collision and subduction. The seismogenic layers from shallow to deep are separately the result of ductile-brittle transition, detachment and decoupling between basement and cover; ductile lower crust and brittle upper crust, and ductile lower crust and brittle upper mantle.
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Key words:
- the Qinghai-Tibet plateau /
- intraplate earthquake /
- focal depth /
- seismogenic layer
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图 1 青藏高原1970年以来(M > 5.0) 地震震中分布(CENC目录数据)
Fig. 1. Earthquake distributions in Qinghai-Tibet plateau (M > 5.0, since 1970, data source: CENC)
图 2 青藏高原现代5.0级以上地震震源深度一频度(%)直方图
a.CENC目录数据; b.ISN目录数据
Fig. 2. Histograms of earthquake focal depths in Qinghai-Tibet plateau (M>5.0, since 1970)
图 3 青藏高原1997—2007年5.0级以上地震震源深度-纬度(a)和深度-经度(b)分布剖面(CENC目录数据)
Fig. 3. Focal depth profile along latitudes from (a) 25° to 40'N and (b)75° to 110'E(M>5.0, since 1970, data source: CENC)
图 4 青藏高原地震深源深度-频度(%) 分布图(CENC目录数据)
a. 0~10级; b. 5.0级以上
Fig. 4. Prequencies of earthquake focal depths in Qinghai-Tibet plateau (since 1970, data source: CENC)
图 5 青藏高原多震层与低速、低阻层、Moho面对应关系(图中地壳结构源于崔作舟等, 1992)
Fig. 5. Low-velocity & resistivity layer and Frequencies of earthquake focal depths in Qinghai-Tibet plateau
图 6 青藏高原地壳结构与多震层对应关系(图中地壳结构数据源于李秋生等, 2004)
Fig. 6. Variation of the Moho as crossing the plateau from north to south and Frequencies of earthquake focal depths
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[1] Chen, W. P., Molnar, P., 1983. Focal depths of intracontinental and intraplate earthquakes and their i mplications for the thermal and mechanical properties of the lithosphere. Journal of Geophysical Research, 88 (B5): 4183-4214. doi: 10.1029/JB088iB05p04183 [2] Chen, W. P., 1988. A brief update on the focal depths of intracontinental earthquakes and their correlations with heat flowand tectonic age. Seismological Research Letters, 59 (4): 263-272. doi: 10.1785/gssrl.59.4.263 [3] Chen, W. P., Yang, Z. H., 2004. Earthquakes beneath the Himalayas and Tibet: Evidence for strong lithospheric mantle. Science, 304 (5679): 1949-1952. doi: 10.1126/science.1097324 [4] Cui, Z. Z., Yin, Z. X., Gao, E. Y., et al., 1990. The structure and tectonics of the crust and their relation with earthquakes in the Qinghai-Xizang plateau. Bulletin of The Chinese Academy of Geological Sciences, 21: 215-225 (in Chininese). [5] Cui, Z. Z., Yin, Z. X., Gao, E. Y., et al., 1992. Velocity structure and deep-seated structure of the Qinghai-Tibet plateau. Geological Publishing House, Bejing, 1-112 (in Chinese). [6] Li, D. W., 1992. On tectonic asymmetrical evolution of the Himalayan orogenic belt. Earth Science—Journal of China University of Geosciences, 17 (5): 539-545 (in Chinese with English abstract). [7] Li, D. W., 1993. The style of continental structure and model of continental dynamics. Advance in Earth Sciences, 8 (5): 88-93 (in Chinese with English abstract). [8] Li, D. W., 1995a. Speculations on continental tectonics. Earth Science—Journal of China University of Geosciences, 20 (1): 10-18 (in Chinese with English abstract). [9] Li, D. W., 1995b. On continental tectonics and its dynamics. Earth Science—Journal of China University of Geosciences, 20 (1): 19-26 (in Chininese with English abstract). [10] Li, D. W., Ji, Y. L., 2000. Laminar flow in the lower continental crust and its significance for continental dynamics. Seismology and Geology, 22 (1): 89-96 (in Chininese with English abstract). [11] Li, D. W., Wang, J. Y., 2001. Geological anomaly of continental lower crust and its tectonic significance. Geological Science and Technology Information, 20 (3): 11-15 (in Chinese with English abstract). [12] Li, D. W., 2003. A new model for uplifting mechanism of Qinghai-Tibet Plateau. Earth Science—Journal of China University of Geosciences, 28 (6): 593-600 (in Chininese with English abstract). [13] Li, D. W., 2005. Intraplate active faults and earthquake mechanism in the Qinghai-Tibet plateau. In: Wu, Z. H., Zhao, Z. Z., Yang, M. L., et al., eds., Geological process and its effect on the environment and disaster of the Tibetan plateau. Seismic Press, Beijing, 118-124 (in Chinese). [14] Li, Q. S., Peng, S. P., Gao, R., 2004. A review on the Moho discontinuity beneath the Tibetan plateau. Geological Review, 50 (6): 598-612 (in Chininese). [15] Ma, Z. J., Zhang, J. S., Liu, G. D., et al., 1990. Current state of research on continental seismogenic layer-international workshop held in Beijing, Apri l27-30, 1990. Seismology and Geology, 12 (3): 262-264 (in Chininese). [16] Maggi, A., Jackson, J. A., McKenzie, D., et al., 2000. Earthquake focal depths, effective elastic thickness, and the strength of the continental lithosphere. Geology, 28 (6): 495-498. doi: 10.1130/0091-7613(2000)28<495:EFDEET>2.0.CO;2 [17] Molnar, P., 1988. Continental tectonics in the aftermath of plate tectonics. Nature, 335 (186): 131-137. [18] Pan, G. T., Wang, P. S., Xu, Y. R., et al., 1990. Cenozoic Tectonic Evolution of the Qinghai-Tibet Plateau. Geological publishing House, Bejing, 1-163 (in Chininese). [19] Ranalli, G., Murphy, D. C., 1987. Rheological stratification of the lithosphere. Tectonophysics, 132: 281-295. doi: 10.1016/0040-1951(87)90348-9 [20] Wang, C. Y., Wang, X. L., Su, W., et al., 2006. Seismological evidence of the crust flowing under the eastern boundary part of Qinghai-Tibet plateau. Earthquake Research in Sichuan, 4: 1-4 (in Chininese with English abstract). [21] Wong, I. G., Chapman, D. S., 1990. Deep intraplate earthquakes in the Western United States and their relationship to lithospheric temperatures. Bulletin of the Seismological Society of America, 80 (3): 589-599. [22] Zeng, R. S., Zhu, J. S., Zhou, B., et al., 1992. 3D seismic wave velocity structure of easten Qinghai-Tibet plateau and its adjacent areas and continental collision model. Acta Seismologica Sinica, 14 (Suppl. ): 523-533 (in Chininese with English abstract). [23] Zhang, G. M., Wang, S. Y., Li, L., et al., 2002. Focal depth research of earthquakes in Mainland China: Implication for tectonics. Chinese Science Bulletin, 47 (9): 663-668 (in Chininese with English abstract). doi: 10.1360/csb2002-47-9-663 [24] Zhao, J. L., Yuan, Y. M., Li, D. W., et al., 2007. Geophysical anomaly of lower crust of Qinhai-Tibet plateau and its adjacent regions. Geological Science and Technology Information, 26 (2): 13-18, 29 (in Chininese with English abstract). [25] Zhou, F. H., Yao, Z. X., Liu, Z. J., et al., 2002. The origin and implication of the NNE-trendingdeep negative magnetic anomaly zone in central Qinghai-Tibet plateau. Ge-ophysical & Geochemical Exploration, 26 (1): 12-16 (in Chininese with English abstract). [26] 崔作舟, 尹周勋, 高恩元, 等, 1990. 青藏高原地壳结构构造及其与地震的关系. 中国地质科学院院报, 21: 215-225. https://www.cnki.com.cn/Article/CJFDTOTAL-DQXB199002020.htm [27] 崔作舟, 尹周勋, 高恩元, 等, 1992. 青藏高原速度结构和深部构造. 北京: 地质出版社, 1-112. [28] 李德威, 1993. 大陆构造样式及大陆动力学模式初探. 地球科学进展, 8 (5): 88-93. https://www.cnki.com.cn/Article/CJFDTOTAL-DXJZ199305010.htm [29] 李德威, 1995a. 关于大陆构造的思考. 地球科学——中国地质大学学报, 20 (1): 10-18. https://www.cnki.com.cn/Article/CJFDTOTAL-DQKX201905005.htm [30] 李德威, 1995b. 再论大陆构造与动力学. 地球科学——中国地质大学学报, 20 (1): 19-26. https://www.cnki.com.cn/Article/CJFDTOTAL-DQKX501.002.htm [31] 李德威, 纪云龙, 2000. 大陆下地壳层流作用及其大陆动力学意义, 地震地质, 22 (1): 89-96. doi: 10.3969/j.issn.0253-4967.2000.01.012 [32] 李德威, 王家映, 2001. 大陆下地壳地球物理异常及其构造意义. 地质科技情报, 20 (3): 11-15. doi: 10.3969/j.issn.1000-7849.2001.03.003 [33] 李德威, 2003. 青藏高原隆升机制新模式. 地球科学——中国地质大学学报, 28 (6): 593-600. https://www.cnki.com.cn/Article/CJFDTOTAL-DQKX200306002.htm [34] 李德威, 2005. 青藏高原板内活动断层与地震成因. 吴珍汉, 赵志中, 杨美玲, 等. 青藏高原地质过程与环境灾害效应文集. 北京: 地震出版社, 118-124. [35] 李秋生, 彭苏萍, 高锐, 2004. 青藏高原莫霍面的研究进展. 质论评, 50 (6): 598-612. doi: 10.3321/j.issn:0371-5736.2004.06.011 [36] 马宗晋, 张家声, 刘国栋, 等, 1990. 大陆多震层研究现状和讨论. 地震地质, 12 (3): 262-264. https://www.cnki.com.cn/Article/CJFDTOTAL-DZDZ199003010.htm [37] 潘桂棠, 王培生, 徐耀荣, 等, 1990. 青藏高原新生代构造演化. 北京: 地质出版社, 1-163. [38] 王椿镛, 王溪莉, 苏伟, 等, 2006. 青藏高原东缘下地壳流动的地震学证据. 四川地震, 4: 1-4. https://www.cnki.com.cn/Article/CJFDTOTAL-SCHZ200604000.htm [39] 曾融生, 朱介寿, 周兵, 等, 1992. 青藏高原及其东部邻区的三维地震波速度结构与大陆碰撞模型. 地震学报, 14 (增刊): 523-533. https://www.cnki.com.cn/Article/CJFDTOTAL-DZXB1992S1002.htm [40] 张国民, 汪素云, 李丽, 等, 2002. 中国大陆地震震源深度及其构造含义. 科学通报, 47: 663-668. doi: 10.3321/j.issn:0023-074X.2002.09.004 [41] 赵继龙, 袁晏明, 李德威, 等, 2007. 青藏高原及周边地区下地壳地球物理异常及成因. 地质科技情报, 26 (2): 13-18, 29. doi: 10.3969/j.issn.1000-7849.2007.02.003 [42] 周伏洪, 姚正煦, 刘振军, 等, 2002. 青藏高原中部北北东向深部负磁异常带的成因及其意义. 物探与化探, 26 (1): 12-17. doi: 10.3969/j.issn.1000-8918.2002.01.003 -
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