三峡水库区上地壳三维精细速度结构成像

Abstract

Abstract: In this paper, tomoDD method is applied to determine detailed 3D velocity structure of the upper crust and the hypocenter parameters simultaneously in the Three Gorges reservoir area using the phase arrival times from 4967 seismic events recorded by 48 instruments. The resolution of the inversion result is 0.05°. The following conclusions are drawn:The heterogeneity of medium is obvious, reflecting the complex media structure in the reservoir area. The V_S distribution is bounded by the Xiangxi River between the Zigui Basin and the Huangling anticline. It shows a high V_S distribution to the east of the Xiangxi River including the reservoir dam. To its west, there are obvious large-scale low V_S distributions, including the Zigui basin, the Gaoqiao fault, and the Yangtze River. The distributions of low V_P and V_S in the Zigui Basin show that the sedimentary thickness of the basin is between 6 km and 8 km respectively. The low V_S anomaly in the margins of the basin and Xiangxi River is significantly higher than V_P, and fluid diffusion and infiltration may occur at the edge of the basin. The seismic events in the reservoir area, which clusted in the Badong area along the Yangtze River coast west of Xietan and the Xiannvshan area, forms a A-frame pattern, which is consistent with pervious observation. The lower boundary of focal depth is deeper from west to east with a dominant distribution between 0 and 10 km. The earthquakes along Gaoqiao fault in the Badong area occurred in the low or weak V_S areas, implying the relationship between the occurrences of these earthquakes with the lithological conditions in this area. The December 2013 M_S5.1 earthquake is located within a high V_P and V_S area and also at the bottom of a strip formed by shallow to deep earthquakes . The two M4 earthquakes in December 2016 located in the high V_P and V_S zone, the M_S4.1 on March 27, 2014 and the M_S4.7 earthquake on March 30, 2014 are located in the margin of high V_P and V_S areas as well.

Key words: Three Gorges reservoir area, tomoDD, 3D velocity structure, Seismic relocation

CLC Number:

P315.7

ZHANG Na, ZHAO Cui-ping, Zhou Lian-Qing. Upper Crust Velocity Structure Tomography of the Three Gorges Reservoir Area based on Dense Observation[J]. EARTHQUAKE, 2018, 38(4): 37-48.

References

[1] 李玶, 李愿军, 杨美娥. 长江三峡库区水库诱发地震的研究[J]. 中国工程科学, 2005, 7(6): 14-20.
[2] 廖武林, 张丽芬, 姚运生. 三峡水库地震活动特征研究[J]. 地震地质, 2009, 31(4): 707-714.
[3] 马文涛, 徐长朋, 李海鸥, 等. 长江三峡水库诱发地震加密观测及地震成因初步分析[J]. 地震地质, 2010, 32(4): 552-563.
[4] Haggag H M, Bhattacharya P M, Kamal S, et al. Seismicity and 3D velocity structure in the Aswan Reservoir Lake area, Egypt[J]. Tectonophysics, 2009, 476(3-4): 450-459.
[5] Zhou L, Zhao C, Chen Z, et al. Three-Dimensional V, P, and V, P, / V, S, Structure in the Longtan Reservoir Area by Local Earthquake Tomography[J]. Pure & Applied Geophysics, 2012, 169(1-2): 123-139.
[6] Dixit M MKumar SCatchings R D, et al. Seismicityfaultingand structure of the Koyna-Warna seismic region Western India from local earthquake tomography and hypocenter locations[J]. Journal of Geophysical Research: Solid Earth, 2014, 119(8): 6372-6398.
[7] 廖武林, 姚运生, 丁志峰, 等. 三峡地区P波速度层析成像研究[J]. 大地测量与地球动力学, 2007, 27(3): 80-84.
[8] 李强, 赵旭, 蔡晋安, 等. 三峡水库坝址及邻区中上地壳P波速度结构[J]. 中国科学, 2009, (4): 427-436.
[9] 李强, 赵旭, 蔡晋安, 等. 三峡水库坝址及邻区中上地壳S波速度结构[J]. 地震学报, 2011, 33(1): 39-50.
[10] 罗佳宏, 马文涛. 三峡库区上地壳速度结构初步研究[J]. 地震地质, 2016, 38(2): 329-341.
[11] 王小龙, 马胜利, 郭志, 等. 利用地震背景噪声成像技术反演三峡库区及邻近地区地壳剪切波速度结构[J]. 地球物理学报, 2013, 56(12): 4113-4124.
[12] 邹志辉, 周华伟, 张建中. 三峡地区上地壳结构的远震虚震源反射地震成像[J]. 地球物理学报, 2015, 58(2): 411-423.
[13] Zhang H, Thurber C H. Double difference tomography: The method and its application to the Hayward fault, California[J]. Bull Seismol Soc Am, 2003, 93, 1875-1889.
[14] 陈德基等.三峡工程地质研究[M]. 湖北: 科学技术出版社, 1997.
[15] 丁原章等.水库诱发地震[M]. 北京: 地震出版社, 1989.
[16] 高士均等.长江三峡地区地壳应力场与地震[M]. 北京: 地震出版社, 1992.
[17] 袁曲, 董建辉. 三峡水库地震孕震机理与未来地震趋势初探[J]. 地震地磁观测与研究, 2005, (b10): 37-47.
[18] Kissling E, Ellsworth W L, Eberhart-Phillips D, et al. Initial reference models in local earthquake tomography[J]. Journal of Geophysical Research Solid Earth, 1994, 99(B10): 19635-19646.
[19] 周连庆. 地球介质衰减特性层析成像[D]. 中国地震局地球物理研究所, 2016.
[20] Scarfì L, Giampiccolo E, Musumeci C, et al. New insights on 3D crustal structure in Southeastern Sicily (Italy) and tectonic implications from an adaptive mesh seismic tomography[J]. Physics of the Earth & Planetary Interiors, 2007, 161(1): 74-85.
[21] 王清云, 张秋文, 李峰. 长江三峡工程库首区诱发地震危险性研究[J]. 大地测量与地球动力学, 2003, 23(2): 101-106.
[22] 狄莉莎. 三峡数字地震台网中心记录典型波形初步分析[J]. 大地测量与地球动力学, 2004, 24(2): 52-57.
[23] 夏金梧, 李长安, 曾新平, 等. 三峡工程库首区高桥断裂特征与地震活动性研究[J]. 大地测量与地球动力学, 2008, 28(2): 8-15.

Upper Crust Velocity Structure Tomography of the Three Gorges Reservoir Area based on Dense Observation

PDF (PC)

Knowledge

Abstract

Cite this article

share this article

References

Related Articles 1

Recommended Articles

Metrics

Comments