新丰江库区二维P波速度结构——英德一河源一陆河深地震测深剖面探测结果
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摘要
以新丰江水库为中心完成了一条深地震宽角反射/折射剖面.采用动力学射线追踪方法获得了沿剖面的壳幔二维速度结构图像.结果表明:在新丰江水库东南的大坝峡谷区至河源一带,上地壳基底界面至C_1界面(上地壳上部的底面)之间速度结构存在较明显的纵横向非均匀性,速度以高、低速相间分布为特征.结合近期新丰江库区地方震精确定位结果分析发现,地震分布与这一结构异常区有较好的相关性.推测剖面120 km桩号附近可能存在至少切至上地壳上部的深部断裂.该断裂主要以水平错动为主,且在近地表并不明显,这与新丰江大坝峡谷区分布的北东东向断裂特征具有一致性.研究区基底埋深约1.2～2.5 km,新丰江水库下方基底相对两侧呈现上隆.上地壳下部层速度较为均匀,层厚度无明显变化,上、下地壳分界面埋深20.5～21.5 km.下地壳存在一弱低速层体,莫霍界面由南东向北西呈缓慢加深的趋势,起伏变化不大.埋深约31.0～32.5 km.沿剖面地壳平均速度6.21～6.25 km/s.
A deep seismic wide-angle reflection/refraction profile has been completed in the Xinfengjiang reservoir area.The two-dimensional crustal velocity structure image along the profile is obtained by using dynamic ray tracing method.The results show that there is a obvious velocity anomalies characterized by alternating high and low velocity between Xinfengjiang Reservoir dam canyon and Heyuan area from the basement interface to C_1 discontinuity(bottom of the upper part of the upper crust).Combining with the recent local earthquakes precise location results of Xinfengjiang reservoir area,we find that these earthquakes is related to the velocity anomalies. We infer that there is a deep fault at least extending to the top surface of the G discontinuity in the upper crust near post 120 km of the profile.The fault mainly behaves as horizontal fracture dislocation,and is not distinguished easily near surface.Which consists with the characteristics of the NEE-trending faults existing in the Xinfengjiang dam canyon regin.The depth of the basement is about 1.2 ~ 2.5 km.The basement rises slightly under the Xinfengjiang reservoir.The variation of the velocity and the thickness is small within the lower part of the upper crust.The boundary between the upper and lower crust is 20.5~21.5 km deep.There is a weak low-velocity body within the lower crust.The Moho discontinuity deepens from southeast to northwest slowly and it is about 31.0~ 32.5 km deep.The average crustal velocity along the profile is 6.21～6.25 km/s.
A deep seismic wide-angle reflection/refraction profile has been completed in the Xinfengjiang reservoir area.The two-dimensional crustal velocity structure image along the profile is obtained by using dynamic ray tracing method.The results show that there is a obvious velocity anomalies characterized by alternating high and low velocity between Xinfengjiang Reservoir dam canyon and Heyuan area from the basement interface to C_1 discontinuity(bottom of the upper part of the upper crust).Combining with the recent local earthquakes precise location results of Xinfengjiang reservoir area,we find that these earthquakes is related to the velocity anomalies. We infer that there is a deep fault at least extending to the top surface of the G discontinuity in the upper crust near post 120 km of the profile.The fault mainly behaves as horizontal fracture dislocation,and is not distinguished easily near surface.Which consists with the characteristics of the NEE-trending faults existing in the Xinfengjiang dam canyon regin.The depth of the basement is about 1.2 ~ 2.5 km.The basement rises slightly under the Xinfengjiang reservoir.The variation of the velocity and the thickness is small within the lower part of the upper crust.The boundary between the upper and lower crust is 20.5~21.5 km deep.There is a weak low-velocity body within the lower crust.The Moho discontinuity deepens from southeast to northwest slowly and it is about 31.0~ 32.5 km deep.The average crustal velocity along the profile is 6.21～6.25 km/s.
引文
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[8]郭贵安,冯锐.新丰江水库三维速度结构和震源参数的联合反演[J].地球物理学报,1992,35(3):331-342. Guo G A,Feng R.The joint inversion of 3-D velocity structure and source parameters in Xinfengjiang reservoir[J].Chinese J. Geophys.(in Chinese),1992,35(3):331-342.
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[11]万永芳,叶东华,陈大庆.广东新丰江地区地震研究[J].华南地震,2008,28(2):60-66. Wan Y F,Ye D H,Chen D Q.Study on Earthquake Characteristics in Xinfengjiang Region[J].South China Journal of selsmology,2008,28(2):60-66.
[12]王洪体,庄灿涛,薛兵,等.精密主动地震监测[J].地球物理学报,2009,52(7):1808-1815. Wang H T,Zhuang C T,Xue B,et al.Precisely and actively seismic monitoring[J].Chinese J.Geophys.(in Chinese), 2009,52(7):1808- 1815.
[13]Michel B,Him A.Velocity-depth estimation from wide angle seismic reflection arrivals[J].Annales Geophysique,1980,36 (1):107-118.
[14]Scheidegger A E,Willmore P L.The use of a least square method for the interpretation of data from seismic surveys [J].Geophysics,1957,22,1,9-22.
[15]Hole J A.Nonlinear high-resolution three-dimensional seismic travel time tomography[J].J Geophys Research,1992,135. 6553-6562.
[16]Cerveny V.Ray theoretical soismograms for laterally inhomogrenous structures[J].Geophysics,1979,46:335-342.
[17]廖其林,王振明,王屏路,等.福州-泉州-汕头地区地壳结构的爆破地震研究[J].地球物理学报,1988,31(3):270-280. Liao Q L,Wang Z M,Wang P L,et al.Explosion seismic study of the crustal structure in Fuzhou-Quanzhou-Shantou region[J].Chinese J.Geophys.(in Chinese),1999,31(3): 270-280.
[18]熊绍柏,金东敏,孙克忠,等.福建漳州地热田及邻近地区的地壳深部构造特征[J].地球物理学报,1991,34(1):55-63. Xiong S B,Jin D M,Sun K Z,et al.Some characteristics of deep structure of the Zhangzhou geothermal filed and it's neighbourhood in the Fujian province[J].Chinese J. Geophys.(in Chinese),1999,34(1):55-63.
[19]朱金芳,方盛明,张先康,等.漳州盆地及其邻区地壳深部结构的探测与研究[J].中国地震,2006,22(4):405-417. Zhu J F,Fang S M,Zhang X K,et al.Exploration and research of deep crustal structure in the Zhangzhou Basin and Its Vicinit[J].Earthquake research in china,2006,22(4): 405-417.
[20]尹周勋,赖明惠,熊绍柏,等.华南连县—博罗—港口地带地壳结构及速度分布的爆炸地震探测结果[J].地球物理学报, 1999,42(3):383-392. Yin Z X,Iai M H,Xiong S B,et al.Crustal structure and velocity distribution from deep seismic sounding along the profile of Lianxian-Boluo-Gangkou in South China[J]. Chinese J.Geophys.(in Chinese),1999,42(3):383-392.
[2]丁原章,潘建雄,肖安予,等.新丰江水库诱发地震的构造条件[J].地震地质,1983,5(3):63-74. Ding Y Z,Pan J X,Xiao A Y,et al.Tectonic environment of reservoir induced earthquake in the Xinfengjiang reservoir area [J].Seismology and Geology,1983,5(3):63-74.
[3]丁原章,曾宪译,陈益明.新丰江水库区诱发地震的余震活动[J].地震地质,1982,4(1):23-29. Ding Y Z,Zeng X Y,Chen Y M.The aftershock activities of induced earthquakes in the Xinfengjiang reservoir areas[J]. Seismology and Geology,1982,4(1 ):23 - 29.
[4]王妙月,杨懋源,胡毓良,等.新丰江水库地震的震源机制及其成因的初步探讨[J].中国科学(A辑),1976,1:85-97. Wang M Y,Yang M Y,Hu S L,et al.A preliminary study on the mechanism of the reservoir impounding earthquakes at Hsinfengkiang[J].Science in China,Ser.A,1976,1:85-97.
[5]潘建雄,肖安予.新丰江水库区地震构造及其活动特征的初步研究[J].地震地质,1982,4(2):53-58. Pan J X,Xiao A Y.The preliminary study of seismic structures and their characteristic activity in Xinfengjiang reservoir area [J].Seismology and Geology,1982,4(2):53-58.
[6]吴建春,冯锐,宋仲和.CT技术在新丰江台网中的应用[J].中国地震,1990,6(4):85-92. Wu J C,Feng R,Song Z H.Application of Computerized Tomography on the Xinfengjiang Reservoir Network[J]. Earthquake Research in China,1990,6(4):85-92.
[7]魏柏林,陈庞龙,李富光,等.新丰江地震震源机制解及构造应力场[J].地震学报,1991,13(4):462-479. Wei B L,Chen P L,Li F G,et al.Focal mechanisms and tectonic stress fleld of the Xinfengjiang earthquakes[J].Acta Seismologica Sinica,1991,13(4):462-479.
[8]郭贵安,冯锐.新丰江水库三维速度结构和震源参数的联合反演[J].地球物理学报,1992,35(3):331-342. Guo G A,Feng R.The joint inversion of 3-D velocity structure and source parameters in Xinfengjiang reservoir[J].Chinese J. Geophys.(in Chinese),1992,35(3):331-342.
[9]丁原章,王仁,孙荀英,等.深层构造新活动性的影响—新丰江水库区构造的三维数学模拟计算[J].中国科学(B辑),1992, 2:194-205. Ding Y Z,Wang R,Sun X Y,et al.Influence of the deep structure new activity-three-dimensional mathematical simulation of the tectonics in Xinfengjiang reservoir area[J]. Science in China,Ser.B,1992,2:194-205.
[10]官幼雄,李亚林,颜玉定.1962年3月19日新丰江6.1级水库诱发地震时的构造应力[J].华南地震,2005,25(3):83- 86. Gong Y X,Li Y L,Yan Y D.A study on the tectonic stress variation caused by Xinfengjiang Ms6.1 reservoir induced earthquake occured on March 19,1962[J].South China Journal of selsmology,2005,25(3):83 - 86.
[11]万永芳,叶东华,陈大庆.广东新丰江地区地震研究[J].华南地震,2008,28(2):60-66. Wan Y F,Ye D H,Chen D Q.Study on Earthquake Characteristics in Xinfengjiang Region[J].South China Journal of selsmology,2008,28(2):60-66.
[12]王洪体,庄灿涛,薛兵,等.精密主动地震监测[J].地球物理学报,2009,52(7):1808-1815. Wang H T,Zhuang C T,Xue B,et al.Precisely and actively seismic monitoring[J].Chinese J.Geophys.(in Chinese), 2009,52(7):1808- 1815.
[13]Michel B,Him A.Velocity-depth estimation from wide angle seismic reflection arrivals[J].Annales Geophysique,1980,36 (1):107-118.
[14]Scheidegger A E,Willmore P L.The use of a least square method for the interpretation of data from seismic surveys [J].Geophysics,1957,22,1,9-22.
[15]Hole J A.Nonlinear high-resolution three-dimensional seismic travel time tomography[J].J Geophys Research,1992,135. 6553-6562.
[16]Cerveny V.Ray theoretical soismograms for laterally inhomogrenous structures[J].Geophysics,1979,46:335-342.
[17]廖其林,王振明,王屏路,等.福州-泉州-汕头地区地壳结构的爆破地震研究[J].地球物理学报,1988,31(3):270-280. Liao Q L,Wang Z M,Wang P L,et al.Explosion seismic study of the crustal structure in Fuzhou-Quanzhou-Shantou region[J].Chinese J.Geophys.(in Chinese),1999,31(3): 270-280.
[18]熊绍柏,金东敏,孙克忠,等.福建漳州地热田及邻近地区的地壳深部构造特征[J].地球物理学报,1991,34(1):55-63. Xiong S B,Jin D M,Sun K Z,et al.Some characteristics of deep structure of the Zhangzhou geothermal filed and it's neighbourhood in the Fujian province[J].Chinese J. Geophys.(in Chinese),1999,34(1):55-63.
[19]朱金芳,方盛明,张先康,等.漳州盆地及其邻区地壳深部结构的探测与研究[J].中国地震,2006,22(4):405-417. Zhu J F,Fang S M,Zhang X K,et al.Exploration and research of deep crustal structure in the Zhangzhou Basin and Its Vicinit[J].Earthquake research in china,2006,22(4): 405-417.
[20]尹周勋,赖明惠,熊绍柏,等.华南连县—博罗—港口地带地壳结构及速度分布的爆炸地震探测结果[J].地球物理学报, 1999,42(3):383-392. Yin Z X,Iai M H,Xiong S B,et al.Crustal structure and velocity distribution from deep seismic sounding along the profile of Lianxian-Boluo-Gangkou in South China[J]. Chinese J.Geophys.(in Chinese),1999,42(3):383-392.
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