三峡水库坝址及邻区中上地壳S波速度结构
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摘要
利用三峡数字地震台网记录的Sg波到时资料,采用地震层析成像技术,重建了三峡水库坝址及邻区中上地壳的三维速度图象,研究了地壳深部构造,主要结论是:①黄陵背斜的岩性具有固结程度高、岩体均匀完整、埋藏深度至少达14km的特征;②秭归盆地与边缘构造由于岩层一致,而速度结构相同;构造变形的强度决定了秭归盆地及周缘区域沉积层的厚度分布和速度结构特征;③中上地壳中存在上地幔部分熔融物质,主要分布在秭归盆地和培石附近下方;④结晶基底的构造不均匀,顶面和底面起伏变化大,厚度和速度变化较大;⑤速度梯度带与重力梯级带位置一致,重力梯级带成因需要考虑深部构造和介质因素.
A 3-D S-wave velocity structure of upper and middle crust beneath the Three Gorges reservoir dam and in adjacent region was reconstructed by means of the seismic tomography using the absolute Sg-arrivals from the earthquakes observed by the Three Gorges seismic network.Main research results of the crustal structure are as follows.① The lithology of the Huangling anticline is highly solidified,with uniformity and integrity.Its buried depth is not less than 14 km.② The rock strata of the Zigui basin are consistent with that of its marginal region,so their velocity structures are the same.The depth distribution and velocity structure characteristics of the Zigui basin and its adjacent areas depended on the intensity of the tectonic deformation.③ The partially molten substances,located in upper and middle crust and intruded from upper mantle,mainly distribute beneath the Zigui basin,as well as nearby the Peishi region.④ The crystalline basement was constructed inhomogeneously,its top and bottom boundary,and the basement thickness and corresponding velocity structure,show significant regional variation.⑤ The velocity gradient zone is generally consistent with the gravitational gradient zone.
A 3-D S-wave velocity structure of upper and middle crust beneath the Three Gorges reservoir dam and in adjacent region was reconstructed by means of the seismic tomography using the absolute Sg-arrivals from the earthquakes observed by the Three Gorges seismic network.Main research results of the crustal structure are as follows.① The lithology of the Huangling anticline is highly solidified,with uniformity and integrity.Its buried depth is not less than 14 km.② The rock strata of the Zigui basin are consistent with that of its marginal region,so their velocity structures are the same.The depth distribution and velocity structure characteristics of the Zigui basin and its adjacent areas depended on the intensity of the tectonic deformation.③ The partially molten substances,located in upper and middle crust and intruded from upper mantle,mainly distribute beneath the Zigui basin,as well as nearby the Peishi region.④ The crystalline basement was constructed inhomogeneously,its top and bottom boundary,and the basement thickness and corresponding velocity structure,show significant regional variation.⑤ The velocity gradient zone is generally consistent with the gravitational gradient zone.
引文
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张爱民,李强.2006.双差定位在三峡库区地震定位中的应用[J].大地测量与地球动力学,26(3):73--77.
赵旭,李强,蔡晋安.2007.三峡库首区最小一维速度模型研究[J].大地测量与地球动力学,27(增刊):1--7.
朱天飞,刘福田.1982.用地震资料测定岩石层的三维速度结构[J].地球物理学报,25(6):500--508.
Cerveny V,Molotkov I A,Psencik I.1977.Ray Method in Seismology[M].2nd ed.Prague:Univerzita Karlova:1--65.
Kissling E,Ellsworth WL,Eberhart-phillips D,Krodolfer U.1994.Initial reference models in local earthquake tomo-graphy[J].J Geophys Res,99(B10):19635--19646.
Kissling E.1988.Geotomography withlocal earthquake data[J].Rev Geophys,26(4):659--698.
Waldhauser F,Ellsworth WL.2000.Adouble-difference earthquake location algorithm:Method and application to theNorthern Hayward fault[J].Bull Seism Soc Amer,90(6):1353--1368.
陈步云,高文海.1986.贾家湾—沙园剖面地壳结构的初步研究[J].地壳变形与地震,4(1):357--364.
陈德基(主编).1987.三峡地区重力场和应力场研究[C]∥长江三峡工程对生态和环境影响及其对策研究论文集.北京:科学出版社:596--612.
陈德基(主编).1997.三峡工程地质研究[M].武汉:湖北科学技术出版社:1--78.
陈学波,陈步云,张四维.1994.长江三峡工程坝区及外围深度构造特征研究[M].北京:地震出版社:1--29.
江麟生,陈铁龙.2002.黄陵地区的几个主要基础地质问题[J].湖北地矿,16(1):8--13.
李强,赵旭,蔡晋安,刘瑞丰.2009.三峡水库坝址及邻区中上地壳P波速度结构[J].中国科学:D辑,39(4):427--436.
李安然,韩晓光,徐永健.1987.鄂西三峡区域重力场特征及其地震构造意义[J].地震地质,9(3):71--78.
刘传正,谭周地.1989.长江三峡库首区诱发地震的环境工程地质研究[C]∥长江三峡工程地质地震专题论证文集.北京:科学出版社:427--442.
刘福田,李强,吴华,刘建华,胡戈.1989.用于速度图象重建的层析成像法[J].地球物理学报,32(1):46--61.
刘福田,朱天飞.1984.震源位置和速度结构的联合(1):理论和方法[J].地球物理学报,27(2):167--175.
马达铨,杜绍华,肖志发.2002.黄陵花岗岩基的成因[J].岩石矿物学杂志,21(2):151--161.
马宗晋.1964.鄂西中生代地质构造的力学分析[J].地质科学,(1):76--90.
杨智娴,陈运泰,郑月军,于湘伟.2003.双差地震定位法在我国中西部地区地震精确定位中的应用[J].中国科学:D辑,33(增刊):129--134.
张爱民,李强.2006.双差定位在三峡库区地震定位中的应用[J].大地测量与地球动力学,26(3):73--77.
赵旭,李强,蔡晋安.2007.三峡库首区最小一维速度模型研究[J].大地测量与地球动力学,27(增刊):1--7.
朱天飞,刘福田.1982.用地震资料测定岩石层的三维速度结构[J].地球物理学报,25(6):500--508.
Cerveny V,Molotkov I A,Psencik I.1977.Ray Method in Seismology[M].2nd ed.Prague:Univerzita Karlova:1--65.
Kissling E,Ellsworth WL,Eberhart-phillips D,Krodolfer U.1994.Initial reference models in local earthquake tomo-graphy[J].J Geophys Res,99(B10):19635--19646.
Kissling E.1988.Geotomography withlocal earthquake data[J].Rev Geophys,26(4):659--698.
Waldhauser F,Ellsworth WL.2000.Adouble-difference earthquake location algorithm:Method and application to theNorthern Hayward fault[J].Bull Seism Soc Amer,90(6):1353--1368.
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