漳州盆地及其邻区地壳深部结构的探测与研究
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摘要
漳州盆地及其邻区地处我国大陆东南沿海地震带中段。通过该地区高分辨率折射及宽角反射/折射地震探测剖面,获得了该区地壳几何结构与速度结构、地壳深浅部断裂的几何形态和构造关系等。结果表明,该区地壳分为上地壳和下地壳。上地壳的厚度为16.5~18.8km,下地壳厚度为12.0~13.0km。上地壳分为上下两部分。在上地壳下部有一个低速层,速度约为6.00km/s,低速层顶面深度为12.0km左右,厚度约为5.0km。下地壳也分为上下两部分。Moho界面的深度为29.0~31.8km。该区6条地壳浅部正断层大部分向地下延伸深度不超过4km,最大延伸深度达5km左右。据推测,浅部正断层下方有一条高倾角地壳深断裂带,该断裂带向下断至Moho面,向上断至上地壳下部低速层中。深浅部断裂构造不相连接。漳州盆地深浅部构造组合特征表明,九龙江断裂带是该区内一条特征明显、具有复杂深浅构造背景的深断裂带。这一深地震探测成果的获得,使得该地区深部资料解释的可靠性和探测精度比以往显著提高;对深浅部构造的组合可作统一解释,地壳的分层和结构特征更为确切和精细;首次发现上地壳的拉张性构造及铲式正断层组合特征,不仅有助于对漳州及其邻区地震危险性的综合判定,而且对深化东南沿海地震带深部动力学过程的认识具有重要意义。
The Zhangzhou basin and its vicinity is located at the middle section of the China southeast coast seismic belt.The geometry and velocity structure of this area and the relationship between the deep and shallow faults are obtained based on deep seismic wide-angle reflection and refraction profiling.The seismic profile indicates that the crust can be divided into two layers.The thickness of the upper crust is 16.5～18.8km and the thickness of the lower crust is 12～13km. The upper crust can also be divided into an upper and a lower layer.There is a low-velocity region in the lower part of upper crust where velocity is about 6km/s.The depth of the top of the low-velocity region is about 12km and the thickness is about 5km.The depth of the Moho interface is 29～31.8km. Six shallow listric faults developed in upper crust extend to the shallow depth of less than 4km and the maximum depth is about 5km.A high angle fault is explained to locate under the shallow normal faults which extend downwards into the Moho interface and upwards into the low-velocity layer.This indicates that there is no connection between the shallow and the deep faults.The structural pattern of the Zhangzhou basin indicates that the Jiulongjiang fault belt has special characteristics and complex structural background.This exploration result improves the reliability and precision of explanation of deep crustal structure in this area.The pull-apart and listric normal fault model shows that the upper crust structure accords to the dynamic process of Taiwan Strait.This is helpful for seismicity estimation of Zhangzhou and its vicinity and important for obtain more of the dynamic process of the south-east coast seismic belt.
The Zhangzhou basin and its vicinity is located at the middle section of the China southeast coast seismic belt.The geometry and velocity structure of this area and the relationship between the deep and shallow faults are obtained based on deep seismic wide-angle reflection and refraction profiling.The seismic profile indicates that the crust can be divided into two layers.The thickness of the upper crust is 16.5～18.8km and the thickness of the lower crust is 12～13km. The upper crust can also be divided into an upper and a lower layer.There is a low-velocity region in the lower part of upper crust where velocity is about 6km/s.The depth of the top of the low-velocity region is about 12km and the thickness is about 5km.The depth of the Moho interface is 29～31.8km. Six shallow listric faults developed in upper crust extend to the shallow depth of less than 4km and the maximum depth is about 5km.A high angle fault is explained to locate under the shallow normal faults which extend downwards into the Moho interface and upwards into the low-velocity layer.This indicates that there is no connection between the shallow and the deep faults.The structural pattern of the Zhangzhou basin indicates that the Jiulongjiang fault belt has special characteristics and complex structural background.This exploration result improves the reliability and precision of explanation of deep crustal structure in this area.The pull-apart and listric normal fault model shows that the upper crust structure accords to the dynamic process of Taiwan Strait.This is helpful for seismicity estimation of Zhangzhou and its vicinity and important for obtain more of the dynamic process of the south-east coast seismic belt.
引文
福建省地质矿产局,1985,福建省区域地质志,北京:地质出版社。
国家地震局永平爆破联合观测小组,1988,中国大陆深部构造的研究与进展,北京:地质出版社,67~91。
廖其林、王振明、王屏路等,1988,福州-泉州-汕头地区地壳结构的爆炸地震研究,地球物理学报,31(3),270~280。
廖其林、王振明、邱陶兴等,1990,福州盆地及其周围地区地壳深部结构与构造的初步研究,地球物理学报,33(2),163~173。
马杏垣,1989,中国岩石圈动力学图集,北京:中国地图出版社。
徐锡伟、吴卫民、张先康等,2002,首都圈地区地壳最新构造变动与地震,北京:科学出版社,1~376。
张先康、王椿镛、刘国栋等,1996,延庆-怀来地区地壳细结构———利用深地震反射剖面,地球物理学报,39(3),356~364。
张友南、孙君秀,1999,华北北部克拉通地壳岩石的波速特征与地壳物质组成,地震地质,21(2),147~155。
朱金芳、徐锡伟、黄宗林等,2005a,福州市活断层探测与地震危险性评价,北京:科学出版社。
朱金芳、徐锡伟、张先康等,2005b,福州盆地及邻区地壳精细结构的深地震反射与高分辨率折射及宽角反射/折射联合探测研究,中国科学D辑,35(8),738~749。
朱金芳、方盛明、张先康等,2006,泉州盆地及其邻区地壳深部结构的探测与研究,中国地震,22(3),41~50。
Fountain D M,Arculus R,Kay R W,1992,Continental Lower Crust,Amsterdam:Elsevier,1~485.
Rutter E H,Khazanehdari J,Brodie K H,et al,1999.Synthetic seismic reflection profile through the Ivrea zone-Serie dei Laghicontinental crustal section,northernwestern Italy,Geology,27(1),79~82.
ZhuJinfang,Huang Zonglin,Xu Xiwei,2005,Active Faults Exploration and Seismic Hazard Assessment in Fuzhou City.EarthquakeReserchin China,19(3),224~239.
国家地震局永平爆破联合观测小组,1988,中国大陆深部构造的研究与进展,北京:地质出版社,67~91。
廖其林、王振明、王屏路等,1988,福州-泉州-汕头地区地壳结构的爆炸地震研究,地球物理学报,31(3),270~280。
廖其林、王振明、邱陶兴等,1990,福州盆地及其周围地区地壳深部结构与构造的初步研究,地球物理学报,33(2),163~173。
马杏垣,1989,中国岩石圈动力学图集,北京:中国地图出版社。
徐锡伟、吴卫民、张先康等,2002,首都圈地区地壳最新构造变动与地震,北京:科学出版社,1~376。
张先康、王椿镛、刘国栋等,1996,延庆-怀来地区地壳细结构———利用深地震反射剖面,地球物理学报,39(3),356~364。
张友南、孙君秀,1999,华北北部克拉通地壳岩石的波速特征与地壳物质组成,地震地质,21(2),147~155。
朱金芳、徐锡伟、黄宗林等,2005a,福州市活断层探测与地震危险性评价,北京:科学出版社。
朱金芳、徐锡伟、张先康等,2005b,福州盆地及邻区地壳精细结构的深地震反射与高分辨率折射及宽角反射/折射联合探测研究,中国科学D辑,35(8),738~749。
朱金芳、方盛明、张先康等,2006,泉州盆地及其邻区地壳深部结构的探测与研究,中国地震,22(3),41~50。
Fountain D M,Arculus R,Kay R W,1992,Continental Lower Crust,Amsterdam:Elsevier,1~485.
Rutter E H,Khazanehdari J,Brodie K H,et al,1999.Synthetic seismic reflection profile through the Ivrea zone-Serie dei Laghicontinental crustal section,northernwestern Italy,Geology,27(1),79~82.
ZhuJinfang,Huang Zonglin,Xu Xiwei,2005,Active Faults Exploration and Seismic Hazard Assessment in Fuzhou City.EarthquakeReserchin China,19(3),224~239.
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