厦门-金门大桥地区地震地质稳定性与桥线选择之研究
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摘要
厦门-金门大桥桥址地处闽东南沿海断隆带和泉州-汕头地震带南段,濒临台湾海峡,具有独特的地震地质构造环境。为了保障跨海大桥的长期安全性,无疑应对桥址地区的地震地质稳定性进行必要的研究,以期为工程设计提供科学依据。 本文依据近30多年来,对该地区地质构造调查、陆海地球物理探测、地壳形变观测、地震活动性、地壳动力学和工程场地特征等资料进行了比较系统研究,结果表明该区断块构造自晚第四纪以来,呈间歇性上升运动,速率约1-2.3毫米/年,史今地震能量释放速率为(2.737-7.999)×107焦耳/公里2/年。现代地壳水平运动的速度矢量指向南东东,速度值为9-13毫米/年。从震源机制揭示,区域现代构造应力场主压应力轴(P轴)为SE125°,仰角2-8°,引张轴(T轴)为SW215°,仰角2-10°,中间轴(N轴)近垂直。这导致台湾动力触角对闽东南沿海产生强烈的推挤作用。形成潜在震源区。历史上在漳州和金门海外曾发生过61/4至61/2级地震,但桥区内未有破坏性地震(Ms≥43/4级)发生,表明厦门-金门地区构造稳定性介于泉州与南澳岛海外Ms≥7.0级地震的不稳定区之间,为相对较稳定区,适宜建跨海大桥。从地形地貌、工程地质条件显示,桥场地区由花岗岩、变质岩形成的丘陵、红土台地和第四系海陆交互相沉积层所组成。依据场地不同特点与
The site of Xiamen-jingmen bridge which is near Taiwang strait locates in the rapture uplift coastal area of southeast Fujian and the southern part of seismic belt of Quanzhou-shantou, therefore its seismogeological structure environment is unique.
Base on the system study of the materials of geological structure research, geophysics exploration, observation of crustal deformation, geodynamics and engineering site feature in the past 30 years, the fault-block structure at this area uplift intermittent and its uplift velocity is 1-2. 3mm/a, the velocity of seismic energy release is 2. 737-7. 999107jouel/km2/a. The direction of the velocity vector of the modern crustal horizontal movement towards SEE, and its value is 9-13mm/a. It can be inferred from the solve of focal mechanism that the azimuth of main compression stress axis(P axis) is , and its elevation angle is , while the azimuth and elevation angle is and respectively of T axis, and the N axis is almost perpendicular, thus the coastal area of southeast Fujian is strongly compressed by the dynamic force from Taiwan, therefore potential hypocenter area is formed. The earthquake which magnitude is and happened in the sea area near Zhangzhou and Jinmen at one time in history, but there is no destructive earthquake happened in the site of bridge, indicating that the structure stability of the area of Xiamen-Jinmen is between Quanzbou and the instability see area near Nanao island where there was Ms7.0 earthquake happened, so it is a relative stable area and suitable to build great cross-over sea bridge. It can be inferred from the conditions of topography and engineering geology that the site of bridge is mainly formed by the granite, metamorphic rock hills, laterite platform and quaternary interactive marine-continental sedimentary deposit.
The site of Xiamen-jingmen bridge which is near Taiwang strait locates in the rapture uplift coastal area of southeast Fujian and the southern part of seismic belt of Quanzhou-shantou, therefore its seismogeological structure environment is unique.
Base on the system study of the materials of geological structure research, geophysics exploration, observation of crustal deformation, geodynamics and engineering site feature in the past 30 years, the fault-block structure at this area uplift intermittent and its uplift velocity is 1-2. 3mm/a, the velocity of seismic energy release is 2. 737-7. 999107jouel/km2/a. The direction of the velocity vector of the modern crustal horizontal movement towards SEE, and its value is 9-13mm/a. It can be inferred from the solve of focal mechanism that the azimuth of main compression stress axis(P axis) is , and its elevation angle is , while the azimuth and elevation angle is and respectively of T axis, and the N axis is almost perpendicular, thus the coastal area of southeast Fujian is strongly compressed by the dynamic force from Taiwan, therefore potential hypocenter area is formed. The earthquake which magnitude is and happened in the sea area near Zhangzhou and Jinmen at one time in history, but there is no destructive earthquake happened in the site of bridge, indicating that the structure stability of the area of Xiamen-Jinmen is between Quanzbou and the instability see area near Nanao island where there was Ms7.0 earthquake happened, so it is a relative stable area and suitable to build great cross-over sea bridge. It can be inferred from the conditions of topography and engineering geology that the site of bridge is mainly formed by the granite, metamorphic rock hills, laterite platform and quaternary interactive marine-continental sedimentary deposit.
引文
① 国家地震局地球物理所,福建省地震局:厦门高集海峡大桥场址工程地震工作报告,1986。
② 王洪涛、林锦华等人:厦门市地震地质灾害小区划研究报告,闽南示范区震害预测及减灾对策研究,福建省地震局,95-06-02-03Q子专题,2000。
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[2] 王洪涛等人:试论中国东南陆缘活动构造及深层构造性状演化的有序性,第三十届国际地质大 会,福建省地学论文集,福建省地图出版社,1996。
[3] 丁祥焕等人:福建东南沿海活动断裂与地震,福建科学技术出版社,1999。
[4] 强祖基、王洪涛:《活动构造研究》,北京地震出版社,1992。
[5] 王洪涛等人:台湾海峡地质构造及其地震活动研究,中国地震学研究进展,陈运泰主编,北京地震出版社,1997。
[6] 王洪涛等人:闽台地震构造及其地球物理场特征,地壳形变与地震,4(4) ,1984。
[7] 廖其林等人: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) ,1988。
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