【摘要】 通过在上海地区开展深、浅地震反射、地震宽角反射/折射、高分辨地震折射和大地电磁测深等联合剖面探测,获得了该地区近地表至Moho面的精细速度结构、电性结构和深浅构造关系.结果表明,该地区地壳可划分为上、中、下三个组成部分.其中,上地壳厚为12~14km,波速为5.7~5.9km/s;中地壳厚度约为10km,波速为5.9~6.2km/s;下地壳厚为10~11km,波速为6.2~6.3km/s,Moho面深度约为32km.剖面浅部地质构造复杂,共解释出12条特征明显的断裂.其中,除3条断裂错断结晶基底(G界面)并向下延伸至上地壳底界面外,其他断裂均在深度3~5km以上终止或收敛于G界面之上.此外,仅在剖面西侧基底下部约13~15km埋深处发现一厚度在2km左右的壳内高导层.所以,在综合各方面资料后分析认为,在剖面经过地区不存在发生大地震的深部构造条件,近地表所存在的活动断层是未来产生对该区有影响地震的震源区.更多还原

【Abstract】 The fine seismic velocity structure, electrical conductivity structure and geometrical construction of the crust in Shanghai region and the coupled relationship between the deep and shallow structures are investigated by using multi_geophysics exploration methods, such as shallow seismic reflection, deep seismic reflection, high_resolution seismic refraction, deep seismic wide angle reflection/refraction and magnetotelluric sounding. The research results indicate that the crust in the region can be divided into three layers, namely upper, middle, and lower crust. The upper crust is 12～14km thick with a seismic velocity of 5.7～5.9km/s, the middle crust is about 10 km thick with a velocity of 5.9～6.2 km/s, and the lower crust is 10～11 km thick with a velocity of 6.2～6.3 km/s. The depth of Moho in the region is 31～33 km. There are 12 main faults explained in the experimental profile. Except for three faults, which have dislocated G interface (crystalline basement) and extended down to the bottom interface (whose depth is about 10 km) of the upper crust, the other faults have ended above G interface at 3 to 5 km depth, or have converged at G interface. Moreover, there is only a high conductivity layer (about 2 km thick) within crust at 13～15 km depth. Therefore, there is no deep structure condition for potential big earthquakes in the local region. However, the active rupture zones near the earth’s surface are potential seismic source zone. The experimental profiling is the first high-resolution comprehensive deep survey profile in Shanghai and its conjoined regions.更多还原