摘要
采用深、浅地震反射和钻孔地质剖面相结合的探测方法,对太行山东缘汤阴地堑的地壳结构和隐伏活动断裂进行了研究.结果表明,该区地壳厚度约36～42km,莫霍面从华北平原区向太行山下倾伏.汤阴地堑是一个受汤东断裂控制的半地堑构造,其基底面形态与莫霍面展布呈"镜像"关系.汤东断裂是1条继承性的隐伏活动断裂,该断裂向上错断了埋深约20m的中更新世晚期地层,向下延伸至上地壳底部.综合分析深地震反射和已有深地震宽角反射/折射剖面结果,发现深地震反射剖面上的中-下地壳强反射层和壳幔过渡带反射,与深地震宽角反射/折射剖面上出现的中-下地壳正负速度梯度变化层有着较好的对应关系,这表明本区中-下地壳和壳幔过渡带可能为一系列速度递变层或高低速物质的互变层,埋深约15～16km的强反射带为上地壳与中-下地壳的转换带,壳幔过渡带的底界为地壳与地幔的分界.研究结果为深入理解该区的深部动力学过程、分析研究深浅构造关系、评价断裂的活动性提供了依据.
We used a method combining deep/shallow seismic reflection and drilling geological section to explore the crustal structure and buried active faults of the Tangyin graben in the eastern margin of Taihang mountain.The results show that the Moho dips from North China Plain to Taihang mountain,which corresponds to a depth ranging from ～36 to ～42 km.Tangyin Graben is a half-graben structure,which is controlled by Tangdong fault and its basement morphology has an apparent mirror image relationship with Moho interface.Tangdong fault is an inheritance buried active fault,which breaks the late Mid-Pleistocene stratum with burial depth of 20 m and extends downward to bottom of upper crust.According to synthetic analysis of coincident deep seismic reflection and wide-angle reflection/refraction data,we find the prominent reflector from middle-lower crust and the strong reflector associated with crust-mantle transition zone in coincident deep seismic reflection profile,obviously corresponded with the positive and negative velocity gradient variation belt in deep seismic wide-angle reflection/refraction profile.This result indicated a series of velocity gradation layers or high and low velocity alternative layers exhibited in middle-lower crust.The strong reflection belt at the depth approximately 15～16 km is an transition zone between upper crust and middle-lower crust,and the bottom of crust-mantle transition zone is the boundary between crust and upper mantle.The result provides the evidence for understanding the deep dynamic processes,further research of the relationship between shallow and deep tectonics,and assessment of fault activity.
出处
《地球物理学报》
SCIE
EI
CAS
CSCD
北大核心
2012年第10期3266-3276,共11页
Chinese Journal of Geophysics
基金
中国地震活动断层探察-华北构造区项目(200908001)
河南安阳市活断层探测项目共同资助
关键词
汤阴地堑
深地震反射剖面
浅层地震勘探
钻孔地质剖面
地壳结构和构造
Tangyin graben
Deep seismic reflection profile
Shallow seismic exploration
Drilling geological section
Crustal structure and tectonics
