摘要
在中国大陆科学钻探孔区 (江苏省东海县南部 )进行了系统的地球物理调查 ,包括二维地震测网和专门的地震剖面 ,大地电磁法和位场方法等 .地震调查表明 ,在超高压变质岩出露区上地壳充满了反射体 ,包括倾斜反射体与上拱的反射弧 .本文介绍大陆科学钻探先行研究中地震调查的成果 .根据大陆科学钻探预先导孔的岩芯和测井资料、井旁VSP和数值模拟结果证实 ,高波速的榴辉岩体、破碎断裂带和大型韧性剪切带都可引起倾斜的地震反射 ,而上拱的弧形反射体则是由近似直立的榴辉岩体和其中的破碎带的综合反映 .由于地壳深部广泛分布着经受变质的岩石 ,上述研究结果对标定地壳中的反射地震信号具有一定意义
Geophysical investigations have been carried out in the Chinese Continental Scientific Drilling (CCSD) site, including 2D seismic reflection, MT, gravity and magnetic surveys. Seismic surveys show that many reflectors, such as dipping reflectors and arch reflectors, occur in the upper crust of the drilling area. This paper shows the seismic results and interpretation of the seismic reflectors. Based on cores and well logging data from an CCSD pre pilot hole, VSP data and synthetic computations, we demonstrate that dipping reflectors can be caused by high velocity eclogite bodies, fractures and ductile shear zones. However, arch reflectors are resulted from steep eclogites plus low velocity fractures. As upper crust usually contains metamorphic rocks, the interpretation should be useful for calibration of deep reflection signals.