地质雷达在活动断裂研究中的应用

Application of Ground Penetrating Radar in the Study of Active Faults

对于快速发生沉积和侵蚀的地区,断裂附近的古地震遗迹会很快被掩埋。获取这些地区断裂的位置、上断点的埋深和标志层的断距等方面的数据至关重要。本文利用地质雷达探测技术探测这些被埋藏的古地震遗迹。以北京平原区正断性质的新夏垫断裂和青藏高原东北缘六盘山地区逆冲性质的六盘山东麓断裂为实验区。通过探测发现,对于断裂两侧地表覆盖层主要为粉土或粉质粘土的新夏垫断裂,地质雷达可精确定位断裂通过的位置,指示上断点的埋深,但无法在地质雷达剖面上识别出各套地层。对于在T1基座阶地上通过的六盘山东麓断裂,地质雷达不但可以精确定位断裂的位置,而且可以在地质雷达剖面上识别出各套地层,进而求得断裂两侧基座的断距。

For some areas where sedimentation and erosion complete are at fast rates, marks of paleoearthquakes on faults may be buffed below the surface. However, it is important to know the location, displacement and other aspects of the fault. We apply ground penetrating radar （GPR） technology to investigate the buffed traces of a paleoearthquake. We choose the new Xiadian fault which is a normal fault located in Beijing Plain, and the eastern Liupanshan piedmond fault which is a reverse fault located in the northeastern margin of the Tibetan Plateau as two experimental areas. We found that, at the site of the new Xiadian fault which is mainly covered by silt or silty clay, the GPR can accurately detect the location and the depth of the breakpoint of the new Xiadian fault, but it cannot image layers at the each side of the fault. At the site of the eastern Liupanshan piedmond fault where the fault cut the basement of a T1 river terrace, the GPR can not only accurately located the fault, but also image layers at the both sides of the fault, thus we could obtain the fault displacement of the basement of the T1 river terrace.