用高分辨率地震技术研究活动断层

基于重大工程前期区域工程地质勘查的需要,在华北平原北部XY地区进行了一次高分辨率P波三维地震和S波二维地震描述、刻画地下活断层的试验研究,取得了本地区浅、中、深不同深度的地震成果。其中F1断层是该区一条重要控制断层,其重、磁、电资料虽有微弱显示,但位置不准确,难以对其活动性进行评价。经过本次综合勘探后,落实了该断层的存在,并发现该断层在工区范围内的中部分裂成F1-1及F1两条断层,F1-1、F1断层在平面上呈北东向“Y”字型展布,断距在纵、横向都呈现显著的分段特征,其断距最小90m,最大可达300m。该次勘探所获纵波反射主频达120～150Hz,活动断层地震成象十分清楚。可见高分辨率三维地震与超浅层横波反射地震相结合,可有效评价活动断层,为防震减灾工程研究提供可靠信息。

Active Fault Investigation through High Resolution Seismic Prospecting Technology

Based on the requirement of major engineering projects regional engineering geological exploration, carried out a high resolution P wave 3D seismic and S wave 2D seismic prospecting to describe and depict underground active fault experimental investigations in XY area, northern North China Plain, have gotten prospecting results from different depths of shallow, medium and deep. In which, F1 is a major controlling fault in the area, although it has feeble presentations on gravitational, magnetic and electric prospecting data, but its position is out of true and hard to estimate its activity. After this integrated prospecting, its existence is ascertained and found the fault has split into F1-1 and F1 two faults in the middle of working area and showing ＂Y＂ type NE extending on plane. Longitudinally and transversally the fault throw has presented sectional characteristics with its minimum throw 90m and maximum 300m. Obtained prospecting compression wave reflection dominant frequency 120-150Hz, seismic image of the active fault is very clear. Thus the combination of high resolution 3D seismic prospecting and ultra-shallow shear wave reflection seismic prospecting can judge of active fault effectively and provide reliable information for precautions against earthquake and disaster mitigation researches.