关键词: 复杂介质结构, 活断层探测, 哈格多恩原理, 折射波前成像, 福州

Abstract: In urban active fault prospecting, the shallow structures usually display strong lateral inhomogeneity, appearing as the heavy fluctuation of interfaces and considerable variation of layer velocities. In this case, the traditional refraction data processing and interpreting methods based on homogeneous layered structures with level interfaces can't be directly applied to the prospecting. It is very important, therefore, to study the seismic behaviors in these complex structures and to deve~lop a new technique that can be used to process and interpret seismic refraction data obtained from urban areas. In this paper, forward computing of wave field is carried out by using wavefront expanding method in terms of Huygens' principle. Furthermore, in the light of Hagedoorn wavefront refractor imaging principle a new processing method of seismic refraction data and the corresponding interpretation software are developed, in which Hole's original finite-difference codes were modified with Lecomte's five operators for computing seismic travel times. Applying this technique, we successfully process the data from two refraction profiles recently completed in Yixu, Fuzhou City during urban buried fault prospecting. The results show that the shallow structures in the investigation area display three layers, which are sedimentary cover, strongly weathered layer and bedrock, respectively. The buried depth of the upper surface of bedrock ranges from 52m to 58m or so. The variation of P wave velocity in sedimentary cover is considerable.

Key words: complex structures, active fault prospecting, Hagedoorn principle, refractor wavefront imaging, Fuzhou City