SUBSURFACE EVALUATION OF THE NEW SOHAG CITY SITE USING SEISMIC REFRACTION TECHNIQUE

Tomographic traveltime inversion of seismic compressional P wave data is used to delineate subsurface geology of the shallow sedimentary secession at the New Sohag City Site. The inversion method is based on a local approximation of the real velocity cross-section by homogeneous functions of two coordinates. Eight seismic refraction profiles were measured to cover the study area. The interpretation technique was applied to the obtained data of the traveltime curves of the first arrivals. Seismic velocity field models, structural sections and, consequently geoseismic velocity sections were constructed. The interpreted models resolved four seismic zones in some areas with velocities ranging from <800 to >3200 m/s. Moreover, some lateral differentiation in the velocity gradient is observed within most of the resolved zones. This may be related to lithologic variation which indicat the highly heterogeneous 3-D medium. In addition, minor faults or fractures remarked in some places in the structural sections. The resultant velocity models were found to be compatible with knowledge supplied by previous geological, geophysical work and the nearest borehole data.