VELOCITY IMAGING OF THE NEAR-SURFACE STRUCTURES BY DIVING-WAVE TOMOGRAPHY, DIVING-WAVE PENETRATION CORRECTION AND CONVENTIONAL REFRACTION ANALYSES

In this paper, seismic refraction data obtained along a single profile was used to construct a velocity image and to build up a velocity model beneath it by applying different approaches. The simplest one is the conventional refraction analysis or layer refraction which assumes an average constant velocity value for each layer. The second approach is the diving-wave tomography or refraction tomography that has been applied for velocity imaging along the same profile assuming a linear continuous increase of velocity with depth. The third algorithm is the application of the diving-wave penetration correction and construction of a velocity image for the constant velocity soil layer and the vertical velocity gradient bedrock. A comparison between the results of these three approaches has been carried out to show the velocity concurrence of their images.
Velocity-depth model curves have also been established to reflect the linear increase of the velocity with depth. A rapid velocity increase with depth within the shallower part of the vertical velocity gradient limestone bedrock followed by a smaller velocity gradient at greater depths can be noticed. Finally, seismic parameters have been calculated for estimation of the rock material quality of the vertical velocity gradient bedrock. It is concluded that an intensively or completely weathered shallower part of the limestone bedrock exists which is confirmed by the drilling results.