High definition 3D seismic refraction tomography to image underground voids and it´s application

A method for 3-D seismic refraction tomography is presented. We have applied a new approach for processing 3D seismic refraction data using waveform modeling to image underground pipes using short channel spacing. This approach successfully obtained accurate high definition 3D ground model. More than 10 surveys were done to image underground pipes and voids. The purpose of this study is to test the ability of a true 3D refraction tomography algorithm using short (1.5´) channel spacing to characterize the subsurface.The pipe´s types range from concrete wall water pipes, aluminum pipes for electrical wires and PVC water pipes. The true 3D waveform refraction tomography algorithm is based on numerical modeling using the discrete element method and finite difference interpolation. Inversion was calculated simultaneously in three dimensions to obtain true 3D tomography. 3D models of imaged subsurface were generated revealed pipes´ locations, shapes and sizes. The pipe walls and the center void volume are clearly distinguished in the 3D model. Results from the field application are presented and show the high accuracy and the benefit of assessing seismic refraction data using the true 3D approach.