Seismic transmission tomography a configurative approach
Seismic Transmission Tomography provides a method for direct estimation of velocity distribution in the subsurface from the P- or S-wave first arrival traveltime data. Both the data acquisition configuration and the reconstruction algorithm are equally important in imaging the subsurface lithostratigraphic unit. Out of the three transmission tomographic configurationssurface-to borehole, borehole-to-surface and cross-hole, the latter is ussually used in the transmission tomographic fiels investigation. The present study has two aims: (i) to test the performance of the SimultaneousInterative Reconstruction Technique (SIRT) algorithm coded here, and (ii) to show the necessity of a combined interpretation of the three source-reciver configurations. Using the standard formulations, initial parametrization is possible but not exact solution in terms of the velocity distribution in the subsurface and the location of an anomalous body in the halfspace. The SIRT scheme is found to yield satisfactory estimates of the subsurface from the data acquired by the three configurations. Both the synthetic and actual shear wave seismic tomographic data for the detection of galleries at North Searsole Colliery, Raniganj Coalfields, West Bengal, India, are used for an extensive analysis. The resoults presented in the form of raster images undoubtedly show the effectiviteness of SIRT scheme and also the good resolution acheved by a combined interpretation of the surface-ti-borehole, borehole-to-surface and cross hole omographic data.
bibliogr. 14 poz., rys.