Utility of Seismic Tomography in Site Characterization

Seismic tomography is fast emerging powerful and smart tool in site characterization. It is helpful in providing detailed information about the soil and rockmass properties. Assessment of rockmass quality is utmost important in planning and excavation of caverns as well as foundations in Hydroelectric Projects.

Seismic tomographic scanning of a section gives rise to a point-to-point reconstruction of seismic velocities in the scanned area, which can be interpreted in terms of geological structures. This can also be utilized for precise in-situ determination of both compressional and shear waves seismic velocities, rockmass quality assessment, computation of dynamic elastic parameter, demarcation of bedrock configuration and also for defining subsurface geological status and disposition of the strata.

The paper includes brief outline of seismic tomography and three case studies related to dam seat scanning, delineation of rock overburden interface and determination of in-situ engineering properties of rockmass respectively. In first case study the dam seat area was scanned for confirmation of absence of apprehended fault The second case study demonstrates the usefulness of the technique in delineation of rock – overburden interface & rockmass characteristics. In the third case study depth wise rockmass parameters of dam seat were estimated.