APPLICATION OF SEISMIC INTERFEROMETRY IN SURFACEWAVE VELOCITY ANALYSIS

Abstract

The naturally occurring waves from passive sources like winds, sea waves or natural earthquakes can be used as a source of vibrations rather than deploying destructive explosive for generating seismic waves. Seismic interferometry uses the background noise as a signal which was earlier considered as undesirable noise in the conventional approach. The idea behind seismic interferometry is to cross-correlate the responses at stations for the purpose of Green’s function retrieval. We have numerous of existing method for imaging the subsurface but they have few drawbacks like: we have to be attentive regarding the data stationarity, no theoretical justification regarding the wavelet characteristic is available. Majority of these drawbacks can be tackled using seismic interferometry. But seismic interferometry has its own demerit and one among them is the occurrence of non-physical reflections. The only way to solve this issue is to carryout convolution in source-receiver interferometry (SRI). But at times non-physical reflections can be used for obtaining primary reflections and internal multiples. These can also be used to estimate interval velocities and thickness of subsurface layers provided we carry out convolution with physical reflections. Source receiver interferometry has been found to give better estimate of inter receiver Green’s function compared to cross-correlation or cross-convolution interferometry. Using this approach, the surface wave velocity in a seismically quiescent region of the Northern Himalaya, lying in the state of Jammu and Kashmir, India is estimated in this work.