Determination and sensitivity analysis of the seismic velocity of a shallow layer from refraction traveltimes measures

Abstract

In this paper, we are interested in determining the seismic velocity of ashallow under-ground layer from refraction traveltimes measures. Wepresent a study case taken from an experimental seismic survey. The studycase is a wide-angle seismic inversion using experimental traveltimesmeasures and based on ray tracing technique and genetic algorithms. Thehypothesis on the velocity distribution, coming from the seismicexperiment, makes the computation of some seismic rays expensive intime. We propose to reduce the computations time by introducing aformulation of the inverse problem that avoids such costly rays, hence theinversion becomes feasible.Also we present a sensitivity analysis based on a singular valuedecomposition of the jacobian of the traveltimes with respect to velocity.We give the relationship between the traveltimes measure errors and thevelocity estimation error. We discuss the advantages of this method overthe classical one based on the resolution matrix.