Inversion of Explosive Source Land Seismic Data to Determine Source Parameters

Abstract

Summary I present a new method to estimate the source time functions of explosion source seismic data, using a modified acquisition method. Two shots of different size are fired into the same geophone spread with source-receiver geometry arranged such that the Green’s functions are essentially the same. The spectral ratio of corresponding seismic traces is then the spectral ratio of the source time functions. A corresponding synthetic ratio filter is calculated from Blake’s explosion source model for the sources within each pair. Each modelled source is defined by five parameters: the minimum radius of the elastic zone, the internal pressure at this radius, the density of the rock, and two elastic constants for an isotropic rock, the P-wave velocity and Poisson’s ratio. A grid search finds the source parameters that minimise the difference between the measured and synthetic filters for each source pair, thus yielding the two source time functions, but not their absolute amplitudes. Deconvolution of the shot records within each pair for the minimum-phase source time functions recovers the estimated earth impulse response gathers, convolved only with the response of the recording system.