Location of a subsurface source using reverse-ray backpropagation

Craig A. Coulombe, Robert R. Stewart

A reverse-ray backpropagation algorithm is used to estimate the location of a subsurface source using the travel times from the source to a spread of surface geophones. The technique involves tracing rays from the receiver through a known geologic model until the time of the ray equals the observed travel tune. The end point of each ray is a possible source position. The mode of all ray end points from many receivers is the source position.

Reverse-ray backpropagation of numerically modeled synthetic travel times resulted in the source position being accurate to +/- 1 m for the 2-D case of a buried source and a line of receivers. Picking travel times from acoustic physical model data resulted in a source estimation accurate to +/- 5 m for a similar geometry.