A comprehensive system for interpreting seismic-refraction arrival-time data using interactive computer methods

Abstract

A set of interactive computer programs are described whose purpose is to calculate velocity and depth models from refraction arrival-time data. The intent is to arrive at one or more such models which, if reinverted into travel times will satisfy the initial data to within the limits of reading accuracy. Three main programs, in the form of subroutines, have been written to accomplish this. One program, named RECIP, calculates depths and velocities of a refracting horizon from reversed arrival-time data given a velocity distribution for the overlying layers. Another program, named GRIT, calculates depths of a refracting horizon from unreversed arrival-time data given a velocity distribution in the overlying layers and an assumed velocity distribution of the refracting horizon. The third program, called RAYTRACE, calculates arrival-time data points for the refracting horizons of a velocity model from assumed shotpoint locations and depths. Numerous other subordinate subroutines are included for manipulating and extending data, inserting hidden layers and otherwise varying the velocity distribution so that any legitimate arrival-time data set can be analyzed and will yield valid results. In addition, a section on manipulating input data to provide an internally consistent set of plots, and also a section on theory are included. Numerous example problems are provided.