A flexible algorithm for seismic refraction interpretation using program REFRACT

Abstract

AbstractREFRACT is an interactive seismic refraction interpretation software package, based on the Reciprocal and Intercept Time methods, developed by the Roads and Traffic Authority of New South Wales (Australia). REFRACT operates in graphic and spreadsheet displays on PCs and preserves much of the flexibility of manual methods. The power of REFRACT lies in its treatment of a seismic line as a single data set, combining overlapping segments and handling lateral velocity changes in all layers, and in its optimization of manual interpretation operations. After entry of first arrival times the T-X data may be checked and edited for shot depth and reciprocal times. Interpretation includes operations such as parallelism testing and layer labelling (Segmentation) on the T-X graph, Phantoming of overlapping segments, minus times Velocity Analysis, automatic Thickness Calculation and edits to the interpreted section. The interpretation stages employ a number of optimization routines that may be applied with default settings or may be reset and manipulated for close control of the interpretation process over part or all of the T-X data set. The Distance Range is a fundamental concept in REFRACT that controls the application of the Reciprocal and Intercept Time methods for the calculation of time depths, intercept times and harmonic mean velocities. REFRACT provides a new standard for seismic refraction interpretation.