The hidden layer in seismic prospecting

Abstract

One condition which has to be fulfilled in seismic-refraction prospecting is an increasing velocity distribution. But even if this condition is met, one intermediate layer may pass undetected. When such a situation occurs, with a hidden layer, it can give rise to considerable errors in the depth determination. The problem here is that the hidden layer is impossible to detect when only the first arrivals are used in the interpretation. In this work, sets of curves are given for a three-layer case which clearly show the maximum thickness of a hidden layer for a given velocity distribution and also show the maximum error which can occur when an intermediate layer passes undetected.