GRAVITY ANOMALIES OF A FAULT CUTTING A SERIES OF BEDS

Abstract

The gravity anomaly due to a single horizontal semi‐infinite block terminated by a vertical or dipping fault has been discussed by several authors previously. Geldart, Gill, and Sharma (1966) gave a new and simple expression for calculating the gravity anomaly due to a block cut by an inclined fault at an arbitrary angle and used this expression to obtain the gravity anomaly due to a fault cutting a single bed. In their derivation the effects of both the upthrown and the downthrown blocks were taken into consideration. It is, however, only in the unusual situation that faults cut a single bed of uniform density. More often, faults cut a series of beds of different densities and thicknesses. If the densities and the thicknesses of the various beds differ greatly, an interpretation based upon replacement of the series of beds by a single bed of uniform density may be highly erroneous. Starting from the single block expression given by Geldart et al, an expression can be derived giving the gravity anomaly due to a fault cutting a series of beds having different densities and thicknesses.