Computer modelling of geomagnetic anomalies associated with block-faulting

Abstract

The finite element method was used in a computer model to calculate stress distributions in a segment of the upper crust responding to dip-slip movements on a buried vertical fault. This structural style is characteristic of block-faulting. Based on the theory of the piezo-magnetic effect, changes in the local geomagnetic field associated with stress-induced changes in rock susceptibility and remanent magnetization were simulated. Model results show that regions of uplift and subsidence are marked by positive and negative magnetic anomalies respectively, while the amplitudes are controlled by the magnitude of the displacements on the basement fault. This result is important because of its bearing on the interpretation of some components of geomagnetic anomalies in terms of crustal movements, especially in tectonically active parts of the Earth.