The Polarization of Micropulsations and Geo-electric Structure

Abstract

Summary A study is made of how electromagnetic induction in crustal conductivity anomalies affects the observed polarization characteristics of micro- pulsations. Use is made of a new linear technique of modelling conductivity anomalies in the Earth. This technique allows any curved interface between two layers of different conductivity to be modelled by using Fourier composition of solutions for a sinusoidal interface. Two particular models are studied, one representing a sedimentary basin on the surface and the other a buried fault. It is found that the polarization characteristics of long-period pulsations (>100 s) are only slightly affected by both models. However, although the buried anomaly has little effect on the polarization of medium- and short-period pulsations (< 100 s), anomalies near or on the surface can change their polarization characteristics considerably. It is concluded that more care should be taken in the siting of geomagnetic observatories and in the interpretation of micropulsation data.