A magnetometer array experiment in New Zealand

Abstract

An array of three-component magnetometers recording at 1-min intervals was operated throughout New Zealand between November 1991 and April 1992. Typical station spacing was 150 km, but along six lines of stations across the South Island the typical station spacing was 50 km. Transfer functions were computed for 34 sites. The resulting induction arrows show the predominance of the geomagnetic coast effect, with channelling of electric current through Cook Strait having a strong local effect. A thin sheet numerical model confirms that the coast effect predominates, and differences in the overall responses in the North Island and in the South Island suggest the presence of induction effects associated with structural features underlying the New Zealand land surface. It is evident that the effects of such features are small compared to the coast effect and that the model needs to cover a larger area and to include more detailed bathymetry in order to clearly resolve structural features.