A magnetotelluric study of the Alpine Fault, New Zealand

Magnetotelluric soundings have been made at seven locations on a 4 km profile crossing the Alpine Fault in the South Island of New Zealand. The 'distortion' techniques of Groom & Bailey (1989) and Lilley (1998 a,b) have been used to derive regional apparent resistivity and phase curves that correspond to electromagnetic induction in orientations parallel and perpendicular to the fault. 2-D inversion of the regional responses reveals that a narrow (<1 km wide) conductive zone is associated with the Alpine Fault. This conductor is most probably related to the heating of deep circulating meteoric water in a region in which enhanced temperatures occur at shallow depth due to the tectonic uplift of the Southern Alps.