Self-Potential and Audio-Magnetotelluric Survey in White Island Volcano

Abstract

A Self-potential survey and a audio-magnetotelluric survey were carried out in White Island volcano, New Zealand. SP anomalies of positive polarity are present over the active geothermal features where upflow must take place. Negative SP anomaly overlies the centre of the eastem subcrater and the north-eastem half of the central subcrater, where subsurface downflow could exist. The SP distributions observed in 1993 and 1996 are almost similar, except for the area close to the 1978/90 Crater Complex due to a change in volcanic activity. We assume there is a volcano-hydrothemal system beneath the Main Crater floor, which supplies upflow to thermal features along the edge of the subcraters. The audiomagnetotelluric data suggests altered clay layers at the surface and very conductive layer comparable to sea-water resistivity in the eastern subcrater. This layer suggests sea hydrothermal water in the volcano-hydrothermal system.