Multi-electrode Resistivity Surveys around the Hot Lakes of the Waimangu Geothermal Area, NZ

Abstract

We conducted a series of multi-electrode surveys around the Waimangu thermal area, using 1.26 km of cable with 20 m electrode spacing. A Wenner configuration gave the most consistent results, producing a detailed image of the electrical resistivity in the top 200 metres.

There were very low resistivity zones under active thermal areas, including the Warbrick Terrace-Iodine Pool area, Raupo Pond, Inferno Crater, Frying Pan Lake, which had the largest and deepest low resistivity zone, and South Crater. Surface low resistivity areas were globally well correlated with high 1 metre ground temperatures and high CO2 fluxes.

We repeated a profile past Inferno Crater 7 days later, and could see resistivity changes near the crater, indicating fluid movement associated with the cycling of Inferno Crater, which was overflowing during the first survey, but was a couple of metres lower by the time of the second survey.