Electrical Imaging of Shallow Geothermal Aquifers Using Fixed Loop TEM Soundings in the Otumuheke Spring Area, Taupo, New Zealand.

Abstract

Delineating potential fluid pathways of geothermal fluids through near-surface geological strata can help to provide a better understanding of the interaction between geothermal fluids and shallow groundwater aquifers. It can also help explain the presence or absence of surface geothermal features and potential sub-surface hydraulic links between groups of surface features.

The fixed loop transient electromagnetic (TEM) method was used to map the near-surface (less than 200 m) electrical structure in detail around the Otumuheke Spring area, Taupo, New Zealand. The vertical component of the TEM signal was modelled in 1-D for 308 sites. The resulting 1-D electrical cross-sections compare favourably to existing conceptual models and to available geological data. They provide an insight into the possible pathways of the source fluids for some geothermal surface features through the near-surface strata in the Otumuheke Spring area.