3-D Modelling of the Electrical Resistivity Structure of Mount Ruapehu

Abstract

This thesis describes the Magnetotelluric survey undertaken on Mount Ruapehu in 2005. The aim of the survey was to extend the geographical coverage to the southwest of the mountain, to confirm the integrity of previous MT measurements, and to investigate the resistivity structure of Mount Ruapehu through the use of 3-D modelling. The structural background to the area is described along with a review of previous surveys performed around Mount Ruapehu. These surveys are compared with more general geophysical evidence regarding the underlying structure of the Taupo Volcanic Zone to derive evidence for specific structural features beneath Mount Ruapehu. The theory underlying the magnetotelluric method and its relevance to the current work is briefly described. The document then goes on to describe the current magnetotelluric survey, including the measurement process, the data processing undertaken, the consequent 1-D modelling of the data and its structural interpretation. The concept of 3-D modelling, plus the assumptions and simplifications introduced is outlined, along with the initial attempts at establishing an early model. The model development lifecycle is then described, which includes both shallow structure stabilisation within the model and attempts to fit longer period data to the model.