oa Joint inversion of gravity and magnetotelluric data

An emerging field in geophysics is joint inversions that aim to improve the reliability of subsurface modelling (Haber & Oldenberg 1997, Gallardo & Meju 2004 ). Such inversions are where two complementary geophysical data sets are simultaneously inverted to yield a unified model. Individual inversions can produce highly varied models that fit the data equally well. Joint inversions may help to reduce this ambiguity without having to introduce external constraints. The integrated models also allow for more rigorous interpretations.

The difficulty with joint inversion is how to link different data sets. There are two approaches to linking the different data sets, the petrophysical approach and the structural approach. The petrophysical approach links geophysical parameters through rock properties such as porosity. The structural approach is based on the premise that the geological conditions that control changes in one parameter will also affect the other parameter. This means changes in one parameter should coincide with changes in the other parameter.

We look to explore both joint inversion approaches in the first instance by combining gravity and magnetotelluric (MT) data. Both techniques offer cost effective ways of determining the Earth’s subsurface properties. Gravity is already widely accessible and ATT data is being increasingly acquired. This creates many opportunities to apply the inversions.