Inversion of marine MMR data

摘要

The magnetometric resistivity (MMR) is an electromagnetic (EM) exploration method that has been successfully used for investigation of electrical resistivity tructures of the sea-floor. Because of unique characteristics associated with this method, there are some practical problems still need to be addressed. For example, transmitters and receivers are often located at different depths due to the bathymetry of the sea-floor or because of convenience of data acquisition. This geometry difference can have a significant effect on the measured data and ignoring it, as has often been done, can lead to marginalized interpretations. In addition, for logistical reasons, many more vertical transmitters (electric bipoles) than receivers (magnetometers) are generally deployed in a field survey. Consequently, it is much more effcient to use the generalized reciprocity (or adjoint) formulation in both 3-D forward modelling and inverse problems. In this presentation we: (1) quantify the effect of T_x-R_x geometry differences; (2) derive a new apparent resistivity formula, which is better than other two commonly used ones; (3) invert marine MMR data using the adjoint formulation for forward modelling.