Regionalization of global electromagnetic induction data: a theoretical model

Systematic differences are noted between those global response functions (Q = I₁/E₁; $\text{W}\text{= Z/H}$) derived from single observatories and those derived from global averages. Using a simple first-order model to simulate global scale lateral heterogeneities, we argue that reasonable differences in the depth to the conductosphere (d (average) = 400 km in one hemisphere, 600 km in the other) result in significant differences in the response functions at single observatories. These differences appear to be easily resolvable within the expected error-bars of actual observations. At this point it is believed that regional differences in global response parameters can indeed be used to infer large-scale differences in the depth to the conductosphere, providing that systematic biases introduced in data processing and interpretation are minimized.