Percolation in the crust derived from distortion of electric fields

Abstract

Fractal crack distributions in the crust have been discussed in the context of earthquake cycles, fluid percolation, and the electrical conduction mechanism. With the impedance matrix rotation analysis in magnetotellurics (MT), a special type of apparent amplification of variational electric fields in one horizontal direction was detected. Here a possible link between crustal fracture networks and MT distortion is suggested. It is shown that the strong electric field amplification can be explained with a very heterogeneous crack network which in one direction stays in the vicinity of the percolation threshold. The apparent similarity to fluid percolation models does not automatically support the fluids paradigm, but rather allows for a choice between present fluid percolation and ‘paleopercolation’ to be the origin of the conductivity structure. In the latter model, the fluid caused the precipitation of graphite which now forms a partly interconnected network.