SH Seismoelectric Response of a Glacier

Abstract

In this work we derive the analytic solutions to the system of equations modeling, within the framework of Pride's theory, the seismic-to-electromagnetic conversions taking place in a glacial environment. Considering a one-dimensional approach, we set a pure shear horizontal wave seismic source on top of an elastic medium representing the glacier, which overlies a porous medium fully saturated with water, representing the glacier bed. The obtained solutions allow to separately represent and analyze the induced electromagnetic responses, the so called coseismic waves, for both the electric and magnetic fields along with the signals originated at the glacier bottom, the electric interface response, and magnetic interface response. We also propose approximate solutions, useful to be used in a fast inversion algorithm. We analyze the characteristics of the induced electromagnetic signals and their dependence on the type of glacier bed, considering an unconsolidated one and a consolidated one. The main results of the present paper are manifold, on the one hand, the mentioned analytic solutions, on the other hand, that the electric interface response originated at the glacier bottom is proportional to the electric current density at this depth, and depends on textural and electrical properties of the basement. We also showed that the amplitude of the electric interface response is three orders of magnitude higher than the amplitude of the electric coseismic field. This fact reinforces the idea proposed in our previous works that it would be interesting to test shear horizontal seismoelectrics as a possible geophysical prospecting and monitoring tool.