Electrokinetic and magnetic fields generated by flow through a fractured zone: A sensitivity study for La Fournaise volcano

A number of electric and magnetic signals have been observed on La Fournaise volcano, attributed to electrokinetic effects. A simple model is proposed here to check this hypothesis. The volcano is idealized as a 2d heterogeneous structure composed of a fractured zone located between two porous zones through which meteoritic waters flow downwards; flow occurs predominantly in the fractured zone and induces electromagnetic fields. Correct orders of magnitude are obtained for the measured surface fields. The importance of the heterogeneous character of the underground medium is demonstrated; local measurements of various quantities are recommended.