  The magnetotelluric approximation of the Maxwell's equations is used to model
the propagation of low frequency electro-magnetic waves in the Earth's
subsurface, with the purpose of reconstructing the presence of mineral or oil
deposits. We propose a classical Schwarz method for solving this
magnetotelluric approximation of the Maxwell equations, and prove its
convergence using maximum principle techniques. This is not trivial, since
solutions are complex valued, and we need a new result that the magnetotelluric
approximations satisfy a maximum modulus principle for our proof. We illustrate
our analysis with numerical experiments.
