TRANSIENT ELECTROMAGNETIC RESPONSES IN SEA-FLOOR WITH TRIAXIAL ANISOTROPY

Electrical anisotropy of young oceanic crust at mid-ocean ridges is de tectable by observation of the rate and geometry of the diffusion of e lectromagnetic fields. The anisotropy in electrical properties arises from the presence of conductive seawater in an interconnected network of mostly ridge-parallel cracks. Tn this paper, we first justify the c hoice of a triaxial model to represent young oceanic crust, with three distinct electrical conductivities in the vertical, strike and spread ing directions. We then present an algorithm to calculate the transien t electromagnetic responses generated by an electric dipole source ove r such a triaxially anisotropic seafloor, We show that if the transien t passages are measured with three distinct electric dipole-dipole con figurations, it is possible to discern all three unknown conductivitie s independently of each other.