TELLURIC ANOMALIES CAUSED BY SHALLOW STRUCTURES: ELLIPSOIDAL APPROXIMATIONS

An analytical solution for the electric field near an ellipsoid immersed in a semiinfinite medium is obtained to estimate the effect of shallow structures on telluric measurements. The determinant J of the Jacobean, which transforms telluric field from base to roving stations, may change across the boundary of different media by a factor equal to their resistivity ratio. At distances beyond one length of the intermediate axis from the edge of the ellipsoid, both the J-anomaly and the polarization of the normalized telluric field become negligible.