1. A method for characterizing a subsurface formation, comprising the steps of: disposing within a borehole a logging instrument equipped with at least first transmitter and receiver antennas spaced apart by a first distance, at least one of the first antennas having a tilted magnetic dipole with respect to the longitudinal axis of the instrument, the antennas being oriented about the axis of the logging instrument such that the at least one tilted magnetic dipole corresponds to a first azimuthal angle; azimuthally-rotating the logging instrument within the borehole; while the logging instrument is rotating, activating the first transmitter antenna to transmit electromagnetic energy into the formation; while the logging instrument is rotating, directionally measuring the first voltage signals associated with the transmitted electromagnetic energy using the first receiver antenna, as a function of the azimuthal orientation of the logging instrument, so as to determine the azimuthal variation of the measured first voltage signals; and fitting the azimuthal variation of the measured first voltage signals to approximate functions.