def _compute_distance_scaling(self, rjb, C):
        """
        Compute distance-scaling term (Page 141, Eq 1)
        """
        # Calculate distance according to Page 141, Eq 2.
        rdist = np.sqrt((rjb ** 2.) + (C['h'] ** 2.))
        return C['B5'] * np.log(rdist)