def _get_mean(self, C, mag, rake, dip, rrup, rjb):
        """
        Return mean value (eq. 1, page 319).
        """
        f1 = self._compute_magnitude_scaling(C, mag)
        f2 = self._compute_distance_scaling(C, mag, rrup)
        f3 = self._compute_faulting_mechanism(C, rake, dip)
        f4 = self._compute_far_source_soil_effect(C)
        f5 = self._compute_hanging_wall_effect(C, rjb, rrup, dip, mag)

        mean = (
            C['c1'] + f1 + C['c4'] * np.log(np.sqrt(f2)) + f3 + f4 + f5
        )

        return mean
Return mean value (eq. 1, page 319).