def _compute_geometric_decay_term(self, C, mag, dists):
        """
        Compute and return geometric decay term in equation 3,
        page 970.
        """
        c1 = self.CONSTS['c1']
        return (
            (C['b4'] + C['b5'] * (mag - c1)) *
            np.log(np.sqrt(dists.rjb ** 2.0 + C['b6'] ** 2.0))
        )
Compute and return geometric decay term in equation 3,
        page 970.