def METHOD_NAME(region, vs30):
    """
    Returns the z1.0 normalisation term for Japan (equation 12)
    """
    return (-5.23 / 2.) * np.log(
        (vs30 ** 2. + 412.39 ** 2) / (1360.0 ** 2. + 412.39 ** 2.)) -\
        np.log(1000.0)