def incremental_a_value(bval, min_mag, mag_inc):
    '''
    Incremental a-value from cumulative - using the version of the
    Hermann (1979) formula described in Wesson et al. (2003)

    :param float bval:
        Gutenberg & Richter (1944) b-value

    :param np.ndarray min_mag:
        Minimum magnitude of completeness table

    :param float mag_inc:
        Magnitude increment of the completeness table
    '''
    a_cum = 10. ** (bval * min_mag)
    a_inc = a_cum + np.log10((10. ** (bval * mag_inc)) -
                             (10. ** (-bval * mag_inc)))

    return a_inc
Incremental a-value from cumulative - using the version of the
    Hermann (1979) formula described in Wesson et al. (2003)

    :param float bval:
        Gutenberg & Richter (1944) b-value

    :param np.ndarray min_mag:
        Minimum magnitude of completeness table

    :param float mag_inc:
        Magnitude increment of the completeness table