def get_mean_and_stddevs(self, sites, rup, dists, imt, stddev_types):
        """
        See :meth:`superclass method
        <.base.GroundShakingIntensityModel.get_mean_and_stddevs>`
        for spec of input and result values.
        """
        mean = self._get_mean(sites, rup, dists, imt, stddev_types)
        stddevs = [np.ones(len(dists.rrup))*get_sigma(imt)]
        return mean, stddevs