code: def get_mean_and_stddevs(self, sites, rup, dists, imt, stddev_types):
          
          mean, stddevs = super().get_mean_and_stddevs(
              sites, rup, dists, imt, stddev_types)
          x_vf = _get_min_distance_to_volcanic_front(sites.lon, sites.lat)
          mean = _apply_volcanic_front_correction(mean, x_vf, rup.hypo_depth, imt)
          return mean, stddevs
docs: Implements equation 3.5.1-1 page 148 for mean value and equation
          3.5.5-1 page 151 for total standard deviation.
  
          See :meth:`superclass method
          <.base.GroundShakingIntensityModel.get_mean_and_stddevs>`
          for spec of input and result values.