code: def _compute_imt1100(self, imt, sites, rup, dists):
          
          vs30_1100 = np.zeros_like(sites.vs30) + 1100
          vs30_star, _ = self._compute_vs30_star_factor(imt, vs30_1100)
          C = self.COEFFS[imt]
          mean = (self._compute_base_term(C, rup, dists) +
                  self._compute_faulting_style_term(C, rup) +
                  self._compute_hanging_wall_term(C, dists, rup) +
                  self._compute_top_of_rupture_depth_term(C, rup) +
                  self._compute_large_distance_term(C, dists, rup) +
                  self._compute_soil_depth_term(C, imt, sites.z1pt0, vs30_1100) +
                  # this is the site response term in case of vs30=1100
                  ((C['a10'] + C['b'] * self.CONSTS['n']) *
                  np.log(vs30_star / C['VLIN'])))
  
          return mean
docs: Compute and return mean imt value for rock conditions
          (vs30 = 1100 m/s)