The matching method is used to analyse the scattering of elastic waves by a structural defect made up several atomic chains surmounting an infinite lattice plane. The vibrational dynamics of the structure is considered within the harmonic approximation framework. The propagating continuum associated to the two vibrational eigenmodes of the perfect lattice is determined and discussed. The localised states induced by the defect are calculated and analysed for heavy and light adatom masses. Their interest appears during the investigation of the diffusion spectra. These localised states allow the interpretation of some observed structures in terms of Fano resonances. It is shown that the resonance number decrease in transmission spectra of light adatom case. The Fano resonances can be absent in the transverse mode, but are always present in the longitudinal one. Their position shifts slightly towards the high frequencies when the number N of perturbating chains increases. When N is higher than the unity, oscillations of Fabry-Perot type appear in the transmission spectra. The number of these oscillations is directly related to the number of adatomic linear chains, in the light and heavy mass cases, in both eigenmodes. We also observe the existence of zeros transmission in the spectra. Because of the large size of the dynamical matrices and complicated graphical resolution spectra, we have limited our study to eight perturbating adatomic linear chains.