Abstract. Landslide phenomena involve the northern coast of Malta, affecting in particular the urban area of Xemxija. Limestones overlying a clayey formation represent the shallower lithotypes that characterize the surficial geology of this area, where lateral spreading phenomena and rockfalls take place.Ambient noise records, processed through spectral ratio techniques, were analysed in order to characterize the dynamic behavior of the rock masses affected by the presence of fractures linked to the landslide body existing in the area. Experimental spectral ratios were also calculated after rotating the horizontal components of the seismic signal, and a direct estimate of the polarization angle was also performed in order to investigate the existence of directional effects in the ground motion.The results of the morphologic survey confirmed the existence of large cliff-parallel fractures that cause cliff-edge and unstable boulder collapses. Such phenomena appear connected to the presence, inside the clay formation, of a sliding surface that was identified through the interpretation of the noise measurement data. The boundaries of the landslide area appear quite well defined by the pronounced polarization effects, trending in the northeastern direction, observed in the fractured zone and in the landslide body in particular.

The national seismic networks of Switzerland comprise more than 200 stations. At the station sites, the empirical amplification functions (EAFs) are routinely computed after each earthquake using a generalized inversion method based on separation of source, path, and site effects. The seismic stations are also characterized through geophysical measurements aiming to estimate shear-wave velocity profiles and horizontal-to-vertical spectral ratio of ambient vibrations (HVNR). Using this information, the correlation between the HVNR and EAF is assessed through canonical correlation. Once established, the canonical correlation is used to reconstruct the expected EAFpred at each considered station site in the dataset. The prediction is individually made for all seismic stations in the dataset, excluding every time the investigated station is from the calibration dataset; the reconstruction of the EAFpred is performed resorting to two parallel methods. The first method uses a combination of the canonical correlation parameters and Moran index, and the second one solves in a least-squares sense an overdetermined linear equation system including the canonical couples deemed as reliable. After a first round of predictions, a systematic lower EAFpred in soft sediment sites and a higher EAFpred in hard-rock sites is observed. A possible explanation for this behavior is found in the “normalization” to the Swiss standard rock profile in the computation of the EAF at the Swiss stations. Therefore, to reduce this effect, geological and geophysical parameters are considered in addition to the HVNR in the canonical correlation. We observe that the final solution improves when the least-squares solution approach is used with a combination of HVNR, VS30, and thickness of the ice cover at the last glacial maximum. Moreover, a blind test is performed using data not considered in the calibration dataset. The results highlight the ability of the method to provide an estimate of the site amplification over chosen frequency bins.

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