Site Amplification Analysis to Support Seismic Microzonation in Aachen, Germany: Ambient Noise Observations Complemented by Numerical Simulations

Accurate seismic hazard assessment in urban environments requires comprehensive knowledge of near-surface geological and geotechnical conditions, which significantly influence ground motion amplification. This study presents an integrated dataset to support seismic microzonation of the city of Aachen (Germany), focused on a 5 × 5 km² area targeted for its critical infrastructure and potential fault zones. The investigation incorporates 450 horizontal-to-vertical spectral ratio (HVSR) measurements, six microtremor array measurements (MAMs), six electrical resistivity tomography (ERT) profiles, and 175 geotechnical boreholes. These datasets enabled the spatial characterization of the fundamental frequency (f₀), the site amplification effects, and the Vs₃₀ values. Advanced interpretation methods were applied, including Rayleigh and Love wave dispersion analysis, Rayleigh-wave ellipticity, and horizontal-to-vertical time-frequency analysis (HVTFA). Furthermore, a two-dimensional numerical model of seismic wave propagation was developed along a southwest–northeast profile to simulate peak ground acceleration (PGA), identify amplification zones, and delineate subsurface stratigraphy and active fault geometry. The integration of ambient noise-based techniques with borehole and ERT data significantly improves the resolution of geological modeling in Aachen. The results provide essential input for future ground motion scenarios and contribute to the development of reliable urban seismic response models. This multidisciplinary approach supports risk-informed planning and enhances resilience in regions characterized by moderate seismicity.