Feasibility of Utilizing Continuous Records from Weak And Strong-Motion Recorder Channels of Permanent Stations for Horizontal To Vertical Spectral Ratio (HVSR) Analysis During Calm-Day Conditions

The proposed paper assesses the feasibility of using continuous records acquired from weak and strong-motion recorder channels of permanent earthquake observation stations under calm-day conditions for the HVSR method. The analyses were conducted on 60 tri-axial ambient noise data through HN channels from strong-motion recorders and BH, HH (or EH) channels from weak-motion recorders from 25 stations belonging to various soil and topography classes in the INGV network of Italy. The accuracy and reliability of the proposed HVSR curves were evaluated by benchmarking them with predefined original HVSR curves for each station, using statistical metrics such as the Pearson correlation coefficient and mean absolute error (MAE). The findings demonstrate that weak-motion recorder channels, especially HH and EH, acquire ambient noise, which serves as the primary data for the HVSR method, with higher PSD levels than strong-motion channels due to their inherently lower self-noise threshold. Therefore, while HVSR curves derived through BH channels indicate an average correlation of 84% and MAE of 12%, HH-EH channels demonstrate 91% and %12, respectively. Conversely, HN channels exhibit lower correlation (28%) and higher MAE (31%). Furthermore, topography and soil class influence PSD values, with T1 and C classes exhibiting the highest levels. However, variations in performance across different topographic and soil classes are less pronounced. The analyses suggest that the channel type plays a more critical role in HVSR analysis. This finding highlights the importance of selecting the appropriate channel for accurate HVSR analysis using permanent stations.