EGU25-6821, updated on 14 Mar 2025
https://doi.org/10.5194/egusphere-egu25-6821
EGU General Assembly 2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
Time and space variability of spectral ratio in urban area: the case of Rome (Italy)
Alessia Mercuri1, Giovanna Cultrera1, Maurizio Vassallo2, Giuseppe Di Giulio2, Antonella Bobbio3, and Gaetano Riccio4
Alessia Mercuri et al.
  • 1Istituto Nazionale di Geofisica e Vulcanologia, Roma, Italy (alessia.mercuri@ingv.it)
  • 2Istituto Nazionale di Geofisica e Vulcanologia, L'Aquila, Italy
  • 3Istituto Nazionale di Geofisica e Vulcanologia, Napoli, Italy
  • 4Istituto Nazionale di Geofisica e Vulcanologia, Grottaminarda, Italy

Studies in urban areas are becoming increasingly important for the ground motion prediction, and represent a stimulating challenge due to the presence of many uncontrolled variables: high and variable level of ambient noise, hidden geological features, underground services, limited open spaces for geophysical investigations, high urbanisation and cultural heritage. 

We used data from 24 stations in the urban area of Rome (Italy), belonging to the SPQR temporary seismic network and operating from January to early April 2021 (https://www.fdsn.org/networks/detail/7M_2021/). The stations were installed on very different geological conditions with the aim to reconstruct the properties of the propagation medium below the city by interferometric analysis based on cross correlation of ambient noise. 

The recorded continuous data allowed us to study the network performance in terms of detection threshold for earthquakes and the noise variability over the time during the pandemic restriction due to Covid-19. In particular, we investigated the spatial and temporal variation of the Horizontal to Vertical Spectral ratio on noise (HVSR) computed with the HVNEA software (https://github.com/INGV/hvnea). The coherence analysis between the time series of the HVSR frequency peak values and their related amplitude shows an anti-correlation between the two parameters. Their variability is compared with the total number of vehicles, detected by control units in the all metropolitan area and affected by the movement restrictions imposed by the public authority to contain Covid 19 infections: the correlation is significant in the medium-high frequency range but with different characteristics from site to site; no variations linked to traffic are observed in the low frequency range. 

Following these results, a permanent network of 14 stations, equipped with both velocimeter and accelerometer, is being installed in Rome by the Site Effect Laboratory of INGV (https://www.ingv.it/en/monitoraggio-e-infrastrutture/laboratori/laboratorio-effetti-di-sito), as part of the MEET Project (Monitoring Earth's Evolution and Tectonics, https://meet.ingv.it; National Recovery and Resilience Plan- PNRR). The network will be devoted to site effect studies in such an urban area with unique cultural heritage and heterogeneous city development.

How to cite: Mercuri, A., Cultrera, G., Vassallo, M., Di Giulio, G., Bobbio, A., and Riccio, G.: Time and space variability of spectral ratio in urban area: the case of Rome (Italy), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6821, https://doi.org/10.5194/egusphere-egu25-6821, 2025.