Francesco Panzera

Last Name

Panzera

First Name

Francesco

ORCID

0000-0003-3062-4044

Show all metadata

Search Results

Publications1 - 10 of 48

Geophysical surveys for the dynamic characterization of a cultural heritage building and its subsoil: The S. Michele Arcangelo Church (Acireale, eastern Sicily)
Grassi, Sabrina; Imposa, Sebastiano; Patti, Graziano; et al. (2019)
Journal of Cultural Heritage
Canonical Correlation Analysis Based on Site‐Response Proxies to Predict Site‐Specific Amplification Functions in Switzerland
Panzera, Francesco; Bergamo, Paolo; Fäh, Donat (2021)
Bulletin of the Seismological Society of America
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.
Integrated use of ambient vibrations and geological methods for seismic microzonation
Panzera, Francesco; Romagnoli, Gino; Tortorici, Giuseppe; et al. (2019)
Journal of Applied Geophysics
Reference soil condition for intensity prediction equations derived from seismological and geophysical data at seismic stations
Panzera, Francesco; Bergamo, Paolo; Fäh, Donat (2021)
Journal of Seismology
In 2011, an amplification map achieved by macroseismic information was developed for Switzerland using the collection of macroseismic intensity observations of past earthquakes. For each village, a Delta Imwas first derived, which reflects the difference between observed and expected macroseismic intensities from a region-specific intensity prediction equation. The Delta Imvalues are then grouped into geological/tectonic classes, which are then presented in the macroseismic amplification map. Both, the intensity prediction equation and the macroseismic amplification map are referenced to the same reference soil condition which so far was only roughly estimated. This reference soil condition is assessed in this contribution using geophysical and seismological data collected by the Swiss Seismological Service. Geophysical data consist of shear-wave velocity profiles measured at the seismic stations and earthquake recordings, used to retrieve empirical amplification functions at the sensor locations. Amplification functions are referenced to a generic rock profile (Swiss reference rock condition) that is well defined, and it is used for the national seismic hazard maps. Macroseismic amplification factorsAf, derived from empirical amplification functions, are assigned to each seismic station using ground motion to intensity conversions. We then assess the factorsd Delta fdefined as the difference betweenAfand Delta Im. The factord Delta faccounts for the difference between the reference soil condition for the intensity prediction equation and the Swiss reference rock. We finally analysed relationships betweenAfand proxies for shear-wave velocity profiles in terms of average shear-wave velocity over defined depth ranges, such asV(S,30), providing an estimate of the reference shear velocity for the intensity prediction equation and macroseismic amplification map. This study allows linking macroseismic intensity observations with experimental geophysical data, highlighting a good correspondence within the uncertainty range of macroseismic observations. However, statistical significance tests point out that the seismic stations are not evenly distributed among the various geological-tectonic classes of the macroseismic amplification map and its revision could be planned merging classes with similar behaviour or by defining a new classification scheme.
Ambient vibration measurements to support morphometric analysis of a pyroclastic cone
Panzera, Francesco; D'Amico, Sebastiano; Colica, Emanuele; et al. (2019)
Bulletin of Volcanology
Pyroclastic cones are a typical feature on volcanoes characterized by flank activity. Their distribution and orientation are important markers to obtain information on the maximum horizontal compressional stress acting on a volcano. A geophysical survey was performed on the pyroclastic cone of Mt. Vetore (Mt. Etna volcano, Southern Italy) to obtain information on its internal structural setting and to support the standard morphometric analysis. Results highlighted evident frequency peaks at 1.0 Hz inside the cone, which are attenuated away from it. The random decrement method was applied to this peak to compute damping and then to exclude links with anthropogenic sources. Moreover, time-frequency polarization analysis revealed that ambient vibrations are strongly polarized in a narrow frequency band, centered at a frequency of 1.0 Hz, with a preferred oscillation azimuth of 70–90° N. Array measurement of ambient vibrations was also used to obtain a shear wave velocity profile and then to retrieve the main interfaces with high seismic impedance. Results suggest a cone structure having a feeder dike consisting of fractured rocks with thickness of about 50 m surrounded by pyroclastic material lying on a high-velocity substrate. Finally, a 3D model of Mt. Vetore cone was built employing the finite element method to reproduce an experimental modal frequency of the cone itself. The numerical results successfully reproduced the experimental ones collected by the geophysical survey.
The Earthquake Risk Model of Switzerland, ERM-CH23
Papadopoulos, Athanasios N.; Roth, Philippe; Danciu, Laurentiu; et al. (2024)
Natural Hazards and Earth System Sciences
Understanding seismic risk at both the national and sub-national level is essential for devising effective strategies and interventions aimed at its mitigation. The Earthquake Risk Model of Switzerland (ERM-CH23), released in early 2023, is the culmination of a multidisciplinary effort aiming to achieve for the first time a comprehensive assessment of the potential consequences of earthquakes on the Swiss building stock and population. Having been developed as a national model, ERM-CH23 relies on very high-resolution site-amplification and building exposure datasets, which distinguishes it from most regional models to date. Several loss types are evaluated, ranging from structural-nonstructural and content economic losses to human losses, such as deaths, injuries, and displaced population. In this paper, we offer a snapshot of ERM-CH23, summarize key details on the development of its components, highlight important results, and provide comparisons with other models.
Insights into the dynamics of the Nirano Mud Volcano through seismic characterization of drumbeat signals and V/H analysis
Antunes, Verónica; Planès, Thomas; Obermann, Anne; et al. (2022)
Journal of Volcanology and Geothermal Research
Mud volcanoes are rapidly-evolving geological phenomena characterized by the surface expulsion of sediments and fluids from over-pressurized underlying reservoirs. We investigate the Nirano Mud Volcano, Northern Italy, with seismic methods to better understand the dynamic evolution of the system and shed light on its subsurface structure. Our study allowed to detect and characterize three different types of high-frequency drumbeat signals that are present in the most active part of the mud volcano plumbing system. With a back-projection method based on the cross-correlation envelope of signals recorded at different station pairs, we can determine the source location of the drumbeats. These coincide with the location of V/H (vertical-to-horizontal) amplitude peaks obtained from an ambient vibration profile and resistivity anomalies identified in a previous study. We observe that the drumbeats are P-wave dominated signals, with characteristics similar to those found in magmatic settings, i.e. LPs (long-period signals). We suggest that such tremors originate from the migration of mud and gas inside the mud volcanic conduits. The source location, waveform and frequency content of the drumbeats evolve over time. We found that drumbeat occurrence is directly linked with morphological changes at surface.
Reconstructing a 3D model from geophysical data for local amplification modelling: The study case of the upper Rhone valley, Switzerland
Panzera, Francesco; Alber, Jonas; Imperatori, Walter; et al. (2022)
Soil Dynamics and Earthquake Engineering
The geometry of three-dimensional subsurface structures plays an important role in determining local seismic site effects as in the case of alpine valleys. Detailed knowledge of these structures is fundamental in seismic hazard and risk studies. In this study we investigate an area in the upper Rhone valley around Visp, in the southwestern part of Switzerland. A large dataset of geological and geophysical data, consisting of borehole logs, microtremor horizontal to vertical spectral ratios and shear-wave velocity measurements, was compiled to build a detailed 3D model of the subsurface. By combining fundamental frequency information from noise recordings and shear-wave velocity profiles, three main geophysical discontinuities were identified and their physical properties constrained through a stepwise process. First, the bedrock depth was estimated; in a second step a generic velocity model was defined and finally, combining all the available geological and geophysical information, we developed a 3D geophysical model. The model was compared with a local 3D geological model and a model derived from gravimetric data. The study area is a complex alpine valley where 2D/3D wave propagation phenomena occur. In such case a purely 1D response assumption is considered to be invalid. In order to test the 3D model, we modelled different ambient-vibration wave fields and compared observed and synthetic H/V spectral ratios. We slightly modified our 3D geophysical model in some areas based on this comparison. Finally, a good match between simulated and empirical spectral ratios corroborated the model. The results suggest that the use of ambient vibration techniques are a powerful and cost-effective tools to reconstruct three-dimensional models of the subsurface. Finally, we used the 3D model to predict amplification of earthquake ground motion in the basin. Again, the match between observed and modelled amplification at the locations of the seismic stations is good. This allows us to map amplification inside the study area.
Spatiotemporal evolution of the completeness magnitude of the Icelandic earthquake catalogue from 1991 to 2013
Panzera, Francesco; Mignan, Arnaud; Vogfjörð, Kristin S. (2017)
Journal of Seismology
Empirical evidence of orthogonal relationship between directional site effects and fracture azimuths in an active fault zone: The case of the Mt. Etna lower eastern flank
Panzera, Francesco; Tortorici, Giuseppe; Romagnoli, Gino; et al. (2020)
Engineering Geology
Mt. Etna, in eastern Sicily, is a composite active volcano whose eastern flank is affected by several normal and strike-slip active faults. In this study geological-structural field survey and ambient vibration measurements are performed in the lower eastern flank of Mt. Etna in order to define the role of the tectono-stratigraphic setting in the seismic site response. The sites of measurements are mainly distributed inside the few hundreds of meters long S. Caterina Graben, which is located between two main seismogenic active faults of this volcano sector, the Acireale and the Fiandaca faults. Our study aims at defining the contribution of the fault related active deformation in determining the local ground motion amplification, also providing a subsoil geological model based on the integration of geological and geophysical investigation. Therefore, structural measurements were made in seven sites, revealing coseismic and aseismic extensional fractures mainly striking NNW. The seismic site response was studied processing the ambient vibration measurements through Horizontal-to-vertical spectral ratio. The measured fundamental frequency falls in the range 1.0–4.0 Hz, that we linked to the presence of a velocity contrast at depth of 80–200 m by calibrating a frequency depth function. Moreover, the seismic site effect is due to the stratigraphic setting and is markedly directional, showing maximum amplification along the direction orthogonal to the strike of the observed isooriented extensional fracture field produced by the activity of the S. Caterina Graben. It is noteworthy that, far from the graben on sites of measurements located near the Fiandaca Fault, we observed directional effects parallel to the direction of maximum extension inferred for this tectonic lineament. Our results suggest a linkage between directional site effects and local stress tensors and fractures field orientation. © 2020 Elsevier

Publications1 - 10 of 48

Francesco Panzera

Last Name

First Name

ORCID

Organisational unit

Filters

Search Results