Paolo Bergamo

Last Name

Bergamo

First Name

Paolo

ORCID

0000-0002-7738-2882

Organisational unit

02818 - Schweiz. Erdbebendienst (SED) / Swiss Seismological Service (SED)

Show all metadata

Search Results

Publications 1 - 10 of 29

Geophysical surveys for the characterization of the seismic local response at instrumented sites: a case study from a station of the Swiss strong motion network
Bergamo, Paolo; Panzera, Francesco; Hobiger, Manuel; et al. (2022)
Proceedings of the Third European Conference on Earthquake Engineering and Seismology – 3ECEES
Site characterization surveying is one of the key efforts for the understanding of local amplification effects in earthquake engineering. In this perspective, geophysical measurements for the estimation of the physical properties of the subsurface at instrumented sites are particularly important. For instance, the comparison between simulated site amplification based on the retrieved Vs profile and empirical local response observed at the station allows assessing whether the site is characterized by a purely 1D response or additional 2D-3D effects are present. We present a case study involving a site characterization measurement at a station of the Swiss strong-motion network. The survey includes active seismic data acquisition along two geophone lines, of 15 and 115 m length, for the imaging of the near-surface and deeper layers, respectively. The acquired data were interpreted in terms of P-wave refraction and Rayleigh-wave multi-modal propagation analysis. The reconstructed Vs-Vp profiles achieve a high level of accuracy over a wide depth range and allow modelling the SH-transfer function of the local soil column; the latter is in excellent agreement with the local amplification function estimated by means of empirical spectral modelling of the station’s recordings. The agreement confirms a purely 1D site response for the surveyed station.
Joint estimation of S-wave velocity and damping ratio of the near-surface from active Rayleigh wave surveys processed with a wavefield decomposition approach
Bergamo, Paolo; Marano, Stefano; Fäh, Donat (2023)
Geophysical Journal International
The use of surface wave measurements to derive an S-wave velocity profile of the subsurface has become a widely applied procedure; however, their potential use to reconstruct the S-wave material damping properties of the subsoil is generally overlooked, due to the difficulties in obtaining consistent surface wave amplitude information from field data and translating them into robust estimates of the dissipative properties of the near-surface. In this work, we adapt a wavefield decomposition technique for the processing of elastic surface wave data to the extraction of the complete set of properties of Rayleigh waves generated by a controlled source and propagating in dissipative geomaterials. Retrieved information includes multimodal phase velocity and ellipticity as well as the frequency-dependent attenuation coefficient. We exploit the key advantages of wavefield decomposition processing (joint interpretation of multicomponent recordings, coupled estimation of wave propagation parameters, modelling of multiple superimposing modes) to maximize the robustness of the retrieval of Rayleigh wave properties, especially of the dissipative ones. For the subsequent interpretation of Rayleigh wave dispersion, ellipticity and attenuation data we implement a joint Monte Carlo inversion yielding a coupled estimate of S-wave velocity and damping ratio profile for the subsurface; we incorporate a series of geophysical constraints to narrow down the searched parameter space to realistic soil models. We apply this processing and inversion scheme to a bespoke synthetic data set and to a field survey for the characterization of a strong motion station; in both cases, we succeed in retrieving Rayleigh wave multimodal dispersion, ellipticity and attenuation curves. From the inversion of data from the simulated seismogram we are able to reconstruct the properties of the synthetic model. As for the real case, we determine an S-wave velocity and damping ratio model for the soil column below the station, through which we are able to model the inelastic earthquake local response observed at the site. Basing on the results obtained for the real case, we argue that one of the advantages brought by our processing method-the possibility to process active Rayleigh wave data acquired by a 2-D array illuminated by different source positions-may play a key role in allowing to retrieve dissipative properties of the near-surface closer to the material damping of the soil materials, and less influenced by scattering determined by possible discontinuities in the subsurface.
Systematic assessment of nonlinear soil behavior at KiK-net sites in Japan: Thresholds and controlling site factors
Loviknes, Karina; Bergamo, Paolo; Fäh, Donat; et al. (2025)
Earthquake Spectra
We address two open questions concerning nonlinear soil behavior in a seismic hazard and risk context; (1) which site proxies can be used to predict and map nonlinear site amplification? (2) At which level of ground-motion intensity should such nonlinear models be considered? To answer these questions, we use the KiK-net network in Japan, which includes stations with instruments at both surface and depth, considering events recorded between 1997 and 2024. Using the surface-to-borehole ratio, we systematically capture the empirical effects of nonlinear soil response as the amplitude change and frequency shift between individual events and the linear site response. We then derive station-specific parameters for degree of nonlinearity and threshold for onset of nonlinear behavior. The statistical correlation between nonlinearity and a selection of geotechnical and geological site parameters shows that although parameters characterizing the depth to bedrock and the shallowest part of the soil layer have a promising potential for capturing nonlinear site amplification, the correlation is generally low, suggesting that a single site parameter is not sufficient. As a consistent reference for ground-motion intensity, we empirically calculate PGAemp.rock, as an approximation for PGA recorded on a standard outcropping rock site with VS30 = 760 m/s (average shear-wave velocity of upper 30 m). When analyzing the nonlinear behavior for all recorded events, we define the nonlinear soil behavior as significant when the amplitude change, and frequency shift are greater than 10% for the majority (50%) of the records. We find that in the PGAemp.rock-range 1−3 m/s2 nonlinear soil behavior is significant only for soft soil stations (VS30 < 250 m/s) with intermediate sediment thickness (<30 m). While, according to the mean behavior of all sites, regardless of grouping, nonlinearity is significant only at PGAemp.rock > 3 m/s2. These results show that for nonlinear site-amplification modeling, the onset of nonlinearity is strongly related to the site conditions.
Towards a dynamic earthquake risk framework for Switzerland
Böse, Maren; Danciu, Laurentiu; Papadopoulos, Athanasios N.; et al. (2024)
Natural Hazards and Earth System Sciences
Scientists from different disciplines at ETH Zurich are developing a dynamic, harmonised, and user-centred earthquake risk framework for Switzerland, relying on a continuously evolving earthquake catalogue generated by the Swiss Seismological Service (SED) using the national seismic networks. This framework uses all available information to assess seismic risk at various stages and facilitates widespread dissemination and communication of the resulting information. Earthquake risk products and services include operational earthquake (loss) forecasting (OE(L)F), earthquake early warning (EEW), ShakeMaps, rapid impact assessment (RIA), structural health monitoring (SHM), and recovery and rebuilding efforts (RRE). Standardisation of products and workflows across various applications is essential for achieving broad adoption, universal recognition, and maximum synergies. In the Swiss dynamic earthquake risk framework, the harmonisation of products into seamless solutions that access the same databases, workflows, and software is a crucial component. A user-centred approach utilising quantitative and qualitative social science tools like online surveys and focus groups is a significant innovation featured in all products and services. Here we report on the key considerations and developments of the framework and its components. This paper may serve as a reference guide for other countries wishing to establish similar services for seismic risk reduction.
Systematic assessment of nonlinear soil behaviour at KiK-net sites (Japan) and correlation with geotechnical and geological indicators
Loviknes, Karina; Bergamo, Paolo; Fäh, Donat; et al. (2022)
Proceedings of the Third European Conference on Earthquake Engineering and Seismology – 3ECEES
In this study we propose the SoilGrid database with predicted soil properties down to 2 meters depth and geological maps of Japan as geotechnical indicators with the potential to explain nonlinear site-effects. To test these indicators, we measure the nonlinear site- response in the Japanese Kiban–Kyoshin Network (KiK-net) as the change in amplitude and shift in frequency between strong-motion events and the linear site-response. These measurements are then fitted to a hyperbolic tangent function. We plan to use the coefficients and parameters from the fitted hyperbolic tangent function to explore the correlation between the geotechnical indicators and sites with strong nonlinear soil-behaviour.
Extending ERM-CH23 to shallow induced seismicity in Switzerland
Grigoratos, Iason; Bergamo, Paolo; Cauzzi, Carlo Virgilio; et al. (2025)
The risks from induced seismicity remain a persistent and complex issue that needs to be managed. Appropriate modeling of these risks is essential in order to facilitate both the permitting process of certain energy-production projects and the acquisition of insurance against potential losses. For Switzerland, the most relevant causal factors of induced seismicity are likely hydraulic stimulations for Enhanced Geothermal Systems and fluid disposal for storage. The earthquakes that these activities might trigger are expected to be quite shallow, of mostly small to moderate magnitude. Their nucleation mechanism might also differ, compared to tectonic events. Thus, their source characteristics and the attenuation of their ground motion might be partly incompatible with the modeling assumptions adopted by the national Earthquake Hazard Model of Switzerland (SUIhaz2015; Wiemer et al., 2016; Papadopoulos et al., 2024a). This report investigated these issues, as well as, the possibility that the fragility models of the Earthquake Risk Model of Switzerland (ERM-CH23; Wiemer et al., 2023) might warrant modifications for similar reasons.. The results of these investigations highlighted the need to adjust some aspects of the risk model to render it suitable for (shallow) induced seismicity in Switzerland. In the end, new recommendations were made regarding the minimum and maximum magnitude, two new intensity measures were added to the vulnerability models, while major changes were made to the ground shaking branching level. The latter is now magnitude-dependent, only includes spectral acceleration models and was tilted towards lower stress-parameter values. A ready to use version of the updated risk model, called Induced Earthquake Risk Model of Switzerland (IERM-CH25), is now available. Finally, risk calculations, including sensitivity analyses, were conducted for certain scenario earthquakes at selected sites.
Modello di amplificazione sismica per la Svizzera basato su indicatori di condizione di sito e sulla risposta sismica locale misurata alle stazioni sismiche
Bergamo, Paolo; Panzera, Francesco; Cauzzi, Carlo Virgilio; et al. (2022)
Atti del 40° Convegno Nazionale
Multipath Transfer-Function Correction Method to Predict Site-Specific Amplification at City Scale
Halló, Miroslav; Bergamo, Paolo; Fäh, Donat (2024)
Seismological Research Letters
The site-specific amplification of seismic waves is an essential component of local seismic hazard assessment. It can be evaluated from empirical data, but measurements are feasible just in a limited number of locations. Hence, at the city scale, there is a need for the theoretical prediction and interpolation of the amplification. In this article, we introduce a physics-based method to predict the site-specific amplification and duration in a broad frequency range. The method is based on a novel energy-based concept of the multipath propagation of waves in viscoelastic media with random heterogeneities. The amplification is expressed by the surface-outcrop transfer function of the multipath wave propagation, which is defined by expected values of the energy spectral ratio. The method is applied to the near-surface 2D velocity model in the city of Zürich in Switzerland. The predicted amplification is validated by empirical data at a nearby seismic station, and it is compared with the soil class and other site-condition proxies. Finally, the method performance is demonstrated by the prediction of site-specific seismic waveforms and response spectra for the 2022 ML 4.7 Mulhouse earthquake.
Erneuerung des Starkbebennetzwerks in der Schweiz (2009‐2023) - Abschlussbericht
Fäh, Donat; Duvernay, Blaise; Michel, Clotaire; et al. (2024)
Mit seinem Beschluss vom 18. Februar 2009 hat der Bundesrat den Antrag für die Erneuerung des Starkbebennetzes der Schweiz (Phase 1) gutgeheissen und deren Realisierung in Auftrag gegeben. Das Projekt umfasst in dieser ersten Phase (2009‐2013) die Installation und Inbetriebnahme von 30 modernen Erdbebenstationen. Diese sollen in erster Linie bestehende Lücken in der nationalen Überwachung schliessen. Dabei wurden alte Stationen teilweise ersetzt, aber auch neue Standorte realisiert. Im Rahmen des Projektes wurden neue Standards für die Installation von Starkbebenstationen definiert. Aufgrund der erfolgreichen ersten Phase hat der Bundesrat mit seinem Beschluss vom 30. Januar 2013 der Realisierung der zweiten Phase der Erneuerung des Starkbebenmessnetzes (2013‐2023) zugestimmt. In dieser zweiten Phase werden 70 Starkbebenmessstationen gebaut, davon vier Bohrlochinstallationen. Abbildung 1 gibt einen Überblick über die 100 Starkbebenstationen, die in den Phasen 1 und 2 installiert wurden. Beide Projektphasen wurden von einer Steuerungsgruppe unter der Leitung des Bundesamts für Umwelt (BAFU) begleitet. Für alle installierten Stationen wurde eine Standortcharakterisierung durchgeführt. Dabei kamen Ein‐Stations‐Methoden der seismischen Bodenunruhe, passive Arraymessungen und aktive seismische Messungen zum Einsatz. An Standorten mit besonderen Bodeneigenschaften, die bei Erdbeben zu nichtlinearem Materialverhalten oder Bodenverflüssigung neigen, wurden CPT‐ Messungen durchgeführt. Die Standortcharakterisierung wurde für jeden Standort in einem Bericht zusammengefasst. Die Messdaten und Auswertungen wurden in einer Datenbank gespeichert. Eine Beschreibung der Standorte und die Berichte zur Standortcharakterisierung sowie die Erdbebenaufzeichnungen der Starkbebenstationen sind auf den Webseiten des Schweizerischen Erdbebendienstes zugänglich.
On the seismic response and earthquake-triggered failures of subaqueous slopes in Swiss lakes
Shynkarenko, Anastasiia; Cauzzi, Carlo Virgilio; Kremer, Katrina; et al. (2023)
Geophysical Journal International
Seismically triggered subaqueous mass movements in lakes may generate tsunamis that can cause significant damage on the shore. In this study, we assess the seismic response and stability of subaqueous slopes in Swiss lakes based on recorded seismological data, historical and geological information and geotechnical surveys. We performed seismic investigations at multiple locations in Lake Lucerne using Ocean Bottom Seismometers (OBS). For these locations, we derived ground-motion amplification functions from local and regional earthquakes and horizontal-to-vertical spectral ratios (H/V) from the earthquake and ambient vibration recordings. The results show (1) very high amplification levels, often exceeding values of 50–100 in the frequency range between 1 and 10 Hz, (2) the fundamental frequency of resonance in the range of 0.5–3.5 Hz and (3) laterally variable site response even for closely located stations. We sought also the signatures of non-linear site response in the H/V curves or ground-motion amplification functions but found only weak indicative effects and no clear evidence. This is most likely due to the low levels of ground motion recorded during the OBS campaigns. We conducted back analyses of historical earthquakes in Switzerland with available documental and/or geological evidence of induced (tsunamigenic) subaqueous slope failures in Swiss lakes. The data set of historical events was complemented with a selection of instrumentally recorded earthquakes in Switzerland. For the analyses, we selected multiple sites in Swiss lakes which failed in the past or are prone to failure in the future. We modelled the ground motion at these locations assuming Swiss standard reference rock conditions (vs30 = 1105 m s−1). The modelled ground motion intensity measures (IM) included peak ground acceleration (PGA), peak ground velocity (PGV) and pseudospectral acceleration (PSA) at 0.3, 1 and 2 s. We estimated the minimum ground motion and macroseismic intensity at reference rock conditions required to trigger the failures of subaqueous slopes. In addition, we defined a threshold for the seismic triggering of such failures in terms of moment magnitude (Mw) and epicentral distance (Re) as: Mw = 2.891 + 1.904 log10(Re + 5.166) for Re ≥ 3.7 km. Our results are consistent with previous studies based on worldwide observations. Furthermore, we related the modelled ground motions to the Swiss seismic hazard products and estimated the return period of critical ground shaking responsible for triggering subaqueous slope failures (with potential for tsunami generation) to be in the range of 36–224 yr. Finally, based on previously collected geotechnical data (in situ Cone Penetration Testing and laboratory sediment analysis), we determined the most likely values of the seismic coefficient k to be used with the ground motion IMs modelled at reference rock conditions in infinite slope stability analyses to estimate the factor of safety (FS). For PGA, we found a k = 1; for PGV, k = 2; for PSA0.3s, k = 0.6; for PSA1s, k = 2 and for PSA2s, k = 5.5. These estimates are conservative and affected by the trade-off between the thickness of unconsolidated sediments and the slope angle. Thus, we recommend applying them to slopes with a low-to-moderate gradient (<15◦) and sediment thickness of more than 2 m.

Publications 1 - 10 of 29

Paolo Bergamo

Last Name

First Name

ORCID

Organisational unit

Filters

Search Results