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Papers by Roberto de Ferrari
Ambient vibration tests (AVTs) provide valuable information about the dynamic behavior of existin... more Ambient vibration tests (AVTs) provide valuable information about the dynamic behavior of existing buildings [1]. Their use is well established in Structural Health Monitoring (SHM) applications to detect modification in structural behaviour after ageing, damage and retrofitting [2], and surely to calibrate or build numerical models aimed to the seismic assessment. Moreover, vibration-based methodologies assume great relevance within seismic mitigation strategies to prioritize retrofitting actions at urban scale. In this context, the Italian Department of Civil Protection developed the Seismic Model from Ambient Vibrations (SMAV) [3] which relies on modal parameters extracted by AVTs to evaluate the operational level of strategic buildings following a seismic event. Within the application of the previous procedure, this work presents an extensive measurement campaign carried out in Liguria Region in collaboration with Geamb S.r.l in which full-scale AVTs have been performed on seven...
The paper describes some analyses carried out to establish the slope stability under seismic cond... more The paper describes some analyses carried out to establish the slope stability under seismic condition of some sites within the Genoa district (Italy). For this purpose, the simplified Newmark sliding block analysis (Jibson, 1993) is applied. This method is based on an empirical regression equation to estimate the Newmark displacement as a function of the Arias intensity and the critical acceleration. The Jibson analysis is applied to some slopes affected by stabilized landslides and generally characterized by low values of the safety factor. A probabilistic seismic hazard analysis (PSHA) is performed in order to estimate the ground motion, defined in terms of Arias intensity, with a 10% probability of exceedance in 50 years. A logic tree approach is adopted since it allows us to account for the epistemic uncertainty due to the insufficient knowledge of the input data. The values of the Arias intensity, greater than 0.11 m/s, show that some sites could be subjected to seismic landsl...
Engineering Geology
Abstract In this work, we analyze the macroseismic fields of the main historical earthquakes occu... more Abstract In this work, we analyze the macroseismic fields of the main historical earthquakes occurred in western Liguria (northwestern Italy) in order to identify possible relations between the isoseismal patterns and the local geological setting. Anomalies in the spatial distribution of macroseismic intensities are often attributed to site effects. We observed that, in the region of study, such anomalies are mainly located in areas characterized by outcropping Pliocene soil deposits, mainly made up of stiff silty and marly clays. To investigate the influence of such deposits on ground response, both horizontal-to-vertical spectral ratio measurements and numerical site response analyses were carried out. For all sites analyzed, the spectral ratio curves show marked amplification peaks between 2 and 5 Hz. Following such empirical evidence, equivalent linear ground response analyses were performed in order to examine the relation between the measured resonance frequencies and the response of a set of soil columns presenting Pliocene marly-clayey deposits at their top. To this end, a database of geotechnical and geophysical properties, including > 50 reference soil profiles, was compiled. This database was used to define alternative numerical models considering three different ranges of thickness of the Pliocene marly-clayey deposits (between 5 and 35 m, 30 and 65 m, 60 and 105 m). Results show marked amplification effects in the ranges 1–3 Hz, 2–5 Hz, and 3–10 Hz depending on the thickness of the investigated soil deposits. These frequency ranges are in agreement with those observed from the experimental measurements, which are therefore proved adequately representative of the resonance frequencies of the Pliocene marly-clayey deposits. Therefore, based on our findings, such deposits can be considered an essential factor in producing the “anomalies” observed in the isoseismal patterns of the macroseismic fields of the historical earthquakes occurred in western Liguria.
Near Surface Geoscience 2015 - 21st European Meeting of Environmental and Engineering Geophysics, 2015
The purpose of this work is to study seismic amplification effects at four sites hosting recordin... more The purpose of this work is to study seismic amplification effects at four sites hosting recording stations of the National Accelerometric Network (RAN) managed by the national Department of Civil Protection. At all sites, which are located in the Piedmont region (Northwestern Italy), both active and passive seismic prospecting methods are used, allowing identification of local amplification effects at three out of the four sites analysed. A ground type is then assigned to each site according to the national antiseismic code. Results obtained here will be fundamental to reduce the ground motion variability related to ground motion prediction equations and, consequently, to produce finer site-specific ground shaking hazard maps.
Near Surface Geoscience 2015 - 21st European Meeting of Environmental and Engineering Geophysics, 2015
In this work, with the aim of producing shaking-maps which take into account the local amplificat... more In this work, with the aim of producing shaking-maps which take into account the local amplification phenomena related to litho-stratigrafical condition, a raster map of Vs,30 values at a regional scale is derived for Piedmont, Italy. After the collection and the validation of all data available within the regional databases, a logic procedure in GIS is applied to assign a Vs,30 value to each of the zone with homogeneous seismic behavior already identified in a previous work. The result is a new Vs,30 map for the Piedmont region that allows a better and more reliable reconstruction of ground shaking including a more detailed evaluation of site effects.
The paper describes some analyses carried out to establish the slope stability under seismic cond... more The paper describes some analyses carried out to establish the slope stability under seismic condition of some sites within the Genoa district (Italy). For this purpose, the simplified Newmark sliding block analysis (Jibson, 1993) is applied. This method is based on an empirical regression equation to estimate the Newmark displacement as a function of the Arias intensity and the critical acceleration. The Jibson analysis is applied to some slopes affected by stabilized landslides and generally characterized by low values of the safety factor. A probabilistic seismic hazard analysis (PSHA) is performed in order to estimate the ground motion, defined in terms of Arias intensity, with a 10% probability of exceedance in 50 years. A logic tree approach is adopted since it allows us to account for the epistemic uncertainty due to the insufficient knowledge of the input data. The values of the Arias intensity, greater than 0.11 m/s, show that some sites could be subjected to seismic landslides activation (or re-activation) as inferred by Keefer and Wilson (1989). As a comparison, for the site of Campegli the Newmark displacement is also calculated by applying the original Newmark method (1965). To this purpose, a seismogram of the Salò earthquake (M l = 5.2) which occurred at distance of above 180 km in November 25, 2004 and was recorded at above 10 km from Campegli by a station of the RSNI seismic network (Regional Seismic Network of Northwestern Italy) is used. This earthquake could be related to the acceleration of the Campegli landslide body that was observed from inclinometer and piezometer measures.
First Conference on Proximal Sensing Supporting Precision Agriculture, 2015
Summary The study has presented an integrated approach to viticultural soil characterization usin... more Summary The study has presented an integrated approach to viticultural soil characterization using geophysical and geochemical methods. The purpose of this work is to evaluate the presence of geophysical and geochemical anomalies in soil within a vineyard located in well-known Cinque Terre Zone, North-Western Italy. To this scope soil and bedrock features have been studied with electromagnetic induction (EMI) and spettrophotometry method: both the methods have allowed to realize maps of conductivity anomalies values and major chemical elements distribution respectively for the investigated area. Although still at a preliminar stage, the results presented here are encouraging, indicating a good agreement between EMI and EDXRF data. The geological heterogeneity of the study area is clearly reflected both in the conductivity data and in the geochemical composition of the near-surface soils examined. The approach applied here can be extended to larger agricultural areas used by the agrofood industry, either alone or with the aim of integrating data from standard approaches based on pedological analysis. Correlation among data of different nature can nowadays be simply examined through the use of GIS software
The seismic deformation explains only a small percentage of the total geodetic deformation. The s... more The seismic deformation explains only a small percentage of the total geodetic deformation. The significant discrepancy between seismic and geodetic strain rates may be attributed to aseismic deformation which is not taken into account by seismic data.
During the period October-November 2010, the area surrounding Sampeyre (Piedmont, Italy) was affe... more During the period October-November 2010, the area surrounding Sampeyre (Piedmont, Italy) was affected by an intense seismic activity, which evolved into an earthquake swarm. The whole seismic crisis lasted approximately one month, from October 13 to November 12, 2010. During this period, approximately 550 earthquakes were recorded and localized by the Regional Seismic network of Northwestern Italy - RSNI (http://www.dipteris.unige.it/geofisica/) in the study area. However, including the micro seismicity (i.e., earthquakes with negative magnitude) detected by the nearest stations, the number of events goes up to approximately 3800. Among these events, 179 exceeded a local magnitude (Ml) of 1.0 but only two exceeded Ml = 3.0 (the major event has a magnitude of 3.2). Of note, these two earthquakes occurred close to each other on two consecutive days, precisely on October 23 and 24. The Sampeyre area is located in the inner part of the Dora Maira crystalline massif, which corresponds to...
Ambient vibration tests (AVTs) provide valuable information about the dynamic behavior of existin... more Ambient vibration tests (AVTs) provide valuable information about the dynamic behavior of existing buildings [1]. Their use is well established in Structural Health Monitoring (SHM) applications to detect modification in structural behaviour after ageing, damage and retrofitting [2], and surely to calibrate or build numerical models aimed to the seismic assessment. Moreover, vibration-based methodologies assume great relevance within seismic mitigation strategies to prioritize retrofitting actions at urban scale. In this context, the Italian Department of Civil Protection developed the Seismic Model from Ambient Vibrations (SMAV) [3] which relies on modal parameters extracted by AVTs to evaluate the operational level of strategic buildings following a seismic event. Within the application of the previous procedure, this work presents an extensive measurement campaign carried out in Liguria Region in collaboration with Geamb S.r.l in which full-scale AVTs have been performed on seven...
The paper describes some analyses carried out to establish the slope stability under seismic cond... more The paper describes some analyses carried out to establish the slope stability under seismic condition of some sites within the Genoa district (Italy). For this purpose, the simplified Newmark sliding block analysis (Jibson, 1993) is applied. This method is based on an empirical regression equation to estimate the Newmark displacement as a function of the Arias intensity and the critical acceleration. The Jibson analysis is applied to some slopes affected by stabilized landslides and generally characterized by low values of the safety factor. A probabilistic seismic hazard analysis (PSHA) is performed in order to estimate the ground motion, defined in terms of Arias intensity, with a 10% probability of exceedance in 50 years. A logic tree approach is adopted since it allows us to account for the epistemic uncertainty due to the insufficient knowledge of the input data. The values of the Arias intensity, greater than 0.11 m/s, show that some sites could be subjected to seismic landsl...
Engineering Geology
Abstract In this work, we analyze the macroseismic fields of the main historical earthquakes occu... more Abstract In this work, we analyze the macroseismic fields of the main historical earthquakes occurred in western Liguria (northwestern Italy) in order to identify possible relations between the isoseismal patterns and the local geological setting. Anomalies in the spatial distribution of macroseismic intensities are often attributed to site effects. We observed that, in the region of study, such anomalies are mainly located in areas characterized by outcropping Pliocene soil deposits, mainly made up of stiff silty and marly clays. To investigate the influence of such deposits on ground response, both horizontal-to-vertical spectral ratio measurements and numerical site response analyses were carried out. For all sites analyzed, the spectral ratio curves show marked amplification peaks between 2 and 5 Hz. Following such empirical evidence, equivalent linear ground response analyses were performed in order to examine the relation between the measured resonance frequencies and the response of a set of soil columns presenting Pliocene marly-clayey deposits at their top. To this end, a database of geotechnical and geophysical properties, including > 50 reference soil profiles, was compiled. This database was used to define alternative numerical models considering three different ranges of thickness of the Pliocene marly-clayey deposits (between 5 and 35 m, 30 and 65 m, 60 and 105 m). Results show marked amplification effects in the ranges 1–3 Hz, 2–5 Hz, and 3–10 Hz depending on the thickness of the investigated soil deposits. These frequency ranges are in agreement with those observed from the experimental measurements, which are therefore proved adequately representative of the resonance frequencies of the Pliocene marly-clayey deposits. Therefore, based on our findings, such deposits can be considered an essential factor in producing the “anomalies” observed in the isoseismal patterns of the macroseismic fields of the historical earthquakes occurred in western Liguria.
Near Surface Geoscience 2015 - 21st European Meeting of Environmental and Engineering Geophysics, 2015
The purpose of this work is to study seismic amplification effects at four sites hosting recordin... more The purpose of this work is to study seismic amplification effects at four sites hosting recording stations of the National Accelerometric Network (RAN) managed by the national Department of Civil Protection. At all sites, which are located in the Piedmont region (Northwestern Italy), both active and passive seismic prospecting methods are used, allowing identification of local amplification effects at three out of the four sites analysed. A ground type is then assigned to each site according to the national antiseismic code. Results obtained here will be fundamental to reduce the ground motion variability related to ground motion prediction equations and, consequently, to produce finer site-specific ground shaking hazard maps.
Near Surface Geoscience 2015 - 21st European Meeting of Environmental and Engineering Geophysics, 2015
In this work, with the aim of producing shaking-maps which take into account the local amplificat... more In this work, with the aim of producing shaking-maps which take into account the local amplification phenomena related to litho-stratigrafical condition, a raster map of Vs,30 values at a regional scale is derived for Piedmont, Italy. After the collection and the validation of all data available within the regional databases, a logic procedure in GIS is applied to assign a Vs,30 value to each of the zone with homogeneous seismic behavior already identified in a previous work. The result is a new Vs,30 map for the Piedmont region that allows a better and more reliable reconstruction of ground shaking including a more detailed evaluation of site effects.
The paper describes some analyses carried out to establish the slope stability under seismic cond... more The paper describes some analyses carried out to establish the slope stability under seismic condition of some sites within the Genoa district (Italy). For this purpose, the simplified Newmark sliding block analysis (Jibson, 1993) is applied. This method is based on an empirical regression equation to estimate the Newmark displacement as a function of the Arias intensity and the critical acceleration. The Jibson analysis is applied to some slopes affected by stabilized landslides and generally characterized by low values of the safety factor. A probabilistic seismic hazard analysis (PSHA) is performed in order to estimate the ground motion, defined in terms of Arias intensity, with a 10% probability of exceedance in 50 years. A logic tree approach is adopted since it allows us to account for the epistemic uncertainty due to the insufficient knowledge of the input data. The values of the Arias intensity, greater than 0.11 m/s, show that some sites could be subjected to seismic landslides activation (or re-activation) as inferred by Keefer and Wilson (1989). As a comparison, for the site of Campegli the Newmark displacement is also calculated by applying the original Newmark method (1965). To this purpose, a seismogram of the Salò earthquake (M l = 5.2) which occurred at distance of above 180 km in November 25, 2004 and was recorded at above 10 km from Campegli by a station of the RSNI seismic network (Regional Seismic Network of Northwestern Italy) is used. This earthquake could be related to the acceleration of the Campegli landslide body that was observed from inclinometer and piezometer measures.
First Conference on Proximal Sensing Supporting Precision Agriculture, 2015
Summary The study has presented an integrated approach to viticultural soil characterization usin... more Summary The study has presented an integrated approach to viticultural soil characterization using geophysical and geochemical methods. The purpose of this work is to evaluate the presence of geophysical and geochemical anomalies in soil within a vineyard located in well-known Cinque Terre Zone, North-Western Italy. To this scope soil and bedrock features have been studied with electromagnetic induction (EMI) and spettrophotometry method: both the methods have allowed to realize maps of conductivity anomalies values and major chemical elements distribution respectively for the investigated area. Although still at a preliminar stage, the results presented here are encouraging, indicating a good agreement between EMI and EDXRF data. The geological heterogeneity of the study area is clearly reflected both in the conductivity data and in the geochemical composition of the near-surface soils examined. The approach applied here can be extended to larger agricultural areas used by the agrofood industry, either alone or with the aim of integrating data from standard approaches based on pedological analysis. Correlation among data of different nature can nowadays be simply examined through the use of GIS software
The seismic deformation explains only a small percentage of the total geodetic deformation. The s... more The seismic deformation explains only a small percentage of the total geodetic deformation. The significant discrepancy between seismic and geodetic strain rates may be attributed to aseismic deformation which is not taken into account by seismic data.
During the period October-November 2010, the area surrounding Sampeyre (Piedmont, Italy) was affe... more During the period October-November 2010, the area surrounding Sampeyre (Piedmont, Italy) was affected by an intense seismic activity, which evolved into an earthquake swarm. The whole seismic crisis lasted approximately one month, from October 13 to November 12, 2010. During this period, approximately 550 earthquakes were recorded and localized by the Regional Seismic network of Northwestern Italy - RSNI (http://www.dipteris.unige.it/geofisica/) in the study area. However, including the micro seismicity (i.e., earthquakes with negative magnitude) detected by the nearest stations, the number of events goes up to approximately 3800. Among these events, 179 exceeded a local magnitude (Ml) of 1.0 but only two exceeded Ml = 3.0 (the major event has a magnitude of 3.2). Of note, these two earthquakes occurred close to each other on two consecutive days, precisely on October 23 and 24. The Sampeyre area is located in the inner part of the Dora Maira crystalline massif, which corresponds to...