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The 2012 Emilia earthquake (Italy): Geotechnical characterization and ground response analyses of the paleo-Reno river levees
Abstract
In 2012 Northern Italy was hit by a seismic sequence with earthquakes of moderate local magnitudes and shallow hypocentral depths. After the main shocks of May 20, collapse of buildings and lifeline ruptures were widely observed in the epicentral area within a distance of about 15 km, where large acceleration values with prevailing vertical component were recorded. Locally, at a greater distance, intense and spectacular liquefaction effects were observed. They mainly affected the earthen embankments of the old Reno river channel (paleochannel), and, to a lesser extent, their immediate surroundings. In these far-field areas, ground surface accelerations were significantly low and not consistent with the spreading and extent of the observed liquefaction effects. A detailed geotechnical survey was performed to identify depth, location and behaviour of liquefied soil layers and to analyse their influence on ground response and surface liquefaction effects. Results from in situ and laboratory tests, performed under static and dynamic loading conditions, are presented herein and a complete geotechnical model of the ancient levees and the underlying soil deposit is proposed for numerical site-specific seismic analyses. More attention was paid to analysing the influence of non-linear behaviour of interbedded liquefied sands on the expected surface ground motion. Implications and limits of the results obtained are discussed with, finally, proposals for adjustments to 1-D linear equivalent models operating in the frequency domain, for taking into account stiffness degradation of liquefiable layers at high strain levels.
... These phenomena mainly consisted of sand boils, ground fissures, intense ejection of sand and water (craterlets) from ground cracks or hydraulic wells. To a lesser extent, they induced large horizontal ground displacements (lateral spreading) and foundation settlements (Facciorusso et al., 2015a(Facciorusso et al., , 2016Vannucchi et al., 2012). The irregular distribution of liquefaction effects, which are aligned and clustered along paleoriver beds and crevasse splays (Di Manna et al., 2012;Papathanassiou et al., 2015), was controlled by the abundance of sandy layers in the uppermost 5 m (Emergeo Working Group, 2012). ...
... High susceptibility to liquefaction of saturated, well-sorted, sand of fluvial origin at depths of about 9 m has been reported from recent studies based on a CPT-based approach similar to the one adopted in this work (Chini et al., 2015;Facciorusso et al., 2015a). Grain size analyses performed on ejected liquefied material sampled following the Po Plain 2012 earthquake have shown that the extruded material commonly consists of fine sand to silty sand Facciorusso et al., 2016). Although the primary textural features of subsurface deposits and extruded sand in the study area have been disturbed during coring operations and venting, geochemical composition (i.e., the relatively high vanadium content in Fig. 4) suggests that the material that underwent liquefaction was finer-grained (fine sand) than the typically medium to coarse sand encountered within the Po fluvial-channel sediment bodies. ...
... At these sites, size-grain distribution, sediment composition, and groundwater level depth are commonly favorable to liquefaction, and the presence of static shearing stresses due to the topographic condition may induce even more severe effects on the ground surface (lateral spreading). In the specific case of the Po Plain 2012 earthquake, liquefaction has been inferred to occur in the uppermost 5 m of saturated fluvial sand bodies, below outcropping fluvial ridges (Emergeo Working Group, 2012;Facciorusso et al., 2016). We document from the Quistello-Moglia area that extensive liquefaction phenomena are not necessarily coupled with outcropping fluvial bodies, and that liquefaction may originate at greater depths (7-10 m), away from sub-recent river axes, in areas dominated by muddy deposits at the surface (see Bastin et al., 2015Bastin et al., , 2016. ...
Studies on earthquake-induced liquefaction tied to high-resolution stratigraphic analysis have been rarely undertaken. We report the results of a multidisciplinary study from the Quistello-Moglia area, in the central Po Plain (northern Italy). In this region, combined stratigraphic, sedimentological, geotechnical, and geochemical data allowed assessment of liquefaction potential and identification of the primary source for liquefaction, following the second main shock (Mw ~ 6) of the 2012 Po Plain earthquake. Using Cone Penetration Test (CPT)-based simplified procedures for liquefaction hazard evaluation, we assessed the highest liquefaction potential of Holocene, fluvial-channel and related (crevasse/levee) fine sand-silt facies encased in thick, mud-prone floodplain and swamp successions. The liquefaction potential, and the intensity of the manifestations induced on the ground surface, decreased for the vertically-amalgamated, sheet-like Pleistocene sandy fluvial units encountered at depths greater than 13 m. Floodplain and swamp deposits were virtually non-liquefiable. In the Quistello area, the compositional characterization of sands that were liquefied and extruded during the 2012 earthquake reveals the diagnostic geochemical fingerprint of sediment carried by the Po River, as opposed to the Apennine composition of surficial sediments. These data rule out proximity of liquefied layers to the surface, and attest the buried, meandering Po River system at depths of ~ 7–10 m most likely representing the source for the liquefied sand that vented to the surface. Similarly, at Moglia, liquefied sands were likely sourced from loose and saturated, ribbon-shaped, fluvial sand bodies encased in mud, though at shallower (4–7 m) depths. Pronounced liquefaction phenomena in alluvial plain systems are commonly believed to be associated primarily with elongate topographic ridges following paleo-river courses. Here, we document that under favorable stratigraphic conditions liquefaction may also occur away from surficial channel-levee systems, in areas dominated superficially by overbank fines. Combining subsurface stratigraphic analysis with geotechnical data, thus, is critical to investigate liquefaction patterns and delineate liquefaction hazard zones.
... In light of the above, the aim of the authors is to make a dataset of about 1800 geological, geophysical, geotechnical, and hydrogeological in situ investigations and related parameters collected in the Terre del Reno municipality freely available (Emilia-Romagna region, Italy). The study area is affected by severe seismic hazards and prone to seismically induced effects, as extensively documented by the 2012 seismic sequence which was characterized by more than 2000 earthquakes (Facciorusso et al., 2016). Two main shocks were recorded during the crisis: the first one on 20 May with M L 5.9 and the epicenter in Finale Emilia and the second one on 29 May with M L 5.8 and the epicenter in Medolla, both in Modena Province. ...
... As widely reported in the bibliography, the propagation of seismic waves through the upper portion of the soil can be modified by local site conditions (i.e., Bozzano et al., 2017;Fabozzi et al., 2021;Falcone et al., 2020Falcone et al., , 2021Gautam, 2017;Luo et al., 2020;Meza-Fajardo et al., 2019) and can determine the triggering of earthquakeinduced effects at ground surface (i.e., Forte et al., 2021;Martino et al., 2017Martino et al., , 2019Giannini et al., 2022;Paolella et al., 2022). In Terre del Reno, these earthquakes triggered several earthquake-induced effects (Chini et al., 2015;Papathanassiou et al., 2015), among which linear and punctual liquefaction effects were the most prominent. ...
In 2012, the Emilia-Romagna region (Italy) was struck by a seismic crisis characterized by two main shocks (ML 5.9 and 5.8) which triggered relevant liquefaction events. Terre del Reno is one of the municipalities that experienced the most extensive liquefaction effects due to its complex geostratigraphic and geomorphological setting. This area is indeed located in a floodplain characterized by lenticular fluvial channel bodies associated with crevasse and levee clay–sand alternations, related to the paleo-Reno River. Therefore, it was chosen as a case study for the PERL project, which aims to define a new integrated methodology to assess the liquefaction susceptibility in complex stratigraphic conditions through a multi-level approach. To this aim, about 1800 geotechnical, geophysical, and hydrogeological investigations from previous studies and new realization surveys were collected and stored in the PERL dataset. This dataset is here publicly disclosed, and some possible applications are reported to highlight its potential.
... Nevertheless, the variability of seismic excitation in the intermediate layer is investigated considering largely different seismic inputs in the parametric analysis. The constitutive parameters for each model (see Table 1) have been set from the back analysis of a case study in Terre del Reno (Italy) (Fioravante et al. 2013;Sinatra and Foti 2015;Facciorusso et al. 2016). In this scheme, the upper crust is made of silty-clayey soil (PI = 15 ÷ 20%), while the lower base is made of relatively stiff clays. ...
... The PM4Sand model has been calibrated to capture the cyclic undrained behaviour of the liquefiable sandy layer seen by Facciorusso et al. (2016). In particular, four triaxial undrained cyclic tests have been numerically simulated with the adopted code (FLAC v8, Itasca, 2016) matching the liquefaction resistance curve (CSR vs. N liq ). ...
The extensive injury caused to buildings by liquefaction during past earthquakes, with the uneven spatial distribution of damage, raises the need for rapid predictive tools, applicable at a large scale, that comprehensively account for the properties of earthquake, subsoil and structure. A method is herein proposed to quantify the angular distortion of framed low-rise buildings based on a simple characterization of the above factors. The analysis moves from past literature criteria introduced to quantify the vulnerability of buildings under static conditions and extends their applicability to liquefaction assessment integrating parametric two-dimensional numerical analyses with recent literature predictive formulas and machine learning inference. The numerical calculation, performed for variable stratigraphic and mechanical characteristics of the subsoil, ground motion and equivalent flexural stiffness of the foundation, quantifies the role of each factor on the absolute settlement and angular distortion. Then the dependency on the different factors of the angular distortion is inferred with an artificial neural network, grouping parameters to limit the number of input variables and express results with charts that make prediction more accessible.
... Nevertheless, the variability of seismic excitation in the intermediate layer is investigated considering largely different seismic inputs in the parametric analysis. The constitutive parameters for each model (see Table 1) have been set from the back analysis of a case study in Terre del Reno (Italy) (Fioravante et al. 2013;Sinatra and Foti 2015;Facciorusso et al. 2016). In this scheme, the upper crust is made of silty-clayey soil (PI = 15 ÷ 20%), while the lower base is made of relatively stiff clays. ...
... The PM4Sand model has been calibrated to capture the cyclic undrained behaviour of the liquefiable sandy layer seen by Facciorusso et al. (2016). In particular, four triaxial undrained cyclic tests have been numerically simulated with the adopted code (FLAC v8, Itasca, 2016) matching the liquefaction resistance curve (CSR vs. N liq ). ...
The huge impact caused by liquefaction during past earthquakes has raised the need for predictive formulas applicable at the large scale to forecast the movement in the foundation caused by the seismic liquefaction phenomenon in sands. A method herein developed with this aim to quantify angular distortion of framed low-rise buildings based on simple characterization of the seismic input, subsoil and structure. The analysis moves from past literature criteria introduced to quantify the vulnerability of buildings under static conditions and extends their applicability to liquefaction assessment integrating recent literature predictive formulas, parametric two-dimensional numerical analyses and artificial neural networks. Numerical calculation, performed for variable stratigraphic and mechanical characteristics of the subsoil, ground motion and equivalent flexural stiffness of the building, quantifies the role of each factor on the absolute settlement and angular distortion. Then the dependency on the different factors of the angular distortion is inferred with an artificial neural network (ANN), grouping parameters to limit the number of input variables and express results with charts that make prediction more accessible.
... The most important properties of soils influencing seismic wave propagation are stiffness and damping that are commonly expressed in terms of secant shear modulus (G) and damping ratio (D). The damping ratio may assume a critical role in evaluating the response of soils to seismic excitation (Facciorusso, Madiai, and Vannucchi 2012;Facciorusso, Madiai, and Vannucchi 2016;Madiai et al. 2015) because it is used to quantify the dissipation of elastic energy of the traveling waves and the consequent attenuation in seismic motion. For the purposes of seismic wave propagation analyses, soils are usually modeled as a Kelvin-Voigt material because of the mathematical convenience of representing the elastic energy dissipation by means of viscous damping. ...
... Empirical curves from Yokota, Imai, and Konno (1981) threshold volumetric strain, if the same pair of successive peaks is selected and the same strain level is considered, D significantly decreases with increasing PI or σ 0 0 or both, as evidenced by many other authors (Vucetic and Dobry 1991;Darendeli 2001;Facciorusso, Madiai, and Vannucchi 2016;among others). ...
Measurement of soil properties under cyclic and dynamic loading conditions is a critical task in the solution of most geotechnical earthquake engineering problems. The main dynamic properties of soils are usually expressed in terms of shear modulus and damping ratio that are generally obtained from laboratory tests. To date, the resonant column test is considered one of the most accurate ways to determine dynamic soil properties at low to medium-strain levels. Because it allows for investigation of a wide range of strain amplitudes, it is a valuable tool for characterizing the shear soil behavior for a large number of practical geotechnical problems. One of the approaches followed in estimating the damping ratio from the resonant column test is the free vibration method (also called logarithmic decrement or amplitude decay method). It consists of analyzing the time history of the damped free vibrations of the specimen once harmonic loading is cut off after reaching the resonant conditions. The soil damping ratio is determined measuring the logarithmic ratio of the amplitude of any two successive peaks of the system damped motion (logarithmic decrement). In this article, the influence on the damping ratio of the shear strain level, the plasticity index, the confining pressure, and the time interval between the peaks selected in calculating the logarithmic decrement is evaluated from the results of resonant column tests performed on 51 undisturbed isotropically consolidated fine-grained soil specimens.
... The most important properties of soils influencing seismic wave propagation are stiffness and damping that are commonly expressed in terms of secant shear modulus (G) and damping ratio (D). The damping ratio may assume a critical role in evaluating the response of soils to seismic excitation (Facciorusso, Madiai, and Vannucchi 2012;Facciorusso, Madiai, and Vannucchi 2016;Madiai et al. 2015) because it is used to quantify the dissipation of elastic energy of the traveling waves and the consequent attenuation in seismic motion. For the purposes of seismic wave propagation analyses, soils are usually modeled as a Kelvin-Voigt material because of the mathematical convenience of representing the elastic energy dissipation by means of viscous damping. ...
... Empirical curves from Yokota, Imai, and Konno (1981) threshold volumetric strain, if the same pair of successive peaks is selected and the same strain level is considered, D significantly decreases with increasing PI or σ 0 0 or both, as evidenced by many other authors (Vucetic and Dobry 1991;Darendeli 2001;Facciorusso, Madiai, and Vannucchi 2016;among others). ...
Measurement of soil properties under cyclic and dynamic loading conditions is a critical task in the solution of most geotechnical earthquake engineering problems. The main dynamic properties of soils are usually expressed in terms of shear modulus and damping ratio that are generally obtained from laboratory tests. To date, the resonant column test is considered one of the most accurate ways to determine dynamic soil properties at low to medium-strain levels. Because it allows for investigation of a wide range of strain amplitudes, it is a valuable tool for characterizing the shear soil behavior for a large number of practical geotechnical problems. One of the approaches followed in estimating the damping ratio from the resonant column test is the free vibration method (also called logarithmic decrement or amplitude decay method). It consists of analyzing the time history of the damped free vibrations of the specimen once harmonic loading is cut off after reaching the resonant conditions. The soil damping ratio is determined measuring the logarithmic ratio of the amplitude of any two successive peaks of the system damped motion (logarithmic decrement). In this article, the influence on the damping ratio of the shear strain level, the plasticity index, the confining pressure, and the time interval between the peaks selected in calculating the logarithmic decrement is evaluated from the results of resonant column tests performed on 51 undisturbed isotropically consolidated fine-grained soil specimens.
... A direct correlation among the position of the sand boil zones in relation to the paleochannel distribution is particularly evident when analyzing the alluvial stratigraphy below the Reno historical embankments and the surrounding alluvial plain (Figs. 10, 11, and 12). Previous authors agreed that the major effects due to soil liquefaction in the San Carlo and Mirabello area occurred in the sandy saturated layers lying within or below the historical banks of the paleo-Reno River despite several field surveys demonstrated that extensive sand ejection also occurred in the surrounding alluvial plain which are dominated by muddy deposits at the surface (Emergeo Working Group, 2013;Papathanassiou et al., 2015;Caputo et al., 2016;Facciorusso et al., 2016;Stefani et al., 2018). These controversial observations generated speculative inferences that were never adequately addressed. ...
Earthquake-induced liquefaction phenomena are commonly observed at shallow depths or at the ground surface above Holocene alluvial deposits. Nonetheless, a high-resolution examination of the relationship between surface manifestations and alluvial stratigraphy has been rarely attempted. In this study, we provide a detailed subsurface model from a selected sector of the southern Po Plain affected by widespread liquefaction processes triggered by the 2012 Emilia-Romagna seismic crisis. We report a comprehensive sedimentological and CPT-based characterization of the Terre del Reno subsoil and investigate how the stratigraphy controls earthquake-induced liquefaction phenomena. The main facies associations making up the alluvial subsoil constitute the basic elements of the liquefaction system, herein named host, source and sedimentary cap. Their subsurface distribution documents the presence of fluvial bodies prone to liquefaction beneath the earthen levees and across an area dominated by flat muddy floodplain deposits with no physical evidence of paleochannels at the surface. In addition, our observations suggest that vertical and lateral changes in stratigraphy control the mode and location of liquefaction evidence at the surface in both settings. In particular, the relative thickness of fluvial channel bodies vs. channel levee deposits (source-seal couplet) appears to control the severity of sand ejection at the surface. Our findings also suggest that vertical and lateral discontinuities within source layers prevent the occurrence of widespread liquefaction features. Conversely, lateral spreading effects and differential underground hydrostatic pressure at the interface between saturated and less permeable units are accountable for repeated sand ejection along surface fractures.
This case study constitutes a unique natural laboratory thanks to the quality and density of available data. However, we emphasize that a similar approach can be useful to promote source-layer identification in areas characterized by poor or sparse data and to mitigate liquefaction hazards in urban areas built on alluvial plains.
free access until November 16, 2022 at:
https://authors.elsevier.com/a/1fq2J8RVh-Qg6
... The borehole log revealed the presence of a silty clay (CL) crust in the upper 3.5 m with an average plasticity index (PI) of 20%, followed by a nonplastic silty sand with FC typically in the range 25%-35% and therefore classified as SM (Table 2) A selection of grain-size distribution curves determined on the soil samples is provided in Fig. 3(a), whereas the SPT blow counts N SPT recorded in silty sands are plotted in Fig. 3(b), together with values of fines content obtained from sieve analysis. It is worth observing that results from particle-size analysis are in good agreement with the high FC detected for the nonplastic silty-sandy deposits previously investigated in the liquefied areas after the 2012 Emilia-Romagna seismic sequence (e.g., Porcino and Diano 2016;Facciorusso et al. 2016;Fontana et al. 2019). SPT blow counts (N SPT ) turned out to be quite low between 3.5 and 6.0 m in depth, although increasing at greater depth. ...
Following the 2012 Emilia-Romagna seismic sequence, widespread liquefaction of silty sands was observed, providing the opportunity to enhance our knowledge of the influence of fines content on seismic hazard and mitigation works. This paper presents the results of a thorough geotechnical investigation performed in connection with full-scale controlled blast tests in Bondeno, Italy, a small village that suffered liquefaction in 2012. Piezocone (CPTU) and seismic dilatometer (SDMT) tests were performed in natural and improved soils after rammed aggregate pier (RAP) treatment to a depth of 9.5 m to provide accurate soil characterization, evaluate liquefaction, and verify the effectiveness of the ground improvement. The combined use of piezocone (CPTU) and flat dilatometer (DMT) data provided reliable estimates of the overconsolidation ratio and at-rest earth pressure coefficient and highlighted the soil improvement in silty sands between 4 and 9 m in depth. Shear-wave velocity measurements showed a low sensitivity to RAP installation. The treatment effectiveness was also confirmed by the use of the simplified procedures for liquefaction assessment, underlining the important influence of the adopted fines profile and by the blast-induced liquefaction. CPTU and DMT parameters remained approximately unchanged between the piers after the detonation.
... San Felice sul Panaro) have been observed following both the May 20 th and 29 th shocks (Pizzi and Scisciani 2012;Emergeo Working Group 2013). Moreover, the May 20 th aftershocks, occurred within a close time interval (less than 4 minutes with M L between 4.8 and Paolucci et al. (2015) for the M W = 5.9 on May 29 th 5.0), may have had some effects on pore water pressure build-up within the saturated cohesionless layers, especially in the municipality of Terre del Reno (villages of Sant'Agostino, San Carlo, Mirabello) where the most and largest liquefaction effects were observed (Sinatra and Foti 2015;Facciorusso et al. 2016). ...
This paper presents a comprehensive geological and geotechnical study of the whole area affected by liquefaction following the 2012 Emilia earthquakes, including all the available information from the field reconnaissance surveys, in situ tests, and laboratory analyses. The compilation was performed at 120 liquefied sites to verify and validate the reliability of liquefaction charts in alluvial sediments, and to assess liquefaction induced by the 2012 seismic sequence in the Emilia plain. The results reveal a wide range of grain sizes (from clean sands to sandy silts) and compositional characteristics (quartz-rich to litharenitic) in the 2012 ejecta, and show a strong relationship between the liquefaction and stratigraphic architecture of the subsurface. The availability of in situ tests at the liquefied sites makes it possible to verify and validate the reliability of the liquefaction charts in alluvial sediments with respect to the real observations. For the analyzed Emilia case studies, the use of non-liquefiable crust provides better estimations of the liquefaction manifestations when coupled with the thickness of the liquefiable layer rather than with the liquefaction potential index. Altogether, this work makes available to the international scientific community a consistent liquefaction database for in-depth earthquake studies.
... Data yang diperlukan dalam penelitian ini adalah data hasil uji Sondir/CPT (Cone Penetrometer Test) yang diambil dari lokasi penelitian dengan menggunakan alat Sondir/CPT mekanik, namun untuk keperluan analisis data nilai tahanan ujung ( ) dan tahanan friksi ( ) yang didapat dari lapangan dikoreksi terlebih dahulu kedalam nilai sondir elektrik [10]. Selanjutnya, peta bahaya gempa yang digunakan adalah peta gempa tahun 2017, dengan data yang digunakan adalah nilai PGA (Peak Ground Acceleration) kemungkinan telampaui 10% dalam 50 tahun, 7% dalam 75 tahun dan 2% dalam 50 tahun untuk kelas situs tanah lunak dan sedang. ...
ABSTRAKKerusakan infrastruktur yang terjadi di Indonesia bukan hanya diakibatkan oleh beban dinamis gempa, namun juga dipengaruhi oleh respon tanah di bawahnya ketika gempa terjadi, salah satu contohonya adalah fenomena likuefaksi. Proyek Pembangunan Jalan Tol Probolinggo – Banyuwangi, Jawa Timur berada pada zona kerentanan likuefaksi sedang dan berada dekat dengan sesar Probolinggo yang memiliki pegerakan 0,2mm per tahun dan memiliki besar magnitudo 6.5 Mw. Penelitian ini dimaksudkan untuk mengukur potensi likuefaksi yang mungkin terjadi pada proyek pembangunan tol Probolinggo – Banyuwangi dengan menggunakan data Cone Penetration Test (CPT) berdasarkan metode analisis Shibata & Terapaksa, Robertson & Wride, Youd & Idriss, Juang et. al dan Idriss & Boulanger untuk mencari nilai rasio tegangan siklik (CSR) dan rasio tahanan siklik (CRR). Data pendukung lainnya pada analisis potensi likuefaksi ini adalah peta bahaya gempa 2017 dengan klasifikasi situs tanah lunak dan sedang. Hasil penelitian menunjukan bahwa jenis tanah yang terlikuefaksi adalah tanah pasir dan lanau kepasiran, jenis tanah ini sangat berpengaruh terhadap nilai CRR, sedangkan nilai CSR dipengaruhi oleh percepatan puncak gempa dan klasifikasi situs tanah.Kata kunci: gempa, likuefaksi, metode analisis, CSR, CRR, CPT, percepatan puncak ABSTRACTInfrastructure damages that have been found in Indonesia were not only caused by dynamic loads of earthquake, but also by the soil response underneath it while an earthquake occurs and one of it being a phenomenon called liquefaction. The project of Probolinggo-Banyuwangi Toll Road in East Java is within a moderate zone of liquefable soil, located near Probolinggo fault which is moving 0.2mm every year, and a magnitude of 6.5 Mw. This research estimated the liquefaction potential of this project with the soil data obtained by Cone Penetration Test, analyzed by using the method of Shibata & Terapaksa, Robertson & Wride, Youd & Idriss, Juang et. al and Idriss Boulanger, calculating the Cyclic Stress Ratio and Cyclic Resistance Ratio. This analysis of the potential of liquefaction used the map of earthquake in 2017 applied to soft and medium soil class. This research shows that the type of soil liquefied is sand soil and sandy silt soil. Both of these types gave a significant influence in calculating the CRR value, while the CSR value in influenced by the maximum acceleration of earthquake and the soil classification.Keywords: earthquake, liquefaction, analysis method, CSR, CRR, CPT, maximum acceleration
... Thus, at several sites, seismic shaking can considerably exceed the average amplitude of the shaking affecting the surrounding areas (Bakir et al., 2002;Dolce et al., 2003, among others). The evaluation of seismic site effects may be particularly difficult if topography and/or buried structures interact with the waveforms (Hough et al., 2010;Hartzell et al., 2014;Madiai et al., 2016Madiai et al., , 2017Facciorusso et al., 2016;Ba et al., 2017), producing both changes in the vibration direction and in seismic ray path, and generation of surface waves (Sanchez-Sesma et al., 1989;Kawase and Aki, 1990;Kawase, 1996;Rovelli et al., 2001;Narajan and Singh, 2006;Maufroy et al., 2017;Wirth et al., 2018;Jahromi and Karkhaneh, 2019). ...
The estimate of seismic site effects by experimental approaches is based on different assumptions aimed at simplifying the complex actual site conditions and related uncertainties. However, the reliability of the results can increase if the experimental data is focused on quite strong seismic sequences and the on-site acquisition of a large number of signals is deemed strategic for the assessment of the expected phenomena. Based on these considerations, the ground motion at the Red Zone sector of Amatrice hill, violently struck by the 2016–2017 Central Italy seismic sequence, was analyzed via an observational approach. A large set of weak motions (moment magnitudeMw 2.5–3.9) was analyzed in this study by means of standard (SSR) and horizontal to vertical (HVSR) spectral ratio techniques. The results from the experimental analysis of the site effects by using weak motion and noise signals show a significant amplification at the top of Amatrice hill with a remarkable polarization of the motion and changes in spectral shapes according to the topographic setting of the relief.
... Bertolini and Fioroni, 2012;Borgatti et al., 2012;Di Manna et al., 2012;Marcaccio and Martinelli, 2012;Ninfo et al., 2012;Papathanassiou et al., 2012;Pizzi and Scisciani, 2012;Vannucchi et al., 2012;Facciorusso et al., 2015b;Romeo et al., 2015). These studies showed that the location of the 2012 coseismic effects is strongly dependent on the existence of saturated sand layers at shallow depths, mostly corresponding to paleo-channels and crevasse splays (Di Manna et al., 2012;Emergeo, 2012;Facciorusso et al., 2016). Accordingly, the geomorphological evolution and stratigraphy of the Po Plain have been regarded as major factors in the assessment of coseismic effects and seismic hazard in the area. ...
Large portions of the highly populated central Po Plain in northern Italy are susceptible to major liquefaction–induced ground failure and resulting damage, as illustrated by the 2012 Mw 5.6–5.8 earthquake sequence. Our work presents a comprehensive geomorphological, stratigraphic and geotechnical dataset from a 1012 km² study area in the alluvial plain, analysed through the integration of different methodologies. For hazard reduction planning, we qualitatively and quantitatively assess liquefaction potential by the identification of three discrete geomorphological domains. Each geomorphological domain has variable Late Pleistocene to Holocene geological evolution, geotechnical characteristics and thus liquefaction susceptibility, as deduced from interpretation of three 25–m deep continuous cores and calculation of liquefaction potential based on the geotechnical analysis of 239 cone penetration tests (CPTs). For land use planning, we present this information at various map scales consistent with inherent uncertainties of data availability. The investigation procedures and geological–geotechnical interpretations may be applicable to similar liquefaction–prone areas elsewhere.
... The measurement of soil properties under cyclic and dynamic loading conditions is a critical task in the solution of most geotechnical earthquake engineering problems such as ground response analysis, large area microzonation studies, and geotechnical design in the dynamic domain (Ansal et al., 2010;Crespellani, 2014;Facciorusso et al., 2016;Finn, 2000;Madiai et al., 2017;Pagliaroli, 2018;Sa´nchez-Sesma et al., 2002;Stokoe et al., 1999). The most important properties influencing soil behavior under dynamic conditions are stiffness and damping that are commonly expressed in terms of secant shear modulus, G, and damping ratio, D, which can vary with the level of shear strain induced. ...
Measurement of soil properties under cyclic and dynamic loading conditions is a critical task in the solution of most geotechnical earthquake engineering problems. The main dynamic properties of soils are usually expressed in terms of shear modulus, G, and damping ratio, D, and they are generally obtained from laboratory tests at different strain levels. Dynamic geotechnical problems often require a site-level or territorial approach involving a considerable number of dynamic laboratory tests that might be too expensive and time-consuming. Thus, it is a common practice to use empirical relationships between dynamic parameters and measurements from routine geotechnical tests. Therefore, the availability of a large and reliable archive of multiple testing results constitutes a fundamental step for geotechnical earthquake engineers and researchers. To this aim, a large data-set of the index and dynamic parameters measured from 170 undisturbed clay samples obtained from 90 sites in Central and Northern Italy is made available, and its use and application are further described and discussed.
... In Italy, recent strong earthquakes include the earthquake in central Italy that occurred on 24 August 2016 [13], the Emilia Romagna earthquake that occurred on 29 May 2012 [14][15][16], the L'Aquila earthquake that occurred on 6 April 2009 [17,18], the San Giuliano di Puglia earthquake that occurred on 31 October 2002 [19], the Umbria-Marche earthquake sequence of September-October 1997 [20], and the Catania earthquake that occurred on 13 December 1990 in southeastern Sicily. To this aim, seismic microzonation defines the local seismic hazard through the identification of zones characterized by homogeneous seismic behavior that also includes the earthquake-induced effects, such as the slope instability, liquefaction in saturated granular soil, etc. ...
The complex cyclic shear stress path experienced by the soil during an earthquake, which could also induce liquefaction phenomena, can be approximated in the laboratory only by using sophisticated testing apparatuses. Cyclic triaxial tests have been widely used, especially for coarse grained soils, as in this study. In the framework of the design for the seismic retrofitting of the "Ritiro viaduct" foundations along the A20 motorway connecting Messina with Palermo (Italy), a soil liquefaction study was also carried out. With this aim, a detailed geological and geotechnical characterization of the area was performed by in situ and laboratory tests, including seismic dilatometer Marchetti tests (SDMTs), the combined resonant column (RCT) and cyclic loading torsional shear tests (CLTSTs), and undrained cyclic loading triaxial tests (CLTxTs). In particular, the paper presents the results of cyclic triaxial tests carried out on isotropically consolidated specimens of a sandy soil. The seismic retrofitting works include the reinforcement of the foundation and replacement of the decks with newly designed type and structural schemes, mixed steel, and concrete with continuous girder. During the investigation, data were acquired for the characterization of materials, for the definition of degradation phenomena with the relative identification of possible causes, and for the estimation of the residual performance characteristics of the building. The structural campaign of investigations necessary to determine all of the key parameters useful for a correct definition of the residual performance capabilities of the work was divided into two phases: One in situ and one in the laboratory.
... These ground effects occurred within a maximum distance from the earthquake epicenter of about 30 km [3,[5][6][7]. Their location, usually along paleochannels and out-flow fans, has been related to the pervasive occurrence of sand layers, to their geotechnical properties and to the existence of a shallow water table, which are prerequisites to the phenomenon occurrence [5,6,8,9]. ...
A geophysical conceptual model for sites prone to seismic liquefaction is presented, introducing a geophysical protocol to characterize the liquefaction proneness. Three parameters are used to characterize homogeneous units: vs, a proxy of the geotechnical classes of soils, vp related to the saturation degree and vp/vs ratio, related to the liquefaction geophysical susceptibility. A layer is geophysically susceptible to liquefaction when it meets the following criteria: a) vs< 270 m/s and 1300 <vp< 1800 m/s; b) vp/vs> 5. The model has been tested and validated in the Quistello site, where liquefaction occurred during the 2012 Emilia earthquake. The validation of the proposed geophysical model for liquefaction susceptibility against the geotechnical one, calculated from CPTU, indicates the reliability of the proposed approach. This approach was extended to other sites affected by the 2012 seismic swarm. The study demonstrates that the geophysical susceptibility to liquefaction could be an indicator to support microzonation studies concerning the liquefaction proneness of extended areas.
... However, for the reduction of seismic risk, the development of innovative experimental activities that enable the advancement of knowledge in the field of seismic geotechnical hazard assessment of sites and of the vulnerability of infrastructure and civil and industrial facilities is necessary. Geological and geotechnical aspects related to seismic prevention are particularly topical in Italy also in rela-tion to the effects caused by the recent earthquakes in the city of L'Aquila Santucci de Magistris et al., 2013), in the Emilia region [Facciorusso et al., 2016] and in the central Italy. In the past, the study of these problems was often limited to the geotechnical characterization of the sites and to the analysis of phenomena such as, subsidence or local seismic amplification, not reaching consistent suggestions about the possibility to realize soil remediation to ensure the structures preservation. ...
The recent advances in cloud computing have opened new opportunities in emergency management issues due to earthquakes. In this context, Geographic Information System (GIS) based solutions have been recently investigated, with the aim of the prevention and the reduction of seismic risk. The paper focuses on the results of the research project PRISMA - cloud PlatfoRms for Interoperable SMArt Government in which an innovative open source GIS system, based on the knowledge in the field of dynamic characterization of soil has been developed in order to assess the local seismic hazard and the seismic zonation of the Enna area in the south of Italy. The paper describes how the application of prospecting and surveying techniques allowed a decisive improvement in the geological knowledge of the area, contributing to define the subsoil model for the purposes of seismic microzonation. The seismic geotechnical characterization has been performed with laboratory tests including the resonant column and cyclic torsional shear test on undisturbed samples. The interpretation of geophysical and geotechnical data and their correlation with geological units are presented as microzonatic map. Finally, a wireless sensor network has been used for structural monitoring at the aim to highlight the significant benefits when the time available for access is limited, by representing an effective way of managing risks. All the data relating to the monitoring of the buildings and to the geological and geotechnical characterization are available on the web GIS platform, representing an important tool for the prevention and reduction of the seismic risk. © 2018 the Istituto Nazionale di Geofisica e Vulcanologia. All rights reserved.
... The objectives of this experiment were: (i) to evaluate liquefaction induced settlement of Apennine Silts and Sands and Po River Sands; (ii) to determine downdrag forces on pile foundations; (iii) to measure change in shear wave velocity/shear modulus with excess pore pressure; and (iv) to measure change in soil properties with time after liquefaction. The target site selected for the research was located in Mirabello (near Ferrara, northern Italy), a village strongly affected by liquefaction phenomena during the 2012 Emilia Romagna earthquake (Caputo and Papathanasiou 2012, Emergeo Working Group 2013, Fioravante et al. 2013, Vannucchi et al. 2012, Facciorusso et al. 2016. At the trial site, invasive tests, such as piezocone (CPTu) and seismic dilatometer (SDMT) tests, and non-invasive tests were carried out before and after the execution of two blast test sequences to study the variation in physical properties of the soils. ...
... Italy is a high seismic hazard country, characterized by urban areas with significant level of seismic vulnerability Castelli et al. , 2016aCastelli et al. , 2017aGrasso et al. 2016;Monaco et al. 2011). In Italy recent strong earthquakes include the central Italy earthquake of 24th August 2016 (de Silva et al. 2016), the Emilia Romagna earthquake of the 29th May 2012 (Facciorusso et al. 2016), the L'Aquila earthquake of the 6th April 2009 Santucci de Magistris et al. 2013), the St. Lucia earthquake of the 13th December 1990 occurred in the South Eastern Sicily. In particular, during the Emilia Romagna earthquake, liquefaction phenomena occurred in several municipalities. ...
Recent earthquakes frequently showed liquefaction of sandy soils. In these case one of the major challenges is the assessment of the residual strength of liquefied soil. Laboratory researches have clearly indicated that liquefaction susceptibility depend on many factors including soil grain size distribution, effective confining stresses and applied stress path in terms of cyclic shear stress amplitude. The complex cyclic shear stress path experienced by the soil during an earthquake can be reproduced in laboratory only by using sophisticated testing apparatuses. Cyclic triaxial tests have been widely used to asses soil liquefaction potential especially for coarse-grained soils, as in this study. In the framework of the design for the seismic retrofitting of the “Viadotto Ritiro” foundations along the A20 motorway connecting Messina with Palermo, a soil liquefaction study has been carried out. With this aim, a detailed geological and geotechnical characterization of the area has been performed by in situ and laboratory tests including the combined resonant column and torsional shear test and undrained cyclic triaxial tests (CTX). In particular, the paper presents the results of CTX, carried out on isotropically consolidated specimens carried out on specimens of a sandy soil to asses liquefaction strength. The results are plotted in terms of deviator stress q versus axial strain εa , cyclic stress ratio CSR and axial strain εa versus number of cycles Ncyc , effective mean stress p′ versus deviator stress q, cyclic stress ratio CSR and pore pressure ratio Ru versus number of cycles Ncyc . The results show that the cyclic resistance increases with the decrease in the initial confining stress and decreases as the silt content increases and confirme that the coarsest material has a lower tendency to liquefy.
... However, for the reduction of seismic risk, the development of innovative experimental activities that enable the advancement of knowledge in the field of seismic geotechnical hazard assessment of sites and of the vulnerability of infrastructure and civil and industrial facilities is necessary. Geological and geotechnical aspects related to seismic prevention are particularly topical in Italy also in relation to the effects caused by the recent earthquakes in the city of L'Aquila Santucci de Magistris et al. 2013), in the Emilia region (Facciorusso et al. 2016) and in the central Italy (de Silva et al. 2016). ...
Thematic maps, such as seismic risk maps, are a useful tool that researchers use for representing the adverse outcomes that a natural catastrophic event can have over the territory. Generally, in those studies, major attention is focused in urban areas, where the human activities are concentrated. Main concerns are about the existing building stock, mostly composed by structures not compliant with modern seismic design criteria. The realization of a risk map is a complex task that involves the combination of data coming from different field of expertise, such as geology, geotechnical and structural engineering. The paper describes how the application of prospecting and surveying techniques (geological surveys, drilling, down-hole, MASW) allowed a decisive improvement in the geological knowledge of the area, contributing to define the subsoil model for the purposes of seismic microzonation. The interpretation of geophysical and geotechnical data and their correlation with geological units are explained and finally the microzonatic map is presented. The paper also reports the seismic geotechnical characterization executed with laboratory tests including the resonant column and cyclic torsional shear test on undisturbed samples. The results are summarized in terms of variation of stiffness and damping with shear strain. Finally, the use of wireless sensor technology for structural monitoring has significant benefits when the time available for access is often severely limited, by representing an effective way of managing risks once that an area of concern has been identified. The aim of the study is the acquisition of a local knowledge on issues related to seismic risk that may affect urban areas, through the acquisition, management and sharing of complex information. The available information, collected by sensor network, have been combined together in a Geographical Information System tool. The results provide a reliable representation of the seismic risk at urban scale to be used when planning the mitigation measures to be undertaken in order to improve the prevention and reduction of the disastrous effects of the earthquakes.
... Ground response analyses are used to predict surface ground motion and to define elastic response spectra for structural design, vulnerability analyses on existing buildings, and microzoning for urban planning and land use (Madiai et al. 2014). Ground response analyses are performed also to assess stresses and strain vertical profiles in the subsoil for evaluation of liquefaction hazards (Facciorusso et al. 2015(Facciorusso et al. , 2016 and to determine the earthquake-induced forces for slope stability (Facciorusso et al. 2012) or earth-retaining structure analyses (Crespellani et al. 2001). ...
This paper summarizes the main aspects of geotechnical modeling and soil-structure interaction analyses performed for the seismic risk assessment of the San Gimignano towers. Morphological, stratigraphic, and geotechnical characterization of the subsoil is described in the first part of the paper. The results of a geotechnical survey (including two borings with standard penetration tests, downhole tests, and laboratory tests on three undisturbed samples, both in static and dynamic conditions) are described and analyzed. Seismic ground response as well as soil-structure interaction analyses are presented in the second part of the paper. One-dimensional ground response analyses were performed by using a probabilistic approach, and the results were compared with those from ambient noise vibration measurements. The seismic input motions were selected from existing databases of actual strong motion recordings, according to seismic hazard of the site. Soil-structure interaction analyses were performed on a simplified model of the most important San Gimignano tower (Torre Grossa) by applying a numerical multistep method based on the principle of superimposition. The comparison of the obtained results with those presented in previous studies for fixed-base conditions shows small differences (approximately 2%) in the fundamental period of vibration of the tower estimated by means of the different approaches.
... The lessons learned from the earthquakes, which have occurred over the last 50 years (Goodman and Seed, 1966;Sarma, 1975;Chang et al., 1984;Ashford et al., 1997;Martino and Mugnozza, 2005;Lenti and Martino, 2012;Zugic et al., 2014;Gischig et al., 2015), have highlighted the importance of slope dynamic response behaviors and failure mechanisms. At present, investigations of the slope dynamic response behaviors are mainly performed through several methods, including field investigation, seismic station monitoring, numerical simulation, and physical model test (Wang et al., 2003;Yin et al., 2009;Wang et al., 2010;Bozzano et al., 2011;Gischig et al., 2015;Dong and Kutter, 2015;Molnar et al., 2015;Zhang et al., 2015;Facciorusso et al., 2016;Martino et al., 2016). The theory and application in this area are still in the developing stages. ...
Dynamic behavior and failure mechanism of slope during earthquake are hot topics in geotechnical engineering community. In Tianshui area, Northwest of China, the deformation features of loess-mudstone slopes induced by earthquakes are still not well understood. The current study aims to discuss the dynamic behavior of the slope under earthquake, by performing a series of centrifuge shaking table tests and numerical simulations. The results are processed for PGA amplificatory effect study and to evaluate the earthquake induced deformation mechanism. Better agreement is obtained between the results of numerical simulations and centrifuge tests. The results indicated that the acceleration response of the loess-mudstone slope showed several amplifying characteristic: the height effect, lithologic effect and surface effect. It also proves that the displacements in the loess layer are much larger than mudstone. As the input amplitude increased, the shear plastic zone developed along a further slide surface. Tension plastic zone mainly occurred at the crest. Roughly, the regions of earthquake induced deformation state increased with the increase in amplitude of earthquake wave. Deformations occurred at the upper part of the slope. Tensile cracks evolved on the crest and the upper part of slope in loess layer, moreover, failures occurred at slope surface, and only slight deformation at slope toe. Deformations with continuous shear cracks and slope surface upheavals developed at the middle part of slope.
Amatrice is considered the town symbol of the destructive effects induced by 2016 Central Italy seismic sequence. As a result of the two main shocks (August 24th, M=6.0 and October 30th, M=6.5) the ancient urban area of the municipality, located on a hilly promontory, was heavily damaged. Old buildings, but also renovated and new buildings, suffered many cracks and collapses. Subsoil geological, geophysical and geotechnical data were collected in the area and seismic data were also available. By using and interpreting the subsoil data, a 3D-GIS model was developed, that is the basic geometrical model for SiSeRHMap hybrid-analysis. Several 2D sections crossing the seismic station sites were extracted from this model and analyzed by 2D-FEM numerical approaches. Comparison of numerical results and seismic experimental data allowed to: i) validate the subsoil model used in the simulations; ii) show the significant role of the topographic effects in the area under study; and iii) point out the variability of the 2D numerical results depending on the direction of the analyzed cross-sections. © 2019 Associazione Geotecnica Italiana, Rome, Italy.
Recent earthquakes frequently showed liquefaction of sandy soil. In these case one of the major challenges is the selection of the appropriate residual strength of liquefied materials to assess the post-liquefaction stability of embankments and soil structures. Cyclic triaxial tests have been widely used to asses soil liquefaction potential especially for coarse-grained soils, as in this work. In the framework of the design for the seismic retrofitting of the "Viadotto Ritiro" foundations along the A20 motorway connecting Messina with Palermo, a soil liquefac-tion study has been carried out. With this aim, a detailed geotechnical characterization has been performed by in situ and laboratory tests including the combined resonant column and torsional shear test (RCTS) and undrained cyclic triaxial tests (CTX). In particular, the paper presents the results of laboratory tests carried out on specimens of a sandy soil to asses liquefaction potential.
This study is concerned with the results of the research carried out, in the central sector of the Po Plain, specifically in the area between Modena and the Po river. From a methodological point of view, the geomorphological map of the area was prepared after having analyzed the geological literature, interpreted large-scale aerial photographs, analyzed the relief maps with isolines equidistant 1 m, and conducted detailed field research. The area comprised between Modena and the Po river corresponds to the alluvial plain through which the Po itself and its Apennine affluents have wandered almost exclusively in the last 4000-5000 yr. -from Author
Significant and widespread liquefaction effects, which caused panic of inhabitants and damage to buildings and infrastructures, were observed in various areas of Emilia-Romagna region, Italy, during the seismic events of May 20 and 29, 2012, with magnitude respectively of Ml 5.9 and Ml. 5.8. In Italian seismic literature these phenomena represent an interesting case study for a number of reasons: for the exceptional impacts, for the size of the area in which liquefaction effects were observed, for the amount of damage produced, for the rarity of soil liquefaction Italian case histories. Immediately after the earthquake of 20 May an extensive field reconnaissance was conducted through the natural and built environment to capture as quickly as possible surface evidences of liquefaction and to document the extent and the severity of damage. The most significant and widespread liquefaction impacts were found in the two settlements of San Carlo and Mirabello. With the aim of a better understanding of the observed scenarios, a detailed investigation program, including geophysical surveys and geotechnical testing (soundings, cone penetration tests, seismic cone penetration tests, cross-hole and down-hole tests as well as many cyclic laboratory tests), was planned. These investigations are now in progress and will be object of forecoming technical notes. This paper summarizes the observation of soil liquefaction effects made during field investigations and presents a first interpretation, based on available information on ground shaking and soil conditions, of the factors that may have contributed to determine the low liquefaction resistance of soils.
p>On May 20, 2012, a Ml 5.9 earthquake (T1) occurred in the Emilia-Romagna Region of northern Italy. This was preceded by a Ml 4.1 foreshock on May 19, 2012, and followed by several aftershocks, including two Ml 5.1 events, both on the same day. On May 29, 2012, a second strong event of Ml 5.8 (T2) hit the same region, with its epicenter ca. 12 km to the WSW of the first mainshock, T1. The epicentral area of the seismic sequence covers an alluvial lowland that is occupied by both agricultural and urbanized areas, and there were 17 casualties and about 14,000 people left homeless. […] In the present study, we provide a preliminary model of the seismogenic source(s) responsible for the two mainshocks, by comparing the seismic reflection profile interpretation with the available seismological and interferometric data. Furthermore, we show the coseismic ground effects that were observed in the epicentral area during two field survey campaigns: the first conducted after the May 20, 2012, event and the second soon after the May 29, 2012, earthquake, when several sites were revisited to observe the occurrence of newly formed or 're-activated' liquefaction features. Hence, we discuss the origin and location of the coseismic features observed in the context of the local geological–geomorphological setting and with respect to the epicentral distance. Finally, we provide our interpretation for the question: "Why did the mainshock ruptures not break the surface?" […]
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p>Most of the inhabitants of northern Italy were woken up during the night of May 20, 2012, by the Mw 6.1 earthquake [QRCMT 2012] that occurred in the eastern Po Plain. The mainshock was preceded a few hours before by a Mw 4.3 shock, and it was followed by a dozen Ml >4 aftershocks in May and June, amongst which 11 had Ml ≥4.5. On May 29, 2012, a second Mw 6.0 mainshock struck roughly the same area [QRCMT 2012], which resulted in further victims, most of whom were caught under the collapse of industrial warehouses. Such earthquakes are an unexpected event in this region, as testified by the lack of local epicenters in the Italian seismic catalog [Rovida et al. 2011: CPTI11 from now] and by the consequent low level of the local seismic classification (seismic zone 3) [DPC 2012]. Apart from the warehouses and hundreds of old, crumbling farmsteads, severe damage was focused on ancient, tall buildings, such as churches, bell towers, castles, towers and palaces. Residential buildings generally suffered only light and/or moderate effects, apart from some exceptional cases. Using the Mercalli–Cancani–Sieberg (MCS) scale [Sieberg 1930], we began a macroseismic survey in the early morning of May 20, 2012, that ultimately included visits to almost 200 localities, 52 of which were carried out before the second mainshock. […]
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This paper presents the methodology and the results of the local seismic analyses, performed in the bank areas of the Po River (Lombardia and Emilia-Romagna regions, northern Italy) characterized by the highest seismic hazard and finalized for the seismic stability analyses of the banks themselves. The proposed methodology includes the following steps: collection of the pre-existing information and geologic maps; deployment of in-situ investigations by collecting soil samples for geotechnical laboratory tests; definition of the geologic-geophysical and geotechnical model; individuation of the expected seismic inputs; analyses of local seismic response. In this paper, we mainly discuss the results obtained in order to illustrate how the methodology employed enables the definition of the local seismic hazard and allows performing the future stability analyses of the banks. The results are given in term of amplification factors, expected accelerograms and acceleration response spectra modified by the litho-stratigraphic characteristics of the sites.
On the May 20, 2012 (04:03:52 local time; 02:03:52 UTC), a moderate earthquake (Ml 5.9) [Scognamiglio et al. 2012, this volume] with a focal mechanism showing E-W-trending, S-dipping, reverse-faulting occurred in the eastern sector of the alluvial plain of the Po River, close to the border between the Regions of Emilia-Romagna and Lombardia (northern Italy). The tectonic structure is completely blind, but it was well known from a dense grid of seismic profiles for hydrocarbon explorations [e.g., Pieri and Groppi 1981, Toscani et al. 2009]. The earthquake triggered extensive liquefaction-induced ground effects at the surface, and caused severe structural damage to nonreinforced masonry and precast industrial buildings within the broader epicentral area. The hypocenter was at 44.89 ˚N, 11.23 ˚E, at a depth of 6.3 km [Scognamiglio et al. 2012], while the maximum acceleration was recorded in Mirandola, with peak ground acceleration 310 cm/s2 and 264 cm/s2 along the vertical and horizontal components, respectively [Bozzoni et al. 2012, this volume]. In this report, we focus on a zone including the Sant'A-gostino, San Carlo and Mirabello villages (west Ferrara Province), which were built along an abandoned reach of the Reno River and where liquefaction phenomena were particularly diffuse, with very intense local effects. […]
Geomorphological aspects of the flood hazard in the area between the rivers Po, Secchia and Panaro (Po Plain, Northern Italy). This paper examins the geomorphological aspects of the flood hazard in the area between the rivers Po, Secchia and Panaro. The River Po, which flows in the northern part of the study area, and the Rivers Secchia and Panaro, which flowing northwards cross the study area, have periodically caused flooding in their territory. The flood hazard, related to morphological factors, is much higher in the sector north of Modena (where the rivers flow elevated over the surrounding plain between high banks) than in the sector south of the town (where the watercourses run deep in the alluvial plain). North of Modena. in order to defend the territory from the flood hazard the systematic practice to build, strengthen and increase in height artificial banks was adopted. Moreover several meander cuts were carried out along the Rivers Secchia and Panaro (the length reductions correspond to about 11÷12% of their overall length in the plain). As these interventions resulted to be ineffective, flow-regulation systems were constructed in the area of Modena along both rivers. They consists of a regulating dam built across the riverbed and a storage basin bordered by embankments. The historical flood events show that the banks breaches often occured near to paleochannels and that the flooded waters were collected in the lower areas and had as boundaries the embankements and/or the fluvial ridges flanks; sometimes the flooded waters remained for long periods in the areas where mainly clay superficial deposits crop out. Therefore, an important contribution to assess the flood hazard can be given by the geomorphological investigation through the implementation of GIS georeferenced thematic documents (Digital Elevation Model, microrelief, surface deposits and geomorphological maps) and related Data Base.
La determinazione del profilo del modulo di taglio a piccole deformazioni Go risulta particolarmente importante negli studi di interazione terreno-struttura soprattutto in quelle aree ove è possibile il verificarsi di eventi sismici. Nel presente lavoro sono criticamente analizzate le correlazioni disponibili per la determinazione di Go da prove dilatometriche in sito. In particolare, si sono utilizzati i risultati di prove dilatometriche eseguite nel sito "Le saline" di Augusta per determinare, con le correlazioni disponibili in letteratura, il profilo di Go. I valori così ottenuti sono stati confrontati con quelli ricavati da prove Cross-Hole in sito e da prove di colonna risonante e taglio torsionale eseguite in laboratorio su campioni indisturbati prelevati con campionatori Osterberg e Shelby.
The evolution of the central Po plain (N-Italy) during the Holocene is the result of the interplay between fluvial dynamics, natural subsidence, sea level changes, forest cover, and, during the last four thousand years, of land use and exploitation. After a phase of lateglacial entranchement of the fluvioglacial plain, the alpine rivers tributaries of the Po river, among which the Mincio river, were constrained within their terraced valleys, so that the evolution of their valley floor was controlled by the dynamics of the Po river (i.e. the main river) and by the interplay of tectonics and subsidence. One of the most important of the Etruscan villages (Forcello, 16 m a.s.l., VI to IV century b.C.) settled along the valley floor of the Mincio river acted as a river harbour for fluviatile trades connecting the eastern Mediterranean Basin and continental Europe (De Marinis & Rapi, 2005). We presente here multidisciplinary stratigraphical and palaeoenvironmental evidence that this harbour actually rose on a large perifluvial lake (the "Bagnolo lake"), formed into the terraced valley at the beginning of the Iron Age. Independent archeological evidence suggests the lake was dammed by the main river, after diversions related to the "Iron age cold phase" alluvial events (VIII sec. b.C.). The diversion of the main river modified the fluviatile network of the lower alluvial plain, and promoted upstream shipping from the northern Adriatic till the Bagnolo perifluvial lake, were a main harbour was thus settled. The Bagnolo lake was kept until Middle Age reclaming, hence lacustrine sediments enregistered the forest history and human activities since the time of the Etruscan settlement till XIV century AD. A palynological and archeobotanical record, supported by radiocarbon dating on terrestrial macrofossils, testifies the Roman forest clearings and shows the unprecedented evidence of an early Middle Age phase of abandoning. Finally, an overall change in land use is dated at the X century AD.
The resonant-column technique was used to measure the vibration shear modulus of a normally consolidated kaolinite under various anisotropic states of stress. The effects of the deviatoric and isotropic components of stress, void ratio, and other secondary effects are studied. Data from these tests along with other previously published test results for other clays with different structures lead to the following conclusions: (1) The vibration shear modulus is independent of the deviatoric component of ambient stress (octahedral shear stress); (2) the vibration shear modulus decreases with increasing void ratio and Eq. 4 in the paper is a fair representation of the effect of void ratio; the effects of structure seem to be mostly accounted for by the void ratio parameter; (3) considering the isotropic component of ambient effective stress (effective octahedral normal stress), σ¯0, as an independent variable, and not including the effects of void ratio and secondary time effects, the vibration shear modulus varies with σ¯0 to the 0.5 power; and (4) there is a secondary increase of the vibration shear modulus with time, at constant effective stress, not accounted for by changes in void ratio. This stiffness build-up is sensitive to particle disturbance and can be partially or totally destroyed by changes in effective stress. This effect may be quite important for soils in situ.
The shear modulus (G) and damping ratio (D) of two natural clays and both siliceous and carbonatic pluvially-deposited dry sands have been measured at the authors' laboratory by means of a Resonant Column/Torsional Shear apparatus for a strain range of 0·0001% up to 1%. Different kinds of tests were performed on hollow cylindrical specimens off all the: (a) monotonic loading torsional shear tests at constant stress rate, (b) cyclic loading torsional shear tests at constant strain rate or at constant frequency and (c) Resonant Column tests. The results of the above tests enabled the authors to analyse the influence of strain level (&ama;), loading rate (&amadot;), number of loading cycles (N) and type of loading (monotonic or cyclic) on the measured values of G and D.
Les auteurs ont mesuré le module de cisaillement (G) et le rapport d'amortissement (D) de deux argiles naturelles et de dépôts pluviaux de sables secs silicieux et carbonatitiques dans leur laboratoire à I'aide d'essais à colonne résonante et d'essais de cisaillement par torsion dans une plage de contraintes de 0,0001% à 1%. Différents types d'essais ont été effectués avant tout sur des éprouvettes cylindriques creuses: (a) des essais de cisaillement par torsion à charge monotone et à taux de contrainte constant, (b) des essais de cisaillement par torsion à charge cyclique à taux de contrainte constant on à fréquence constante, et (c) des essais à colonne résonante. Les résultats de ces essais ont permis aux auteurs d'analyser I'influence du niveau de deformation, du taux de charge, du nombre de cycles de charge (N) et du type de charge (monotone ou cyclique) sur les valeurs mesur6es de G et D.
Several charts exist for evaluating soil type from electric cone penetration test (CPT) data. A new system is proposed based on normalized CPT data. The new charts are based on extensive data available from published and unpublished experience worldwide. The new charts are evaluated using data from a 300 m deep borehole with wire-line CPT. Good agreement was obtained between samples and the CPT data using the new normalized charts. Recommendations are provided concerning the location at which to measure pore pressures during cone penetration. Key words: soil classification, cone penetration test, in situ, case history.Several charts exist for evaluating soil type from electric cone penetration test (CPT) data. A new system is proposed based on normalized CPT data. The new charts are based on extensive data available from published and unpublished experience worldwide. The new charts are evaluated using data from a 300 m deep borehole with wire-line CPT. Good agreement was obtained between samples and the CPT data using the new normalized charts. Recommendations are provided concerning the location at which to measure pore pressures during cone penetration. Key words: soil classification, cone penetration test, in situ, case history.
On May 20, 2012 an earthquake of magnitude ML=5.9 struck the Emilia Romagna Region of Italy and a little portion of Lombardia Region. Successive earthquakes occurred on May 29, 2012 with ML=5.8 and ML=5.3. The earthquakes caused 27 deaths, of which 13 on industrial buildings. The damage was considerable. 12,000 buildings were severely damaged; big damages occurred also to monuments and cultural heritage of Italy, causing the collapse of 147 campaniles. The damage is estimated in about 5-6 billions of euro. To the damage caused to people and buildings, must be summed the indirect damage due to loss of industrial production and to the impossibility to operate for several months. The indirect damage could be bigger than the direct damage caused by the earthquake.
The resilience of the damaged cities to the damage to the industrial buildings and the lifelines was good enough, because some industries built a smart campus to start again to operate in less of one month and structural and geotechnical guidelines were edited to start with the recovering the damage industrial buildings. In the paper a damage survey is presented and linked with the ground effects. Among these, soil amplification and liquefaction phenomena are analyzed, basing on the soil properties evaluation by field and laboratory tests. Particular emphasis is devoted to the damaged suffered by the industrial buildings and to the aspects of the remedial work linked with the shallow foundation inadequacy and to the liquefaction mitigation effects
p>The Emilia earthquakes of May 20, 2012 (Ml 5.9, INGV; Mw 6.11, http://www.bo.ingv.it/RCMT/) and May 29, 2012 (Ml 5.8, INGV; Mw 5.96, http://www.bo.ingv.it/RCMT/) struck an area that in the national reference seismic hazard model [MPS04; http://zonesismiche.mi.ingv.it, and Stucchi et al. 2011] is characterized by expected horizontal peak ground acceleration (PGA) with a 10% probability of exceedance in 50 years that ranges between 0.10 g and 0.15 g (Figure 1), which is a medium level of seismic hazard in Italy. The strong impact of the earthquakes on a region that is not included among the most hazardous areas of Italy, and the ground motion data recorded by accelerometric networks, have given the impression to the population and the media that the current seismic hazard map is not correct, and thus needs to be updated. Since the MPS04 seismic hazard model was adopted by the current Italian building code [Norme Tecniche per le Costruzioni 2008, hereafter termed NTC08; http://www.cslp.it/cslp/] as the basis to define seismic action (the design spectra), any modification to the seismic hazard model would also affect the building code. The aim of this paper is to briefly present the data that support the seismic hazard model in the area, and to perform some comparisons between recorded ground motion with seismic hazard estimates and design spectra. All of the comparisons presented in this study are for the horizontal components only, as the Italian hazard model did not perform any estimates for the vertical component. […]
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In this paper we present the geological effects induced by the 2012 Emilia seismic sequence in the Po Plain. Extensive liquefaction phenomena were observed over an area of �1200 km2 following the 20 May, ML 5.9 and 29 May, ML 5.8 mainshocks; both occurred on about E–W trending, S dipping blind thrust faults. We collected the coseismic geological evidence through field and aerial surveys, reports from local people and Web-based survey. On the basis of their morphologic and structural characteristics, we grouped the 1362 effects surveyed into three main categories: liquefaction (485), fractures with liquefaction (768), and fractures (109). We show that the quite uneven distribution of liquefaction effects, which appear concentrated and aligned, is mostly controlled by the presence of paleoriverbeds, out-flow channels and fans of the main rivers crossing the area; these terrains are characterised by the pervasive presence of sandy layers in the uppermost 5 m, a local feature that, along with the presence of a high water table, greatly favours liquefaction. We also find that the maximum distance of observed liquefaction from the earthquake epicentre is �30 km, in agreement with the regional empirical relations available for the Italian Peninsula. Finally, we observe that the contour of the liquefaction observations has an elongated shape almost coinciding with the aftershock area, the InSAR deformation area, and the I�6 EMS area. This observation confirms the control of the earthquake source on the liquefaction distribution, and provides useful hints in the characterisation of the seismogenic source responsible for historical and pre-historical liquefactions.
Historical research performed in the 1990s has updated previous compilations of liquefaction-induced phenomena that occurred during the last millenium in Italy. Liquefaction indications are reported in Italy for earthquakes with I o >5–6 (MCS) and M s ≥4.2, 90% of the cases falling within 50 km of the epicenter. The recently re-evaluated seismic parameters of the Italian historical earthquakes, together with the location of 317 indications of liquefaction features, provide a relatively complete database, permitting the author to highlight the distribution of intensity/magnitude values versus epicentral distance. In paleoseismic analyses these relationships may be considered a tool in evaluating the minimum energy of an earthquake that induced liquefaction features. © 2000 Elsevier Science B.V. All rights reserved.
This paper describes a case-history of liquefaction occurred near the village of Vittorito after the April 6, 2009 L’Aquila
earthquake (moment magnitude Mw = 6.3), approximately 45km far from the epicentre. In the document, first, an estimation of the seismic motion in the area
has been made. Thereafter, the performed geotechnical investigation is described, followed by the application of some fast
assessment criteria for the occurrence of liquefaction, recently proposed by the new Italian Building Code. A careful assessment
of all the parameters involved in conventional Seed and Idriss (1971) liquefaction analyses is considered. The cyclic resistance ratio CRR is evaluated by cone penetration tests CPT and by in
situ seismic dilatometer tests SMDT; in the latter case CRR is evaluated by different empirical correlations with shear wave
velocity Vs and horizontal stress index KD. Analytical data confirmed the observed occurrence of the liquefaction in Vittorito, even if the acceleration field in the
area, produced by the L’Aquila earthquake, was very low.
KeywordsL’Aquila earthquake–Attenuation relationships–Cone penetration test–Seismic Dilatometer Test–Liquefaction
Thesis (Ph. D.)--University of California, Los Angeles, 1993. Vita. Includes bibliographical references (leaves 309-320).
A Hardin oscillator was used to apply a steady-state, torsional vibratory load to remolded specimens of kaolinite and calcium bentonite inside a triaxial chamber and under an isotropic consolidation pressure. The principles of the resonant column test were used to determine the dynamic shear modulus. After completion of primary consolidation, the response was studied as a function of time for both drained and undrained conditions. Regression analyses were performed on these data and relationships are presented which show the effects that void ratio, effective stress, and time have on the dynamic response of these two clays. The shear modulus was shown to increase with increasing pressure, decreasing void ratio and time for both materials. This increase was approximately 10% of kaolinite and 40% for bentonite per logarithmic cycle of time after completion of primary consolidation for constant effective stress.
Significant and widespread liquefaction effects were observed in the area of San Carlo and Mirabello villages during the Emilia-Romagna earthquake of May 20 and 29, 2012. After the earthquake, an intensive program of laboratory and in situ (mostly CPT’s) tests was carried out in the affected area. The stratigraphic and geotechnical conditions have been found to predispose the soil deposits to liquefaction phenomena. The triggering conditions, i.e. the design earthquake parameters, have been evaluated according to the most recent seismic hazard analyses and local seismic response analyses. The liquefaction risk, expressed in term of liquefaction potential index (LPI), was determined by using the CPT-based simplified method of Robertson and Wride. The obtained results are not consistent with the observed liquefaction effects and the liquefaction risk seems to be systematically underestimated. In the present paper the reason of this underestimation is investigated and a possible correction for applying the simplified cyclic stress approaches is proposed.
Significant and widespread liquefaction phenomena were observed after the main shock of the Emilia earthquake (Italy) on May 20, 2012. A considerable number of surveys were subsequently performed to accurately test the susceptibility to liquefaction of soil deposits affected by the most severe liquefaction-induced effects and damage. Ground surface morphology was defined in detail by means of LIDAR survey results; subsoil stratigraphy and water table level were inferred from CPT tests and soundings; physical properties and mechanical parameters of soils were obtained from laboratory tests or indirectly inferred from the results of a large number of CPT tests carried out in the area. Two main sandy layers susceptible to liquefaction were identified and appropriately characterized. Seismic loading induced by the main shocks of the sequence was carefully estimated from the peak ground acceleration map produced by the National Institute of Geophysics and Volcanology. More than 90 sites were examined in the area of interest where the most significant cases of liquefaction occurred. A number of statistically independent CPT-based liquefaction field case histories were selected, the critical layer towards liquefaction was identified, and the liquefaction resistance parameter and loading parameter were assessed. Key parameters for each site and critical layer were provided to be added to a select larger and worldwide liquefaction case history database proposed by other authors for estimating CPT-based liquefaction-triggering resistance curves. Finally, applicability to the case study of some more widely used CPT-based simplified approaches was tested. A systematic underestimation of liquefaction potential was found and is discussed, possible reasons are explored, and suggestions are proposed. (C) 2015 American Society of Civil Engineers.
Extensive and spectacular phenomena of soil liquefaction were observed during the Emilia seismic sequence that struck northern Italy on May–June 2012. A back-analysis with simplified procedures based on empirical correlations reveals a small liquefaction potential, which apparently underestimates the observed surface effects. Multiple and close-in-time events were a peculiar aspect of the sequence but cannot be accounted for within the simplified procedure. This study investigates their possible role in excess pore pressure build-up and hence liquefaction triggering. Results of a numerical analysis suggest that aftershocks played a determinant role, leading liquefaction phenomena to such a great extent as observed in the field. This evidence is to be considered when assessing the results obtained with empirical correlations.
Undrained triaxial tests were conducted on cylindrical specimens prepared from the undisturbed samples after they had been thawed, saturated and consolidated. The results of the field and laboratory tests indicate that: (1) the liquefaction resistance of the high-quality undisturbed samples shows a good correlation with N1 in such a way that the liquefaction resistance increases abruptly as N1 exceeds a certain critical value, which increases with an increase in the number of load cycles; (2) the liquefaction resistance vs. N1 relationship of the high-quality undisturbed samples is consistent with the previously published relationship based on field records of liquefaction during earthquakes; and (3) the liquefaction resistance of the tube samples shows a good correlation with N1 over a range between 18 and 30, although the liquefaction resistance is considerably lower than that of the in situ frozen samples.
A cooperative test program of cyclic undrained triaxial tests was performed by five laboratories for both loose (D//r equals 50%) and dense (D//r equals 80%) air-pluviated specimens of Toyoura Sand, which is a clean fine uniform sand having sub-angular to angular shaped particles. This test material has been widely used in Japan for the study of sand liquefaction. The tests were performed following the specified test procedures described in this paper. It was found that the cyclic undrained strength value for a specimen diameter of 5 cm is slightly larger than that for a specimen diameter of 7-10 cm. The major part of the scattering of the data was found due to different specimen diameters. For a similar specimen diameter, a very good degree of agreement for cyclic undrained strength value was obtained.
In this paper we present the geological effects induced by the 2012 Emilia seismic sequence in the Po plain. Extensive liquefaction phenomena were observed over an area of ~1200 km2 following the May 20, Ml 5.9 and May 29, Ml 5.8 mainshocks, both occurred on about E-W trending, S dipping blind thrust faults. We collected the coseismic geological evidence through field and aerial surveys, reports from local people and web-based survey. On the basis of their morphologic and structural characteristics we grouped the 1362 effects surveyed into three main categories: liquefaction (485), fractures with liquefaction (768), fractures (109). We show that the quite uneven distribution of liquefaction effects, that appear concentrated and aligned, is mostly controlled by the presence of paleo-river beds, out-flow channels and fans of the main rivers crossing the area; these terrains are characterized by the pervasive presence of sandy layers in the uppermost 5 m, a local feature that, along with the presence of a hi
In saturated clean medium-to-dense cohesionless soils, liquefaction-induced shear deformation is observed to accumulate in a cycle-by-cycle pattern cyclic mobility. Much of the shear strain accumulation,occurs rapidly during the transition from contraction to dilation near the phase transformation,surface,at a nearly constant low shear stress and effective confining pressure. Such a stress state is difficult to employ as a basis for predicting the associated magnitude of accumulated permanent shear strain. In this study, a more convenient,approach,is adopted,in which,the domain,of large shear strain is directly defined by strain space parameters. The observed cyclic shear deformation is accounted for by enlargement and/or translation of this domain in deviatoric strain space. In this paper, the model,formulation,details involved,are presented,and,discussed. A calibration phase,is also described,based,on data from,laboratory sample,tests and dynamic,centrifuge experiments,for Nevada sand at a relative density of about 40%. DOI: 10.1061/ASCE1090-02412003129:121119 CE Database subject headings: Liquefaction; Constitutive models; Cyclic plasticity; Soil dynamics; Centrifuge models.
Threshold shear strain for cyclic pore-water pressure, gamma(t), is a fundamental property of fully saturated soils subjected to undrained cyclic loading. At cyclic shear strain amplitude, gamma(c), larger than gamma(t), residual cyclic pore-water pressure changes rapidly with the number of cycles, N, while at gamma(c) < gamma(t) such changes are negligible even at large N. To augment limited experimental data base of gamma(t) in cohesive soils, five values of gamma(t) for two elastic silts and a clay were determined in five special cyclic Norwegian Geotechnical Institute (NGI)-type direct simple shear (NGI-DSS), constant volume equivalent undrained tests. Threshold gamma(t) was also tested on one sand, with the results comparing favorably to published data. The test results confirm that gamma(t) in cohesive soils is larger than in cohesionless soils and that it generally increases with the soil's plasticity index (PI). For the silts and clay having PI = 14-30, gamma(t)=0.024-0.06% was obtained. Limited data suggest that gamma(t) in plastic silts and clays practically does not depend on the confining stress. The concept of evaluating pore water pressures from the NGI-DSS constant volume test and related state of stresses are discussed.
The volumetric cyclic threshold shear strain for cyclic settlement, gamma(tv), is evaluated for seven different sands and clays at different degrees of saturation, S, from the results of 11 Norwegian Geotechnical Institute-type direct simple shear, multistage cyclic settlement tests. Each test included several cyclic strain-controlled stages at cyclic shear strain amplitudes, gamma(c), slightly smaller and slightly larger than gamma(tv), such that gamma(tv) could be evaluated from each single test. At gamma(c) < gamma(tv), specimens did not experience a permanent change in volume or settle even after a large number of cycles, while at gamma(c) > gamma(tv) they did. The data show that gamma(tv) is larger for clays than for sands and that it generally increases with the soil's plasticity index (PI). For example, gamma(tv)approximate to0.01-0.02% was obtained for sands and gamma(tv)approximate to0.04- 0.09% was obtained for clays having PIapproximate to30. A rather consistent gamma(tv) versus PI correlation for cyclic settlement is presented. No obvious trends were found between gamma(tv) and S and vertical stress.
Based on a synthesis of published laboratory data, two types of cyclic threshold shear strain are examined and their approximate magnitudes identified for different types of soils. They are the linear cyclic threshold shear strain, γtl and the volumetric cyclic threshold shear strain, γtv, with γtv>γtl. These strains represent boundaries between fundamentally different categories of cyclic soil behavior. For cyclic strains below γtl, soil behaves essentially as a linearly elastic material. Between γtl and γtv, soil becomes markedly nonlinear but remains largely elastic because permanent changes of its microstructure still do not occur or are negligible. Above γtv, soil becomes increasingly nonlinear and inelastic, with significant permanent microstructural changes taking place under cyclic loading. That is, γtv, = the threshold separating cyclic strains that cause or do not cause significant permanent changes of soil microstructure. In practical terms, these microstructural changes are manifested in residual cyclic pore‐water pressures in fully saturated soils and permanent volume change in dry or partially saturated soils. Both γtl and γtv depend on the type of soil and are correlated to soils plasticity index (PI). Based on these correlations with PI, a new rational categorization of cyclic shear strains with respect to their magnitude and type of soil is proposed. This categorization enables selection of appropriate type of soil dynamics analysis for given soil and anticipated level of cyclic shear strain.
In an attempt to correlate the monotonic peak strength and the cyclic strength of sand-silt mixtures over a wide range of
parameters and to clarify some of the existing confusing conclusions in the literature regarding the undrained strength response
of sand-silt mixtures, a series of stress controlled cyclic and strain controlled monotonic triaxial tests was carried out
on sand-silt mixture specimens of 50mm diameter and 100mm height with varying silt content. In these experiments, various
measures of sample density was adopted through different approaches such as constant gross void ratio approach, constant relative
density approach, constant sand skeleton void ratio approach, and constant interfine void ratio approach. Also the effect
of relative density and confining pressure on these strengths was studied. It is observed that the limiting fines content
and the relative density of a specimen play the key role in deciding the cyclic and monotonic resistance of sand-silt mixtures
when studied through any approach. For any silt content with relative density more than 70%, cyclic and monotonic resistances
are observed to be independent of silt content. When the undrained cyclic strengths of these specimens are plotted against
their respective undrained monotonic peak strengths, it is observed that there exists a definite exponential relationship
between the two with an excellent correlation coefficient. An expression is proposed in this regard to help engineers assess
the cyclic strength of sand-silt mixtures from monotonic test results.
KeywordsMonotonic peak strength–Cyclic strength–Gross void ratio–Sand skeleton void ratio–Interfine void ratio–Limiting silt content
We present a comprehensive study of the recent and active tectonics of the external part of the Northern Apennines (Italy)
by using morphotectonic, geological–structural, and stratigraphic analysis, compared with the current seismicity of the region.
This analysis suggests that the external part of the Northern Apennines is characterised by presence of three major systems
of Quaternary compressive structures corresponding to (1) the Apenninic watershed, (2) the Apennines–Po Plain margin (pede-Apenninic
thrust front), and (3) the Emilia, Ferrara, and Adriatic Fold systems buried below the Po Plain. Geological data and interpreted
seismic sections indicate a roughly N–S Quaternary deformation direction, with rates <2.5mm/year. The shortening decreased
since the Pliocene, when our data indicate compression in a NNW–SSE direction and rates up to 7mm/year. The trend and kinematics
of the structures affecting the Apennines–Po Plain margin and the Po Plain subsoil fit well the pattern of the current seismicity
of the area, as well as recent GPS and geodetic levelling data, pointing to a current activity of these thrust systems controlled
by an overall compressive stress field. Close to the Apenninic watershed, earthquake focal mechanisms indicate that shallow
extension is associated to deep compression. The extensional events may be related to a secondary extensional stress field
developing on the hangingwall of the thrust system affecting the Apenninic watershed; alternatively, this thrust system may
have been recently deactivated and overprinted by active normal faulting. Deeper compressive events are related to the activity
of both a major basement thrust that connects at surface with the pede-Apenninic thrust front and a major Moho structure.
KeywordsActive tectonics–Northern Apennines (Italy)–Compressive structures
A set of Ground Motion Prediction Equations (GMPEs) for the Italian territory is proposed, exploiting a new strong-motion
data set become available since July 2007 through the Italian Accelerometric Archive (ITACA). The data set is composed by
561 three-component waveforms from 107 earthquakes with moment magnitude in the range 4.0–6.9, occurred in Italy from 1972
to 2007 and recorded by 206 stations at distances up to 100km. The functional form used to derive GMPEs in Italy (Sabetta
and Pugliese in Bull Seismol Soc Am 86(2):337–352, 1996) has been modified introducing a quadratic term for magnitude and
a magnitude-dependent geometrical spreading. The coefficients for the prediction of horizontal and vertical peak ground acceleration,
peak ground velocity and 5% damped acceleration response spectra are evaluated. This paper illustrates the new data set, the
regression analysis and the comparisons with recently derived GMPEs in Europe and in the Next Generation Attenuation of Ground
Motions (NGA) Project.
KeywordsGround motion prediction equation-Strong ground motion-Peak ground acceleration-Peak ground velocity-Acceleration response spectra
Liquefaction phenomena along the paleo-Reno River caused by the
- G Papathanassiou
- R Caputo
- D Rapti-Caputo
Papathanassiou G, Caputo R, Rapti-Caputo D. Liquefaction phenomena along
the paleo-Reno River caused by the May 20, 2012, Emilia (Northern Italy)
earthquake. Ann Geophys 2012;55(4):735-42.
Geotechnical earthquake engineering
- S L Kramer
Kramer SL. Geotechnical earthquake engineering. New Jersey, USA: Prentice
Hall; 1996. p. 653.
Primo rapporto sugli effetti della liquefazione osservati a S. Carlo, frazione di S. Agostino (Provincia di Ferrara)
- Regione Emilia-Romagna
- Gruppo Di Lavoro Liquefazione
Regione Emilia-Romagna, Gruppo di Lavoro Liquefazione, PG.2012.0134978
del 31/5/2012. Primo rapporto sugli effetti della liquefazione osservati a S.
Provincia di Ferrara)
- Di S Carlo
- Agostino
Carlo, frazione di S. Agostino (Provincia di Ferrara); 2012. 〈http://ambiente.
regione.emilia-romagna.it/geologia/temi/sismica/liquefazione-gruppo-di-la
voro〉 [28.05.14].
0134978 del 31/5/2012. Rapporto sugli effetti della liquefazione osservati a Mirabello (Provincia di Ferrara)
- Regione Emilia-Romagna
- Gruppo Di Lavoro Liquefazione
Regione Emilia-Romagna, Gruppo di Lavoro Liquefazione, PG.2012.0134978
del 31/5/2012. Rapporto sugli effetti della liquefazione osservati a Mirabello
(Provincia di Ferrara); 2012. 〈http://ambiente.regione.emilia-romagna.it/geo
logia/temi/sismica/liquefazione-gruppo-di-lavoro〉 [28.05.14].
Rapporto preliminare sui diffusi fenomeni di liquefazione verificatisi durante il terremoto in pianura padana emiliana del maggio 2012
- T Crespellani
- J Facciorusso
- A Ghinelli
- C Madiai
- S Renzi
- G Vannucchi
Crespellani T, Facciorusso J, Ghinelli A, Madiai C, Renzi S, Vannucchi G. Rapporto preliminare sui diffusi fenomeni di liquefazione verificatisi durante il
terremoto in pianura padana emiliana del maggio 2012. Internal Report,
University of Florence; 2012. 〈http://ambiente.regione.emilia-romagna.it/geo
logia/temi/sismica/liquefazione-gruppo-di-lavoro〉 [28.05.14].
The last 40 kyr evolution of the Central Po Plain between the Adda and Serio rivers. Géomorphologie, relief, processes, Environment 2
- C Ravazzi
- M Deaddis
- De Amicis
- M Marchetti
- M Vezzoli
- G Zanchi
Ravazzi C, Deaddis M, De Amicis M, Marchetti M, Vezzoli G, Zanchi A. The last
40 kyr evolution of the Central Po Plain between the Adda and Serio rivers.
Géomorphologie, relief, processes, Environment 2; 2012. p. 131-54, DOI:
http://dx.doi.org/10.4000/geomorphologie.9794. 〈http://geomorphologie.re
vues.org/9794〉 [28.05.14].
Milano: Ed. Unicopli, Studi e Ricerche sul Territorio
- M Cremaschi
Cremaschi M. Paleosols and Vetusols in the Central Po Plain (Northern Italy),
vol. 28. Milano: Ed. Unicopli, Studi e Ricerche sul Territorio; 1987. p. 305.
Channel changes on the Po river, Mantova Province, Northern Italy
- Castaldini
Castaldini D, Piacente S. Channel changes on the Po river, Mantova Province,
Northern Italy. In: Hickin EJ, editor. River Geomorphology. USA: Wiley & Sons;
1995. p. 193-207.
Saggio di storia, geografia e bibliografia sismica italiana con 136 sismocartogrammi
- M Baratta
- Terremoti D'italia
Baratta, M. I terremoti d'Italia. Saggio di storia, geografia e bibliografia sismica
italiana con 136 sismocartogrammi. Torino, Italy: Arnaldo Forni Editore; 1901.
p. 105-7.
Atlas of isoseismal maps of Italian earthquakes. Quad
- D Postpischl
Postpischl D. Atlas of isoseismal maps of Italian earthquakes. Quad. "La ricerca
scientifica", vol. 114. Bologna: National Research Council; 1985.