ALBERT

Description: The aim of this paper is to evaluate empirical attenuation relationships in order to validate peak values and pseudo-velocity spectra to calibrate shaking scenarios for the Molise area, which was struck by two earthquakes of Mw ¼ 5.7 (INGV-Harvard European- Mediterranean Regional Centroid-Moment tensor project) on October 31st and November 1st, 2002. Before the earthquake occurrence this region was classified as not hazardous, according to the former Italian seismic code. After the main-shocks, felt in many towns of the Molise and Puglia regions, a strong motion and a seismic temporary network were installed in the epicentral area and surrounding regions. This allowed the collection of a large data set, useful to characterize this area. The joint velocity-acceleration data set has been used to derive ground motion models for peak ground acceleration, peak ground velocity, and pseudo-velocity response spectra for both maximum horizontal and vertical components of the motion. The results obtained for the Molise area have been compared with the attenuation pattern of the Umbria-Marche region (central Italy) and the Italian territory. Remarkable differences have been observed leading to a discussion of the possible regional dependence of ground motion.

Description: Published

Description: 198–211

Description: 4T. Sismicità dell'Italia

Description: 5T. Sismologia, geofisica e geologia per l'ingegneria sismica

Description: JCR Journal

Description: reserved

Description: The plain of Gubbio is located in a northwest-southeast oriented, 4-km wide, 20-km long intermountain basin in the northern Apennines, central Italy. The moderate-magnitude earthquakes of the 1997 Umbria-Marche seismic sequence, occurred 40 km southeast of Gubbio, generated displacements as large as 6 cm within the basin. The large amplitude phase, not observed outside of the basin, was followed by low-frequency wave trains lasting up to 1 minute. In order to investigate the mechanism of possible local amplification effects, different kind of geophysical and geological investigation of the basin started within the framework of the Italian DPC-INGV projects. In particular, the GFZ and the INGV deployed two linear seismic arrays. The first one was composed of ten seismological stations with 1-s receivers. It operated from June until December 2005. The array was oriented north-south, approximately: all the stations but two were installed on the sedimentary deposits. The remaining two stations (the northernmost and the southernmost) were installed on rock outcrops at the edges of the basin. The second array, composed by 10 stations with 5-s receivers, was deployed along the main axis of the basin, and is recording since November 2005. For 45 days, the two arrays worked simultaneously. A selected dataset of 250 earthquakes has been analyzed. H/V spectral ratio results show that systematic low-frequency (0.3-0.4 Hz) amplification affects the stations in the middle of the basin. The resonance frequency peaks are consistent with the thickness and the average S-wave velocity of soft sediments derived from microtremor measurements in the basin. The conventional spectral ratio results show a more complex broad-band (0.3-10 Hz) amplification. The analysis of selected records by means of a sonogram approach highlights the arrival of strong late phases increasing the signal duration at the stations located in the middle of the basin.

Description: Unpublished

Description: Geneva, Switzerland

Description: open

Description: Earthquake early warning systems (EEWS), based on real-time prediction of ground motion or structural response measures, may play a role in re- ducing vulnerability and/or exposure of buildings and lifelines. Indeed, seismologists have recently developed efficient methods for real-time es- timation of an event’s magnitude and location based on limited informa- tion of the P-waves. Therefore, when an event occurs, estimates of magni- tude and source-to-site distance are available, and the prediction of the structural demand at the site may be performed by Probabilistic Seismic Hazard Analysis (PSHA) and then by Probabilistic Seismic Demand Analysis (PSDA) depending upon EEWS measures. Such an approach contains a higher level of information with respect to traditional seismic risk analysis and may be used for real-time risk management. However, this kind of prediction is performed in very uncertain conditions which may affect the effectiveness of the system and therefore have to be taken into due account. In the present study the performance of the EWWS under development in the Campania region (southern Italy) is assessed by simu- lation. The earthquake localization is formulated in a Voronoi cells ap- proach, while a Bayesian method is used for magnitude estimation. Simu- lation has an empirical basis but requires no recorded signals. Our results, in terms of hazard analysis and false/missed alarm probabilities, lead us to conclude that the PSHA depending upon the EEWS significantly improves seismic risk prediction at the site and is close to what could be produced if magnitude and distance were deterministically known.

Description: Published

Description: 211-232

Description: 4.1. Metodologie sismologiche per l'ingegneria sismica

Description: reserved

Description: Predictive relationships for the ground motion in the Marmara region (northwestern Turkey) are parametrized after regressing three-component waveforms from regional earthquakes, in the frequency range: 0.4–15.0 Hz, and in the distance range: 10–200 km. The data set consists of 2400 three-component recordings from 462 earthquakes, recorded at 53 stations. Moment magnitudes, Mw, range between 2.5 and 7.2. The largest event for which we have waveforms available (Mw 7.2) occurred in Duzce on 1999 November 12. The aftershocks of that earthquake, together with the aftershocks of the 1999 August 17 Izmit event (Mw = 7.4), are included in the dataset. Regressions are performed, independently, on Fourier velocity spectra and on peak ground velocities, for a large number of sampling frequencies. A simple model is used to relate the logarithm of the measured ground motion to excitation, site, and propagation terms. Results obtained for peak velocities are used to define a piecewise continuous geometrical spreading function, g(r), a frequency-dependent Q(f ), and a distance-dependent duration function. The latter is used, through random vibration theory (RVT), in order to predict time-domain characteristics (i.e. peak values) of the ground motion. The complete model obtained for the peak ground motion was used to match the results of the regressions on the Fourier amplitudes. Fourier velocity spectra for the combined horizontal motion are best fit by a hinged quadrilinear geometrical spreading function for observations in the 10–200 km hypocentral distance ranges as a function of frequency: f 〈 1.0 Hz, r−1.2 for r ≤ 30 km; r−0.7 for 30 〈 r ≤ 60 km; r−1.4 for 60〈r ≤100 km; r−0.1 for r 〉100, f ≥1.0 Hz, r−1.0 for r ≤30 km; r−0.6 for 30〈r ≤ 60 km; r−0.9 for 60〈r ≤100 km; r−0.1 for r 〉100 km. The frequency-dependent crustal shearwave quality factor Q (f ) coefficient Q( f )=180 f 0.45. The T (5–75 per cent) duration window provides good agreement between observed and predicted peak values. By modelling the behaviour of the small earthquakes at high frequency, we also quantified a regional parameter κ = 0.055 s. Spectral models with one single-corner frequency (Brune), and with two-corner frequencies (Atkinson and Silva) fit the observed high-frequency excitation levels equallywell, whereas the model by Atkinson and Silva fits the low-frequency observations slightly better than Brune’s. RVT is used to predict the absolute levels of ground shaking, following Boore’s implementation of the stochastic ground motion model (Boore’s SMSIM codes). Our regional empirical predictive relationships are compared to the ones adopted in several regions of the world, from California to Western United States.

Description: Published

Description: 635-651

Description: JCR Journal

Description: reserved

Description: Taking advantage of a large displacement-release experiment on a twostory reinforced concrete building located in Bagnoli (Naples, Italy), we performed free-field measurements using 3D seismometers, accelerometers, and a 100-m-long vertical array. The ground motion was noticeable: near the building, the acceleration exceeded 5% g. At each measurement point, it was possible to recognize two source terms, due to the tested building and to the reaction structure. The two sources generated different wave trains. High-frequency accelerations propagated as Rayleigh waves, whereas 1–2 Hz waves carrying most of the displacement propagated only as body waves. The experiment lends further support to the hypothesis that buildings are able to modify substantially the free-field ground motion in their proximity: the peak ground acceleration we observed is the 20% of the ground acceleration required to produce a displacement on the building equal to the one imposed during the release test. We recognize, however, the difficulty of a realistic modeling of wave propagation in the topmost layer of a densely urbanized area.

Description: Published

Description: 2457–2464

Description: 5T. Sismologia, geofisica e geologia per l'ingegneria sismica

Description: JCR Journal

Description: open

Description: We analyze the dispersion characteristics of ambient noise vibrations. For this purpose, two-dimensional (2D) seismic array data were acquired in four different sites in the Colfiorito plain, an alluvial intramountain basin that exhibits strong site effects. Assuming seismic noise being mainly composed of surface waves, we derive one-dimensional (1D) shallow shear-velocity profiles through the inversion of dispersion curves measured by frequency–wavenumber (f-k) methods. The inverted shear-wave velocity profiles are consistent with a priori information for those sites that can be approximated by 1D simple models. In these cases, the use of passive records of seismic vibrations can be a valuable tool for determining the shallow velocity profile if a detailed depiction of velocity structure is not required. The theoretical dispersion curves for Rayleigh and Love waves were compared with the measured dispersion curves for vertical and horizontal components, respectively. This allows us to discuss qualitatively the composition of ambient vibrations (outlining a large proportion of Love waves in the noise wave field) and the effects of higher modes. We also use the single-station method for investigating the origin of the horizontal-to-vertical (H/V) peak in the plain of Colfiorito in terms of ellipticity of the fundamental Rayleigh mode.

Description: Published

Description: 1915-1933

Description: reserved

Description: The city of Palermo (southern Italy) was severely damaged in the past by moderate-magnitude earthquakes located tens of kilometres offshore. The historical monumental heritage and the high density of population motivated large efforts for the seismic risk assessment. We present the geological and seismological studies performed in downtown Palermo as a study case to show how the complexity of an urban environment can be approached with multidisciplinary investigations. Downtown Palermo is characterized by sea deposits in the coastal zone and the alluvial deposits of two rivers (Papireto and Kemonia) of about 150 m width, which were buried and filled during the XVII century. The difficulty of surface geological surveys was compensated through an analysis of aerial photos and more than 2000 borehole data organized in the City-GIS of the Department of Geology and Geodesy of the University of Palermo. A previous study on the well-documented historical damage indicated the major role played by the two river valleys and the sea deposits in controlling the damage distribution, above the assumption of a fairly homogeneous vulnerability of the existing buildings in downtown. To test the feasibility of using ambient noise for recognizing the presence of alluvial deposits in a densely urbanized environment, a large microtremor measurement campaign was performed in Palermo across several profiles. The frequency peaks inferred from the horizontal-to-vertical spectral ratio were compared with numerical simulations to assess the seismic velocity profile and the soil stratigraphy. Moreover, noise data were analyzed through a statistical approach to establish a possible correlation between damage, resonance frequency and amplitude, and geology. After the moderate earthquake of September 6, 2002 (Mw=5.9, 50 km far away), the analysis of the aftershock sequence provided a well documented estimate of the variation of ground motion within the city in the case of linear soil response. Using these aftershocks we computed also synthetic accelerograms of the main shock through Empirical Green’s Functions that provided ground accelerations as large as 50 gals, consistently with the documented EMS-98 intensity. Synthetic accelerograms showed a large variability of horizontal ground motion within the city (a factor of 3 – 4) that confirms the role of local geology in causing an increase of the seismic hazard on sea and alluvial deposits. Finally, we discuss the comparison between the acceleration response spectra calculated for different soil categories and the design elastic spectra provided by EC8.

Description: Unpublished

Description: Lisbon, Portugal

Description: open

Description: The Colfiorito basin is located at the boundary between Umbria and Marche districts in Central Italy. The area was struck by several strong earthquakes in the past, and during the September 1997 to April 1998 seismic sequence, the macroseismic intensity was as large as IX (MCS scale) in the region. Ambient noise measurements are carried out over fifty points in the basin; H/V spectral ratios as well as spectral ratios using a reference rock site are calculated. Polarization analyses are also performed in narrow frequency bands where spectral amplitude peaks are observed to dominate, to discriminate preferential directions of propagation in the noise wave field which could be related to source or path effects, other than site effects. In the spectral ratios, the frequencies of the most pronounced peaks generally agree with the resonance frequencies computed for the measurement sites on the basis of 1-D velocity models, at least where no strong lateral variations of the sediment thickness are present.

Description: Unpublished

Description: Nice, France

Description: open

Description: A hybrid statistical-deterministic approach has been applied to estimate strong ground motion parameters (PGA, spectral ordinates) in South-Eastern Sicily for a M = 7 earthquake. A number of 100 different rupture processes has been simulated along a composite fault system representing two segments of the Ibleo-Maltese fault scarp. Map at regional scale of mean PGA in the 0.5–20 Hz frequency band shows highest values (0.4–0.5 g) nearby and North of Catania, due to a dominant directivity effect. The COV parameter, which expresses the variability of PGA values as a function of source complexity, is higher in the region nearby and South of the town of Augusta, where, depending on the rupture history, rather large PGA values can be observed (〉 0:4 g). PGA attenuation curves suggest that an azimuthal variation could be related to the source extent and directivity. The response and pseudo acceleration spectra are computed for different sites in the town of Catania including an approximate 1D site response. Ground motion amplification effects at high frequency (5–20 Hz) are produced by thin shallow layer of soft clay, loose pyroclastites and fill. We observe small amplification effects, in the frequency ranges 2–3 Hz and 5–10 Hz, in sites where recent alluvia reach a thickness of some tens of meters. Otherwise, sites located on outcrops of massive lavas show moderate attenuation

Description: Published

Description: 279-288

Description: reserved

Description: We evaluate the goodness of fit of attenuation relations commonly used for the Italian national territory (Sabetta and Pugliese, 1996) by using the maximum likelihood approaches of Spudich et al. (1999) and Scherbaum et al. (2004). According to the classification scheme proposed by Scherbaum et al. (2004), the Sabetta and Pugliese (1996) relationships show consistent discrepancies between the predicted and the observed peak ground acceleration (PGA) at rock sites in the Umbria- Marche region, central Italy; however, at soft sites the agreement between observations and prediction is satisfactory. The bias of the residuals, computed with the Sabetta and Pugliese (1996) models for PGA, peak ground velocity, (PGV) and pseudovelocity response spectrum (PSV) (for Ml 4–6 and epicentral distances up to 100 km) is negative. This means that on the average, the predictions overestimate the observations, but the overestimation decreases with increasing magnitude. Then, we present regional predictive relations (UMA05) for maximum horizontal PGA, PGV, and 5%-damped PSV, derived from the strong-motion data recorded in the Umbria-Marche area and classified as to four site categories. The UMA05 attenuation relationships for rock sites are log10 (PGA) 2.487 0.534Ml 1.280 log10 (R2 3.942)0.5 0.268 log10 (PGV) 1.803 0.687Ml 1.150 log10 (R2 2.742)0.5 0.300 and log10 (PGA) 2.500 0.544Ml 1.284 log10 Rh 0.292 log10 (PGV) 1.752 0.685Ml 1.167 log10 Rh 0.297, where PGA is measured in fraction of g and PGV in centimeters per second, Ml is the local magnitude in the range 4–6, R is the epicentral distance in the range 1–100 km, and Rh is the hypocentral distance in kilometers. We used the random effect model (Brillinger and Priesler, 1985; Abrahamson and Youngs, 1992; Joyner and Boore, 1993; Joyner and Boore, 1994) to estimate the component of variance related to the earthquake-to-earthquake, station-to-station, and record-to-record variability, and to quantify the benefit of introducing a site classification in the attenuation model to reduce the variance. The introduction of the site classification in the attenuation model allows a reduction of the station-to-station component of variability (from 0.19 to 0.14 for PGA, and from 0.21 to 0.18 for PGV). We also found that the recordto- record component represents the largest contribution to the model uncertainty.

Description: Published

Description: 984-1002

Description: JCR Journal

Description: reserved

Description: During three moderate-magnitude earthquakes occurred in September–October 1997 in the central Apennines, Italy, accelerations larger than 0.5 g were recorded in the town of Nocera Umbra, 10 to 15 km N-NW of the epicenters. The accelerograph is sited in a fault zone, close to a N30 E tectonic contact. Six temporary seismological stations installed across the fault recorded 82 aftershocks occurred in two seismogenic zones: the Colfiorito-Sellano area, S-SE of the array, and the Gualdo Tadino area, to the north. The array data reveal large variations in terms of both peak ground motions and spectral amplitudes. Within the fault zone, amplifications show a strong dependence on the source azimuth. At the accelerograph site, the effects are particularly large for events from S-SE: peak ground motions are a factor of 14 larger than those of a reference site and conventional spectral ratios attain amplitudes as large as 50 at 7 Hz along the N30 E direction of motion, parallel to the strike of the fault. Nineteen strong motion accelerograms were then used to compare ground motion properties between weak and strong events up to M0 = 1.2 1025 dyn cm. A particle motion analysis shows that the directional effect is also present in the strongest motions, even though the amplification of peak ground motion decreases when M0 increases. Results from stochastic simulations indicate that such a behavior is not due to nonlinearity: applying the empirical weak motion transfer functions in a purely linear model the observed peak ground motions of the largest events are fit satisfactorily.

Description: Published

Description: 2156

Description: JCR Journal

Description: reserved

Description: During the two mainshocks of September 26, 1997 in the Umbria-Marche border a strong-motion accelerograph recorded peak ground accelerations as large as 0.6 g, approximately, in the town of Nocera Umbra, at distances of 10 to 15 km from the epicentres. This value is significantly larger than expected on the basis of the usual regressions with magnitude and distance. A broad-band amplification up to a factor of 10 was consistently estimated in previous papers, using both weak and strong motion data recorded at the accelerograph site during local moderate earthquakes. To study the cause of this amplification we deployed six seismologic stations across the tectonic contact between the Ceno-Mesozoic limestone and the Mesozoic marly sandstone where the accelerograph is installed. Seismograms of 21 shallow aftershocks in the magnitude range from 2.2 to 4.0 and a subcrustal Mw = 5.3 event are analysed. Regardless of epicentre location, waveforms show a large complexity in an approximately 200 m wide band adjacent to the tectonic contact. This is interpreted as the effect of trapped waves in the highly fractured, lower velocity materials within the fault zone.

Description: Published

Description: 543-554

Description: JCR Journal

Description: reserved

Description: In order to empirically obtain the scaling relationships for the high-frequency ground motion in the Western Alps (NW Italy), regressions are carried out on more than 7500 seismograms from 957 regional earthquakes. The waveforms were selected from the database of 6 three-component stations of the RSNI (Regional Seismic network of Northwestern Italy). The events,MW ranging between 1.2 and 4.8, were recorded within a hypocentral distance of 200 km during the time period: 1996–2001. The peak ground velocities are measured in selected narrow-frequency bands, between 0.5 and 14 Hz. Results are presented in terms of a regional attenuation function for the vertical ground motion, a set of vertical excitation terms at the reference station STV2 (hard-rock), and a set of site terms (vertical and horizontal), all relative to the vertical component of station STV2. The regional propagation of the ground motion is modeled after quantifying the expected duration of the seismic motion as a function of frequency and hypocentral distance. A simple functional form is used to take into account both the geometrical and the anelastic attenuation: a multi-variable grid search yielded a quality factor Q( f ) = 310 f 0.20, together with a quadri-linear geometrical spreading at low frequency. A simpler, bilinear geometrical spreading seems to be more appropriate at higher frequencies (f 〉 1.0 Hz). Excitation terms are matched by using a Brune spectral model with variable, magnitude-dependent stress drop: at Mw 4.8, we used σ = 50MPa. A regional distanceindependent attenuation parameter is obtained (κ0 = 0.012 s) by modelling the average spectral decay at high frequency of small earthquakes. In order to predict the absolute levels of ground shaking in the region, the excitation/attenuation model is used through the Random Vibration Theory (RVT) with a stochastic point-source model. The expected peak-ground accelerations (PGA) are compared with the ones derived by Ambraseys et al. (1996) for the Mediterranean region and by Sabetta and Pugliese (1996) for the Italian territory.

Description: Published

Description: 315-333

Description: JCR Journal

Description: reserved

Description: The West side of lake of Garda, in Northern Italy, was struck by a ML=5.2 earthquake on November 24, 2004. The felt area is rather large (from Venice to Milan) and the damaged area consists of 66 municipalities, with a number of homeless of about 2200 and estimated direct damages of 215 millions of euros. Most of the damaged structures are old masonry buildings and churches, while there were almost no damage to reinforced concrete structures. The observed distribution of macroseismic intensity shows a strong azimuthal dependence, with high intensity level in a 10x10 km2 area located SW to the epicentre and rather large dispersion of values (ranging from V to VII-VIII) in the first 10 km epicentral distance. Taking into account the vulnerability level of the damaged structures and the features of the geological formations, we tried to explain the observed damage distribution in terms of finite fault properties of the source, despite the moderate magnitude of the event. Thus we hypothesised a fault geometry from seismotectonic considerations and we simulated the event by a high frequency simulation technique (Deterministic Stochastic Method, DSM). The synthetic ground motion parameters were converted into intensity values by empirical relationships and local geological conditions were considered to explain some discrepancies between simulated and observed intensities. It was possible to adequately reproduce both the observed distribution of macroseismic intensity and the ground motion recorded by an accelerometric station located at about 13 km epicentral distance.

Description: Unpublished

Description: Geneva, Switzerland

Description: open

Description: The investigation of local amplification phenomena by seismic signal analysis is a fundamental step in carefully defining the seismic response of an area. In this study we investigate the use of teleseismic recordings in assessing seismic wave amplification in the Pellice Valley (North-western Alps, Italy). Assuming that teleseismic P-waves are sensitive to the deep structure of a basin, we deal with the computation of horizontal to vertical spectral ratios and with the estimate of teleseismic P-wave arrival time delays and P-wave amplifications with respect to a reference site. The reliability of the H/V results obtained by considering teleseismic signals is confirmed by the agreement with the results coming from both H/V of noise and H/V of S-wave of local events methods. Strong correlation between the P-wave arrival time delays and the relative P-wave amplifications with respect to thickness of the low velocity layers and the geometry of the bedrock is found.

Description: Unpublished

Description: open

Description: After the 2002 Molise earthquake, a wide survey of the damage and the seismic vulnerability of the churches was carried out, using specific forms extensively tested and recently acknowledged at a national scale (G.U. 07/03/2006). This approach has allowed one to compare the observed and the expected medium damage, calculated through vulnerability curves correlated to the specific form used. This comparison has enabled to evaluate inhomogeneous values in some cases, pointing out how the surveyed damage could not be put down just to a structural lack of the building. Studying the sites morphology for the churches located on the ridges, it was observed a damage level always greater than expected. To study the influence of the local amplification phenomena due to the topography, it has been analyzed some churches damaged by the Appennino Abruzzese (1984) and Molise (2002) earthquakes. These churches are located on the ridges top, with slope in-clination alfa≥15°, height H≥30m and characterized by homogeneous lithological subsoil, almost to consider it having an elastic behavior under dynamical stress. Taking into account this hazard increase inside a vulnerability analyses (based on a macroseismic or a mechanical approach), it has been proposed a double approach, validated through local seismic response (RSL) modeling of the ground (estimation of amplification factors and of elastic response spectra) and through the seismic response of the macroelements, damaged by the reference earth-quake (linear and not-linear kinematic analysis). Through the vulnerability analysis based of the macroseismic approach, the influence of the site morphology on the building behavior has been preliminary defined by a vulnerability modifier (deltaVml), that represents an additional parameter to reach the equivalent value between the surveyed and the expected damage. The study of the amplification effects has been performed using the BEM numerical analysis; the results are represented by the amplification factors (Fa), defined as the ratio between the spectral intensity of output and input, considering the range period of 0.1s-0.5s, and the corresponding elas-tic response spectra: they confirm the results of the macroseismic approach. Considering the mechanical approach, two churches have been examined in detail (S Pietro in Vincoli at Castellino del Biferno and S. Michele Arcangelo at Campolieto): the kinematic analyses have been performed applied the calculated amplified and not-amplified response spectra (considering the earthquake 2002) and the design response spectrum. The analyses show that the results obtained applying the calculated amplified response spectrum are better correlated to the surveyed damage of the churches than the results obtained applying the not-amplified response spectrum.

Description: Published

Description: Pisa, Italia

Description: 4.1. Metodologie sismologiche per l'ingegneria sismica

Description: open

Description: The damage and vulnerability survey of the monumental buildings, damaged by the 2002 earthquake in the Molise Region, has allowed singling out of a correlation between the observed damage of the churches and their morphological site conditions. The vulnerability model connected to the survey methodology provides an evaluation of the expected mean damage. Comparison with the observed damage determined the introduction of a local morphological behaviour modifier, able to take into account the vulnerability increase due to the site effects. In order to validate the previous results, a numerical 2-D analysis of the seismic local response has been performed. In particular, a numerical code, working with boundary elements, has been applied to the analyzed situations. The results, in terms of pseudo-acceleration response spectra and amplification factors, allow one to compare the numerical and the observed analyses. This comparison shows good agreement and allows one to find some correlations between the geometric characteristics of the sites, the values of the amplification coefficients and the damage mechanism activated.

Description: Published

Description: Thessaloniki, Greece

Description: 4.1. Metodologie sismologiche per l'ingegneria sismica

Description: 4.2. Scenari e mappe di pericolosità sismica e danno

Description: open

Description: We perform a regional study in order to provide the seismic hazard community of Israel with new predictive relationships for the earthquake-induced ground motion in Israel. This work is essential for the development of a new generation of hazard maps, for the planning of the development of the Israel’s region, and the design of earthquake resistant structures and facilities. The main goals of our work is to provide a quantitative description of the expected ground motion within the Israel region, as a function of the hypocentral distance and frequency of motion. For this purpose we use the regression technique that was proposed by Yazd (1993), Herrmann (1999), Raoof et al., (1999) and Malagnini et al.,(2002). The undoubted advantage of this method is the possibility to use for analysis the data of frequent, small earthquakes that are typical for this region. In our analyses we use 4786 waveforms recorded by 30 stations of the Israel Seismic Network from 2000 to 2005. We restricted our analysis to events recorded at 10 or more stations, resulting in 330 appropriate earthquakes, with a magnitude range between 1.8 and 5.2. We derive the empirical excitation, site, and regional attenuation terms by regressing the peak amplitudes of narrowband-filtered seismograms around the shear-waves arrivals, and the rms Fourier spectral amplitudes taken around the specific sampling frequency. A theoretical modeling effort is performed by using Random Vibration Theory (RVT) on the parameters derived from the observations. For prediction we use the quality parameter Q(f)=270f^0.7 , whereas the geometrical spreading g(r) used in the model was parameterized as a bilinear, piecewise function: r^-0.95 for r〈60 km , and r^-0.5 for r〉60 km . The modeling of the excitation terms is based on the Brune’s source spectrum.

Description: Submitted

Description: 4.1. Metodologie sismologiche per l'ingegneria sismica

Description: JCR Journal

Description: reserved

Description: We describe the characteristics of crustal wave propagation in eastern Sicily by using the background seismicity of the area. We follow the approach described by Malagnini, Hermann, and Di Bona (2000) and Malagnini et al. (2002). Our data set consists of 106 earthquakes recorded by nine three-component digital seismic stations between 1994 and 2001. We used only crustal events (depths shallower than 25 km), with local magnitudes ranging from 1.0 to 4.3, and hypocentral distances from 10 to 130 km. Peak ground velocities from 1311 narrow bandpass-filtered waveforms are measured in the frequency range 1.0–16.0 Hz, and regressed to define crustal propagation, excitation, and site characteristics, with respect to a reference station. A subsequent modeling effort is carried out, through the use of random vibration theory (RVT), for obtaining a quantitative evaluation of the apparent geometrical spreading g(r), and of the crustal quality factor Q( f ). An attenuation parameter, j0, is also evaluated relative to a reference rock site. The attenuation and source parameters estimated in this study are used through the RVT in order to predict the peak horizontal ground acceleration (PGA), and the 5% damping pseudoacceleration spectra (PSA).

Description: This study was supported by the Ministero dell’Universita’ e della Ricerca Scientifica, Dipartimento per la Programmazione, il Coordinamento e gli Affari Economici, Servizio per lo Sviluppo e il Potenziamento delle Attivita’ di Ricerca (SSPAR), under contract FIRB, Prot. RBAU013NRZ.

Description: Published

Description: 568-578

Description: 4.1. Metodologie sismologiche per l'ingegneria sismica

Description: JCR Journal

Description: reserved

Description: For early-warning applications in particular, the reliability and efficiency of rapid scenario generation strongly depend on the availability of reliable strong ground-motion prediction tools. If shake maps are used to represent patterns of potential damage as a consequence of large earthquakes, attenuation relations are used as a tool for predicting peak ground-motion parameters and intensities. One of the limitations in the use of attenuation relations is that these have only rarely been retrieved from data collected in the same tectonic environment in which the prediction has to be performed. As a consequence, strong ground motion can result in underestimations or overestimations with respect to the recorded data. This also holds for Italy, and in particular for the Southern Apennines, due to limitations in the available databases, both in terms of distances and magnitude. Moreover, for “real-time” early-warning applications, it is important to have attenuation models for which the parameters can be easily upgraded when new data are collected, whether this has to be done during the earthquake rupture occurrence or in the post-event, when all the strong motion waveforms are available. Here we present a strong-motion attenuation relation for early-warning applications in the Campania region (Southern Apennines), Italy. The model has a classical analytical formulation, and its coefficients were retrieved from a synthetic strong-motion database created by using a stochastic approach. The input parameters for the simulation technique were obtained through the spectral analysis of waveforms of earthquakes recorded by the Istituto Nazionale di Geofisica e Vulcanologia (INGV) network for a magnitude range Md (1.5,5.0) in the last fifteen years, and they have been extrapolated to cover a larger range. To validate the inferred relation, comparisons with two existing attenuation relations are presented. The results show that the calibration of the attenuation parameters, i.e., geometric spreading, quality factor Q, static stress drop values along with their uncertainties, are the main concern.

Description: Published

Description: 133-152

Description: 4.1. Metodologie sismologiche per l'ingegneria sismica

Description: reserved

Description: In the framework of an ongoing project financed by the Campania Region, a prototype system for seismic early and post-event warning is being developed and tested, based on a dense, wide dynamic seismic network (ISNet) and under installation in the Apennine belt region. This paper reports the characteristics of the seismic network, focussing on the required technological innovation of the different seismic network components (data-logger, sensors and data communication). To ensure a highly dynamic recording range, each station is equipped with two types of sensors: a strong-motion accelerometer and a velocimeter. Data acquisition at the seismic stations is performed using Osiris-6 model data-loggers made by Agecodagis. Each station is supplied with two (120 W) solar panels and two 130 Ah gel cell batteries, ensuring 72-h autonomy for the seismic and radio communication equipment. The site is also equipped with a GSM/GPRS programmable control/alarm system connected to several environmental sensors (door forcing, solar panel controller, battery, fire, etc) and through which the site status is known in real time. The data are stored locally on the hard-disk and, at the same time, continuously transmitted by the SeedLink protocol to local acquisition/analysis nodes (Local Control Center) via Wireless LAN bridge. At each LCC site runs a linux Earthworm system which stores and manages the acquired data stream. The real-time analysis system will perform event detection and localization based on triggers coming from data-loggers and parametric information coming from the other LCCs. Once an event is detected, the system will performs automatic magnitude and focal mechanism estimations. In the immediate post-event period, the RISSC performs shaking map calculations using parameters from the LCCs and/or data from the event database. The recorded earthquake data are stored into an event database, to be available for distribution and visualization for further off-line analyses. The seismic network will be completed in two stages: • Deployment of 30 seismic stations along the southern Apennine chain (to date almost completed) • Setting up a carrier-class radio communication system for fast and reliable data transmission, and installation of 10 additional seismic stations.

Description: Published

Description: 325 - 341

Description: 4.1. Metodologie sismologiche per l'ingegneria sismica

Description: reserved

Description: The area of Serravalle, sited in the northern part of the town of Vittorio Veneto (TV), NE Italy, has been the target of a seismic microzonation campaign. 10 seismic stations have been deployed for a 7 months period to record in continuous mode. Three stations were installed on bedrock outcrops and seven on sedimentary sites with variable cover thickness. Spectral analyses have been performed on the collected data-set using the Generalized Inversion Technique (GIT, e.g. Andrews, 1986). In particular, spectral ratios have been calculated for each station relatively to the average of the three reference, bedrock sites. The spectral ratios provide quantitative estimates of the seismic motion amplifications which occur in each of the monitored sites. Two sites show high values of amplification, 5 times larger than signal amplitude at the reference sites, in correspondence of well discernible peak frequencies of 5 Hz. Results for the other stations show smaller amounts of site amplification spreading over a broad range of frequencies. Sites where the highest amplifications were recorded all lie on the left bank of the Meschio River and in areas farther away from its outlet into the plain correlating with the presence of thick layers of Quaternary deposits.

Description: Published

Description: 31-49

Description: 4.1. Metodologie sismologiche per l'ingegneria sismica

Description: JCR Journal

Description: reserved

Description: In this paper we present a deterministic study to estimate seismic ground motions expected in urban areas located near active faults. The purpose was to generate bedrock synthetic time series to be used as seismic input into site effects evaluation analysis and loss estimates for the urban area and infrastructures of Thessaloniki (Northern Greece). Two simulation techniques (a full wave method to generate low frequency,~〈 1Hz, and a hybrid deterministic-stochastic technique to simulate high-frequency seismograms, ~〉 1 Hz) were used to compute time series associated with four different reference earthquakes having magnitude from 5.9 to 6.5 and located within 30 km of Thessaloniki. The propagation medium and different source parameters were tested through the modeling of the 1978 Thessaloniki earthquake (M 6.5). Moreover two different nucleation points were considered for each fault in order to introduce additional variability in the ground motion estimates. Between the two cases, the quasi-unilateral rupture propagation toward the city produces both higher median PGA and PGV values and higher variability than bilateral ones. Conversely, the low-frequency ground motion (PGD) is slightly influenced by the position of the nucleation point and its variability is related to the final slip distribution on the faults of the reference earthquakes and to the location of the sites with respect to the nodal planes of the radiation pattern. To validate our deterministic shaking scenarios we verified that the synthetic peak ground motions (PGA, PGV) and spectral ordinates are within one standard deviation of several ground-motion prediction equations valid for the region. At specific sites we combined the low- and high-frequency synthetics to obtain broadband time series that cover all the frequency band of engineering interest (0-25 Hz). The use of synthetic seismograms instead of empirical equations in the hazard estimates provides a complete evaluation of the expected ground motions both in frequency and time domains, including predictions at short distances from the fault (0 – 10 km) and at periods larger than 2 – 3 seconds.

Description: In press

Description: 4.2. TTC - Scenari e mappe di pericolosità sismica

Description: JCR Journal

Description: open

Description: Progetto INGV-DPC S3 “Scenari di scuotimento in aree di interesse prioritario e/o strategico”

Description: Published

Description: 4.2. TTC - Scenari e mappe di pericolosità sismica

Description: open

Description: A predominantly deterministic viewpoint has been adopted for computing seismic ground motion both for urban areas (SP10) and infrastructures loss modeling (SP11) at three selected areas: the cities of Lisbon (Portugal) and Thessaloniki (Greece), and the metropolis of Istanbul (Turkey). The generation of earthquake ground motion scenarios involves both the particular choice of earthquake sources with associated fault rupture parameters, and the ensuing ground motion field calculated by an appropriate numerical tool, or empirically estimated, at a set of selected points within the urban area of interest. Ground shaking values are predicted for rock conditions and for two distinct frequency bands, i.e. the high frequency range (from 1.0 Hz to 4-5 Hz) in the case of damage evaluation for the vast majority of ordinary building, and the low frequency (≤ 2 Hz) more appropriate for lifeline system damage assessment. The advanced simulation techniques allowed to properly consider the finite fault effects and directivity, which imply extreme expected values, and they are capable of quantifying the spatial variability of the ground motion near the extended fault.

Description: Published

Description: Hotel Villa Carlotta, Belgirate (VB)– Italy

Description: 4.2. TTC - Scenari e mappe di pericolosità sismica

Description: open

Description: Progetto INGV-DPC S3 “Scenari di scuotimento in aree di interesse prioritario e/o strategico”

Description: Published

Description: 4.2. TTC - Scenari e mappe di pericolosità sismica

Description: open

Description: Vengono presentate nuove relazioni empiriche, definite per il territorio italiano, per la stima dell’intensità in un dato sito a partire da informazioni epicentrali o relative a località vicine. Queste relazioni, espresse in forma probabilistica e quindi direttamente utilizzabili per la stima della pericolosità sismica, condividono la stessa formalizzazione e la medesima base informativa. In particolare, sono state seguite tre diverse strategie: le prime due hanno portato alla definizione di una relazione di attenuazione per la stima dell’intensità al sito da dati epicentrali utilizzando una forma parametrica rispettivamente Gaussiana e Binomiale; la terza analisi è stata invece mirata a definire le modalità di “correzione” del valore locale di intensità, dedotto dalle informazioni epicentrali, con dati di risentimenti osservati in località vicine al sito in esame.

Description: Istituto Nazionale di Geofisica e Vulcanologia

Description: Published

Description: 5.1. TTC - Banche dati e metodi macrosismici

Description: open

Description: GIS effetti suolo Gubbio (DVD)

Description: Progetto S3 - Scenari di scuotimento in aree di interesse prioritario e/o strategico

Description: Published

Description: 4.2. TTC - Scenari e mappe di pericolosità sismica

Description: open

Description: Progetto INGV-DPC S3 “Scenari di scuotimento in aree di interesse prioritario e/o strategico”

Description: Published

Description: 4.1. Metodologie sismologiche per l'ingegneria sismica

Description: open

Description: On 6 September 2002 a Mw 5.9 earthquake occurred in the southern Tyrrhenian sea, 40 km off the coast of Palermo (Italy). In the days after the mainshock, eight temporary stations were installed in the city to record aftershocks on different geological formations. Seismograms of about 30 earthquakes with magnitude 〉 2.8 are analyzed. The data analysis confirms the role of near-surface geology in causing locally significant variations of the ground-shaking level as already inferred by Guidoboni et al. (2003) from historical damage scenario studies. The largest spectral variations estimated through aftershock recordings result in a factor of 10 difference between stiff and soft sites, in frequency bands varying from 1 to 3.5 Hz. The geological structure of the study area is reconstructed by using data from more than 2000 boreholes organized in a Geographic Information System specifically dedicated to the assessment of natural hazards in urban areas. Vertically varying velocity models are used for a comparison with the observed data. In general, 1D transfer functions fit the largest amplification frequency but underestimate amplitudes of observations probably because of 2D and 3D complexity. Because the seismic stations were not installed in free field but at ground or underground level inside buildings, a possible influence of the structure was also investigated. Simultaneous ambient noise measurements were performed on the top, at the base, and outside the buildings where stations were installed. For all but one site, this analysis shows that the estimated ground-motion amplifications do not reflect the building vibration modes and therefore, in these cases, soil–structure interaction does not bias the free-field response of the study sites. Finally, speculations on the effect of the local geology in terms of response spectra of the Mw 5.9 mainshock are discussed in the framework of the Eurocode 8 prescriptions.

Description: Published

Description: 2328-2341

Description: reserved

Description: Distance scaling of earthquake-induced ground motion is studied in the Erzincan region, located in the eastern part of the North Anatolian Fault zone. The data set used in this study consists of 170 aftershocks of the MS ! 6.8 Erzincan earthquake of 13 March 1992, with moment magnitudes between 1.5 and 4.0. In order to empirically obtain the scaling relationships for the high-frequency S-wave motion, regressions are carried out on 352 horizontal-component short-period seismograms, all recorded within a hypocentral distance of 40 km, to empirically obtain the scaling relationships for the high-frequency S-wave motion. Peak ground velocities are measured in selected narrow-frequency bands, in the frequency range of 1.0–16.0 Hz, and are subsequently regressed to define a piecewise linear attenuation function, a set of excitation terms, and a set of site terms. Results are modeled in the framework of random vibration theory, using a bilinear geometrical spreading function, g(r), characterized by a crossover distance at 25 km: g(r)!r"1.1 is used for r ! 25 km, whereas g(r)!r"0.5 is used for larger distances. An extremely low-quality factor, Q(f ) ! 40(f /f ref)0.45, is used to describe the anelastic crustal attenuation in the region, consistently with the independent results of Akinci and Eyidogan (1996, 2000). Excitation terms are well matched by using a Brune spectral model with stress drop Dr ! 10 MPa (taken from the recent literature, Grosser et al., 1998). An effective high-frequency, distance-independent rolloff spectral parameter, jeff ! 0.02 sec, is obtained in this study. Peak ground acceleration predictions based on these parameters show a much more rapid decrease with distance than the relations usually used in Turkey, indicating that our results should only be applied to the Erzincan region itself.

Description: This study has been supported by Istituto Nazionale di Geofisica e Vulcanologia, INGV, Internal Project: “Attenuazione e leggi di scala nei paesi dell’area Mediterranea” (internally funded). R. B. Herrmann’s participation was supported by INGV and by the Earthquake Engineering Research Centers Program of the National Science Foundation under Award Number EEC-9701785.

Description: Published

Description: 1446-1455

Description: 4.1. Metodologie sismologiche per l'ingegneria sismica

Description: JCR Journal

Description: reserved

Description: A large data set of ground-velocity time histories from earthquakes that occurred in Friuli-Venezia Giulia (northeastern Italy) was used to define regional predictive relationships for ground motion, in the 0.25- to 14.0-Hz frequency band. The bulk of the data set was provided by the seismic network run by Centro Ricerche Sismologiche (CRS), a department of the Istituto Nazionale di Oceanografia e Geofisica (OGS). A collection of 17,238 selected recordings from 1753 earthquakes was compiled for the years 1995–1998, with magnitudes ranging from Mw !1 to 5.6. Ninety-six three-component strong-motion waveforms belonging to the largest events of the 1976–1977 Friuli seismic sequence were also taken from the ENEAENEL accelerogram database and included in our data set. For the strongest event, which occurred on 6 May 1976 at 20:00 local time, an average local magnitude ML 6.6 was computed by Bonamassa and Rovelli (1986). The inclusion of a large number of acceleration time histories from this earthquake and six others, from magnitudes from Mw 5.2 to magnitude Ms 6.1 (three of them of Ms !6.0), extends the validity of the predictive relationships proposed in this study up to the highest magnitude ever recorded in the region. A total of 10,256 vertical-component and 6982 horizontal-component seismograms were simultaneously regressed for excitation and site characteristics, as well as for the crustal propagation, in the hypocentral distance range 20–200 km. Results are given in terms of excitation, attenuation, and specific site for the vertical ground motion, together with a horizontal-to-vertical ratio for each existing horizontalcomponent seismometer. The regional propagation was modeled in the 0.5- to 14.0- Hz frequency band by using a frequency-dependent piece wise continuous linear (in a log–log space) geometrical spreading function and a frequency-dependent attenuation parameter: Q( f ) ! 260( f /1.0)0.55 The excitation spectra of larger events were modeled by using the regional propagation, a single-corner frequency Brune spectral model characterized by an effective stress parameter, Dr ! 60 MPa, and by a regional estimate of the near-surface, distance-independent, networkaveraged attenuation parameter j0 ! 0.045 sec that was estimated from the rolloff of the empirical source spectra obtained from the regressions. Other studies (De Natale et al., 1987; Cocco and Rovelli, 1989; Singh et al., 2001) suggested large stress drops (Dr ! 30–100 MPa,) to explain the highfrequency amplitude levels of the seismic radiation of the largest quakes of the 1976 sequence. Predictions for peak ground acceleration (PGA) and pseudo–spectral velocity (PSV) (5% damping) were computed through the use of the random vibration theory (RVT), with the parameters obtained from the regressions of this study.

Description: This study was supported by the Gruppo Nazionale Difesa dai Terremoti, (GNDT) through the project Terremoti probabili in Italia tra l’anno 2000 e il 2030: elementi per la definizione di priorita` degli interventi di riduzione del rischio sismico, task 3.1. The contribution of R. B. Herrmann was supported in part by the Earthquake Engineering Research Center’s Program of the National Science Foundation under Award No. EEC-9701785.

Description: Published

Description: 2186-2204

Description: 4.1. Metodologie sismologiche per l'ingegneria sismica

Description: JCR Journal

Description: reserved

Description: In this study, we simulate and compare ground motion shaking in the city of Lisbon and surrounding counties (metropolitan area of Lisbon (MAL)), using two possible earthquake models: the onshore source area of Lower Tagus Valley, M5.7 and M4.7 and the offshore source area, Marques de Pombal Fault, M7.6, one of the possible source of the 1755 Lisbon earthquake. The stochastic and a new hybrid stochastic-deterministic approach (DSM) are used in order to evaluate the ground shaking and to characterize its spatial variability. Results are presented in terms of response acceleration spectra (PSA) and peak ground acceleration (PGA) with respect to bedrock and surface. Site effects are evaluated by means of equivalent stochastic non-linear one-dimensional ground responses analysis, performed for a set of stratified soil profile units properly designed to cope with the soil site conditions of MAL region. A sensitive study is carried out using different input parameters and different approaches in order to give the basic information to evaluate the range of uncertainty in seismic scenarios.

Description: In press

Description: 4.1. Metodologie sismologiche per l'ingegneria sismica

Description: JCR Journal

Description: reserved

Description: We simulated strong motion records from the Umbria-Marche, Central Italy earthquake (Mw 6) of September 1997 using a frequency-dependent S-wave radiation function. We compared the observed acceleration spectra, from strong-motion instruments located in the near field and at regional distances, with those simulated using the stochastic modeling technique of Beresnev and Atkinson (1997, 1998), and modified to account for a frequency dependent radiation pattern correction. By using the frequency-dependent radiation function previously obtained by Castro et al. (2006) we reduced the overall fitting error of the acceleration spectra by about 9%. In general, we observed that the frequency-dependent radiation pattern correction has a small effect on the spectral amplitudes compared with site effects, which is an important factor controlling the strong-motion records generated by the 1997 Umbria-Marche earthquake. In addition, we modeled the observed ground-motion records using the dynamic corner frequency model of Motazedian and Atkinson (2005) to reproduce the directivity effects, reducing the average error of the spectral amplitudes by 24%. We concluded that although the frequency-dependent radiation pattern correction affects the frequency content of the spectral amplitudes simulated, site and directivity effects are more relevant.

Description: In press

Description: 4.1. Metodologie sismologiche per l'ingegneria sismica

Description: JCR Journal

Description: open

Description: Within the Italian Project S3 (DPC-INGV) “Shaking seismic scenarios in area of strategic and/or priority interest” the urban area of Gubbio has been chosen as a test site for the calculation of ground shaking scenarios for forecasting purposes. The area has been selected because the urban and / or geomorphologic characteristics of the town of Gubbio and its surrounding are good representatives of many areas in Central Italy: an historical centre of high cultural and artistic value founded on a rocky hillside with new residential and industrial areas developed on the alluvial plain. A great deal of effort has been put in the seismic characterisation of the Gubbio basin, since the general purpose of this work has been the quantification of site effects in intra-mountain basins. Recent studies have shown in fact that significant site effects take place in the Eugubina plain, as evidenced by the generation of surface waves. In particular, the strong motions recorded at the accelerometric station GPB, belonging to the RAN (Rete accelerometrica italiana), installed within the alluvial basin, shows strong amplification and lengthening of significant duration respect to rock sites (Pacor et al; 2007). Several investigations with active and passive seismic survey techniques have been planned and carried out in the plain, also favoured by the intense seismic activity typical of the area (see PS3-Deliverable 21). All data are collected in a GIS herewith enclosed (section 7). The estimates of the empirical transfer functions in the basin have been related to the monitoring activities of 4 temporary transects of seismometric stations (Figure 1.1), operating between June 2005 and May 2006 and described in this Deliverable. The velocemetric records are collected in PS3-Deliverable D26 The amplitude transfer functions for sites corresponding to the stations installed in the basin have been determined by applying three different methods, namely the horizontal-to-vertical spectral ratio (H/V), the standard spectral ratio (SSR) and the generalized inversion technique (GIT).

Description: Progetto INGV-DPC S3 “Scenari di scuotimento in aree di interesse prioritario e/o strategico” (coord. F.Pacor e M. Mucciarelli).

Description: Published

Description: 4.2. TTC - Scenari e mappe di pericolosità sismica

Description: open

Description: Abstract The source parameters of 523 aftershocks (0.5 ML 5.9) of the 1999 Kocaeli earthquake are determined by performing a two-step spectral fitting procedure. The source spectrum, corrected for both site and propagation effects, is described in terms of a standard x-square model multiplied by an exponential term of frequency. The latter term is introduced to estimate the high-frequency (f 12 Hz) fall-off of the acceleration source spectra by computing the j parameter. The seismic moments obtained range between 1.05 1014 and 2.41 1017 N m, whereas the Brune stress drops are between 0.002 and 40 MPa. The j value varies between 0.00 and 0.08 sec, indicating a decay of the acceleration level at the higher frequency part of the spectrum greater than that assumed by the x 2 model. Both the stress drop and the j parameter show the tendency of increasing with aftershock magnitude. No evidence of self-similarity breakdown is observed between the source radius and M0. Finally, both the seismic moment and the moment magnitude are compared with the local magnitude to derive new moment–magnitude relationships for the area.

Description: Published

Description: 655-660

Description: 3.3. Geodinamica e struttura dell'interno della Terra

Description: JCR Journal

Description: partially_open

Description: Uno dei principali obiettivi degli studi di pericolosità sismica è la quantificazione della risposta di sito, che può modificare in maniera significativa il moto registrato in superficie durante un terremoto rispetto al moto osservato su sito rigido. In questo lavoro si presentano i risultati di uno studio finalizzato alla determinazione della risposta sismica del bacino di Gubbio, ottenuti nell’ambito del Progetto INGV-DPC S3 (2005-2007) “Scenari di scuotimento sismico in aree strategiche e/o prioritarie”. In tale area, infatti, recenti studi, basati sull’analisi di registrazioni della stazione accelerometrica GBP, installata nella piana e della stazione vicina GBB, localizzata su sito rigido, hanno evidenziato la presenza di effetti locali legati al bacino alluvionale. Nella piana sono state programmate e svolte molteplici indagini sperimentali sia di sismica attiva che passiva, finalizzate alla determinazione di un modello di riferimento del bacino ed alla stima della risposta di sito. In particolare è stata svolta un’attività di monitoraggio con l’installazione di 4 transetti temporanei di stazioni sismometriche, che hanno operato da Giugno 2005 fino a Maggio 2006. Due transetti sono stati posizionati in direzione trasversale all’asse della piana, uno in direzione longitudinale e l’ultimo presso il centro storico di Gubbio. Durante l’esperimento, grazie all’intensa attività sismica della zona, sono stati registrati più di 300 terremoti locali e regionali, con una magnitudo massima pari a M 4.7. Con un data set selezionato, sono state valutate le funzioni di amplificazione empiriche utilizzando diverse tecniche spettrali. In particolare sono stati applicati il metodo SSR basato sul rapporto spettrale delle componenti orizzontali o verticali rispetto ad un sito di riferimento e la tecnica di inversione generalizzata GIT. Inoltre è stata utilizzata la tecnica H/V, consistente nel rapporto spettrale tra la componente orizzontale e verticale registrata da una singola stazione, per la stima delle frequenze di risonanza. I risultati hanno mostrato che i metodi basati sui rapporti spettrali rispetto ad una stazione di riferimento su roccia (SSR) evidenziano impressionanti effetti di bacino 2D-3D, mentre i rapporti spettrali H/V forniscono utili indicazioni sulla risposta 1D del bacino. Le risposte di sito ottenute nella piana con il GIT e la tecnica SSR sono infatti caratterizzate da elevatissime amplificazioni con ampiezze fra 5 e 20 in una ampia banda di frequenze compresa fra 0.2-0.3Hz fino a 3–4 Hz, in accordo con il contenuto spettrale delle onde di superficie generate localmente. Viceversa, dal picco principale del rapporto H/V, è possibile stimare solo la frequenza fondamentale di risonanza dei siti e, congiuntamente ad altre informazioni sulle velocità delle onde S, gli spessori dei sedimenti.

Description: Published

Description: Roma

Description: 4.1. Metodologie sismologiche per l'ingegneria sismica

Description: open

Description: In the recent years, two Italian research projects have been devoted to the simulation of ground shaking scenarios in different areas. A large part of the activities has been performed in the Umbria region and was in particular related to the 1997 Colfiorito earthquake. In general the statistical-deterministic approach was adopted for evaluating the scenarios for strong motion parameters (peak values, spectral ordinates, signal integral quantities, and so on) associated with the occurrence of a characteristic earthquake on a given fault. This approach is based on the realistic occurrence of a single earthquake related to the fracture of an a priori well identified active fault. According to the characteristic earthquake model, an earthquake rupture can repeatedly occurs along the same fault (or fault system) with an almost constant geometry, mechanism and seismic moment, these parameters being mainly related to the direction and intensity of the large scale tectonic stress regime. These ideas are supported by numerous paleoseismic studies of active faults in different tectonic environments [e.g., Pantosti and Valensise, 1990]. On the other hand, each faulting process may not repeat the same style of nucleation, propagation and arrest during successive rupture episodes occurring along a given fault zone, depending these characteristics on the pre-fracturing conditions of rock strength and/or yielding stress along the fault zone. It is therefore assumed that the large scale source characteristics (i.e., fault size and position, focal mechanism and seismic moment) are a priori known as the result of previous geological, geophysical and historical seismicity investigations. The variability of the rupture process is expected to produce variable strong ground motions at the earth surface, depending on the distribution of the kinematic parameters (final slip distribution, rupture velocity, slip duration …) along the faulting surface. In order to account for the possible variation of the source process from one rupture event to another, a large number of synthetic seismograms should be computed for different (and possible) rupture histories occurring along the characteristic fault selected, so to provide a representative set of strong motion records to be used for hazard estimation. By this strategy, the massive computation of synthetics for different possible rupture models does not provide a single earthquake scenario (as for the standard deterministic approach) but a set of possible scenarios whose variability substantially reflects the heterogeneity of the source process. The advantage of this approach is that the variability of the selected strong ground motion parameter at a given site can be described by the statistical quantities inferred from the large number of simulations available. The earthquake scenario can then be represented, for example, by a couple of maps, one describing the spatial distribution of the mean value of the considered ground motion parameter and the other representing the associated variability for example in terms of standard deviation.

Description: Published

Description: Roma, Università degli Studi Roma TRE

Description: 4.1. Metodologie sismologiche per l'ingegneria sismica

Description: open

Description: Within the framework of four research projects (RISK-EU, EUROSEISRISK, SRM_LIFE and LESSLOSS) extensive calculations were carried out assessing the seismic hazard in the Thessaloniki and surrounding area. The main results were derived from probabilistic and deterministic approaches taking into account rock site conditions for each examined site in the Metropolitan area of Thessaloniki. The expected strong-ground motions were calculated applying different methodologies. Two different groups worked for the assessment of the seismic hazard, the first one constituted of the INGV (Istituto Nazionale di Geofisica e Vulcanologia, Italy) and LSMF (Laboratory of Soil Mechanics and Foundation Engineering, Thessaloniki, Greece) and the second one of LSMF and ITSAK (Institute of Engineering Seismology and Earthquake Engineering, Thessaloniki, Greece).

Description: Published

Description: Thessaloniki (Greece)

Description: 4.2. TTC - Scenari e mappe di pericolosità sismica

Description: open

Description: This study presents the results of 90 seismic ambient noise measurements in Palermo, the main city of Sicily (Italy). The dataset has been processed using the horizontal-to-vertical spectral ratio (HVNSR) technique and interpreted in terms of local geology, which is characterized by the presence of alluvial sediments of two river-beds masked by urbanization since the 17th century. HVNSRs show significant variations in the study area: when the transition stiff-to-soft is crossed, a typical spectral peak appears in the HVNSRs, mostly in the frequency band 1 to 2 Hz, and exceeding a factor of 3 in amplitude. Using available information on sub-surface geological structure we compute theoretical 1- and 2-D transfer functions. The resonance frequencies of soft soils obtained by HVNSR are well reproduced by the fundamental frequencies from numerical modeling. The distribution of frequency peaks of HVNSR and their amplitudes are also compared with the local damage caused by historical earthquakes. Previous studies demonstrated that damage variations in Palermo were controlled more by near-surface geology than building vulnerability. A uniform vulnerability is an ideal condition to test statistical methods and their capability in seeking correlation between HVNSR and potential damage due to local geological conditions. We apply two well-established multivariate statistical methodologies (factor analysis and canonical correlation) to the HVNSR dataset and macroseismic data (damage grades of the European Macroseismic Scale). Through these analyses we quantify the significance of the correlation between the HVNSR peak in the low-medium frequency range (0.5-3 Hz) and the occurrence of the highest damage grades. This approach allows us i) to estimate the threshold value in the resulting linear combination of the HVNSR amplitudes which separates zones of light damage from zones of significant damage, and therefore ii) to improve the spatial definition of potentially high hazard zones through a denser grid of microtremor measurements.

Description: In press

Description: 4.1. Metodologie sismologiche per l'ingegneria sismica

Description: JCR Journal

Description: open

Description: Seismic noise recorded by broad-band stations in the middle of and around the Colfiorito plain is analyzed in the frequency band 0.1 to 10 Hz. Small daily variations in noise amplitude are found, on the order of 2 for f 〉 1 Hz. In contrast, long-term amplitude variations due to weather conditions are significant throughout the analyzed frequency band; for f 〈 1 Hz, the amplitude increase can be as large as a factor of 50. In the low-frequency band, horizontal components vary much more than the vertical at both firm and soft sites. However, these noise variations at low frequencies do not contaminate significantly the 0.9-Hz peak of the H/V spectral ratio that fits the fundamental eigenfrequency of the sedimentary fill of the basin, resonating during earthquakes. Correlating the long-term variations of noise with different meteorological parameters, we find that wind speed best matches the low-frequency noise disturbances.

Description: Published

Description: reserved

Description: The report describes the methods used for retrieving data and selecting a suitable earthquakes dataset from the recordings of the seismic stations used by the INGV Rome team involved in the study of the influence of surface geology on ground motion. It describes also the programs used in the spectral analyses for computing spectral ratios both on earthquake and ambient seismic noise datasets.

Description: Istituto Nazionale di Geofisica e Vulcanologia

Description: Published

Description: open

Description: This study is aimed at predicting the strong ground shaking in the Phlegraen Fields area, in the western part of the city of Naples, by the use of synthetic simulations of the seismic radiation possibly produced by earthquakes occurring on active faults of the southern Apennines range. Given their distance, geometry and expected mechanism these faults have been selected as the potentially most dangerous ones for the city of Naples. We selected the seismogenic sources associated with earthquakes having caused intensity equal or above VII in the city of Naples and having occurred in the past 700 years (the most reliable time window for the historical earthquake catalogue). All seismogenic sources were taken from INGV’s DISS database. These faults are long and relatively shallow structures (length greater than 25 km and maximum depth within 13 km) having seismic moment and focal mechanism comparable to the 1980, M 6.9 Irpinia earthquake. According to the literature, the latter is included in our simulation study by considering the occurrence of three separate rupture processes along three distinct fault segments. A suite of synthetic seismograms at the basement rock in Naples for each considered fault has been generated by using the discrete wavenumber method proposed by Bouchon (1981) numerically implemented for the computation of complete wave field Green’s function in a flat-layered medium. We adopted a simplified source model (line source Haskell model) to simulate the kinematic rupture process along an extended source, allowing for rupture nucleation in the middle (bi-lateral) and at the edge (uni-lateral) of the Haskell line. This approach has been preliminary tested and validated with the comparison between synthetic and observed 10-Hz low-pass filtered 1980 Irpinia earthquake records. The investigated site is located in the eastern part of the Phlegraen caldera, a plain area filled with recent (〈 12,000 yr) pyroclastic soils. Several specific experiments were performed to evaluate the effect of surface geology on ground shaking. The experimental data used in this study come from a 2D active refraction seismic survey, from the spectral analysis of the shot-induced multichannel surface-waves (MASW), and from a 2D small-aperture array that recorded both natural earthquakes and ambient noise. Simultaneously, a firm-site reference station was also operating on an outcrop of yellow Neapolitan tuff (lithoid facies), about 1 km away from the array. These data, integrated with stratigraphy available from boreholes drilled in the plain, allowed us to reconstruct a 1D vertical profile of shear-wave velocities at the site of interest. This velocity model was mostly based on the inversion of the dispersion curves obtained from ambient noise measured at the array combined with MASW results from the refraction survey. The fundamental resonance frequency of the site was assessed around 1 Hz. At this frequency, the soft-to-firm spectral ratios computed from the recorded earthquakes are consistent with the theoretical transfer function of the model in terms of both predominant frequency and amplitude. The rock-site synthetic seismograms were then convolved by the site theoretical transfer function in a linear-equivalent approach, where shear-modulus and damping curves for the soft materials of the uppermost layers are taken from the literature. Acceleration and displacement response spectra were computed from the convolved synthetics. A comparison of the retrieved response spectra with those required by the Italian seismic code (Italian government ordinance PCM 3274 of 20 March 2003) suggests that our results are consistent with expectations at short-periods (T〈 2 s) but some discrepancies arise at longer periods, where our predictions exceed the spectral ordinates of the seismic codes. This finding stresses the need for more thorough investigations of intermediate-period surface waves

Description: Unpublished

Description: Vienna

Description: open

Description: By using small-to-moderate-sized earthquakes located within ~200 km of San Francisco, we characterize the scaling of the ground motions for frequencies ranging between 0.25 and 20 Hz, obtaining results for geometric spreading, Q(f), and site parameters using the methods of Mayeda et al. (2005) and Malagnini et al. (2004). The results of the analysis show that, throughout the Bay Area, the average regional attenuation of the ground motion can be modeled with a bilinear geometric spreading function with a 30 km crossover distance, coupled to an anelastic function ! exp " #fr $Q( f ) % & ' ( ) * , where: Q(f)=180 f 0.42. A body-wave geometric spreading, g(r)= r -1.0, is used at short hypocentral distances (r 〈 30 km), whereas g(r)= r -0.6 fits the attenuation of the spectral amplitudes at hypocentral distances beyond the crossover. The frequency-dependent site effects at 12 of the Berkeley Digital Seismic Network (BDSN) stations were evaluated in an absolute sense using coda-derived source spectra. Our results show: i) the absolute site response for frequencies ranging between 0.3 Hz and 2.0 Hz correlate with independent estimates of the local magnitude residuals (dML) for each of the stations; ii) moment-magnitudes (MW) derived from our path and sitecorrected spectra are in excellent agreement with those independently derived using fullwaveform modeling as well as coda-derived source spectra; iii) we use our weak-motionbased relationships to predict motions region wide for the Loma Prieta earthquake, well above the maximum magnitude spanned by our data set, on a completely different set of stations. Results compare well with measurements taken at specific NEHRP site classes; iv) an empirical, magnitude-dependent scaling was necessary for the Brune stress parameter in order to match the large magnitude spectral accelerations and peak ground velocities with our weak-motion-based model.

Description: Submitted

Description: open

Description: On October 31st and November 1st, 2002 two moderate earthquakes of moment magnitude Mw=5.7 (INGV-Harvard European-Mediterranean Regional Centroid-Moment tensor project) occurred in southern Italy. After the mainshocks, felt in many municipalities of the Molise and Puglia region, a strong motion and a seismic temporary network were installed in the epicentral area and surrounding regions. The strong motion network was composed by 9 stations, integrating the accelerometers of the permanent Rete Accelerometrica Nazionale (RAN network), and operated until December 2003. The strong motion data set is composed by 195 recordings from 51 earthquakes (2.5〈Ml〈5.4) recorded by 29 accelerometers (Dipartimento della Protezione Civile et al., 2004). In addition to the strong motion network, several Italian research institutions (Istituto Nazionale di Geofisica e Vulcanologia, INGV; Istituto Nazionale di Oceanografia e Geofisica, INOGS; Dipartimento per lo studio del Territorio e delle sue Risorse, University of Genoa, Dip.Te.Ris) installed a temporary regional network, composed by 35 seismic stations. This network aimed at monitoring and studying the evolution in time and space of the seismic sequence. More than 1900 aftershocks were recorded in the period November 1st - December 5th, 2002 (Chiarabba et al., 2005). The unified velocity-acceleration data set has been considered to derive ground motion models for peak ground acceleration and peak ground velocity for both maximum horizontal and vertical components. The results obtained for the Molise area have been compared with the attenuation pattern of the Umbria-Marche region (central Italy), that was recently investigated by Bindi et al. (2006). The remarkable differences observed indicate the need of a regional attenuation relation for the area and the need of further investigations, to better identify the role of source characteristics, anelastic and geometric attenuation and site effects in the evaluation of peak ground motion values.

Description: Unpublished

Description: Geneva, Switzerland

Description: open

Description: To define more accurately the near field and the directivity effect, different methodologies of finite-fault modelling have been used to describe the behaviour of ground shaking based on deterministic, stochastic and hybrid stochastic-deterministic approaches as in the framework of the ongoing European project “LESSLOSS – Risk Mitigation for Earthquakes and Landslides”. In this study, we simulate and compare seismic scenarios obtained from the complex source characteristic of the 1980 Irpinia earthquake, M 6.9, Southern Italy, using models based on the source models hypothesized in Bernard and Zollo (1989) and in Valensise et al. (1990). Furthermore, two finite-fault numerical approaches are used: 1. The approach RSSIM [Carvalho et al., 2004] that is a non-stationary stochastic simulation method that synthesizes the ground motion due to an extended source; 2. The approach EXSIM [Motazedian and Atkinson, 2005] that is a new version of FINSIM [Beresnev and Atkinson, 1998] introducing a new variation based on a “dynamic corner frequency”. The shaking scenarios are computed in terms of Response Acceleration Spectra (PSA), time series, peak ground acceleration (PGA) at bedrock level. Source and path propagation parameters taken from other studies were tested and the computed shaking scenarios are compared to acceleration records to eight different stations. Preliminary results are here presented in terms of PGA maps for the Campania region (Southern Italy).

Description: Unpublished

Description: Geneva, Switzerland

Description: open

Description: A seismic rehabilitation program is being implemented to address the vulnerability of a large proportion of Italian building stock. A risk management framework, initially only for Italian school buildings, has been developed to assign priorities for the rehabilitation, and to give timescales within which retrofit or demolition must take place. Since it is not practical to carry out detailed assessment for around 60,000 Italian public schools, the framework is a multiplelevel procedure which aims to identify the highest-risk buildings based on filters of increasing detail, and reduces the size of the building inventory at each step. Finally, priorities and timescales are assigned based on vulnerability, seismic hazard and building occupancy, within a general framework with parameters which must be assigned by the relevant authorities. The methodology is transparent, technically-based, and flexible enough to be adapted for other building types or other regions.

Description: Submitted

Description: reserved

Description: Acceleration time series recorded by the Italian Strong Motion Network (RAN) during the October 31, 2002 (Mw=5.8), Molise earthquake, are employed in order to investigate source effects on the ground motion in the epicentral area. We consider two different seismogenic sources: a fault model inferred from inversion of teleseismic, regional and local seismic signals [Vallée and Di Luccio, 2005], and a fault model based on seismotectonic data [Basili and Vannoli, 2005]. Both source studies suggest a deep location of the earthquake fault plane (ranging from 6.0 to 20.1 km and from 12.0 to 19.9 km, respectively), however, with considerably different fault lengths (5.2 and 10.5 km, respectively), and widths (14.2 and 8 km, respectively). Due to these differences, only the second model allows for effective horizontal unilateral rupture propagation. Finite fault effects are modelled by the Deterministic-Stochastic-Method (DSM) [Pacor et al., 2005], and the Hybrid Integral-Composite source model (HIC) [Gallovic and Brokesova, 2006]. In both methods k-square slip distributions on the faults are considered. We simulate the October 31, 2002 earthquake considering: 1) Vallée and Di Luccio [2005] faultwith a bilateral rupture propagation, and 2) Basili and Vannoli [2005] fault with unilateral directions of the rupture propagation. The spectral attenuation is modelled using a regional estimate of the quality factor [Castro et al., 2004] and k values estimated from acceleration records. Comparison between synthetic and recorded data at nearby stations (hypocentral distances 〈 60 km) performed in terms of frequency content and peak ground motion, favours the model with unilateral propagation of the rupture. Assuming the source model with unilateral rupture propagation, we utilize both asymptotic and full wave field methods in order to simulate ground shaking scenarios for an area extending up to 150 km epicentral distance. These results are then subjected to comparison with peak ground accelerations recorded in the far field.

Description: Unpublished

Description: Geneva, Switzerland

Description: open

Description: We present an update of the local magnitude scale previously calibrated for Northwestern Turkey by Baumbach et al. (2003). The path coverage in the westernmost part of the analysed area has been increased, as well as the number of amplitudes for distance greater than 110 km. Furthermore, a set of recordings from accelerometric stations operated by the Kandilli Observatory and Earthquake Research Institute (KOERI) has been merged with the recordings by the Sapanca-Bolu and GermanTaskForce seismological networks. In all, 4047 recordings from 528 earthquakes recorded by 31 seismometers and 23 accelerometers are considered to calibrate the local magnitude scale over a hypocentral distance range from 10 to 190 km. By analyzing the unit covariance matrix and the resolution matrix, we show how the source-to-station geometries of the seismic and strong motion networks affect the uncertainties of the computed station corrections, attenuation coefficients, and magnitudes. The assumptions made concerning the reference station correction, and the change in the amplification for the Wood-Anderson torsion seismograph from 2800 to 2080 (Uhrhammer and Collins, 1990) introduced an offset of about 0.34 in the magnitudes with respect to Baumbach et al. (2003), with the updated local magnitude scale ranges from 0.50 to 5.91. The distribution of the residuals with distance confirms that the extension of both the magnitude and distance ranges and the improved path coverage have preserved the high quality that characterized the data set analyzed by Baumbach et al. (2003).

Description: Submitted

Description: open

Description: By using small-to-moderate-sized earthquakes located within ~200 km of San Francisco, we characterize the scaling of the ground motions for frequencies ranging between 0.25 and 20 Hz, obtaining results for geometric spreading, Q(f), and site parameters using the methods of Mayeda et al. (2005) and Malagnini et al. (2004). The results of the analysis show that, throughout the Bay Area, the average regional attenuation of the ground motion can be modeled with a bilinear geometric spreading function with a 30 km crossover distance, coupled to an anelastic function exp(-pi*f*r/V*Q(f)) , where: Q(f)=180f^0.42. A body-wave geometric spreading, g(r)= r^-1.0, is used at short hypocentral distances (r 〈 30 km), whereas g(r)= r^-0.6 fits the attenuation of the spectral amplitudes at hypocentral distances beyond the crossover. The frequency-dependent site effects at 12 of the Berkeley Digital Seismic Network (BDSN) stations were evaluated in an absolute sense using coda-derived source spectra. Our results show: i) the absolute site response for frequencies ranging between 0.3 Hz and 2.0 Hz correlate with independent estimates of the local magnitude residuals (dML) for each of the stations; ii) moment-magnitudes (MW) derived from our path and site-corrected spectra are in excellent agreement with those independently derived using full-waveform modeling as well as coda-derived source spectra; iii) we use our weak-motion-based relationships to predict motions region wide for the Loma Prieta earthquake, well above the maximum magnitude spanned by our data set, on a completely different set of stations. Results compare well with measurements taken at specific NEHRP site classes; iv) an empirical, magnitude-dependent scaling was necessary for the Brune stress parameter in order to match the large magnitude spectral accelerations and peak ground velocities with our weak-motion-based model.

Description: Published

Description: 843-862

Description: 4.1. Metodologie sismologiche per l'ingegneria sismica

Description: JCR Journal

Description: partially_open

Description: In the text

Description: Regione Campania Provincia di Benevento Comune di Benevento C.C.I.A.A. Benevento ESRI Italia Delisa S.p.a., Trento Infotel S.r.l., Taranto

Description: Published

Description: Benevento, Italy

Description: 4.1. Metodologie sismologiche per l'ingegneria sismica

Description: open

Description: We present a physically based methodology to predict the range of ground-motion hazard for earthquakes along specific faults or within specific source volumes, and we demonstrate how to incorporate this methodology into probabilistic seismic hazard analyses (PSHA). By ‘physically based,’ we refer to ground-motion syntheses derived from physics and an understanding of the earthquake process. This approach replaces the aleatory uncertainty that current PSHA studies estimate by regression of empirical parameters with epistemic uncertainty that is expressed by the variability in the physical parameters of the earthquake rupture. Epistemic uncertainty can be reduced by further research.We modelled wave propagation with empirical Green’s functions. We applied our methodology to the 1999 September 7 Mw = 6.0 Athens earthquake for frequencies between 1 and 20 Hz.We developed constraints on rupture parameters based on prior knowledge of the earthquake rupture process and on sources within the region, and computed a sufficient number of scenario earthquakes to span the full variability of ground motion possible for a magnitude Mw = 6.0 earthquake with our approach. We found that: (1) our distribution of synthesized ground motions spans what actually occurred and that the distribution is realistically narrow; (2) one of our source models generates records that match observed time histories well; (3) certain combinations of rupture parameters produced ‘extreme,’ but not unrealistic ground motions at some stations; (4) the best-fitting rupture models occur in the vicinity of 38.05!N, 23.60!Wwith a centre of rupture near a 12-km depth and have nearly unilateral rupture toward the areas of high damage, which is consistent with independent investigations.We synthesized ground motion in the areas of high damage where strong motion records were not recorded from this earthquake. We also developed a demonstration PSHA for a single magnitude earthquake and for a single source region near Athens. We assumed an average return period of 1000 yr for this magnitude earthquake and synthesized 500 earthquakes distributed throughout the source zone, thereby having simulated a sample catalogue of ground motion for a period of 500 000 yr. We then used the synthesized ground motions rather than traditional attenuation relations for the PSHA.

Description: This project was partially funded by the National Observatory of Athens, Greece, which also contributed significant data and data processing. The University of Athens, Greece contributed significant computational facilities and data. This project was partially supported by the University of California, Lawrence Livermore National Laboratory under the auspices of the U.S. Department of Energy under contract W-7405-Eng-48.

Description: Published

Description: 659-680

Description: 4.1. Metodologie sismologiche per l'ingegneria sismica

Description: JCR Journal

Description: reserved

Description: A prototype system for earthquake early warning and rapid shake map evaluation is being developed and tested in southern Italy based on a dense, dynamic seismic network (accelerometers + seismometers) under installation in the Apenninic belt region (Irpinia Seismic Network). It can be classified as a regional Earthquake Early Warning System consisting of a broad-based seismic sensor network covering a portion or the entire area which is threatened by the quake's strike. The real time magnitude estimate will take advantage from the high spatial density of the network in the source region and the broad dynamic range of installed instruments. Based on the offline analysis of high quality strong-motion data bases recorded in Italy, several methods are envisaged, using different observed quantities (peak amplitude, dominant frequency, square velocity integral, …) to be measured on seismograms, as a function of time, both on P and early-S wave signals. Results from the analysis of the Italian strong motion database point out the possibility of using low-pass filtered displacement and velocity peak amplitudes measured in time windows lasting less than 3-4 sec after the first P- or S-wave arrivals. These parameters show they are robustly correlated with moment magnitude. The correlation found of 3Hz low-pass filtered PGV and PGD with magnitude is discussed and interpreted in terms of plausible dynamic models of the earthquake rupture process during its initial stage.

Description: Published

Description: 45-63

Description: 4.1. Metodologie sismologiche per l'ingegneria sismica

Description: reserved

Description: The aims of this work are to review the Northern-Italy ground motion prediction equations (hereinafter GMPEs) for amplitude parameters and to propose new GMPEs for frequency content and duration parameters. Approximately 10.000 weak and strong waveforms have been collected merging information from different neighbouring regional seismic networks operating in the last 30 years throughout Northern Italy. New ground motion models, calibrated for epicentral distances ≤ 100 km and for both local (Ml) and moment magnitude (Mw), have been developed starting from a high quality dataset (624 waveforms) which consists of 82 selected earthquakes with Ml and Mw up to 6.3 and 6.5 respectively. The vertical component and the maximum of the two horizontal components of motion have been considered, for both acceleration (PGHA and PGVA) and velocity (PGHV and PGVV) data. In order to make comparisons with the most commonly used prediction equations for the Italian territory (Sabetta and Pugliese, 1996 and Ambraseys et al. 2005a,b hereinafter named SP96 and AM05) the coefficients for acceleration response spectra (SHA and SVA) and for pseudo velocity response spectra (PSHV and PSVV) have been calculated for 12 periods ranging between 0.04 s and 2 s and for 14 periods ranging between 0.04 s and 4 s respectively. Finally, empirical relations for Arias and Housner Intensities (IA, IH) and strong motion duration (DV) have also been calibrated. The site classification based on Eurocode (hereinafter EC8) classes has been used (ENV, 1998). The coefficients of the models have been determined using functional forms with an independent magnitude decay rate and applying the random effects model (Abrahamson and Youngs, 1992; Joyner and Boore, 1993) that allow the determination of the inter-event, inter-station and record-to-record components of variance. The goodness of fit between observed and predicted values has been evaluated using the maximum likelihood approach as in Spudich et al. (1999). Comparing the proposed GMPEs both with SP96 and AM05 it is possible to observe a faster decay of predicted ground motion, in particular for distances greater than 25 km and magnitudes higher than 5.0. The result is a fit improvement of about one order of size for magnitudes spanning from 3.5 to 4.5.

Description: In press

Description: 4.1. Metodologie sismologiche per l'ingegneria sismica

Description: JCR Journal

Description: open

Description: Various authors, analysing the set of accelerograms recorded at Gubbio Piana (GBP) (central Italy), have demonstrated that strong amplification occurs at this accelerometric station, which is installed within an alluvial basin. In particular, Ambraseys et al. [(2005a), Bull Earthq Eng 3:1–53; (2005b), Bull Earth Eng 3:55–73] observed that the strong motion peaks at GBP greatly exceed the median values predicted by the attenuation relationships they derived for Europe. In this work, we analyse and discuss some characteristics of the ground motion recorded at the GBP station. We show that the ground motion parameters, such as peak-ground acceleration and peak-ground velocity, are strongly influenced by the presence of locally induced surface waves that produce both a lengthening of the significant shaking duration and an increase in the peak values with respect to a nearby bedrock site. The basin-induced surface waves are observed in the three components of motion and their effects on the peak values are particularly evident in the vertical component. In the frequency domain, the energy of the surface waves is mostly restricted to the frequency band 0.4–0.8Hz for both the horizontal and vertical components. The horizontal and vertical Fourier amplitudes are also very similar, and this indicates that the H/V spectral ratio technique is not applicable to describing the site response due to the propagation of seismic wave in a complex 2D/3D geological structure. Finally, a preliminary polarization analysis shows that the directions of polarization, as well as the degree of elliptical polarization, exhibit a strong variability with time, that may be related to a complex propagation of Love and Rayleigh waves within the basin.

Description: Published

Description: 27-43

Description: 4.1. Metodologie sismologiche per l'ingegneria sismica

Description: JCR Journal

Description: partially_open

Description: The investigation of local amplification phenomena by seismic signal analysis is a fundamental step in carefully defining the seismic response of an area. In this study we investigate the use of teleseismic recordings in assessing seismicwave amplification in the Pellice Valley (northwestern Alps, Italy). Assuming that teleseismic P waves are sensitive to the deep structure of a basin, we deal with the computation of horizontal-to-vertical spectral ratios (HVSRs) and with the estimate of teleseismic P-wave arrival time delays and P-wave amplifications with respect to a reference site. The reliability of the HVSR results obtained by considering teleseismic signals is confirmed by the agreement with the results coming from both the HVSR of noise and HVSR of S wave of local events methods. Strong correlation between the P-wave arrival time delays and the relative P-wave amplifications with respect to thickness of the low-velocity layers and the geometry of the bedrock is found.

Description: Published

Description: 605-613

Description: 4.1. Metodologie sismologiche per l'ingegneria sismica

Description: JCR Journal

Description: reserved

Description: The main goal of Task 6 is the computation of the bedrock and site seismic scenarios in the Gubbio town and in the Gubbio basin (Central Italy). This area represents one of the prediction case studies, planned in the framework of Project S3 which aims at simulating ground shaking scenarios for moderate magnitude earthquakes. Deterministic shaking scenarios, described in this report, are computed for the Maximum Credible Earthquake. This is associated with two sources capable of generating an earthquake with M equal to 6 and located at about 10km from the sites. Starting from these sources bedrock shaking scenarios at different level of complexity are computed by ground motion prediction equations (scenarios of level 0), high frequency (f〉0.5Hz) simulations (scenarios of level 1) and broad band (0-20 Hz) simulations (scenarios of level 2). However since many sites have to be simulated for accurately sampling the basin, the bedrock ground motions for evaluating the seismic response of the valley are generated at level 1. For four test sites a comparison between time series computed at different levels of complexity have been performed in order to verify the approximations introduced in level 1. Before computing the predicted shaking scenarios, we evaluate the modelling capability of the adopted simulation techniques reproducing the observed ground motions occurred during the 1984 Gubbio earthquake (M 5.7). Finally we apply the probabilistic-deterministic approach for a characteristic earthquake scenario proposed by Convertito et al. (2006) to perform hazard analysis considering the two seismogenic faults at three sites of interest in the Gubbio area (paragraph 3.3). In this way, respect to the deterministic approach, we produce ‘dynamic shaking scenarios’ introducing the time variable. The shaking scenarios generated in the Gubbio area allow us to show how the prediction of the ground motion can be tackled using different methodologies and which strategy should be followed to select mean shaking scenario. As the available information increases, we could gradually adopt approaches more and more sophisticated and provide shaking scenarios that account for specific effects related to the source and propagation (e.g., directivity, radiation pattern distribution,…). Furthermore, the adoption of different approaches allows a cross check of the results guaranteeing the reliability of the ground motion estimates.

Description: Progetto INGV-DPC S3 “Scenari di scuotimento in aree di interesse prioritario e/o strategico”

Description: Published

Description: 4.2. TTC - Scenari e mappe di pericolosità sismica

Description: open

Description: The main goal of this report is the computation of the bedrock seismic motion at 5 municipalities located in the Molise area (Bonefro, S.Giuliano, Colletorto, S.Croce di Magliano, Ripabottoni, hereafter referred to as sites BNF, SGI, CLT, SCM and RPB, respectively). This area represents one of the validation case studies, planned in the framework of Project S3 which aim is the production of ground shaking scenarios for moderate magnitude earthquakes. Indeed, the recently occurred Molise earthquake represents a proper opportunity to compare synthetic simulations with real data. Acceleration time series were recorded during the October 31, 2002 and November 1, 2002 main shocks by analog and digital instruments managed by the Italian Civil Protection Department [DPC-SSN, 2004] while acceleration and velocity records were collected during the first month of seismic activity by DPC, INGV, INOGS, Dip.Te.Ris.(Genoa) (see §2.1 and Deliverable D6). Both strong and weak motion data were employed to infer regional ground motion prediction equations and spectral attenuation models (§2.3 and §2.4) while acceleration time series recorded during the first main shock by nearby stations were used to constrain the seismogenic sources of the October 31 and November 1, 2002 twin earthquakes (§4.1). Bedrock shaking scenarios at different level of complexity were produced by ground motion prediction equations (scenarios of level 0, §4.2), high frequency (f〉1Hz) simulations (scenarios of level I, §4.3) and broad band (0-12 Hz) simulations (scenarios of level II, §4.4). Comparison of results obtained with different simulations methods confirms the complexity of the Molise area as regard to both seismogenic and attenuation properties of the crust. Especially for this area the ground motion prediction is constrained by the demand of simulations reproducing different features of the seismic wavefield. In particular, the input motion for site effect modelling, performed at sites located in the epicentral area, was computed with a broad band technique able to reproduce the complete wave field in the frequency band 0-10 Hz in terms of acceleration time series (scenarios of level II scenarios).

Description: Progetto INGV-DPC S3 “Scenari di scuotimento in aree di interesse prioritario e/o strategico”

Description: Published

Description: 4.2. TTC - Scenari e mappe di pericolosità sismica

Description: open

Description: WebGis scenari di scuotimento area Garda

Description: Progetto S3 - Scenari di scuotimento in aree di interesse prioritario e/o strategico

Description: Published

Description: 4.2. TTC - Scenari e mappe di pericolosità sismica

Description: open

Description: Sansepolcro, one of the most significant city of Tuscan Tiber Valley, is located in an area close to the eastern edge of the Upper Tiber Valley, characterized by a wide local seismicity, related to the Altotiberina Fault (ATF) activity and not far from the main seismogenic areas of Mid-Northern Apennines (Montefeltro, Forlì, Gubbio, etc.). The Upper Tiber Valley has felt in the past several strong earthquakes: in 1789 (VIII MCS in the city of Sansepolcro), in 1917 (〉 VIII MCS), in 1948 (〉 VII MCS), in 1964 (VII MCS). Furthermore, many seismic sequences took place in recent years (1987, 1990, 1997), the last one in 2001 (November, 26, 2001, ML = 4.4). From May 2005, some seismic stations have been deployed in the center of Sansepolcro and its vicinities. Five sites were covering different geologic environments, along a direction approximately orthogonal to the valley axis. The seismic array has recorded more than 100 local and regional seismic events. 20 seismic events, with magnitude ranging from 2.0 and 3.8, distributed with a good azimuthal coverage in an area of 150 km radius centered on the city, have been selected. They were recorded by all the seismic stations with a signal to noise ratio higher than 3 in the frequency band of interest (0.5-10 Hz). The selected events have been analyzed with HHSR and HVSR techniques, to obtain the average spectral ratios for each site. Moreover, we analyzed seismic ambient noise in order to evaluate HVNSR, to be compared with the curves obtained by earthquake analysis. The results allow to give a preliminar evaluation of amplification effects due to the surface geology in the urban area. The three average spectral ratios (HHSR, HVSR and HVNSR) provide a good agreement: they show peaks with a raising amplitude centered on frequencies which point to long period moving from east to the center of the valley. The good agreement with 1D theoretical transfer functions, obtained from stratigraphic data and velocity downhole profiles (Vp e Vs), available for the monitored sites, suggests the hypothesis of being in geologic environment characterized by the presence of a stiff layer, identifiable in the well logs and in the velocity profiles obtained by downhole measurements, which seems to be the reason of surface amplification effects. This layer mainly made by firm cobble-stone associated to the sedimentary phases of Afra torrent, a Tiber tributary that flows close to the SE border of the city, is characterized by shear waves velocities comparable with those of a bedrock and it is recognizable in all the locations, at depths that increase from few meters to 100 m, moving from east to west. This layer, that seems to determine the distinct impedance contrast with the fluvial-lacustrine superficial layers, is not bottom of the basin which should be at a depth of more than 1000 m, as shown by the results of recent 3D analysis (Ciaccio e Barchi, 2006).

Description: Published

Description: Vienna

Description: 4.2. TTC - Scenari e mappe di pericolosità sismica

Description: open

Description: Several cases of strong motion data recorded in alluvial basins show very high amplification effects that exceed, at medium and long periods, those predicted by empirical relations or included in standard reference codes. Among others, we recall here the earthquakes of San Fernando (1972), Northridge (1994) (BSSA, 1996) and the Umbria-Marche sequence of 1997, during which the shaking recorded in the Gubbio Plain (Pacor et al, 2007) provided strong evidence of the phenomenon: extremely high spectral amplification values (higher than reference codes) for 2 〈 T 〈 4 s (see Fig. 4). The main reason why these amplifications (“basin effects”) take place lies in the generation, by diffraction at the edges of the valley, of long period surface waves that travel horizontally in the upper sediments of the valley. While the influence of alluvium filled basins on site response has been the subject of substantial research, the resulting modifications on the response spectra at the basin surface (especially for T 〉 1 - 2 s) has not been as thoroughly investigated (see e. g. Chávez e Faccioli, 2000) despite its importance in structural design. Significant previous studies tried to estimate basin amplification effects through the analysis of strong-motion data and most of them quantified basin geometry only in terms of sediment depth (Trifunac and Lee, 1978), introducing such term in newly developed attenuation models (Campbell, 1997; Field, 2000; Lee and Anderson, 2000). Other studies tried to relate basin effects also to the relative location of source and site position in the basin (Choi et al., 2005), or to the distance to the basin edge (Joyner, 2000). In the S5 project, specific parametric studies involved two different types of basins (both typical of the Italian Peninsula): “enclosed” basins and “open” basins. Results gave great insight of how basin effects amplify seismic motion in connection with the geometry of the basin, with the fault mechanism and with the different valley-fault configurations. Critical in all analyses is the value of the fundamental 1D vibration period of valley centre, T01D, that acts as the theoretical upper limit to 2D basin amplification effects, as stated in Chàvez-García and Faccioli (2000). Its calculation appears thus crucial in the study of the seismic response of valleys and basins. In addition, a detailed study has been devoted to the identification and classification of alluvium filled basins in Italy, and particularly to the parameters that the previous analyses highlighted as the most critical ones in the modification of response spectra.

Description: Progetto INGV-DPC S5 “Definizione dell'input sismico sulla base degli spostamenti attesi"

Description: Published

Description: 4.1. Metodologie sismologiche per l'ingegneria sismica

Description: open

Description: The analysis of data coming from a dense 95-station array installed on the Cavola landslide (northern Apennines) is presented. The array extended along a 112X80 m2 area covered by clay deposits related to a recent and still active landslide. It operated along a four month time period in a continuous mode recording. Both earthquake and noise data are used to assess the amplification effects and relate them to thickness and geophysical properties of outcropping terrain. Compared to a reference site, earthquake data recorded on the landslide show a ground motion amplification up to a factor of 4 in the 2.5 to 5 Hz frequency band. Moreover, the study of the predominant frequency distribution derived from spectral analysis of ambient noise allows to infer thickness variations along the array. We then identify zones with small lateral variations to select sub-arrays with homogenous geometrical subsoil conditions where passive and active 1D and 2D array data analysis techniques are applied to evaluate shear waves velocity in the landslide body. Available drilling and down-hole data are used to calibrate the velocity model inferred from seismic surface data. This analysis permits to reconstruct an approximate 2D geometry used as a base for modelling waveform changes along the array.

Description: Unpublished

Description: Grenoble (france)

Description: open

Description: During the ML = 5.6 and 5.8 earthquakes occurred in central Italy on 26 September 1997 the historic centre of Nocera Umbra, lying on top of a 120 m high hill, was diffusely damaged (VII-VIII degrees of MCS intensity). Some recently built houses in the modern part of the town suffered an even higher level of damage. A temporary seismic array was deployed to investigate a possible correlation between local amplifications of ground motion in this area and the observed pattern of damage. After a geologic and macroseismic survey, eight sites were selected as representative of different local conditions, such as topographic irregularities, sharp hard-to-soft lithology transitions, alluvium-filled valleys, and both undisturbed and deformed rocks. Horizontal-to-vertical spectral ratios for both microtremor and earthquake recordings, as well as spectral ratios referred to undisturbed rock sites, were used to quantify local variations of ground motion. In spite of the diffuse damage in the historic centre of Nocera Umbra, a small amplification is observed at the stations on the hill’s top. This suggests that the higher vulnerability of the ancient buildings mainly accounts for the diffuse damage in that part of the town. In the frequency band of engineering interest (1 to 10 Hz) the largest amplifications of ground motion are found at soft sites: in the Topino river valley, where many episodes of severe structural damage occurred, spectral amplification is significant over a broad frequency band ranging from 2 Hz to more than 20 Hz. In particular, in the central part of the valley high amplification (〉 4) is found from 3 to 10 Hz, reaching a maximum of 20 around 4 Hz. At the edge of the valley, close to the soil-to-rock transition, amplification is as large as 10 in a frequency band ranging from 4 to more than 20 Hz. A significant amplification (by a factor of 10 around 10 Hz) is observed also at one of the rock sites, possibly due to the presence of a cataclastic zone related to the activity of a regional fault that altered the mechanical properties of the rock.

Description: Published

Description: 555-565

Description: JCR Journal

Description: reserved

Description: What can be learned about absolute site effects on ground motions, with no geotechnical information available, in a very poorly instrumented region? In addition, can reliable source spectra be computed at a temporary deployment? These challenges motivated our current study of aftershocks of the 2001 Mw 7.6 Bhuj earthquake, in western India, where we decouple the ambiguity between absolute source radiation and site effects by first computing robust estimates of coda-derived moment-rate spectra of about 200 aftershocks in each of two depth ranges. Crustal attenuation and spreading relationships, based on the same data used here, were determined in an an earlier study. Using our new estimates of source spectra, and our understanding of regional wave propagation, for direct S waves we isolate the absolute site terms for the stations of the temporary deployment. Absolute site terms for each station were determined in an average sense for the three components of the ground motion via an L1-norm minimization. Results for each site were averaged over wide ranges of azimuths and incidence angles. The Bhuj deployment is characterized by a variable shallow geology, mostly of soft sedimentary units. Vertical site terms in the region were observed to be almost featureless (i.e., flat), with amplifications slightly 1.0 within wide frequency ranges. As a result, the horizontal-to-vertical (H/V) spectral ratios observed at the deployment mimic the behavior of the corresponding absolute horizontal site terms, and they generally overpredict them. This differs significantly from results for sedimentary rock sites (limestone, dolomite) obtained by Malagnini et al. (2004) in northeastern Italy, where the H/V spectral ratios had little in common with the absolute horizontal site terms. Spectral ratios between the vector sum of the computed horizontal site terms for the temporary deployment with respect to the same quantity computed at the hardest rock station available, BAC1, are seriously biased by its nonflat, nonunitary site response. This indicates that, occasionally, the actual behavior of a rock outcrop may be far from that of an ideal, reference site (Steidl et al., 1996).

Description: Published

Description: 456-466

Description: JCR Journal

Description: reserved

Description: Paleoseismic evidence and seismic-hazard analysis suggest that the city of Rome, Italy, has experienced considerable earthquake ground motion since its establishment more than 2000 years ago. Seismic hazards in Rome are mainly associated with two active seismogenic areas: the Alban Hills and the Central Apennines regions, located about 20 km southeast and 80–100 km east of central Rome. Within the twentieth century, M 6.8 and M 5.3 earthquakes in the Apennines and the Alban Hills, respectively, have generated intensities up to Mercalli-Cancani-Sieberg scale (MCS) VII in the city. With a lack of strong-motion records, we have generated a 3D velocity model for Rome, embedded in a 1D regional model, and estimated long-period ( 1 Hz) ground motions for such scenarios from finite-difference simulations of viscoelastic wave propagation. We find 1-Hz peak ground velocities (PGVs) and peak ground accelerations (PGAs) of up to 14 cm/sec and 44 cm/sec2, respectively, for a M 5.3 Alban Hills scenario, largest near the northwestern edge of the Tiber River. Our six simulations of a M 7.0 Central Apennine scenario generate 0.5-Hz PGVs in Rome of up to 9 cm/sec, as well as extended duration up to 60 sec. The peak motions are similar to, but the durations much longer than those from previous studies that omitted important wave-guide effects between the source and the city. The results from the two scenarios show that the strongest ground-motion amplification in Rome occurs in the Holocene alluvial areas, with strong basin edge effects in the Tiber River valley. Our results are in agreement with earlier 2D SHwave results showing amplification of peak velocities by up to a factor of 2 in the alluvial sediments, largest near the contact to the surrounding Plio-Pleistocene formations. Our results suggest that both earthquakes from the Alban Hills and the Central Apennines regions contribute to the seismic hazards in Rome. Although earthquakes from the former area may generate the larger peak motions, seismic waves from the latter region may generate ground motions with extended durations capable of causing significant damage on the built environment.

Description: Published

Description: 133-146

Description: JCR Journal

Description: reserved

Description: The job illustrates the activities, the normative and procedural dispositions of the reconstruction in Molise that has been on its way after the 2002 earthquake. The individualized run has been characterized by numerous technical innovations, consequent to the emanation of the new seismic code (OPCM n. 3274/2003). The President of the Region, Delegated Commissioner for the reconstruction after-earthquake 2002, has programmed and coordinated all the activities, using structures of consultation, of address and of technical support. Particularly, the Scientific Technical Committee (CTS) has taken care of the containing directives, the criterions and the general norms for the trial of the reconstruction, emanate through the Ordinance of the Delegated Commissioner n. 13/2003. The Committee for the Microzonation (CMS) has predisposed indications and guidelines, while the CNR Institute for the Technologies of the Construction, in collaboration with the University of Basilicata and Dicat-University of Genoa, has up the guidelines for the investigations of vulnerability and for the interventions on the scholastic buildings, on the churches and on the monumental buildings. Finally, the Delegated Commissioner has ordered that the Local Corporate Bodies were made themselves responsible for the reconstruction realization. In the Campobasso province , with exception of the S.Giuliano diPuglia common, have been compiled about 16.200 preliminary projects (PPS). It is esteemed a general economic requirement of about 1.800 million of Euros for the residential buildings and of about 900 million of Euros for the public works. The reconstruction is in advanced realization and involves the buildings affected by an evacuation measure (Priority A).

Description: Published

Description: Pisa, Italia

Description: 4.2. Scenari e mappe di pericolosità sismica e danno

Description: open

Description: The damage and vulnerability survey of the monumental buildings, damaged by the 2002 earthquake in the Molise Region, has allowed singling out of a correlation between the observed damage of the churches and their morphological site conditions. The vulnerability model connected to the survey methodology provides an evaluation of the expected mean damage. Comparison with the observed damage determined the introduction of a local morphological behaviour modifier, able to take into account the vulnerability increase due to the site effects. In order to validate the previous results, a numerical 2-D analysis of the seismic local response has been performed. In particular, a numerical code, working with boundary elements, has been applied to the analyzed situations. The results, in terms of pseudo-acceleration response spectra and amplification factors, allow one to compare the numerical and the observed analyses. This comparison shows good agreement and allows one to find some correlations between the geometric characteristics of the sites, the values of the amplification coefficients and the damage mechanism activated.

Description: Published

Description: Thessaloniki, Greece

Description: 4.1. Metodologie sismologiche per l'ingegneria sismica

Description: open

Description: The U.S. Geological Survey deployed a digital seismic station in Oceano, California, in February 2004, to investigate the cause of damage and liquefaction from the 22 December 2003 Mw 6.5 San Simeon earthquake. This station recorded 11 Mw 2.8 aftershocks in almost 8 weeks. We analyze these recordings, together with recordings of the mainshock and the same aftershocks obtained from nearby stations in Park Hill and San Luis Obispo, to estimate the mainshock ground motion in Oceano. We estimate the Fourier amplitude spectrum using generalized spectral ratio analysis. We test a set of aftershocks as Green’s functions by comparing simulated and recorded acceleration amplitude spectra for the mainshock at San Luis Obispo and Park Hill. We convolve the aftershock accelerograms with a stochastic operator to simulate the duration and phase of the mainshock accelerograms. This approximation allows us to extend the range of aftershocks that can be used as Green’s functions to events nearly three magnitude units smaller than the mainshock. Our realizations for the mainshock accelerogram at Oceano yield peak ground accelerations distributed as 28% +/- 4%g. We interpret these realizations as upper bounds for the actual ground motion, because our analysis assumes a linear response, whereas the presence of liquefaction indicates that the ground behaved nonlinearly in Oceano.

Description: U.S.G.S University of Naples “Federico II” University of Rome “La Sapienza,”

Description: Published

Description: 1437–1447

Description: 4.1. Metodologie sismologiche per l'ingegneria sismica

Description: JCR Journal

Description: reserved

Description: The goal of our research has been to estimate the economic impact of the seismic hazard studies on the reconstruction phase after the 2002 Molise earthquake. The study has been carried out adopting the vulnerability model, connected to the GNDT II level form, on a sample of existing masonry buildings of Campobasso province. A procedure has been provided to recover the necessary parameters for the vulnerability evaluation, using the AeDES 05/2000 forms, which are the basic support for the safety assessment in the post-earthquake phases. Assuming a set of structural seismic upgrading intervantions, a correlation between the cost of ret-rofitting interventions and different limit state has been evaluated, taking into account the litologi-cal site characteristics, according to the recent studies of seismic microzonation of the earthquake epicentral area. The results show a substantial difference of the seismic upgrading costs, varying the hazard (PGA) and the litological site characteristics, particularly in the 1st and 2nd Zones of the Italian Seismic Classification (OPCM 3519/06). These considerations put in evidence once again the necessity to invest important economic re-sources in the building national heritage knowledge and in the seismic microzonation of the urban areas; only in this way an effective preventive planning of risk reduction can be perfomed.

Description: Published

Description: Pisa, Italia

Description: 4.1. Metodologie sismologiche per l'ingegneria sismica

Description: 4.2. Scenari e mappe di pericolosità sismica e danno

Description: open

Description: We present ground motion models for northwestern Turkey using the aftershocks of the Mw 7.4, 1999 Kocaeli earthquake. We consider 4047 velocity and acceleration records for each component of motion, from 528 earthquakes recorded by stations belonging to regional networks. The ground motion models obtained provide peak ground velocity, peak ground acceleration, and spectral accelerations for 8 different frequencies between 1 and 10 Hz. The analysis of the error distribution shows that the record-to-record component of variance is the largest contribution to the standard deviation of the calibrated ground- motion models. Furthermore, a clear dependence of inter-event error on stress drop is observed. The empirical ground-motion prediction equations, derived for both the larger horizontal and vertical components, are valid in the local magnitude range from 0.5 to 5.9, and for hypocentral distances up to 190 km. Citation: Bindi, D., S. Parolai, H. Grosser, C. Milkereit, and E. Durukal (2007), Empirical ground-motion prediction equations for northwestern Turkey using the aftershocks of the 1999 Kocaeli earthquake,

Description: Published

Description: L08305

Description: 4.1. Metodologie sismologiche per l'ingegneria sismica

Description: JCR Journal

Description: partially_open

Description: The main goal of this report is the computation of the bedrock seismic scenarios in the Potenza city (Southern Italy) to be used for evaluating damage scenarios (described in PS3-Deliverables D18-D19-D24). This area represents one of the prediction case studies, planned in the framework of Project S3 which aim is the production of ground shaking scenarios for high and moderate magnitude earthquakes. The area around Potenza was affected by several destructive earthquakes in historical time (Table 2.1.1) and a number of individual sources representing the causative faults of single seismic events with magnitude up to 7 were identified. Deeper and smaller faults are present very close to the Potenza city, generating events with M up to 5.7 (1990 Potenza earthquake). Due to the involved source-to-site distances (about 25 km) and to the computation resolution of the simulation techniques, the site is represented by a single point. In total 9 faults were identified and the deterministic shaking scenarios are computed for each of them. The following strategy is adopted to provide ground motions. We compute shaking scenarios at level 1, using a simplified simulation technique (DSM, Pacor et al.; 2005) for all the faults. By these simulations we identify the three faults (F3, F7. and F8) producing the maximum expected shaking at the Potenza city, in terms of peak ground acceleration, peak ground velocity and Housner intensity. Based on these results, simulations at level 2, using the broad band technique HIC (Gallovic and Brokeshova, 2007) have been performed at Potenza for F3, F7 and F8 sources. For the Potenza city, we decided to predict the shaking scenarios at level 2, in order to provide suitable estimates of the low frequency ground motion (e.g. velocity time series) and engineering parameters (e.g. Arias intensity) strictly related to the duration of the signals. For each source, we generated hundreds of rupture models varying slip distribution, nucleation points and rupture velocity, and for each model we simulated the acceleration time series by HIC. Then we computed the probability density functions (PDF) of the ground motion parameters (PGA, PGV, PGD, Arias and Housner intensities) and estimated several statistical quantities in order to select families of accelerograms to be used for damage analysis: mean and associated standard deviation, median, 75% percentile, 84% percentile, mode, minimum and maximum. Finally we provided to the engineering Research Unit 6 of this project three sets of 7 accelerograms, having ground motion parameters equal to the statistical requirements computed by the synthetic distributions. The first set includes 7 accelerograms (three components), each of them having PGA equal to the mean, median, mode, 75-percentile, 84-percentile, minimum and maximum values of the PGA distribution. The second set and third sets include 7 accelerograms (horizontal components only), having PGA and Housener Intensity in the neighborhood of the median values of the corresponding distributions. A further comparison of adopted procedure for the predicted ground motion at Potenza was performed with respect to stochastic ground motions generated with EXSIM method (Motazedian and Atkinson; 2005). Even if the scenarios modelling was carried out varying different kinematic parameters, the statistical parameter were quite similar. Finally to provide shaking scenarios in term of macroseismic intensity, we applied a probabilistic empirical approach, developed in Progetto DPC-INGV S1.

Description: Progetto INGV-DPC S3 “Scenari di scuotimento in aree di interesse prioritario e/o strategico”

Description: Published

Description: 4.2. TTC - Scenari e mappe di pericolosità sismica

Description: open

Description: L’importanza di un terremoto non dipende solo dalla sua intensità epicentrale. Quello del 26 maggio 1798 (Io VII MCS secondo CPTI04) non si può dire una catastrofe ma è di certo un evento «strategico». Si tratta, infatti, del massimo terremoto storico conosciuto per Siena, che è una delle maggiori attrazioni turistiche e quindi uno dei luoghi più frequentati di questo paese. Nell’ultimo ventennio il terremoto del 1798 è stato più volte studiato, sia da sismologi storici nell’ambito delle attività di revisione del catalogo PFG promosse dal GNDT e dall’ING/INGV (Castelli e Camassi, 1995; Castelli et al., 1996; Boschi et al., 1997; Boschi et al., 2000), sia da storici dell’architettura (Gennari, 2005). Siamo ancora lontani dall’aver completamente esplorato la copiosissima documentazione storica potenzialmente utile per una ricostruzione degli effetti di questo terremoto nel centro urbano senese. Tuttavia il campione reso disponibile dagli studi fatti finora è abbastanza significativo da rendere possibile l’avvio di un progetto di microzonazione del centro storico senese e di una serie di indagini miranti a comprendere cosa realmente successe a Siena il 26 maggio 1798 e, per conseguenza, quali effetti ci si possa attendere in occasione di un futuro terremoto di analoga portata. Il centro storico senese ha infatti conservato, almeno nelle grandi linee, una fisionomia molto simile a quella che aveva del 1798 e questa circostanza offre l’opportunità di attualizzare l’esperienza del terremoto del 1798 contribuendo alla identificazione delle eventuali criticità attese in caso di terremoti futuri. Si è perciò creato un gruppo di studio interdisciplinare (geofisica, architettura, sismologia storica, ingegneria sismica, geologia, ecc.) che ha cominciato a predisporre gli elementi necessari per questa ricostruzione. La base di dati storici di cui si dispone comprende descrizioni di danno più o meno dettagliate per circa seicento edifici senesi, su un migliaio da cui era composto il centro urbano nel 1798. Questo campione comprende sia edifici monumentali o comunque di vaste proporzioni (palazzi gentilizi e case di abitazione multipla, chiese, conventi, opifici) sia edifici non monumentali. Il nostro primo scopo è una ricostruzione dettagliata della distribuzione del danno del terremoto del 1798 nell’area urbana. Utilizzando cartografia storica pressoché coeva al terremoto (cfr. Gennari, 2005) e grazie all’impiego di un GIS, è stato possibile trasporre le informazioni storiche sottoforma di carte tematiche (Danno, Vulnerabilità, Interventi richiesti, eccetera). Le Figg. 1 e 2 presentano due esempi di tematismi derivati da dati archivistici. In parallelo a questa analisi verrà svolta una indagine a campione su una ventina di edifici rappresentativi per i quali si eseguiranno stime di comportamento dinamico con la tecnica del tremore sismico ambientale. A completamento della caratterizzazione della risposta sismica dei terreni nell’area del centro storico saranno svolte analisi geologiche e sismiche per definire le aree in cui l’assetto del sottosuolo rende ipotizzabili fenomeni di amplificazione del moto sismico del suolo. Tutti i risultati verranno raccolti in una base dati comune e implementati nel GIS (Figura 2) L’analisi congiunta dei dati di danno (opportunamente interpretati in termini di risposta sismica locale utilizzando il metodo proposto da Goretti e Dolce, 2004; Goretti, 2006) e delle analisi geofisiche e geologiche permetterà di individuare quelle parti del patrimonio edilizio storico più esposte a danno in caso di futuri eventi sismici.

Description: Published

Description: Roma

Description: 4.1. Metodologie sismologiche per l'ingegneria sismica

Description: open

Description: GIS scenari di scuotimento area Garda (DVD)

Description: Progetto S3 - Scenari di scuotimento in aree di interesse prioritario e/o strategico

Description: Published

Description: 4.2. TTC - Scenari e mappe di pericolosità sismica

Description: open

Description: L'analisi dinamica del livello di sicurezza ingegneristico, in particolare per strutture strategiche in una zona ad elevato potenziale sismogenetico, tiene conto dei parametri di picco e di diverse caratteristiche del moto del suolo, come ad esempio la durata, la “non-stazionarietà” e i “critical-pulse” (McGuire, 1995). Di conseguenza, è richiesta una modellazione dettagliata sia della struttura sia dell’input sismico necessario a verificarne la risposta sismica. I codici per la progettazione in zona sismica richiedono che l’input sismico per le analisi dinamiche sia composto da un set di “time-histories” a cui la struttura deve resistere durante la sua esistenza, e da un livello di pericolosità caratteristico della zona sismogenetica in cui la struttura di interesse è ubicata. A tale scopo l’input sismico e la pericolosità di un’area sono stimati con approcci di tipo deterministico o probabilistico. La scelta dell'approccio da adottare per le valutazioni di pericolosità non è immediata, poiché i due metodi sono molto diversi e presentano entrambi vantaggi e svantaggi. In generale l’approccio deterministico valuta l’entità del moto sismico causato da uno specifico evento di cui si considera nota la localizzazione e la magnitudo; l’approccio probabilistico definisce invece la probabilità che un determinato parametro dello scuotimento sia superato in un particolare intervallo temporale (ad esempio 10% di probabilità di superamento in 50 anni) a partire dallo studio sulla sismicità dell’area. La differenza fondamentale tra l’approccio deterministico e quello probabilistico è che nel primo vengono simulate le serie temporali, ma non si associa alcuna probabilità al parametro di scuotimento valutato, viceversa nel secondo sono descritti solo alcuni parametri del moto e la probabilità è inclusa direttamente nell’analisi.

Description: Progetto INGV-DPC S3 “Scenari di scuotimento in aree di interesse prioritario e/o strategico”

Description: Published

Description: 4.1. Metodologie sismologiche per l'ingegneria sismica

Description: open

Description: Within the framework of the project S3 “Ground shaking scenarios for some strategic areas in Italy-Task6” the town of Gubbio has been selected as a test site to compute ground motion taking into account finite fault and site effects. Gubbio is located in central Italy, on the northern slopes of one of the many valleys characterising the central Appennines. The historical settlement is located on a rocky slope, while new developments extend on the Quaternary fluvio-lacustrine deposits filling the basin. The Gubbio basin was chosen as a test site for a number of reasons: its geomorphological setting is very common in central and southern Italy, the area is characterised by frequent near events of moderate magnitude (Mmax 6) and large amplifications were observed there for the Colfiorito seismic sequence of the 1997/98. In order to understand the mechanisms controlling the 3D seismic response of the basin, a subsurface model has been constructed. The reconstruction of the model has been done using data coming from different surveys (figure A). Several active and passive seismic measurements have been carried out in the plain, also favoured by the intense seismic activity typical of the area. These investigations mainly consisted of monitoring activities of 4 temporary transects of seismometric stations, operating between June 2005 and May 2006 and described in detail in PS3- Deliverables D22-D23. Two transects have been positioned perpendicularly to the valley axes (GFZ and Ge2 Transects), one parallel (INGV transect) and one near Gubbio (Ge1 transect). More than 300 local and regional earthquakes have been recorded, with maximum magnitude equal to 4. A 2D array was run as well from June to September 2006, to better understand the generation of surface waves. All data are collected in a GIS (Progetto S3 Deliverable D23) Parallel to these activities, ambient noise data have been collected in the field for 90 sites, using the single station technique for the estimation of the fundamental resonance frequencies. Furthermore, 4 noise measurements with a seismic array have been collected to build an S-wave velocity profile of soft sediments, considered representative for the whole plain. The geometry of the basin below 500 m of depth has been investigated through the acquisition of an active seismic line 4.5 km long, in correspondence of one of the transects. This has been used to perform a tomography of arrival times which allowed to recognise the position and shape of the reflecting horizons. As a final step the first 30 metres of deposits have been characterised over a 30 km2 area, using both stratigraphic investigations provided by the Gubbio Municipality and data collected from in-situ surveys and lab tests. In this deliverable we describe the input data for the 3D model of the Gubbio basin and we outline the steps performed to define the geometry, the layers and their seismic properties on the base of the experimental data collected during the project and of the available geological information.

Description: Progetto INGV-DPC S3 “Scenari di scuotimento in aree di interesse prioritario e/o strategico” (coord. F.Pacor e M. Mucciarelli)

Description: Published

Description: 4.1. Metodologie sismologiche per l'ingegneria sismica

Description: open

Description: Recent accelerometric recordings of earthquakes with moderate and intermediate magnitude (4.0 〈 ML 〈 5.9), at both local and regional distances, show a significant ground-motion amplification effect at low frequencies (0.6 Hz) in the city of L’Aquila (central Italy). The effect involves very long durations characterized by low frequencies in the coda. Starting from these observations, a series of supplementary investigations was performed in the urban area of L’Aquila by collecting and analyzing both weak-motion data from earthquakes with magnitudes ranging from 2.2 to 4.9 at distances from 20 to 105 km and ambient noise data. All the collected weak-motion data share the same characteristics as the strong-motion records and give a better image of the amplification effect in the city. In order to interpret observations in terms of the local geology, we performed 2D numerical modeling of the sedimentary basin underlying the city of L’Aquila using both finite elements and boundary elements based on a geological section derived from gravity measurements. This analysis indicates that the ground-motion amplification in the city of L’Aquila is related to the presence of a sedimentary basin, filled by lacustrine sediments, with a maximum depth of about 250 m. The combined approach to data collection and analysis used here gives useful information for risk assessment in the city of L’Aquila and can be recommended for many other urban areas that share similar characteristics.

Description: Published

Description: 1469-1481

Description: reserved

Description: Various authors, analysing the set of accelerograms recorded at Gubbio Piana (GBP) (central Italy), have demonstrated that strong amplification occurs at this accelerometric station, which is installed within an alluvial basin. In particular, Ambraseys et al. [(2005a), Bull Earthq Eng 3:1–53; (2005b), Bull Earth Eng 3:55–73] observed that the strong motion peaks at GBP greatly exceed the median values predicted by the attenuation relationships they derived for Europe. In this work, we analyse and discuss some characteristics of the ground motion recorded at the GBP station. We show that the ground motion parameters, such as peak-ground acceleration and peak-ground velocity, are strongly influenced by the presence of locally induced surface waves that produce both a lengthening of the significant shaking duration and an increase in the peak values with respect to a nearby bedrock site. The basin-induced surface waves are observed in the three components of motion and their effects on the peak values are particularly evident in the vertical component. In the frequency domain, the energy of the surface waves is mostly restricted to the frequency band 0.4–0.8Hz for both the horizontal and vertical components. The horizontal and vertical Fourier amplitudes are also very similar, and this indicates that the H/V spectral ratio technique is not applicable to describing the site response due to the propagation of seismic wave in a complex 2D/3D geological structure. Finally, a preliminary polarization analysis shows that the directions of polarization, as well as the degree of elliptical polarization, exhibit a strong variability with time, that may be related to a complex propagation of Love and Rayleigh waves within the basin.

Description: Published

Description: JCR Journal

Description: reserved