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We perform a spectral decomposition of the Fourier amplitude spectra disseminated along with the Engineering Strong Motion (ESM) flat file for Europe and Middle East. We apply a non-parametric inversion schema to isolate source, propagation and site effects, introducing a regionalization for the attenuation model into three domains. The obtained propagation and source components of the model are parametrized in terms of geometrical spreading, quality factor, seismic moment, and corner frequency assuming a ω2 source model. The non-parametric spectral attenuation values show a faster decay for earthquakes in Italy than in the other regions. Once described in terms of geometrical spreading and frequency-dependent quality factor, slopes and breakpoint locations of the piece-wise linear model for the geometrical spreading show regional variations, confirming that the non-parametric models capture the effects of crustal heterogeneities and differences in the anelastic attenuation. Since they are derived in the framework of a single inversion, the source spectra of the largest events which have occurred in Europe in the last decades can be directly compared and the scaling of the extracted source parameters evaluated. The Brune stress drop varies over about 2 orders of magnitude (the 5th, 50th and 95th percentiles of the ∆σ distribution are 0.76, 2.94, and 13.07 MPa, respectively), with large events having larger stress drops. In particular, the 5th, 50th and 95th percentiles for M > 5.5 are 2.87, 6.02, and 23.5 MPa, respectively whereas, for M < 5.5, the same percentiles are 0.73, 2.84, and 12.43 MPa. If compared to the residual distributions associated to a ground motion prediction equation previously derived using the same Fourier amplitude spectra, the source parameter and the empirical site amplification effects correlate well with the inter-event and inter-station residuals, respectively. Finally, we calibrated both non-parametric and parametric attenuation models for estimating the stress drop from the ratio between Arias intensity and significant duration. The results confirm that computing the Arias stress drop is a suitable approach for complementing the seismic moment with information controlling the source radiation at high frequencies for rapid response applications. [ABSTRACT FROM AUTHOR]

We derive a harmonized local magnitude scale across Europe using data disseminated by network operators through the European Integrated Data Archive (EIDA). We first calibrate simultaneously a set of non-parametric attenuation functions regionalized by considering six different regions covering central and southern Europe, anchoring the models to the Richter's scale at 17 km. Uncertainties on the attenuation coefficients, station corrections and magnitude values are evaluated through bootstrap analysis. The obtained attenuation functions show significant differences among the regions, up to 0.4 m.u. at 400 km, being the attenuation of the Wood–Anderson amplitude stronger for regions in the Mediterranean area. The non-parametric attenuation functions capture the changes in the rate of attenuation with distance due to the effects of later arrivals generated by crustal heterogeneity. A second calibration is performed to derive a parametric attenuation model. We consider a piece-wise linear function to describe the attenuation with the logarithm of distance, introducing two breakpoint distances at 10 and 60 km. For distances above 10 km, we also consider the anelastic attenuation term. We apply a mixed effect regression with network-dependent random effects on the anelastic coefficients. The parametric analysis confirms the stronger attenuation for networks operating in the Mediterranean area, such as the Italian and Greek networks, with respect to networks located in continental Europe. The network-dependent random effects allow us to quantify the between-network variability for different networks operating in the same region or country. The observed between-network variability is within ±0.2 m.u. smaller than the variability among the six regions. [ABSTRACT FROM AUTHOR]

We present the results of a consistency check performed over the flatfile extracted from the engineering strong motion (ESM) database. The flatfile includes 23,014 recordings from 2179 earthquakes in the magnitude range from 3.5 to 7.8 that occurred since the 1970s in Europe and Middle East, as presented in the companion article by Lanzano et al. (Bull Earthq Eng, 2018a). The consistency check is developed by analyzing different residual distributions obtained from ad-hoc ground motion prediction equations for the absolute spectral acceleration (SA), displacement and Fourier amplitude spectra (FAS). Only recordings from earthquakes shallower than 40 km are considered in the analysis. The between-event, between-station and event-and-station corrected residuals are computed by applying a mixed-effect regression. We identified those earthquakes, stations, and recordings showing the largest deviations from the GMPE median predictions, and also evaluated the statistical uncertainty on the median model to get insights on the applicable magnitude-distance ranges and the usable period (or frequency) range. We observed that robust median predictions are obtained up to 8 s for SA and up to 20 Hz for FAS, although median predictions for Mw ≥ 7 show significantly larger uncertainties with 'bumps' starting above 5 s for SA and below 0.3 Hz for FAS. The between-station variance dominates over the other residual variances, and the dependence of the between-station residuals on logarithm of Vs30 is well-described by a piece-wise linear function with period-dependent slopes and hinge velocity around 580 m/s. Finally, we compared the between-event residuals obtained by considering two different sources of moment magnitude. The results show that, at long periods, the between-event terms from the two regressions have a weak correlation and the overall between-event variability is dissimilar, highlighting the importance of magnitude source in the regression results. [ABSTRACT FROM AUTHOR]

The size of an earthquake can be defined either from the seismic moment (M 0) or in terms of radiated seismic energy (E r). These two parameters look at the source complexity from different perspectives: M 0 is a static measure of the earthquake size, whereas E r is related to the rupture kinematics and dynamics. For practical applications and for dissemination purposes, the logarithms of M 0 and E r are used to define the moment magnitude M w and the energy magnitude M E, respectively. The introduction of M w and M E partially obscure the complementarity of M 0 and E r. The reason is due to the assumptions needed to define any magnitude scale. For example, in defining M w, the apparent stress (i.e. the ratio between M 0 and E r multiplied by the rigidity) was assumed to be constant, and under this condition, M w and M E values would only differ by an off-set which, in turn, depends on the average apparent stress of the analysed data set. In any case, when the apparent stress is variable and, for example, scales with M 0, the value of M E derived from M w cannot be used to infer E r. In this study, we investigate the similarities and differences between M w and M E in connection with the scaling of the source parameters using a data set of around 4700 earthquakes recorded at both global and regional scales and belonging to four data sets. These cover different geographical areas and extensions and are composed by either natural or induced earthquakes in the magnitude range 1.5 ≤ M w ≤ 9.0. Our results show that M E is better than M w in capturing the high-frequency ground shaking variability whenever the stress drop differs from the reference value adopted to define M w. We show that M E accounts for variations in the rupture processes, introducing systematic event-dependent deviations from the mean regional peak ground motion velocity scaling. Therefore, M E might be a valid alternative to M w for deriving ground motion prediction equations for seismic hazard studies in areas where strong systematic stress drop scaling with M 0 are found, such as observed for induced earthquakes in geothermal regions. Furthermore, we analyse the different data sets in terms of their cumulative frequency–magnitude distribution, considering both M E and M w. We show that the b values from M w (b Mw) and M E (b ME) can be significantly different when the stress drop shows a systematic scaling relationship with M 0. We found that b ME is nearly constant for all data sets, while b M w shows an inverse linear scaling with apparent stress. [ABSTRACT FROM AUTHOR]

We present a ground motion prediction equation (GMPE) for probabilistic seismic hazard assessments (PSHA) in low-to-moderate seismicity areas, such as Germany. Starting from the NGA-West2 flat-file (Ancheta et al. in Earthquake Spectra 30:989-1005, 2014), we develop a model tailored to the hazard application in terms of data selection and implemented functional form. In light of such hazard application, the GMPE is derived for hypocentral distance (along with the Joyner-Boore one), selecting recordings at sites with vs30 ≥ 360 m/s, distances within 300 km, and magnitudes in the range 3 to 8 (being 7.4 the maximum magnitude for the PSHA in the target area). Moreover, the complexity of the considered functional form is reflecting the availability of information in the target area. The median predictions are compared with those from the NGA-West2 models and with one recent European model, using the Sammon's map constructed for different scenarios. Despite the simplification in the functional form, the assessed epistemic uncertainty in the GMPE median is of the order of those affecting the NGA-West2 models for the magnitude range of interest of the hazard application. On the other hand, the simplification of the functional form led to an increment of the apparent aleatory variability. In conclusion, the GMPE developed in this study is tailored to the needs for applications in low-to-moderate seismic areas and for short return periods (e.g., 475 years); its application in studies where the hazard is involving magnitudes above 7.4 and for long return periods is not advised. [ABSTRACT FROM AUTHOR]

In this study, we analyse a regional data set composed by about 9000 waveforms from 231 earthquakes in the magnitude range from 3 to 6 and recorded in central Italy in the time period 2008-2013. We derive a seismological model whose source, attenuation and site parameters are used to explain the ground motion variability associated with a set of ground motion prediction equation (GMPE) calibrated ad hoc for both Fourier and acceleration response spectra. The main results are the following: (1) the between-event residuals δBe show a clear dependence on the stress drop for frequencies above 2 Hz; (2) the standard deviation τ of δBe is strongly reduced (up to 80 per cent) by introducing in the functional form the stress drop values estimated from each source spectrum; (3) the standard deviation τ depends on the magnitude scale used to calibrate the GMPE: while the moment magnitude better describes the source variability at low frequency, the local magnitude better capture the source-related ground motion variability at frequencies larger than 2 Hz; (4) for frequencies higher than 10 Hz, the observed increase of τ with frequency correlate well with the attenuation parameter ksource, computed from the high-frequency slope of the source spectra. Regarding the station-to-station residuals δS2S, their frequency dependency is in good agreement with the site amplifications extracted from the S-wave spectra. Finally, while the overall dependences of the ground motion variability on seismological parameters are similar when observed either in the Fourier or in the response spectra domains (e.g. the dependency of the between event on stress drop), differences in the results suggest that the response spectra do not allow to fully capture the ground motion variability, as well as the site amplifications, at high frequencies. [ABSTRACT FROM AUTHOR]

The availability of computationally powerful and energy-efficient wireless sensing units or WSUs (one or more arranged in the form of a network in the vicinity and/or within a structure of interest) has led to new developments in the field of building and seismic strong motion monitoring. These WSUs can serve several functions. Those of largest earthquake engineering and engineering seismology interest are the recording of ground shaking the building is subjected to, as well as its response, and the capability of running rapid seismic risk analyses on the basis of vulnerability models of the structure, possibly coupled with recorded data. The REAKT project has shed light on a number of prospective applications of the last generation of monitoring devices for seismic risk management of critical structures. These applications refer to real-time and near-real-time risk assessment, that is: earthquake early warning, immediate post-event response evaluations based on recorded shaking, and short-term aftershock risk management for automated building tagging. This paper summarizes these perspectives that, despite still presenting some challenges that may limit readiness to date, have potential for scientific innovation in the field. [ABSTRACT FROM AUTHOR]

In this study, we assess the dynamic characteristics of an 8-story RC-building composed by two units connected through a structural joint. This building, belonging to one of the largest hospitals in northern Greece, has been selected in the framework of an European funded project as test site for developing a structural health monitoring system and it is instrumented with a permanent strong motion network. The assessment of the dynamic characteristics is performed using ambient vibration recorded by a temporary seismic network installed inside the structure. Non-parametric identification methods, namely the peak picking and frequency domain decomposition, are applied to perform operational modal analysis and extract the natural frequencies and mode shapes of the structural system. Since the detection of changes in the shear wave velocity inside the building is relevant for health monitoring analysis, we use the ambient vibration recordings to perform a deconvolution interferometry. Moreover, a shear-beam model is considered to estimate the velocity in the first three floors, where the distribution of internal sources introduces complex patterns in the impulse response functions. The velocity for lowest part of the building is estimated by optimizing the match between the arrival times of the empirical and theoretical pulses. Finally, the velocities and quality factors estimated from ambient vibration analysis are consistent with preliminary results obtained analyzing earthquake data recorded in the same building. [ABSTRACT FROM AUTHOR]

This article presents a set of Ground-Motion Prediction Equations (GMPEs) for Europe and the Middle East, derived from the RESORCE strong motion data bank, following a standard regression approach. The parametric GMPEs are derived for the peak ground acceleration, peak ground velocity, and 5 %-damped pseudo-absolute acceleration response spectra computed over 23 periods between 0.02 and 3 s, considering the average horizontal-component ground-motions. The GMPEs are valid for distances less than 300 km, hypocentral depth up to 35 km and over the magnitude range 4-7.6. Two metrics for the source-to-station distance (i.e. Joyner-Boore and hypocentral) are considered. The selected dataset is composed by 2,126 recordings (at a period of 0.1 s) related to 365 earthquakes, that includes strong-motion data from 697 stations.The EC8 soil classification (four classes from A to D) discriminates recording sites and four classes (normal, reverse, strike-slip, and unspecified) describe the style of faulting. A subset which contains only stations with measured Vs30 and earthquakes with specified focal mechanism (1,224 records from 345 stations and 255 earthquakes) is used to test of the accuracy of the median prediction and the variability associated to the broader data set. A random effect regression scheme is applied and bootstrap analyses are performed to estimate the 95 % confidence levels for the parameters. The total standard deviation sigma is decomposed into between-events and within-event components, and the site-to-site component is evaluated as well. The results show that the largest contribution to the total sigma is coming from the within-event component. When analyzing the residual distributions, no significant trends are observed that can be ascribed to the earthquake type (mainshock-aftershock classification) or to the non-linear site effects. The proposed GMPEs have lower median values than global models at short periods and large distances, while are consistent with global models at long periods $$(\hbox {T} > 1)$$ s. Consistency is found with two regional models developed for Turkey and Italy, as the considered dataset is dominated by waveforms recorded in these regions. [ABSTRACT FROM AUTHOR]

A correction to the article "Pan-European ground-motion prediction equations for the average horizontal component of PGA, PGV, and 5 percent-damped PSA at spectral periods up to 3.0 s using the RESORCE dataset" that was published in the January 31, 2014 issue is presented.

We apply the Bakun and Wentworth ( Bull Seism Soc Am 87:1502-1521, ) method to determine the location and magnitude of earthquakes occurred in Central Asia using MSK-64 intensity assignments. The attenuation model previously derived and validated by Bindi et al. ( Geophys J Int, ) is used to analyse 21 earthquakes that occurred over the period 1885-1964, and the estimated locations and magnitudes are compared to values available in literature. Bootstrap analyses are performed to estimate the confidence intervals of the intensity magnitudes, as well as to quantify the location uncertainty. The analyses of seven significant earthquakes for the hazard assessment are presented in detail, including three large historical earthquakes that struck the northern Tien-Shan between the end of the nineteenth and the beginning of the twentieth centuries: the 1887, M 7.3 Verny, the 1889, M 8.3 Chilik and the 1911, M 8.2 Kemin earthquakes. Regarding the 1911, Kemin earthquake the magnitude values estimated from intensity data are lower (i.e. MI = 7.8 and MI = 7.6 considering surface wave and moment magnitude, respectively) than the value M = 8.2 listed in the considered catalog. These values are more in agreement with the value M = 7.8 revised by Abe and Noguchi ( Phys Earth Planet In, 33:1-11, ) for the surface wave magnitude. For the Kemin earthquake, the distribution of the bootstrap solutions for the intensity centre reveal two minima, indicating that the distribution of intensity assignments do not constrain a unique solution. This is in agreement with the complex source rupture history of the Kemin earthquake, which involved several fault segments with different strike orientations, dipping angles and focal mechanisms (e.g. Delvaux et al. in Russ Geol Geophys 42:1167-1177, ; Arrowsmith et al. in Eos Trans Am Geophys Union 86(52), ). Two possible locations for the intensity centre are obtained. The first is located on the easternmost sub-faults (i.e. the Aksu and Chon-Aksu segments), where most of the seismic moment was released (Arrowsmith et al. in Eos Trans Am Geophys Union 86(52), ). The second location is located on the westernmost sub-faults (i.e. the Dzhil'-Aryk segment), close to the intensity centre location obtained for the 1938, M 6.9 Chu-Kemin earthquake (MI = 6.9 and MI = 6.8). [ABSTRACT FROM AUTHOR]

Rapidly expanding urban areas in Central Asia are increasingly vulnerable to seismic risk; but at present, no earthquake early warning (EEW) systems exist in the region despite their successful implementation in other earthquake-prone areas. Such systems aim to provide short (seconds to tens of seconds) warnings of impending disaster, enabling the first risk mitigation and damage control steps to be taken. This study presents the feasibility of such a system for Almaty, Kazakhstan. Genetic algorithms are used to design efficient EEW networks, computing optimal station locations and trigger thresholds in recorded ground acceleration. Factors like the possibility of station failure, elevation and access difficulty to a potential site, and the potential usefulness of existing stations in the region are considered. We present a large set of possible efficient networks, to which further selection criteria can be applied by both the installation teams and the end user, such as authorities in Almaty. [ABSTRACT FROM AUTHOR]

Site response analysis plays an important role in seismic hazard and risk assessment, and in defining the optimal engineering design for civil structures. However, due to increasing urbanization, target areas are often too vast to be covered by standard approaches, resulting in large uncertainties in the spatial variability of the expected ground motion. Here, we propose a method to improve the spatial resolution of ground motion variability in terms of Standard Spectral Ratios (SSRs), using earthquakes recorded at a few selected sites for a relatively short amount of time, and seismic noise data collected over a denser grid, taking advantage of clustering and correlation analysis. The method is applied to Bishkek, Kyrgyzstan. Using the K-means clustering algorithm, three clusters of site response types have been identified, based on their similarity of SSRs. The cluster's site responses were adopted for sites where only single station noise measurements were carried out, based on the results of correlation analysis. The spatial variability of the site response correlates well with the main geological features in the area. In particular, variability is noted from south to north, consistent with both the changes in the thickness of the sedimentary cover over the basin and in the Quaternary material outcropping at the surface. This method has therefore the potential to improve the estimation of site effects at the local scale in the future. [ABSTRACT FROM AUTHOR]

We present results from a vertical array of accelerometers that was recently installed in Bishkek (Kyrgyzstan) with the long-term aim of recording strong motion data. Taking advantage of recordings of a Mb 4.7 earthquake that occurred 40 km from the array site during the installation phase, we provide results of some preliminary data analysis. First, estimates of the S-wave velocity and Qs structure are deduced by the inversion of the deconvolved wavefield between the sensors in the borehole. Furthermore, the application of the nonstationary ray decomposition Kinoshita (Earth Planets Space 61:1297-1312, ) allowed at least three reflectors in the shallow velocity structure below the array to be identified. The complex nature of the wavefield (with up-going, down-going waves, and converted phases) due to the coarse, unconsolidated subsoil structure is highlighted by means of numerical simulations of ground motion. [ABSTRACT FROM AUTHOR]

Earthquake early warning systems (EEWS) are considered to be an effective, pragmatic, and viable tool for seismic risk reduction in cities. While standard EEWS approaches focus on the real-time estimation of an earthquake's location and magnitude, innovative developments in EEWS include the capacity for the rapid assessment of damage. Clearly, for all public authorities that are engaged in coordinating emergency activities during and soon after earthquakes, real-time information about the potential damage distribution within a city is invaluable. In this work, we present a first attempt to design an early warning and rapid response procedure for real-time risk assessment. In particular, the procedure uses typical real-time information (i.e., P-wave arrival times and early waveforms) derived from a regional seismic network for locating and evaluating the size of an earthquake, information which in turn is exploited for extracting a risk map representing the potential distribution of damage from a dataset of predicted scenarios compiled for the target city. A feasibility study of the procedure is presented for the city of Bishkek, the capital of Kyrgyzstan, which is surrounded by the Kyrgyz seismic network by mimicking the ground motion associated with two historical events that occurred close to Bishkek, namely the 1911 Kemin ( M = 8.2; ±0.2) and the 1885 Belovodsk ( M = 6.9; ±0.5) earthquakes. Various methodologies from previous studies were considered when planning the implementation of the early warning and rapid response procedure for real-time risk assessment: the Satriano et al. (Bull Seismol Soc Am 98(3):1482-1494, ) approach to real-time earthquake location; the Caprio et al. (Geophys Res Lett 38:L02301, ) approach for estimating moment magnitude in real time; the EXSIM method for ground motion simulation (Motazedian and Atkinson, Bull Seismol Soc Am 95:995-1010, ); the Sokolov (Earthquake Spectra 161: 679-694, ) approach for estimating intensity from Fourier amplitude spectra; and the Tyagunov et al. (Nat Hazard Earth Syst Sci 6:573-586, ) approach for risk computation. Innovatively, all these methods are jointly applied to assess in real time the seismic risk of a particular target site, namely the city of Bishkek. Finally, the site amplification and vulnerability datasets considered in the proposed methodology are taken from previous studies, i.e., Parolai et al. (Bull Seismol Soc Am, ) and Bindi et al. (Soil Dyn Earthq Eng, ), respectively. [ABSTRACT FROM AUTHOR]

Abstract: In the process of updating existing PSHA maps in Central Asia, a first step is the evaluation of the seismic hazard in terms of macroseismic intensity by applying a data driven method. Following the Site Approach to Seismic Hazard Assessment (SASHA) , the evaluation of the probability of exceedance of any given intensity value over a fixed exposure time, is mainly based on the seismic histories available at different locations without requiring any a-priori assumption about seismic zonation. The effects of earthquakes not included in the seismic history can be accounted by propagating the epicentral information through a Intensity Prediction Equation developed for the analyzed area. In order to comply with existing building codes in the region that use macroseismic intensity instead of PGA, we evaluated the seismic hazard at 2911 localities using a macroseismic catalog composed by 5322 intensity data points relevant to 75 earthquakes in the magnitude range 4.6–8.3. The results show that for most of the investigated area the intensity having a probability of at least 10% to be exceeded in 50 years is VIII. The intensity rises to IX for some area struck by strong earthquakes in the past, like the Chou-Kemin-Chilik fault zone in northern Tien-Shan, between Kyrgyzstan and Kazakhstan, or in Gissar range between Tajikistan and Uzbekistan. These values are about one intensity unit less than those evaluated in the Global Seismic Hazard Assessment Program (GSHAP; Ulomov, The GSHAP Region 7 working group ). Moreover, hazard curves have been extracted for the main towns of Central Asia and the results compared with the estimates previously obtained. A good agreement has been found for Bishkek (Kyrgyzstan) and Dushanbe (Tajikistan), while a lower probability of occurrence of I=VIII has been obtained for Tashkent (Uzbekistan) and a larger one for I=IX in Almaty (Kazakhstan). [Copyright &y& Elsevier]

SUMMARY In this study, new intensity prediction equations are derived for Central Asia, considering about 6000 intensity data points from 66 earthquakes encompassing the surface-wave magnitude range of 4.6-8.3. The suitability of the functional form used for constructing the model is assessed by comparing its predictions with those achieved through a non-parametric model. The parametric regressions are performed considering different measures of the source-to-site distance, namely the hypocentral, epicentral and the extended distance metrics. The latter is defined as the minimum distance from the site to a line crossing the epicentres, oriented along the strike of the earthquake and having a length estimated from the event's magnitude. Although the extended distance is introduced as a preliminary attempt to improve the prediction capability of the model by considering the finiteness of the fault extension, the standard deviation of the residual distribution obtained considering the extended distance (σ= 0.734) does not show an improvement with respect to the results for the epicentral distance (σ= 0.737). The similarity of the two models in term of average residuals is also confirmed by comparing the interevent errors obtained for the two regressions, obtaining very similar values for all earthquakes but the 1911, M 8.2 Kemin event. In particular, different evidences suggest that the magnitude of this event could be overestimated by about half a magnitude unit. Regarding the variability of the residual distribution, all the three considered components (i.e. interevent, interlocation and record-to-record variances) are not negligible, although the largest contribution is related to the record-to-record variability, suggesting that both source and propagation as well as site effects not captured by the considered model influence the spatial variability of the intensity values. [ABSTRACT FROM AUTHOR]

Abstract: A risk scenario for Bishkek, capital of the Kyrgyz Republic, is evaluated by considering a magnitude 7.5 earthquake occurring over the Issyk-Ata fault. The intensity values predicted through the application of an attenuation relationship and a recently compiled vulnerability composition model are used as inputs for seismic risk assessment, carried out using the Cedim Risk Estimation Tool (CREST) code. Although the results of this study show a reduction by as much as a factor of two with respect to the results of earlier studies, the risk scenario evaluated in this paper confirms the large number of expected injuries and fatalities in Bishkek, as well as the severe level of building damage. Furthermore, the intensity map has also been evaluated by performing stochastic simulations. The spectral levels of the ground shaking are converted into intensity values by applying a previously derived conversion technique. The local site effects are empirically estimated considering the spectral ratios between the earthquakes recorded by a temporary network deployed in Bishkek and the recordings at two reference sites. Although the intensities computed via stochastic simulations are lower than those estimated with the attenuation relationship, the simulations showed that site effects, which can contribute to intensity increments as large as 2 units in the north part of the town, are playing an important role in altering the risk estimates for different parts of the town. [Copyright &y& Elsevier]

The estimation of shear wave velocity and attenuation in near-surface geology is of primary importance in engineering seismology. In fact, their knowledge is essential for site response studies when preparing improved seismic hazard scenarios. In this study, we propose two approaches for estimating the average shear wave quality factor Qs by using recordings of a vertical array of accelerometers. The methods are mainly based on the deconvolution of the wavefield recorded in a borehole with that recorded at the surface. The first method requires the Fourier transform of the deconvolved wavefield to be fitted with a theoretical transfer function valid for the vertical or nearly vertical (in the case at hand up to 30° incidence angle) propagation of S waves. The second method is based on the spectral fitting of the Fourier transform of only the acausal part of the deconvolved wavefield with a theoretical transfer function. Both methods can be applied without any prior knowledge of the subsoil structure (since they are based on empirical data analysis) and do not require a precise knowledge of the azimuthal orientation of the sensors in the boreholes (which is seldom available). First, we describe the theoretical framework of the proposed methodologies for Qs estimation, which are based on the assumption that the structure in the borehole is weakly heterogeneous in the vertical direction (i.e. no large impedance contrast exists between the borehole sensor and the surface). Second, by using synthetic accelerograms, we verify that in a realistic subsoil structure, the assumption of vertical homogeneity can hold and we investigate the robustness and the suitability of the proposed methods. Finally, only the method that was shown to provide the more stable results, based on fitting the borehole-to-surface spectral ratio with a theoretical function, is applied to earthquakes signals recorded by a vertical array of accelerometers installed in Ataköy (western Istanbul). Results show that using borehole data provides a fair and robust estimate of an average Qs (of about 30, 46 and 99 for the 0–50, 0–70, 0–140 m depth ranges, respectively) that can be used for numerical simulations of ground motion. [ABSTRACT FROM AUTHOR]

The strong motion data of 2009 April 6 L’Aquila (Central Italy) earthquake ( Mw= 6.3) and of 12 aftershocks (4.1 ≤ Mw≤ 5.6) recorded by 56 stations of the Italian strong motion network are spectrally analysed to estimate the source parameters, the seismic attenuation, and the site amplification effects. The obtained source spectra for S wave have stress drop values ranging from 2.4 to 16.8 MPa, being the stress drop of the main shock equal to 9.2 MPa. The spectral curves describing the attenuation with distance show the presence of shoulders and bumps, mainly around 50 and 150 km, as consequence of significant reflected and refracted arrivals from crustal interfaces. The attenuation in the first 50 km is well described by a quality factor equal to obtained by fixing the geometrical spreading exponent to 1. Finally, the horizontal-to-vertical spectral ratio provides unreliable estimates of local site effects for those stations showing large amplifications over the vertical component of motion. [ABSTRACT FROM AUTHOR]

In this work, we analyse continuous measurements of microseisms to assess the reliability of the fundamental resonance frequency estimated by means of the horizontal-to-vertical ( H/ V) spectral ratio within the 0.1–1 Hz frequency range, using short-period sensors (natural period of 1 s). We apply the H/ V technique to recordings of stations installed in two alluvial basins with different sedimentary cover thicknesses—the Lower Rhine Embayment (Germany) and the Gubbio Plain (Central Italy). The spectral ratios are estimated over the time–frequency domain, and we discuss the reliability of the results considering both the variability of the microseism activity and the amplitude of the instrumental noise. We show that microseisms measured by short period sensors allow the retrieval of fundamental resonance frequencies greater than about 0.1–0.2 Hz, with this lower frequency bound depending on the relative amplitude of the microseism signal and the self-noise of the instruments. In particular, we show an example where the considered short-period sensor is connected to instruments characterized by an instrumental noise level which allows detecting only fundamental frequencies greater than about 0.4 Hz. Since the frequency at which the peak of the H/ V spectral ratio is biased depends upon the seismic signal-to-instrument noise ratio, the power spectral amplitude of instrumental self-noise should be always considered when interpreting the frequency of the peak as the fundamental resonance frequency of the investigated site. [ABSTRACT FROM AUTHOR]

In this research a site classification is proposed for the Umbria-Marche area (central Italy), based on geotechnical and geomorphological criteria. Two empirical techniques to evaluate site effects are used, namely the generalised spectral inversion, and the horizontal to vertical spectral ratio. The soil transfer functions obtained by the two techniques are compared in order to capture the features common to each class and verify the accuracy of the classification. We used strong ground motions recorded during the Umbria-Marche seismic sequence (September 1997-May 1998) and we selected 25 sites that were classified into four groups. The results of the empirical techniques have also been tested using theoretical 1-D or 2-D methods that are commonly used to simulate linear soil behaviour. The results, expressed in terms of amplitude transfer functions, are shown according to each soil class and confirm the consistency of the site characterisation. The empirical techniques are efficient in detecting the fundamental frequency of vibration but seldom the higher harmonics. Conversely, the peak amplitude of the transfer functions is not consistently determined, especially for sites located in deep sedimentary basins, where 2-D effects occur and simplified methods, such as the horizontal to vertical spectral ratios (HVSR) or 1-D theoretical models frequently fail. Significant amplifications are also found for 2-D rock structures such as rock crests or cliffs. [ABSTRACT FROM AUTHOR]

We apply the natural pixel (NP) approach to the single-photon emission computed tomography (SPECT) problem. The NP approach allows us to split the tomographic problem into two subproblems. The first is a linear inverse problem. The data are the measured projections and the linear operator is described by a Gram matrix, and provides a set of coefficients. The second consists of computing the solution of the tomographic problem as a linear combination of the elements of the NP basis with respect to the coefficients obtained by solving the first problem, and it provides a solution for any given grid of points. The spatially varying geometric response of the system is taken into account by properly choosing the elements of the basis. The rotational invariance shown by the elements of the considered basis induces a block circulant structure in the Gram matrix. This structure can be used to reduce the computational efforts needed for solving the inverse problem. In particular, we diagonalize (blockwise) the Gram matrix by applying the discrete Fourier transform and we solve the inverse problem in the frequency domain associated with the rotation angles. We develop numerical validation with synthetic data in order to test the performance of the NP approach and to assess the reliability of the results. A reconstruction of a two-dimensional image requires 45–94 s, which is an acceptable time for clinical purposes. Finally, we apply the method to acquired clinical data that consist of a three-dimensional brain scan. © 2002 John Wiley & Sons, Inc. Int J Imaging Syst Technol 12, 1–8, 2002 [ABSTRACT FROM AUTHOR]

In this article, H/V ratio are evaluated using different spectral techniques applied to both earthquake and microtremor data (Nakamura technique). In particular, in order to avoid numerical instability, two different numerical techniques are taken into account: (a) a smoothing procedure applied to the spectra of the seismogram components and (b) a regularization method applied to the H/V ratio (Landweber scheme). The data set consists of more than 70 earthquake events recorded by three component sensors displaced in the town of Fabriano (Central Italy) during the Umbria-Marche sequence started on September 1997. The local magnitudes range between 2.7 and 4.4, while the epicentral distances range between nearly 30 and 60 km. The stations were set to continuous recording so that a huge amount of microtremors was stored. The results are compared in terms of predominant frequencies and amplification levels in order to point out the influence of the adopted methods. The H/V ratio provides similar results if applied to a smoothed version of both earthquake and microtremor spectra, confirming that Nakamura technique is a cheap and a fast method to collect information on the site amplification effects. Moreover, the results relevant to earthquake data seem not to depend on the method used to stabilize the H/V ratio, whereas those relevant to microtremor data does. The explanation of this fact is suggested by the behaviour of the Landweber filter showing that the predominant frequency detected by means of microtremor data lies in a high instability region of the spectra. [ABSTRACT FROM AUTHOR]

This study aims at presenting the analyses of monitoring data that have been used in the context of structural monitoring and Earthquake Early Warning (EEW) for a hospital building in Thessaloniki. Permanent and temporary instrumentation arrays, implemented under the responsibility of Aristotle University of Thessaloniki (SDGEE-AUTH) in close cooperation with German Centre for Geosciences (GFZ) are presented. The ambient noise data recorded at the temporarily installed networks are used for the dynamic characterization of the building based on both vibrational and waveform approaches. Moreover, long-term ambient noise recordings from the permanent array installed within the hospital are used for the investigation of the daily and seasonal wandering of the building resonance frequencies related to environmental effects. The modal identification results are used in a comprehensive framework for the computation of the up-to-date fragility curves representing the actual structural state considering aging effects of the construction materials, possible pre-existing damages and changes in the geometry and mass distribution. The building-specific fragility functions are integrated into two independent EEW systems and rapid damage assessment approaches, namely the PRESTo software and an onsite EEW algorithm on the instruments of the permanent array, to provide the expected level of damage after strong ground shaking at the monitored building. The implemented monitoring networks and the developed operational tools can be used in the context of seismic risk mitigation and preparedness for structural safety assessment under earthquake loading. [ABSTRACT FROM AUTHOR]

In the context of seismic vulnerability assessment of reinforced concrete (RC) buildings, the use of field monitoring data constitutes a significant tool for the representation of the actual structural state, reducing uncertainties associated with the building configuration properties as well as many non-physical parameters (age, maintenance, etc.), enhancing thus the reliability in the risk assessment procedure. In this study, the seismic vulnerability of existing RC buildings is evaluated, combining through a comprehensive methodology, the numerical analysis and field monitoring data. The proposed methodology is highlighted through the derivation of “time-building specific” fragility curves for an eight-storey RC structure (hospital building), built almost five decades ago, that is composed by two adjacent units connected with a structural joint. The assessment of the dynamic characteristics is performed using ambient noise measurements recorded by a temporary seismic network which was deployed inside the hospital. The modal identification results are used to update and better constrain the initial finite element model of the building, which is based on the available design and construction documentation plans. Three-dimensional incremental dynamic analysis is performed to derive the fragility curves for the initial as built model (“building-specific”) and for the real structures as they are nowadays (“time-building specific”). The initial “building specific” curves are evaluated through their comparison with conventional generic curves that are commonly used in risk assessment studies. Moreover, in order to enhance the reliability of the obtained results, the “time-building specific” fragility curves, are compared to time-dependent curves derived for the hospital units adopting an appropriate for the specific case study corrosion scenario. Results derived from both approaches indicate that the consideration of the actual state of structures may significantly alter their expected seismic performance leading to higher vulnerability values. [ABSTRACT FROM AUTHOR]

SUMMARY The estimation of shear wave velocity and attenuation in near-surface geology is of primary importance in engineering seismology. In fact, such knowledge is essential for site response studies when preparing improved seismic hazard scenarios. In this study, we propose a linear inversion of the spectra of a deconvolved wavefield collected by a borehole array in Istanbul, Turkey. The spectra are calculated using as a reference the recordings collected by a sensor at the surface. This allows us to minimize the effect of the deconvolution filter on the peaks' amplitudes. The feasibility of the proposed inversion scheme and the parametrization of the velocity and attenuation models were tested and assessed using synthetic data. The real data inversion is carried out using observation from three weak motion events. Several starting models are used for each event, changing the values of the quality factor Qs, whereas the starting Vs profiles are fixed to what was obtained by the analysis of the deconvolved wavefield in the time domain. Our results showed that fairly well-constrained Vs models can be obtained while the variability of the Qs profile, both between different inversions of the same data set, and between the inversions of different data sets, might be large. This indicates that Qs variations observed in models derived by strong motion data inversions should be considered with care. However, the high agreement of the estimated soil profiles in the uppermost layer, both when using different events and different starting models, suggests that any variation in the S-wave velocity that might be estimated when using strong motion data should be reliable. [ABSTRACT FROM AUTHOR]

Temporary arrays installed in urban areas for investigating the upper-most geological structure typically comprised of a limited number of stations and are arranged in geometries constrained by environmental boundaries. Therefore, it is expected that the frequency–wavenumber images are significantly blurred by the array transfer function and are corrupted by noise. In this paper, the effect of the Richardson–Lucy regularization method applied to the problem of deblurring frequency–wavenumber images is investigated. The images are computed by analysing data from two small-aperture 2-D arrays, installed with different configurations in a test-site within the town of Potenza (Southern Italy) for near-surface investigations. We show that removing the effects of the array response from the frequency–wavenumber images improve the phase-velocity estimation, reducing the relevant level of uncertainty. Furthermore, the Richardson–Lucy regularization method is effective in reducing the level of noise related to spatial aliasing by eliminating spurious peaks, allowing the maxima related to different seismic sources to be better discriminated. [ABSTRACT FROM AUTHOR]

Abstract: Providing quantitative microzonation results that can be taken into account in urban land-use plans is a challenging task that requires collaborative efforts between the seismological and engineering communities. In this study, starting from the results obtained by extensive geophysical and seismological investigations, we propose and apply an approach to the Gubbio basin (Italy) that can be easily implemented for cases of moderate-to-low ground motion and that takes into account not only simple 1D, but also more complicated 3D effects. With this method, the sites inside the basin are classified by their fundamental resonance frequencies, estimated from the horizontal-to-vertical spectral ratio applied to noise recordings (HVNSR). The correspondence between estimates of the fundamental frequency from this method and those derived from earthquake recordings was verified at several calibration sites. The amplification factors used to correct the response spectra are computed by the ratio between the response spectra at sites within the basin and the response spectra at a hard-rock site using data from two seismic transects. Empirical amplification functions are then assigned to the fundamental frequencies after applying an interpolation technique. The suitability of the estimated site-specific correction factors for response spectra was verified by computing synthetic response spectra for stations within the basin, starting from the synthetic recording at a nearby rock station, and comparing them with observed ones. [Copyright &y& Elsevier]

To study the applicability of the passive seismic interferometry technique to near-surface geological studies, seismic noise recordings from a small scale 2-D array of seismic stations were performed in the test site of Nauen (Germany). Rayleigh wave Green's functions were estimated for different frequencies. A tomographic inversion of the traveltimes estimated for each frequency from the Green's functions is then performed, allowing the laterally varying 3-D surface wave velocity structure below the array to be retrieved at engineering–geotechnical scales. Furthermore, a 2-D S-wave velocity cross-section is obtained by combining 1-D velocity structures derived from the inversion of the dispersion curves extracted at several points along a profile where other geophysical analyses were performed. It is shown that the cross-section from passive seismic interferometry provides a clear image of the local structural heterogeneities that are in excellent agreement with georadar and geoelectrical results. Such findings indicate that the interferometry analysis of seismic noise is potentially of great interest for deriving the shallow 3-D velocity structure in urban areas. [ABSTRACT FROM AUTHOR]

We investigate the preparatory phase of the 2009, Mw 6.1 L'Aquila earthquake in central Italy by analyzing the temporal evolution and spatial distribution of the seismic moment, M0, to radiated energy, ES. Our approach focuses on monitoring the deviations of the scaling between M0 and ES with respect to a model calibrated for the background seismicity. The temporal evolution of these deviations, defined as Energy Index (EI), identifies the onset of the activation phase 1 week before the mainshock. We show that foreshocks are characterized by a progressive increase in slip per unit stress, in agreement with the diffusion of highly pressurized fluids before the L'Aquila earthquake proposed by previous studies. Our results suggest that the largest events occur where energy index (EI) is highest, in agreement with the existing link between energy index (EI) and the mean loading stress. Plain Language Summary: Understanding how the machine generating large earthquakes works is one of the fundamental challenging scientific questions. Pioneering studies have shown that large magnitude earthquakes are sometimes anticipated by foreshocks and slip instabilities. Until now, retrospective analyses of foreshocks during the preparatory phase of large earthquakes have focused mainly on their distribution in space, time and magnitude. In this study, we show that also the dynamic properties of the rupture process associated to foreshocks evolve both in time and space. Our results indicate that the temporal evolution of radiated energy and size of small magnitude earthquakes provide useful information to identify the begin of the final activation phase of the 2009 Mw 6.1 L'Aquila, Italy, earthquake, in agreement with seismicity rate information. Our study suggests that, for the investigated case, foreshocks had dynamic characteristics distinct from those of normal rate (background) seismicity. Thus, it can contribute with new evidence to the open debate whether foreshocks are different phenomena from background seismicity. Key Points: We observe foreshocks dynamic characteristics before the 2009, Mw 6.1 L'Aquila earthquake in central ItalyDeviations of radiated energy over seismic moment from a reference model highlight the preparatory phase of the main eventForeshocks are characterized by a progressive increase in slip per unit stress, in agreement with diffusion of highly pressurized fluids [ABSTRACT FROM AUTHOR]

The Agrobacterium rhizogenes rolD gene, coding for an ornithine cyclodeaminase involved in the biosynthesis of proline from ornithine, has been inserted in Lycopersicon esculentum cv Tondino with the aim of studying its effects on plant morphological characters including pathogen defense response. The analysis of plants transgenic for rolD did not show major morphological modifications. First generation transgenic plants however were found to flower earlier, and showed an increased number of inflorescences and higher fruit yield. Transformed plants were also analysed for parameters linked to pathogen defense response, i.e. ion leakage in the presence of the toxin produced by the fungus Fusarium oxysporum f. sp. lycopersici, and expression of the pathogenesis-related PR-1 gene. All the plants harbouring the rolD gene were shown to be more tolerant to the toxin in ion leakage experiments, with respect to the untransformed regenerated controls and the cv Tondino. PR-1 gene expression was quantitated by means of real-time PCR both at the basal level and after treatment with salicylic acid, an inducer of Systemic Acquired Resistance. In both cases the amount of PR-1 mRNA was higher in the transgenic plants. It seems therefore that the transformation of tomato plants with rolD could lead to an increased competence for defense response, as shown by toxin tolerance and increased expression of the Systemic Acquired Resistance marker gene PR-1. The results are finally discussed in view of their possible economic relevance. [ABSTRACT FROM AUTHOR]

We introduce in the on-site earthquake early warning (EEW) a partially non-ergodic perspective from the site effects point of view. We consider the on-site EEW approach where the peak ground velocity (PGV) for S waves is predicted from an early estimate, over the P waves, of either the peak-displacement (PD) or cumulative squared velocity (IV2). The empirical PD-PGV and IV2-PGV relationships are developed by applying a mixed-effect regression where the site-specific modifications of ground shaking are treated as random effects. We considered a large data set composed of almost 31 000 selected recordings in central Italy, a region struck by four earthquakes with magnitude between 6 and 6.5 since the 2009 L'Aquila earthquake. We split the data set into three subsets used for calibrating and validating the on-site EEW models, and for exemplifying their application to stations installed after the calibration phase. We show that the partially non-ergodic models improve the accuracy of the PGV predictions with respect to ergodic models derived for other regions of the world. Moreover, considering PD and accounting for site effects, we reduce the (apparent) aleatory variability of the logarithm of PGV from 0.31 to 0.36, typical values for ergodic on-site EEW models, to about 0.25. Interestingly, a lower variability of 0.15 is obtained by considering IV2 as proxy, which suggests further consideration of this parameter for the design of on-site EEW systems. Since being site-specific is an inherent characteristic of on-site EEW applications, the improved accuracy and precision of the PGV predicted for a target protection translate in a better customization of the alert protocols for automatic actions. [ABSTRACT FROM AUTHOR]

In this study we derive a spectral model describing the source, propagation and site characteristics of S waves recorded in central Italy. To this end, we compile and analyse a high-quality data set composed of more than 9000 acceleration and velocity waveforms in the local magnitude (M1) range 3.0-5.8 recorded at epicentral distances smaller than 120 km. The data set spans the time period from 2008 January 1 to 2013 May 31, and includes also the 2009 L'Aquila (moment magnitudeMw 6.1,M1 = 5.8) sequence. This data set is suitable for the application of data-driven approaches to derive the empirical functions for source, attenuation and site terms. Therefore, we apply a non-parametric inversion scheme to the acceleration Fourier spectra of the S waves of 261 earthquakes recorded at 129 stations. In a second step, with the aim of defining spectral models suitable for the implementation in numerical simulation codes, we represent the obtained non-parametric source and propagation terms by fitting standard parametric models. The frequency-dependent attenuation with distance r shows a complex trend that we parametrize in terms of geometrical spreading, anelastic attenuation and highfrequency decay parameter k. The geometrical spreading term is described by a piecewise linear model with crossover distances at 10 and 70 km: in the first segment, the spectral ordinates decay as r-1.01 while in the second as r-1.68. Beyond 70 km, the attenuation decreases and the spectral amplitude attenuate as r-0.64. The quality factor Q(f) and the high-frequency attenuation parameter k, are Q(ƒ) = 290 ƒ0.16 and k = 0.012 s, respectively, the latter being applied only for frequencies higher than 10 Hz. The source spectra are well described by ω² models, from which seismic moment and stress drops of 231 earthquakes are estimated. We calibrate a new regional relationship between seismic moment and local magnitude that improves the existing ones and extends the validity range to 3.0-5.8. We find a significant stress drop increase with seismic moment for events with Mw larger than 3.75, with so-called scaling parameter ε close to 1.5. We also observe that the overall offset of the stress-drop scaling is controlled by earthquake depth. We evaluate the performance of the proposed parametric models through the residual analysis of the Fourier spectra in the frequency range 0.5-25 Hz. The results show that the considered stress-drop scaling with magnitude and depth reduces, on average, the standard deviation by 18 per cent with respect to a constant stress-drop model. The overall quality of fit (standard deviation between 0.20 and 0.27, in the frequency range 1-20 Hz) indicates that the spectral model calibrated in this study can be used to predict ground motion in the L'Aquila region. [ABSTRACT FROM AUTHOR]

Seismic structural risk analysis of critical facilities may require nonlinear dynamic analysis for which record selection is one of the key issues. Notwithstanding the increasing availability of database of strong-motion records, it may be hard to find accelerograms that fit a specific scenario (e.g., in terms of magnitude and distance) resulting from hazard assessment at the site of interest. A possible, alternative, approach can be the use of artificial and/or simulated ground motion in lieu of real records. Their employment requires systematic engineering validation in terms of structural response and/or seismic risk. Prediction equations for peak and cyclic inelastic single degree of freedom systems' response, based on Italian accelerometric data, are discussed in this study as a possible benchmark, alongside real record counterparts, for the validation of synthetic records. Even if multiple events would be in principle required, an extremely preliminary validation is carried out considering only four simulated records of the 1980 Irpinia (southern Italy) Mw 6.9 earthquake. Simulated records are obtained through a broadband hybrid integral-composite technique. Results show how this simulation method may lead to generally acceptable results. It is also emphasized how this kind of validation may provide additional results with respect to classical signal-to-signal comparison of real and simulated records. [ABSTRACT FROM AUTHOR]

In the last few years in Italy many ground motion prediction equations (hereinafter GMPEs) were calibrated both at national and regional scale using weak and strong motion data recorded in the last 30 years by several networks. Moreover, many of the strongest Italian earthquakes were included in global data sets in order to calibrate GMPEs suitable for the prediction of ground-motion at very large scale. In the last decade, the Sabetta and Pugliese (1996) relationships represented a reference point for ground motion predictions in Italy. At present all Italian strong-motion data, recorded from 1972 by Italian Accelerometric Network, and more recently by other regional networks (e.g., RAIS, Strong motion network of northern Italy), are collected in ITACA (ITalian ACcelerometric Archive). Considering Italian strong-motion data with Mw≥4.0 and distance (Joyner-Boore or epicentral) up to 100 km, new GMPEs were developed by Bindi et al. (2010), aimed at replacing the older Italian relationships. The occurrence of the recent December 23, 2008, Mw 5.4, Parma (northern Italy) earthquake and the April 6, 2009, Mw 6.3, L'Aquila earthquake, allowed us to upgrade the ITACA data set and gave us the possibility of validating the predictive capability of many GMPEs, developed using Italian, European and global data sets. The results are presented in terms of quality of performance (fit between recorded and predicted values) using the maximum likelihood approach as explained in Spudich et al. (1999). Considering the strong-motion data recorded during the L'Aquila sequence, the considered GMPEs on average, overestimate the observed data, showing a dependence of the residuals with distance in particular at higher frequencies. An improvement of fit is obtained comparing all Italian strong-motion data included in ITACA with the European GMPEs calibrated by Akkar and Bommer (2007a, 2007b) and the global models calibrated by Cauzzi and Faccioli (2008). In contrast, the Italian data seem to attenuate faster than the NGA models calibrated by Boore and Atkinson (2008), in particular at higher frequencies. [ABSTRACT FROM AUTHOR]

A new Italian strong-motion database was created during a joint project between the Istituto Nazionale di Geofisica e Vulcanologia (IINGV, Italian Institute for Geophysics and Vulcanology) and the Dipartimento della Protezione Civile (DPC, Italian Civil Protection). The aim of the project was to collect, homogenize and distribute strong motion data acquired by different institutions, namely Ente Nazionale per l'Energia Elettrica (ENEL, Italian electricity company), Ente per le Nuove tecnologie, l'Energia e l'Ambiente (ENEA, Italian energy and environment organization) and the DPC with different purposes, such as permanent strong motion monitoring and temporary monitoring during seismic sequences or before permanent installation in Italy in the time span 1972-2004. The database contains 2182 three-component waveforms generated by 1004 earthquakes with a maximum moment magnitude of 6.9 (1980 Irpinia earthquake) and can be accessed on-line at the site http://itaca.mi.ingv.it. Here a wide range of search tools enables the user to interactively retrieve events, recording stations and waveforms with particular characteristics, whose parameters can be specified, as needed, through user friendly interfaces. A range of display options allows users to view data in different contexts, extract and download time series and spectral data. This article describes the database structure and the working steps which led to the completion of the project. [ABSTRACT FROM AUTHOR]

Investigates the source parameters of the data set of small earthquakes using iterative and constrained deconvolution with empirical Green's functions (EGF) in Italy. Estimation on the relative source time function of the events (RSTF); Use of high-precision relative location to assess the EGF; Determination of the duration of the RSTF.