Improved 2-D attenuation analysis for Northern Italy using a merged dataset from selected regional seismic networks     

Paola Morasca  Marco Massa  Enrica Laprocina  Kevin Mayeda  Scott Phillips  Luca Malagnini  Daniele Spallarossa  Giovanni Costa  Paolo Augliera 《Journal of Seismology》2010,14(4):727-738

A merged, high-quality waveform dataset from different seismic networks has been used to improve our understanding of lateral seismic attenuation for Northern Italy. In a previous study on the same region, Morasca et al. (Bull Seismol Soc Am 98:1936–1946, 2008) were able to resolve only a small area due to limited data coverage. For this reason, the interpretation of the attenuation anomalies was difficult given the complexity of the region and the poor resolution of the available data. In order to better understand the lateral changes in the crustal structure and thickness of this region, we selected 770 earthquakes recorded by 54 stations for a total of almost 16,000 waveforms derived from seismic networks operating totally or partially in Northern Italy. Direct S-wave and coda attenuation images were obtained using an amplitude ratio technique that eliminates source terms from the formulation. Both direct and early-coda amplitudes are used as input for the inversions, and the results are compared. Results were obtained for various frequency bands ranging between 0.3 and 25.0 Hz and in all cases show significant improvement with respect to the previous study since the resolved area has been extended and more crossing paths have been used to image smaller scale anomalies. Quality-factor estimates are consistent with the regional tectonic structure exhibiting a general trend of low attenuation under the Po Plain basin and higher values for the Western Alps and Northern Apennines. The interpretation of the results for the Eastern Alps is not simple, possibly because our resolution for this area is still not adequate to resolve small-scale structures.  相似文献   

Urban seismic stations: soil–structure interaction assessment by spectral ratio analyses     

M. Massa  S. Marzorati  C. Ladina  S. Lovati 《Bulletin of Earthquake Engineering》2010,8(3):723-738

In this work we present and discuss the results of ambient seismic noise analyses computed at four sites where seismic stations, managed by the INGV (Italian Institute for Geophysics and Vulcanology) and the DPC (Italian Department of Civil Protection), are installed inside buildings. The experiments were performed considering different types of installation: sensor located at the bottom of a school, directly installed on rock (case 1); sensor located at the bottom of a medieval fortress, built on an isolate hill, directly installed on rock (case 2); sensor installed on the foundations of a medieval fortress, built on an isolate hill (case 3); sensor installed on the foundations of a school, built on alluvial deposits (case 4). Since recent works proposed the use of spectral ratio techniques to study the dynamic characterization of buildings, ambient seismic-noise measurements were performed for each site close to the stations (at the base of the structures), at the top of the structures and outside the buildings. In order to check the source of vibrations both horizontal to vertical spectral ratio (HVNR) and standard spectral ratio (SSR) techniques were applied. For all stations the results from ambient seismic noise were compared to those obtained from earthquakes (HVSR). In order to detect preferential directions of amplification, for each site average HVNRs and HVSRs were computed considering one azimuth for each set of 5°. We obtain different results for different types of installation: in cases 1 and 2, where the sensors are directly installed on rock, the vibrations of the structure do not affect the noise measures performed close to the stations, which show flat HVNR in the whole frequency range: in both cases the eigenfrequency of the building is given by the HVNR calculated from the measures performed at the top of the structure. In cases 3 and 4, where the sensors are installed on the foundations of the considered structures, both the amplification peaks between 5 and 9 Hz (case 3) and between 5.5 and 7 Hz (case 4) include the contribution of the free oscillations of the buildings. In particular, in case 4, HVNRs performed outside building highlight possible soil–structure resonance effects in case of an earthquake.  相似文献   

Ground motion prediction equations derived from the Italian strong motion database   总被引：7，自引：6，他引：1  

D. Bindi  F. Pacor  L. Luzi  R. Puglia  M. Massa  G. Ameri  R. Paolucci 《Bulletin of Earthquake Engineering》2011,9(6):1899-1920

We present a set of ground motion prediction equations (GMPEs) derived for the geometrical mean of the horizontal components and the vertical, considering the latest release of the strong motion database for Italy. The regressions are performed over the magnitude range 4?C6.9 and considering distances up to 200?km. The equations are derived for peak ground acceleration (PGA), peak ground velocity (PGV) and 5%-damped spectral acceleration at periods between 0.04 and 2?s. The total standard deviation (sigma) varies between 0.34 and 0.38?log₁₀ unit, confirming the large variability of ground shaking parameters when regional data sets containing small to moderate magnitude events (M?<?6) are used. The between-stations variability provides the largest values for periods shorter than 0.2?s while, for longer periods, the between-events and between-stations distributions of error provide similar contribution to the total variability.  相似文献   

Magnetic properties and cation ordering of nanopowders of the synthetic analogue of kuramite, Cu3SnS4     

Francesco Di Benedetto  Daniele Borrini  Andrea Caneschi  Gabriele Fornaciai  Massimo Innocenti  Alessandro Lavacchi  Carlo Andrea Massa  Giordano Montegrossi  Werner Oberhauser  Luca A. Pardi  Maurizio Romanelli 《Physics and Chemistry of Minerals》2011,38(6):483-490

An extensive characterisation of the magnetic properties of synthetic powders of kuramite, with formal composition Cu₃SnS₄, was performed. Powders were investigated through superconducting quantum interference device (SQUID) magnetometry, electron paramagnetic resonance (EPR) spectroscopy, X-ray powder diffraction (XRPD), scanning and transmission electron microscopies (SEM and TEM) and microanalysis. SEM and TEM reveal the presence of nanodimensioned particles. XRPD clearly shows that Cu₃SnS₄ crystallised in a cubic sphalerite-type structural model, in spite of the stannite-type tetragonal structure described for the natural phase. This difference arises from a full random distribution of cations. Synthetic kuramite nanopowders exhibit a marked paramagnetism, originated by the presence of Cu(II), definitely assessed by EPR measurements. Moreover, the overall magnetic behaviour of the sample cannot be simply ascribed to diluted paramagnetism, and this suggests the presence of strong superexchange interactions among Cu(II) ions even at room temperature. The main consequences of these results are the definitive assessment of the chemical formula Cu(I)₂Cu(II)SnS₄ and of a random distribution of Cu(II), Cu(I) and Sn(IV) ions within the available tetrahedral sites.  相似文献   

Einstein-like field equations with conserved source and decreasing ∧ term; Their cosmological consequences     

Corrado Massa 《Astrophysics and Space Science》1996,246(1):153-158

The consequences of a cosmological term varying asS ^–2 in a spatially isotropic universe with scale factorS and conserved matter tensor are investigated. One finds a perpetually expanding universe with positive and gravitational constantG that increases with time. The hard equation of state 3P>U (U mass-energy density,P scalar pressure) applied to the early universe leads to the expansion lawSt (t cosmic time) which solves the horizon problem with no need of inflation. Also the flatness problem is resolved without inflation. The model does not affect the well known predictions on the cosmic light elements abundance which come from standard big bang cosmology.In the present, matter dominated universe one findsdG/dt=2H/U (H is the Hubble parameter) which is consistent with observations provided <10^–57 cm^–2. Asymptotically (S) the term equalsGU/2, in agreement with other studies.  相似文献   

Observations of the 21 June 2001 Total Solar Eclipse     

Derck P. Smits 《Astrophysics and Space Science》2002,282(1):227-234

Total solar eclipses are rare events, but the publicity surrounding them is generating a lot of interest. These events can be used to popularize astronomy and promote science awareness. The internet is gaining popularity as a medium to view eclipses remotely as is evidenced by the number of websites devoted to the 2001 solar eclipse. More internet webcasts are needed to meet the demand that these events generate. The attempt by a team from the Astronomy Department at the University of South Africa to broadcast a streaming video of the 21 June 2001 total eclipse from Lusaka on the internet are described. All the necessary equipment is commercially available. Lessons learnt from this eclipse can be used to prepare for future events. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Einstein-Like Equations with Coupled-to-Matter Λ Term     

Corrado Massa 《Astrophysics and Space Science》2000,271(1):83-89

We consider Einstein-like gravitational equations with Λ term proportional to the trace of the energy tensor. The possibility of Lagrangian formulation is shortly discussed. The theory is consistent with the present-day observations, both at the local and cosmological level. Horizon-free cosmological solutions are found and discussed. The initial condition S(0) = 0 (where S(t) is the expansion factor and t the cosmic time) requires hyperbolic space. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Estimation of topographical effects at Narni ridge (Central Italy): comparisons between experimental results and numerical modelling     

S. Lovati  M. K. H. Bakavoli  M. Massa  G. Ferretti  F. Pacor  R. Paolucci  E. Haghshenas  M. Kamalian 《Bulletin of Earthquake Engineering》2011,9(6):1987-2005

In the present work the seismic site response of Narni ridge (Central Italy) is evaluated by comparing experimental results and numerical simulations. The inhabited village of Narni is located in central Apennines at the top of a steep massive limestone ridge. From March to September 2009 the site was instrumented with 10 weak-motion stations, 3 of which located at the base of the ridge and 7 at the top. The velocimetric network recorded 642 events of M_L up to 5.3 and hypocentral distance up to about 100 km. The great amount of data are related to the April 2009 L’Aquila sequence. The site response was analyzed using both reference (standard spectral ratio, SSR) and non reference spectral techniques (horizontal to vertical spectral ratio, HVSR). Moreover directional analyses were performed in order to evaluate the influence of the ridge orientation with respect to the selected source-site paths. In general the experimental results show amplification factors for frequencies between 4 and 5 Hz for almost all stations installed along the crest. The SSR technique provides amplification factors up to 4.5 in a direction perpendicular to the main elongation of the ridge. The results obtained from the data analyses were used as a target for bidimensional and tridimensional numerical simulations, performed using a hybrid finite-boundary element method and a boundary element method for 2D and 3D modelling, respectively. In general, the results obtained through numerical simulation fit well the experimental data in terms of range of amplified frequencies, but they underestimate by a factor of about 2 the observed amplifications.  相似文献   

Evaluation of site effects in the Aterno river valley (Central Italy) from aftershocks of the 2009 L��Aquila earthquake     

F. Bergamaschi  G. Cultrera  L. Luzi  R. M. Azzara  G. Ameri  P. Augliera  P. Bordoni  F. Cara  R. Cogliano  E. D��Alema  D. Di Giacomo  G. Di Giulio  A. Fodarella  G. Franceschina  F. Galadini  M. R. Gallipoli  S. Gori  P. Harabaglia  C. Ladina  S. Lovati  S. Marzorati  M. Massa  G. Milana  M. Mucciarelli  F. Pacor  S. Parolai  M. Picozzi  M. Pilz  S. Pucillo  R. Puglia  G. Riccio  M. Sobiesiak 《Bulletin of Earthquake Engineering》2011,9(3):697-715

A temporary network of 33 seismic stations was deployed in the area struck by the 6th April 2009, Mw 6.1 (Scognamiglio et?al. in Seism Res Lett 6/81, 2010), L??Aquila earthquake (central Italy), with the aim to investigate the site amplification within the Aterno river Valley. The seismograms of 18 earthquakes recorded by 14 of the 33 stations were used to evaluate the average horizontal to vertical spectral ratio (HVSR) for each site and the standard horizontal spectral ratio (SSR) between a site and a reference station. The obtained results have been compared to the geological and geophysical information in order to explain the resonance frequencies and the amplification levels with respect to surface geology of the valley. The results indicate that there is no uniform pattern of amplification, because of the complex geologic setting, as the thickness and degree of cementation of the deposits is highly variable.  相似文献   

Italian strong motion records in ITACA: overview and record processing     

Francesca Pacor  Roberto Paolucci  Gabriele Ameri  Marco Massa  Rodolfo Puglia 《Bulletin of Earthquake Engineering》2011,9(6):1741-1759

The published version 1.0 of the new Italian strong-motion database ITACA (Italian ACcelerometric Archive, ) includes to date (December 2010) about 4,000 three-component waveforms up to M 6.9, from more than 1,800 earthquakes up to 6.9, recorded by about 400 stations in the period 1972–2009. The uncorrected and corrected strong motion data are archived and can be retrieved with their metadata, concerning events, stations and waveforms. The aim of this paper is to present the procedures for processing the records included in ITACA, accounting for the heterogeneity of this data set, both in terms of quality and amplitude of records as well as illustrating the main features of the ITACA strong-motion dataset. Later, we focus on the “exceptional” ground-motion records, that we, conventionally, denote as those having peak acceleration and peak velocity larger than 300 cm/s² and 15 cm/s, respectively. These records are less than 2% of the whole ITACA dataset but they are the most relevant for the seismic hazard and engineering implications. Such large peak values, recorded at distances up to 30 km, are related not only to the strongest Italian earthquakes, but also to events with magnitude down to 4. Furthermore, we investigate the dependence of the largest peak values on horizontal and vertical directions and on source-to-site distance.  相似文献