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271.
Jessie Mayor Paola Traversa Marie Calvet Ludovic Margerin 《Bulletin of Earthquake Engineering》2018,16(6):2195-2210
In this work, we map the absorption properties of the French crust by analyzing the decay properties of coda waves. Estimation of the coda quality factor \(Q_{c}\) in five non-overlapping frequency-bands between 1 and 32 Hz is performed for more than 12,000 high-quality seismograms from about 1700 weak to moderate crustal earthquakes recorded between 1995 and 2013. Based on sensitivity analysis, \(Q_{c}\) is subsequently approximated as an integral of the intrinsic shear wave quality factor \(Q_{i}\) along the ray connecting the source to the station. After discretization of the medium on a 2-D Cartesian grid, this yields a linear inverse problem for the spatial distribution of \(Q_{i}\). The solution is approximated by redistributing \(Q_{c}\) in the pixels connecting the source to the station and averaging over all paths. This simple procedure allows to obtain frequency-dependent maps of apparent absorption that show lateral variations of \(50\%\) at length scales ranging from 50 km to 150 km, in all the frequency bands analyzed. At low frequency, the small-scale geological features of the crust are clearly delineated: the Meso-Cenozoic basins (Aquitaine, Brabant, Southeast) appear as strong absorption regions, while crystalline massifs (Armorican, Central Massif, Alps) appear as low absorption zones. At high frequency, the correlation between the surface geological features and the absorption map disappears, except for the deepest Meso-Cenozoic basins which exhibit a strong absorption signature. Based on the tomographic results, we explore the implications of lateral variations of absorption for the analysis of both instrumental and historical seismicity. The main conclusions are as follows: (1) current local magnitude \(M_{L}\) can be over(resp. under)-estimated when absorption is weaker(resp. stronger) than the nominal value assumed in the amplitude-distance relation; (2) both the forward prediction of the earthquake macroseismic intensity field and the estimation of historical earthquake seismological parameters using macroseismic intensity data are significantly improved by taking into account a realistic 2-D distribution of absorption. In the future, both \(M_{L}\) estimations and macroseismic intensity attenuation models should benefit from high-resolution models of frequency-dependent absorption such as the one produced in this study. 相似文献
272.
Vincent Perron Aurore Laurendeau Fabrice Hollender Pierre-Yves Bard Céline Gélis Paola Traversa Stéphane Drouet 《Bulletin of Earthquake Engineering》2018,16(6):2211-2225
Seismic signal windowing is the preliminary step for many analysis procedures in engineering seismology (standard spectral ratio, quality factor, general inversion techniques, etc.). Moreover a noise window is often necessary for the data quality control through the signal-to-noise verification. Selecting the noise window can be challenging when large heterogeneous datasets are considered, especially when they include short pre-event noise signals. This study proposes a fully automatic and configurable (i.e., with default parameters that can also be user-defined) algorithm to windowing the noise and the P, S, coda and full signal once the P-wave (T P ) and S-wave (T S ) first arrivals are known. An application example is given on a KiK-net dataset. A Matlab language implementation of this algorithm is proposed as an online resource. 相似文献
273.
Michela?CamelettiEmail author Valerio?De Rubeis Clarissa?Ferrari Paola?Sbarra Patrizia?Tosi 《Stochastic Environmental Research and Risk Assessment (SERRA)》2017,31(7):1593-1602
Seismic intensity, measured through the Mercalli–Cancani–Sieberg (MCS) scale, provides an assessment of ground shaking level deduced from building damages, any natural environment changes and from any observed effects or feelings. Generally, moving away from the earthquake epicentre, the effects are lower but intensities may vary in space, as there could be areas that amplify or reduce the shaking depending on the earthquake source geometry, geological features and local factors. Currently, the Istituto Nazionale di Geofisica e Vulcanologia analyzes, for each seismic event, intensity data collected through the online macroseismic questionnaire available at the web-page www.haisentitoilterremoto.it. Questionnaire responses are aggregated at the municipality level and analyzed to obtain an intensity defined on an ordinal categorical scale. The main aim of this work is to model macroseismic attenuation and obtain an intensity prediction equation which describes the decay of macroseismic intensity as a function of the magnitude and distance from the hypocentre. To do this we employ an ordered probit model, assuming that the intensity response variable is related through the link probit function to some predictors. Differently from what it is commonly done in the macroseismic literature, this approach takes properly into account the qualitative and ordinal nature of the macroseismic intensity as defined on the MCS scale. Using Markov chain Monte Carlo methods, we estimate the posterior probability of the intensity at each site. Moreover, by comparing observed and estimated intensities we are able to detect anomalous areas in terms of residuals. This kind of information can be useful for a better assessment of seismic risk and for promoting effective policies to reduce major damages. 相似文献
274.
Francesca Barbagallo Melina Bosco Edoardo M. Marino Pier Paolo Rossi Paola R. Stramondo 《地震工程与结构动力学》2017,46(7):1099-1119
In the world, many existing buildings with RC framed structure were designed according to old seismic standards and present structural deficiencies. Buckling Restrained Braces (BRBs) can be effective for seismic upgrading of these structures, as pointed out by many studies. Nevertheless, Eurocode 8 (EC8) does not provide any rules for design of BRBs. This lack represents a big obstacle for application of this seismic upgrading technique in Europe. For this reason, a method for the design of seismic upgrading interventions by BRBs is proposed in this paper. The method is obtained as the best between two variants developed, investigated and compared in this paper. Based on a numerical investigation, the parameters that control the design method are calibrated to ensure the fulfillment of the Near Collapse performance objective stipulated in EC8. Finally, the capability of the proposed design method in fulfilling also performance objectives not explicitly considered in design is investigated. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
275.
Ellen Wohl Gary Brierley Daniel Cadol Tom J. Coulthard Tim Covino Kirstie A. Fryirs Gordon Grant Robert G. Hilton Stuart N. Lane Francis J. Magilligan Kimberly M. Meitzen Paola Passalacqua Ronald E. Poeppl Sara L. Rathburn Leonard S. Sklar 《地球表面变化过程与地形》2019,44(1):4-26
Connectivity describes the efficiency of material transfer between geomorphic system components such as hillslopes and rivers or longitudinal segments within a river network. Representations of geomorphic systems as networks should recognize that the compartments, links, and nodes exhibit connectivity at differing scales. The historical underpinnings of connectivity in geomorphology involve management of geomorphic systems and observations linking surface processes to landform dynamics. Current work in geomorphic connectivity emphasizes hydrological, sediment, or landscape connectivity. Signatures of connectivity can be detected using diverse indicators that vary from contemporary processes to stratigraphic records or a spatial metric such as sediment yield that encompasses geomorphic processes operating over diverse time and space scales. One approach to measuring connectivity is to determine the fundamental temporal and spatial scales for the phenomenon of interest and to make measurements at a sufficiently large multiple of the fundamental scales to capture reliably a representative sample. Another approach seeks to characterize how connectivity varies with scale, by applying the same metric over a wide range of scales or using statistical measures that characterize the frequency distributions of connectivity across scales. Identifying and measuring connectivity is useful in basic and applied geomorphic research and we explore the implications of connectivity for river management. Common themes and ideas that merit further research include; increased understanding of the importance of capturing landscape heterogeneity and connectivity patterns; the potential to use graph and network theory metrics in analyzing connectivity; the need to understand which metrics best represent the physical system and its connectivity pathways, and to apply these metrics to the validation of numerical models; and the need to recognize the importance of low levels of connectivity in some situations. We emphasize the value in evaluating boundaries between components of geomorphic systems as transition zones and examining the fluxes across them to understand landscape functioning. © 2018 John Wiley & Sons, Ltd. 相似文献
276.
De Risi Raffaele Jalayer Fatemeh De Paola Francesco Carozza Stefano Yonas Nebyou Giugni Maurizio Gasparini Paolo 《Natural Hazards》2020,100(1):387-415
Natural Hazards - Flood risk maps for the built environment can be obtained by integrating geo-spatial information on hazard, vulnerability and exposure. They provide precious support for strategic... 相似文献
277.
The Plio-Pleistocene stratigraphic record of the Peri-Adriatic basin (eastern central Italy) is well exposed along the uplifted western margin of the basin and consists of a series of coarse-grained slope canyon fills encased in a thick succession of hemipelagic mudstones. This study deals with the detailed sedimentology, stratal architecture, and sequence-stratigraphic interpretation of two of these submarine canyon-fills (namely CMC1 and CMC2) exposed at Colle Montarone. These strata contain widespread evidence of gravity-driven sedimentation processes, with high- and low-density turbidity currents, slumps and cohesive debris flows being responsible for most of the sediment transport and deposition. Beds are organised into four recurrent lithofacies, each corresponding to a specific deep-water depositional element: (i) clast-supported conglomerates (channel complexes); (ii) thin-bedded sandstones and mudstones (levee-overbank); (iii) very thinly-bedded mudstones (tributary channels); (iv) pebbly mudstones and chaotically bedded mudstones (mass-transport complexes). 相似文献
278.
Paola Vannucchi 《Journal of Structural Geology》1999,21(12):51
Meso- and micro-structural studies of the well-exposed Balduini Thrust (Northern Apennines, Italy) indicate that the structure formed during a single folding event, contemporaneous with diagenesis, and is a zone comprising curved, en-échelon fault segments. The geometry of each segment is arcuate with pure compression at one end and right-lateral displacement along the other. The thrust developed during the Tortonian within a single mud-rich formation, the Upper Eocene–Upper Oligocene Scaglia Cinerea, but rheological variations within the unit led to differences in deformation style; zones of scaly fabric are discontinuous and calcite veins vary in abundance. The mesoscopic morphology of the veins and the distribution of calcium carbonate along the formation indicate variations in the distribution of fluids at the time of deformation, which affected both diagenesis and the structural response of the material. Systematic variations of mechanical properties within the thickness of the Scaglia Cinerea Formation account for the curvature of the propagating thrust. Together with the heterogeneity of the stress field, the confinement of the arcing thrust to this single, weak unit lead to repeated initiation of new fractures and hence segmentation of the propagating thrust. Geometric analysis of the calcite veins and their microscopic characters suggests that hydrofracturing was involved, with the Scaglia Cinerea Formation experiencing high fluid pressure followed by rapid water expulsion. The Balduini Thrust is therefore an example of a fluid-driven, refracted compound shear zone. The analysis presented here provides insights into the three-dimensional arrangement of fault zones and fluid-migration patterns during regional faulting. 相似文献
279.
Resistive instabilities in a context referring to the solar corona are rigorously investigated. Various equilibrium configurations are considered, differing, among other things, by their behaviour with respect to fast, ideal instabilities. The computations presented cover in a unified scheme all known regimes of resistive modes and allow one to determine the fastest timescale over which resistivity can play a role. Comparisons with previous work as well as possible extensions are presented. 相似文献
280.
G. M. Di Paola 《Bulletin of Volcanology》1971,35(2):497-506
The Corbetti Caldera area, a recent volcanic complex in the Main Ethiopian Rift Valley, is described. In the area, most of the volcanic products are peralkaline pyroclastics (ignimbrites and pumice). The volcanological history of this complex has been reconstructed. It comprises fissure eruptions, which were followed by a volcano-tectonic collapse. Finally the activity resumed with the birth of two recent peralkaline volcanoes (Urji and Chabbi) inside the caidera. Both these volcanoes are at present in a fumarolic stage. Relations between the tectonic of the Rift Valley and the volcanological evolution of the Caldera Corbetti Area are discussed. 相似文献