GPR survey to confirm the location of ancient structures under the Valencian Cathedral (Spain)     

Vega Prez Gracia  Jos Antonio Canas  Lluis G. Pujades  Jaume Claps  Oriol Caselles  Francesc García  Raul Osorio 《Journal of Applied Geophysics》2000,43(2-4)

This paper describes the ground-penetrating radar (GPR) survey performed inside the Cathedral of Valencia, Spain. It is part of historical studies performed in the Cathedral in order to add information to old maps and documents in the Cathedral Archives and also to analyze the extent and importance of potentially destructive moisture areas that were appearing on the floor. The construction of the Cathedral of Valencia occurred in three stages, all of which are well-documented in the Cathedral Archives with detailed drawings, maps, and charts. The radar data were successful in locating crypts, ossuaries, sepulchers, and graves, and the location of ancient walls that existed before the final Cathedral expansion. Three cultural layers corresponding to the three periods of construction were also identified corresponding to the Roman, Arabian and Middle Age Epochs. Measurements of relative sub-floor moisture were obtained by comparing dielectric permittivity changes and radar velocity differences between materials in humid and non-humid areas.  相似文献   

Ground motion simulations of the SW Iberia margin: rupture directivity and earth structure effects   总被引：1，自引：0，他引：1  

M. Bezzeghoud  J. F. Borges  B. Caldeira 《Natural Hazards》2013,69(2):1229-1245

In this study, we focus on the region between Gorringe Bank and the Horseshoe Fault located in the SW Iberia margin, which is believed to be the site of the great 1755 earthquake. We model ground motions using an extended source located near the Horseshoe scarp to generate synthetic waveforms using a wave propagation code, based on the finite-difference method. We compare the simulated waveforms, for the Algarve Basin and the Lower Tagus Valley Basin (Portugal), using a 3-D velocity model down to the Moho discontinuity with a simple 1-D layered model. The radiated wave field is very sensitive to the velocity model and a small number of source parameters, in particular, the rupture directivity. The rupture directivity, the strike direction and the fault dimensions are critical to the azimuthal distribution of the maximum amplitude oscillations. We show that the use of a stratified 1-D model is inappropriate in SW Iberia, where sources are located in the oceanic domain and receivers in the continental domain. The crustal structure varies dramatically along the ray paths, with large-scale heterogeneities of low or high velocities. Moreover, combined with the geometric limitations inherent to the region, a strong trade-off between several parameters is often observed; this is particularly critical when studying moderate magnitude earthquakes (M < 6), which constitute the bulk of the seismic catalogue in SW Iberia.  相似文献   

Inversion of ambient seismic noise HVSR to evaluate velocity and structural models of the Lower Tagus Basin,Portugal     

J. F. Borges  H. G. Silva  R. J. G. Torres  B. Caldeira  M. Bezzeghoud  J. A. Furtado  J. Carvalho 《Journal of Seismology》2016,20(3):875-887

During its history, several significant earthquakes have shaken the Lower Tagus Valley (Portugal). These earthquakes were destructive; some strong earthquakes were produced by large ruptures in offshore structures located southwest of the Portuguese coastline, and other moderate earthquakes were produced by local faults. In recent years, several studies have successfully obtained strong-ground motion syntheses for the Lower Tagus Valley using the finite difference method. To confirm the velocity model of this sedimentary basin obtained from geophysical and geological data, we analysed the ambient seismic noise measurements by applying the horizontal to vertical spectral ratio (HVSR) method. This study reveals the dependence of the frequency and amplitude of the low-frequency (HVSR) peaks (0.2–2 Hz) on the sediment thickness. We have obtained the depth of the Cenozoic basement along a profile transversal to the basin by the inversion of these ratios, imposing constraints from seismic reflection, boreholes, seismic sounding and gravimetric and magnetic potentials. This technique enables us to improve the existing three-dimensional model of the Lower Tagus Valley structure. The improved model will be decisive for the improvement of strong motion predictions in the earthquake hazard analysis of this highly populated basin. The methodology discussed can be applied to any other sedimentary basin.  相似文献   

Seismicity along the Azores-Gibraltar region and global plate kinematics   总被引：1，自引：0，他引：1  

M. Bezzeghoud  C. Adam  E. Buforn  J. F. Borges  B. Caldeira 《Journal of Seismology》2014,18(2):205-220

Seismicity along the western part of the Eurasia–Nubia plate boundary displays very complex patterns. The average motion is transtensional in the Azores, dextral along the Gloria transform zone and convergent between the SW Portuguese Atlantic margin and the Ibero-Maghrebian zone. To constrain the factors controlling the seismicity, we provide a new seismotectonic synthesis using several earthquakes. We show that the study area can be divided into six different regions, with each characterised by a coherent seismicity pattern. The total seismic moment tensor and the average slip velocities are provided for each region. To determine the spatial distribution of the seismicity, we computed the slip vector for each earthquake based on its focal mechanism and compared it to the relative velocity between the Eurasian and Nubian plates, deduced from global kinematic models. Despite local departures in the Alboran Sea and near the Mid-Atlantic Ridge, we found a good correlation between these two independent vector sets. Quantitatively, the slip velocities display a linear, non-affine correlation with the norms of the relative kinematic velocities. The norms of the slip velocities also seem to depend on the tectonic regime and on the morphology of the plate boundary.  相似文献   

Characterization and Risk Evaluation of Tea Industry Coal Ash for Environmental Suitability          下载免费PDF全文

Linee Goswami  Prasanta Raul  Banashree Sahariah  Satya Sundar Bhattacharya 《洁净——土壤、空气、水》2014,42(10):1470-1476

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智利中部因M8.8地震而最终破裂     

Raul Madariaga  Marianne Métois  Jaime Campos  左玉玲 《国际地震动态》2010,(5):8-10

智利是世界上部分大地震的发生地：那里大概平均每十年就会发生一次8级地震。这些地震都发生在俯冲带：有的发生在南美和Nazca板块之间的界面上,称为板问破裂;有的发生在Nazca俯冲板块内部,称为板内事件。每个世纪都会发生几次巨大的板内、  相似文献   

Ground-Motion Simulation in the Lower Tagus Valley Basin   总被引：1，自引：0，他引：1  

J. F. Borges  M. Bezzeghoud  B. Caldeira  João Carvalho 《Pure and Applied Geophysics》2015,172(9):2411-2420

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Framework for probabilistic assessment of landslide: a case study of El Berrinche   总被引：2，自引：1，他引：1  

Raul Flores Peñalba  Zhe Luo  C. Hsein Juang 《Environmental Earth Sciences》2009,59(3):489-499

Slope failure or landslide is a complex geological/geotechnical problem that involves much uncertainty. In this work, a framework for probabilistic assessment of landslide is presented with a focus on the El Berrinche landslide, Honduras. One unique feature of this case study involving the El Berrinche landslide is that the stability analysis has to be carried out with limited data. Another challenge in this study is to assess possible remedial measures in a way that can easily be communicated to the government and the public. A reliability-based framework for a probabilistic assessment is proposed. With this approach, different levels of risk for landslide are assessed and the associated costs are estimated; and all information is integrated into the decision-making process for choosing a remedial action.  相似文献   

Trans-alkaline magmatism in the Serrinha–Pedro Velho Complex,Borborema Province,NE Brazil and its correlations with the magmatism in eastern Nigeria     

Ignez de Pinho Guimarães  Adejardo F. da Silva Filho  Daniel Brito de Araújo  Cícera Neysi de Almeida  Elton Dantas 《Gondwana Research》2009,15(1):98-110

The Solânea Complex (572 ± 8 Ma) comprises various intrusions that total 200 km². It cuts Palaeoproterozoic migmatized orthogneisses of the Serrinha–Pedro Velho Complex, which is part of the São José do Campestre Massif, North Tectonic Domain of the Borborema Province, NE Brazil. It is a post-collisional intrusion constituted of coarse-grained biotite–amphibole monzogranites, fine-grained leucogranites and diorites. Major, trace and rare earth elements data, used to constrain the origin and nature of these rocks, indicate that the monzogranites display chemical features of weakly peraluminous ferro-potassic trans-alkaline granitoids, similar to coeval occurrences described in eastern Nigerian. Sm–Nd data together with the whole rock geochemical data suggest that: (I) the monzogranites were generated by partial melting of tonalitic gneiss from the lower crust, leaving behind a granulitic residue; (II) the diorites originated by partial melting of an enriched lithospheric mantle; (III) the evolution of the Solânea Complex involved magma mixing between the monzogranites and diorites. K-feldspar and amphibole fractionation appear to have occurred during the evolution of the monzogranites.Leucogranites constituting an elliptical shaped intrusion (80 km²), the Dona Inês Pluton, are intruded to the north of the Solânea Complex. They also occur as small intrusions cross-cutting the border of the Solânea Complex. Geochemical and isotopic data suggest that the leucogranites were generated by melting of crustal Palaeoproterozoic rocks. Rb–Sr data gave an age of 544 ± 16 Ma.Trans-alkaline magmatism is associated with ductile–brittle deformation in the Serrinha–Pedro Velho Complex of the São José do Campestre Massif. This event follows the peak of an extensional-related high-temperature metamorphism (upper amphibolite to granulite facies), with estimated age of 578 to 574 Ma. If a pre-Gondwana reconstruction is considered, this event is seen to extend to the African side of Gondwana in eastern Nigeria.  相似文献   

Effects of excitation frequency on detection accuracy of orthogonal wavelet decomposition for structural health monitoring     

RaulJ.Alonso MohammadNoorit SoheilSaadatt ArataMasuda ZhikunHou 《地震工程与工程振动(英文版)》2004,3(1):101-106

Accurate estimation of stiffness loss is a challenging problem in structural health monitoring. In this study orthogonal wavelet decomposition is used for identifying the stiffness loss in a single degree of freedom spring-mass-damper system. The effects of excitation frequency on accuracy of damage detection is investigated. Results show that pseudo-alias effects caused by the orthogonal wavelet decomposition (OWD), affect damage detectability. It is demonstrated that theproposed approach is sunable for damage detection when the excitation frequency is relatively low. This study shows how a priori knowledge about the signal and ability to control the sampling frequency can enhance damage detectability.  相似文献