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A. Moya V. Schmidt C. Segura I. Boschini K. Atakan 《Soil Dynamics and Earthquake Engineering》2000,20(1-4)
Site effects for 11 selected locations were determined in the capital city of Costa Rica. We used a strong motion network made of eight K2 and three SSA accelerographs. The network recorded more than 60 earthquakes in the magnitude range from 2 to 5 during a period of nine months. The site effects were determined using the sediment-to-bedrock spectral ratio (SBSR) and the horizontal-to-vertical spectral ratio (HVSR) techniques and a time window 4 s beginning from the S-wave arrival. The result suggests that the amplification in the capital city is to be in the range from 2.0 to 3.0. The fundamental frequencies were found to be high in the southern and eastern part of the study area and low in the northern and western part. A possible topographic effect was also observed for one of the stations located nearby a river canyon. The results from earthquake data were compared with the ones obtained from noise data. The horizontal-to-vertical noise ratio (HVNR) technique was used to estimate the site effects using ambient noise. The fundamental frequencies were found to correlate very well between both sets of data; on the other hand, the amplitude given by the noise was observed to be always lower than the one derived from the earthquake data. 相似文献
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Jordi Corominas Ramon Copons José Moya Joan M. Vilaplana Joan Altimir Jordi Amigó 《Landslides》2005,2(4):343-357
Quantitative Risk Assessment (QRA) has become an indispensable tool for the management of landslide hazard and for planning
risk mitigation measures. In this paper we present the evaluation of the rockfall risk at the Solà d’Andorra slope (Andorra
Principality) before and after the implementation of risk mitigation works, in particular, the construction of protective
fences. To calculate the risk level we have (i) identified the potential rockfall release areas, (ii) obtained the volume
distribution of the falling rocks, (iii) determined the frequency of the rockfall events, and (iv) performed trajectographic
analysis with a 3D numerical model (Eurobloc) that has provided both the expected travel distances and the kinetic energy
of the blocks. The risk level at the developed area located at the foot of the rock cliff has been calculated taking into
account the nature of the exposed elements and their vulnerability. In the Forat Negre basin, the most dangerous basin of
the Solà d’Andorra, the construction of two lines of rockfall protection fences has reduced the annual probability of loss
of life for the most exposed person inside the buildings, from 3.8×10−4 to 9.1×10−7 and the societal risk from 1.5×10−2 of annual probability of loss of life to 1.2×10−5. 相似文献
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This paper deals with the quality of two multivariate statistical models based on the Geographical Information System for
shallow landslide susceptibility assessment in a test area at La Pobla de Lillet (Eastern Pyrenees, Spain). The quality, which
was guaranteed by a rigorous methodology based on a suitable diagnosis, validation, and evaluation of the models, ensured
a reliable contrast of the final susceptibility maps. This enables us to transfer the best results to the end user. Landslide
susceptibility models were carried out by logistic regression and discriminant analysis of the significant conditioning factors
related to the characteristics of the slope and the upslope contributing area captured from the digital elevation model and
landslide distribution. The explanatory variables were tested (KS test, principal components and one-way and T-test) to select the most statistically significant ones before being introduced into the logistic and discriminant analyses.
Accuracy statistics and the receiver operating characteristic curve used for diagnosis and validation showed similar prediction
skills and a good fit to the data with more than 85% of unfailed cells properly classified for the two models. The evaluation
of the study area and the correlation function (R
2 = 0.83) between the models revealed that the discriminant model overestimated the susceptibility of the most stable zones
with respect to the logistic model. Different methods of producing susceptibility maps showed marked differences in matching
the models. Substantial spatial agreement (Kappa = 0.741) between binary maps produced by the standard cut-off value descended
moderately (Kappa = 0.540) as a result of superimposing maps with five susceptibility levels defined by landslide percentage.
Despite the fact that the two statistical models are similar in assessing susceptibility in the study area, the implications
for hazard and risk management can be different because of the conservative nature of the discriminant model. 相似文献
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Triassic stretching directions in Iberia and North Africa inferred from magnetic fabrics 总被引:1,自引:0,他引:1
Ruth Soto Antonio M. Casas‐Sainz Beln Oliva‐Urcia Cristina García‐Lasanta Esther Izquierdo‐Llavall Bennacer Moussaid Jos Carlos Kullberg Teresa Romn‐Berdiel Yolanda Snchez‐Moya Alfonso Sopea Sara Torres‐Lpez Juan Jos Villalaín Hamidou El‐Ouardi Inmaculada Gil‐Pea Ann M. Hirt 《地学学报》2019,31(5):465-478
During the Triassic, Iberia and western North Africa displayed a unique situation in relation with the Central and North Atlantic opening and westward expansion of the Tethys. Unravelling the stretching direction in Triassic deposits of the studied area can help in our understanding of this scenario. The tectonic setting is characterized by localized basins with strong thickness variations greatly influenced by previous post‐Variscan mechanical discontinuities. In this work, we revise and compile magnetic fabric data from eight Triassic depocentres in terms of defining the stretching direction (i.e. magnetic lineation), resulting from extensional deformation of this period. Data show the importance of the opening of the Atlantic rift as the leading process during the Triassic. Dextral transtension can explain the deflection of the extensional direction observed in most studied depocentres that is caused by the activity of previous major oblique faults. 相似文献