Accuracy assessment of the Mexican National Forest Inventory map: A study in four ecogeographical areas     

Stéphane Couturier  Jean‐François Mas  Erna López‐Granados  Jorge Benítez  Valdemar Coria‐Tapia  Álvaro Vega‐Guzmán 《Singapore journal of tropical geography》2010,31(2):163-179

The accuracy of the Mexican National Forest Inventory (NFI) map is derived in four distinct ecogeographical areas, using an assessment design tailored for the project. A main achievement of the design was to integrate the high diversity of classes encompassed at the most detailed subcommunity level of the classification scheme within a cost‐controlled statistically sound assessment. A hybrid double sampling strategy was applied to the 2.5 million‐ha study area. A total of 5955 reference sites were verified against their NFI map label. The availability of detailed quasi‐synchronous reference data for the 2000 Landsat‐derived NFI and the high diversity of mapped classes allowed a careful thematic analysis on the selected regions, relevant for national extrapolation. Global accuracy estimates of 64–78 per cent were registered among the four ecogeographical areas (two with mainly temperate climate and the other two with mainly tropical climate), with the lower accuracy levels found in areas more densely covered with forests. According to the estimates, the NFI map tends to underestimate the presence of temperate forest (especially oak) and overestimate the presence of tropical forest in the areas investigated. The analysis of confusions reveals difficulties in unambiguously interpreting or labelling forests with secondary vegetation, herbaceous and/or shrub‐like vegetation as well as distinguishing between aquatic vegetation types. The design proved useful from the perspective of accuracy assessments of regional maps in biodiverse regions.  相似文献   

Sky luminance distribution in Pamplona (Spain) during the summer period     

J.L. Torres  M. de Blas  A. García  A. Gracia  A. de Francisco 《Journal of Atmospheric and Solar》2010,72(5-6):382-388

In this work the outdoor daylight conditions in Pamplona (South Europe) during the summer period have been studied. The selected sky type (from fifteen standards) at a given moment is the one exhibiting the lowest RMSD when comparing the theoretical and experimental luminance distributions in the sky hemisphere. Two year data of luminance distribution registered every 10 min in 145 positions of the sky hemisphere have been used for selecting the sky type. The most frequent sky type in Pamplona is V.5 (cloudless polluted with a broad solar corona), with an occurrence of 29.5%. This result coincides with the one observed in a previous study in Athens.Six types of sky (V.5, IV.4, III.4, III.3, V.4 y II.2) out of the fifteen standards become practically the 80% of all the studied ones. Regarding a possible use in daylight climate studies, the frequency of occurrence of the fifteen types of sky for fourteen solar elevation intervals has been included.  相似文献   

Strong ground-motion relations for Mexican interplate earthquakes     

Danny Arroyo  Daniel García  Mario Ordaz  Mauricio Alexander Mora  Shri Krishna Singh 《Journal of Seismology》2010,14(4):769-785

We derive strong ground-motion relations for horizontal components of pseudo-acceleration response spectra from Mexican interplate earthquakes at rock sites (NEHRP B class) in the forearc region. The functional form is obtained from the analytical solution of a circular finite-source model. For the regression analysis we use a recently proposed multivariate Bayesian technique. The resulting model has similar accuracy as those models derived from regional and worldwide subduction-zone databases. However, there are significant differences in the estimations computed from our model and other models. First, our results reveal that attenuation in Mexico tends to be stronger than that of worldwide relations, especially for large events. Second, our model predicts ground motions for large earthquakes at close distances to the source that are considerably larger than the estimations of global models. Lack of data in this range makes it difficult to identify the most appropriate model for this scenario. Nevertheless, according to the available data at the city of Acapulco, our model seems to estimate seismic hazard more adequately than the other models. These new relations may be useful in computing seismic hazard for the Mexican forearc region, where no similar equations had been yet proposed.  相似文献   

Guest editorial: Structural seismic safety assessment     

Carlos Sousa Oliveira  Aníbal Costa  Raimundo Delgado 《Bulletin of Earthquake Engineering》2010,8(1):1-3

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A multi-scale hierarchical framework for developing understanding of river behaviour to support river management     

A. M. Gurnell  M. Rinaldi  B. Belletti  S. Bizzi  B. Blamauer  G. Braca  A. D. Buijse  M. Bussettini  B. Camenen  F. Comiti  L. Demarchi  D. García de Jalón  M. González del Tánago  R. C. Grabowski  I. D. M. Gunn  H. Habersack  D. Hendriks  A. J. Henshaw  M. Klösch  B. Lastoria  A. Latapie  P. Marcinkowski  V. Martínez-Fernández  E. Mosselman  J. O. Mountford  L. Nardi  T. Okruszko  M. T. O’Hare  M. Palma  C. Percopo  N. Surian  W. van de Bund  C. Weissteiner  L. Ziliani 《Aquatic Sciences - Research Across Boundaries》2016,78(1):1-16

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Surface dynamic deformation estimates from local seismicity: the Itoiz reservoir,Spain     

Miguel A. Santoyo  Patricia Martínez-Garzón  Antonio García-Jerez  Francisco Luzón 《Journal of Seismology》2016,20(3):1021-1039

We analyze the ground motion time histories due to the local seismicity near the Itoiz reservoir to estimate the near-source, surface 3D displacement gradients and dynamic deformations. The seismic data were obtained by a semipermanent broadband and accelerometric network located on surface and at underground sites. The dynamic deformation field was calculated by two different methodologies: first, by the seismo-geodetic method using the data from a three-station microarray located close to the dam, and second, by single station estimates of the displacement gradients. The dynamic deformations obtained from both methods were compared and analyzed in the context of the local free-field effects. The shallow 1D velocity structure was estimated from the seismic data by modeling the body wave travel times. Time histories obtained from both methods result quite similar in the time window of body wave arrivals. The strain misfits between methods vary from 1.4 to 35.0 % and rotational misfits vary from 2.5 to 36.0 %. Amplitudes of displacement gradients vary in the range of 10^?8 to 10^?7 strains. From these results, a new scaling analysis by numerical modeling is proposed in order to estimate the peak dynamic deformations for different magnitudes, up to the expected maximum M _w in the region (M5.5). Peak dynamic deformations due to local M _w5.5 earthquakes would reach amplitudes of 10^?5 strain and 10^?3 radians at the Itoiz dam. The single station method shows to be an adequate option for the analysis of local seismicity, where few three-component stations are available. The results obtained here could help to extend the applicability of these methodologies to other sites of engineering interest.  相似文献   

Hydrological response of an afforested catchment in a Mediterranean humid mountain area: a comparative study with a natural forest   总被引：1，自引：0，他引：1       下载免费PDF全文

Estela Nadal‐Romero  Erik Cammeraat  María Pilar Serrano‐Muela  Noemí Lana‐Renault  David Regüés 《水文研究》2016,30(15):2717-2733

The effects of afforestation on water resources are still controversial. The aim of this paper is to (i) analyse the hydrological response of an afforested area in the Central Pyrenees and (ii) compare the hydrological response of an afforested area with the response observed in a natural undisturbed forest. The Araguás catchment was cultivated until the 1950s, and then afforested with pines in an effort to control the active degradation processes. The hydrological response was variable and complex, because the discharge was generated by a combination of distinct runoff processes. The hydrological response showed that (i) afforestation produced moderate peak discharges, stormflows and recession limbs, and long rising limbs; (ii) no one single variable was able to explain the hydrological response: rainfall volume and intensity did not explain the hydrological response and antecedent rainfall and initial discharge (indicating antecedent moisture conditions) did play an important role; (iii) seasonal differences were observed suggesting different runoff generating processes; and (iv) the effect of forest cover on peak discharges became less important as the size of the hydrological event increased. The stormflow coefficient showed a clear seasonal pattern with an alternation between a wet period, when the catchment was hydrologically responsive, and a dry summer period when the catchment rarely responded to any event, and two transitional periods (wetting and drying). Compared with a natural forest, the afforested area recorded greater flows and peak discharges, faster response times and shorter recession limbs. Afforestation reduces the water yield and the number of floods compared with non‐vegetated areas and abandoned lands. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Geomorphic monitoring and response to two dam removals: rivers Urumea and Leitzaran (Basque Country,Spain)          下载免费PDF全文

Askoa Ibisate  Alfredo Ollero  Daniel Ballarín  Jesús Horacio  Daniel Mora  Amaia Mesanza  Carles Ferrer‐Boix  Vanesa Acín  David Granado  Juan Pedro Martín‐Vide 《地球表面变化过程与地形》2016,41(15):2239-2255

Dam removal has been demonstrated to be one of the most frequent and effective fluvial restoration actions but at most dam removals, especially of small dams, there has been little geomorphological monitoring. The results of the geomorphological monitoring implemented in two dams in the rivers Urumea and Leitzaran (northern Spain) are presented. The one from the River Urumea, originally 3.5 m high and impounding 500 m of river course, was removed instantaneously whereas that in the River Leitzaran, 12.5 m high, and impounding 1500 m of river course, is in its second phase of a four‐stage removal process. Changes in channel morphology, sediment size and mobility and river bed morphologies were assessed. The monitoring included several different techniques: topographical measurements of the channel, terrestrial laser scanner measurements of river bed and bars, sediment grain size and transport; all of them repeated in four (May, August, November 2011 and May 2012) and five (July and September 2013, April and August 2014 and June 2015) fieldwork campaigns in the River Urumea and River Leitzaran, respectively. Geomorphic responses of both dam removals are presented, and compared. Morphological channel adjustments occurred mainly shortly after dam removals, but with differences among the one removed instantaneously, that was immediate, whereas that conducted by stages took longer. Degradational processes were observed upstream of both dams (up to 1.2 m and 4 m in the River Urumea and River Leitzaran, respectively), but also aggradational processes (pool filling), upstream of Inturia Dam (2.85 m at least). Less evident aggradational processes were observed downstream of the dams (up to 0.37 m and 0.50 m in the River Urumea and River Leitzaran, respectively). Flood events, especially a 100 year flood registered during the monitoring period of Mendaraz Dam removal, reactivated geomorphological processes as incision and bank erosion, whereas longitudinal profile recovery, grain‐size sorting and upstream erosion took longer. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Dynamic behavior of buildings with non-uniform stiffness along their height assessed through coupled flexural and shear beams     

Andrés Alonso-Rodríguez  Eduardo Miranda 《Bulletin of Earthquake Engineering》2016,14(12):3463-3483

A novel model for assessing building behavior has been developed by coupling a Bernoulli beam with a quartic stiffness variation and a shear beam with a parabolic stiffness variation, trends that are expected in buildings designed for earthquake actions. Then the partial differential equation of motion governing the behavior of the model has been solved, obtaining analytic expressions (Closed form solutions) for mode shapes in terms of Legendre functions. These closed form solutions were validated with finite element model analyses and effects of non-uniformity of stiffness were assessed in a generalized manner. It was found that period lengthening is mild for the first mode, but for higher modes can be far more noticeable if shear stiffness at beam top is <20 % of its base value. Mode shapes also change notoriously for reductions beyond the same limit, potentially inducing large floor acceleration demands at unexpected locations. Also it was found that drift demands can be noticeably enhanced even if shear stiffness at top is 75 % of the base value, in what would be considered uniform buildings. This model has several applications for assessing the response or large stocks of buildings, calibrate complex models, assess damage on building contents, establishing in short time damage scenarios for large cities, and could be helpful for education, as emphasis is brought back on fundamental concepts.  相似文献   

Reassessment of intensity estimates from vulnerability and damage distributions: the 2011 Lorca earthquake     

S. Martínez-Cuevas  J. M. Gaspar-Escribano 《Bulletin of Earthquake Engineering》2016,14(10):2679-2703

This paper presents a reassessment of the seismic intensity estimated for the 2011 Lorca (southeastern Spain) earthquake based on detailed vulnerability data and its comparison with the observed damage. Building and urban data are gathered in selected areas during a field campaign and are completed with office work. The significance of vulnerability modifiers in the final vulnerability distribution is analyzed, and their relation with observed damage trends is explored. A direct application of the vulnerability modifiers is not capable of reproducing the observed damage patterns. A significant increase of vulnerability related to the performance of buildings presenting soft story is required to reach a damage distribution consistent with intensity estimates in the study areas. Accordingly, an intensity increase in certain study zones (as compared to other areas of the city of Lorca) is suggested. Although the approach followed in this study is applied in a city of Spain, it can be extrapolated to other areas where detailed vulnerability assessment is feasible and damage data are available.  相似文献