Assessing regional geodiversity: the Iberian Peninsula     

A. Benito‐Calvo  A. Pérez‐González  O. Magri  P. Meza 《地球表面变化过程与地形》2009,34(10):1433-1445

Geodiversity is a landscape characteristic related to the heterogeneity of the physical properties of the earth surface. In this work, we quantify and compare geodiversity in several geodynamic zones of the Iberian Peninsula. For this purpose, we have developed a geographic information system (GIS) procedure to carry out a regional terrain classification based on geodiversity factors. A classification process helped to produce a morphometric map (10 classes), a morphoclimatic map (five classes) and a geological map (15 classes). These three maps were combined using an overlay operation (union) to obtain the final terrain classification (419 classes), which was then applied to calculate diversity landscape indices. The latter were calculated using common landscape diversity indices (Patch Richness Density, Shannon's Diversity Index, Shannon's Evenness Index, Simpson's Diversity Index and Simpson's Evenness Index), provided by FRAGSTATS free software. These indices were calculated for the whole landscape of the main Iberian geological regions, thus revealing a close relationship between some index values and the geological and geomorphological characteristics. The highest diversity values are associated with Alpine collisional orogens and reactivated chains of the Precambrian‐Palaeozoic massif. Intraplate orogen with sedimentary cover, characterized by extensive planation surfaces, have lower values. Mesozoic areas with no significant tectonic deformation and Cenozoic basins are characterized by the lowest diversity values. Amongst the latter, the major diversity is associated with the most dissected basins, which also present higher morphoclimatic variety. Though depending on the chosen scale and the landscape classification criteria, these indices provide an objective assessment of the regional geodiversity of Iberia. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Effects of the largest daily events on total soil erosion by rainwater. An analysis of the USLE database     

J.C. González‐Hidalgo  M. de Luis  R. J. Batalla 《地球表面变化过程与地形》2009,34(15):2070-2077

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Late quaternary tephra layers along the Cilento coastline (southern Italy)     

Roberta Marciano  Rosalba Munno  Paola Petrosino  Nicoletta Santangelo  Antonio Santo  Igor Villa 《Journal of Volcanology and Geothermal Research》2008

The results of stratigraphic and tephrostratigraphic analyses of several pyroclastic levels, collected along the coastal sector of the Cilento region (southern Italy), are presented. Some of these levels are here described for the fist time, others, already known in literature, were reconsidered in order to better understand their stratigraphic position and to point out the possible volcanic sources.  相似文献   

Simulating the migration of drifters deployed in the Bay of Biscay, during the Prestige crisis     

Caballero A  Espino M  Sagarminaga Y  Ferrer L  Uriarte A  González M 《Marine pollution bulletin》2008,56(3):475-482

A main conclusion following the oil spill from the Prestige tanker was that improvements in ocean circulation models were necessary; this was in order to predict, more accurately, the trajectories followed by the oil slicks and hence assist in fight against oil pollution operations. In this contribution, the results of the validation of a semi-empirical ocean circulation model, parameterised for the Bay of Biscay and forced with operational oceano-meteorological remote sensing observations, are shown. The model results have been validated with observations from drifting buoys, deployed in the Bay of Biscay during the crisis. The results show that the model explains a relatively large percentage of the current variability. The comparisons between the real and the estimated drifter trajectories indicate that for 3, 5 and 7 day-long trajectories, the drifter position is estimated with errors of approximately 23, 35 and 46km, respectively. The model reproduces relatively well the trajectory followed by the drifter with the shortest period (23 days).  相似文献   

On the reliability of long‐period response spectral ordinates from digital accelerograms     

Roberto Paolucci  Antonio Rovelli  Ezio Faccioli  Carlo Cauzzi  Daniela Finazzi  Manuela Vanini  Carola Di Alessandro  Giovanna Calderoni 《地震工程与结构动力学》2008,37(5):697-710

Using records from co‐located broadband and digital strong motion (SM) instruments, it is first shown that the displacement waveforms obtained by double integration of the accelerogram need not be free of unrealistic baseline drift to yield reliable spectral ordinates up to at least 10 s. Secondly, to provide objective criteria for selecting reliable digital SM records for ground motion predictions at long periods, a set of synthetic accelerograms contaminated by random long‐period noise has been used, and the difference between the original accelerograms and the spurious ones in terms of response spectra has been quantified, by introducing a noise index that can be easily calculated based on the velocity waveform of the record. The results of this study suggest that high‐pass filtering the digital acceleration record from a cutoff period selected to suppress baseline drifts on the displacement waveform appears to be in most cases too conservative and unduly depletes reliable information on long‐period spectral ordinates. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Effects of fish farm waste on Posidonia oceanica meadows: synthesis and provision of monitoring and management tools     

Holmer M  Argyrou M  Dalsgaard T  Danovaro R  Diaz-Almela E  Duarte CM  Frederiksen M  Grau A  Karakassis I  Marbà N  Mirto S  Pérez M  Pusceddu A  Tsapakis M 《Marine pollution bulletin》2008,56(9):1618-1629

This paper provides a synthesis of the EU project MedVeg addressing the fate of nutrients released from fish farming in the Mediterranean with particular focus on the endemic seagrass Posidonia oceanica habitat. The objectives were to identify the main drivers of seagrass decline linked to fish farming and to provide sensitive indicators of environmental change, which can be used for monitoring purposes. The sedimentation of waste particles in the farm vicinities emerges as the main driver of benthic deterioration, such as accumulation of organic matter, sediment anoxia as well as seagrass decline. The effects of fish farming on P. oceanica meadows are diverse and complex and detected through various metrics and indicators. A safety distance of 400 m is suggested for management of P. oceanica near fish farms followed by establishment of permanent seagrass plots revisited annually for monitoring the health of the meadows.  相似文献   

Validation and Verification of Tsunami Numerical Models     

C. E. Synolakis  E. N. Bernard  V. V. Titov  U. Kânoğlu  F. I. González 《Pure and Applied Geophysics》2008,165(11-12):2197-2228

In the aftermath of the 26 December, 2004 tsunami, several quantitative predictions of inundation for historic events were presented at international meetings differing substantially from the corresponding well-established paleotsunami measurements. These significant differences attracted press attention, reducing the credibility of all inundation modeling efforts. Without exception, the predictions were made using models that had not been benchmarked. Since an increasing number of nations are now developing tsunami mitigation plans, it is essential that all numerical models used in emergency planning be subjected to validation—the process of ensuring that the model accurately solves the parent equations of motion—and verification—the process of ensuring that the model represents geophysical reality. Here, we discuss analytical, laboratory, and field benchmark tests with which tsunami numerical models can be validated and verified. This is a continuous process; even proven models must be subjected to additional testing as new knowledge and data are acquired. To date, only a few existing numerical models have met current standards, and these models remain the only choice for use for real-world forecasts, whether short-term or long-term. Short-term forecasts involve data assimilation to improve forecast system robustness and this requires additional benchmarks, also discussed here. This painstaking process may appear onerous, but it is the only defensible methodology when human lives are at stake. Model standards and procedures as described here have been adopted for implementation in the U.S. tsunami forecasting system under development by the National Oceanic and Atmospheric Administration, they are being adopted by the Nuclear Regulatory Commission of the U.S. and by the appropriate subcommittees of the Intergovernmental Oceanographic Commission of UNESCO.  相似文献   

An Upper Limit to Ground Deformation in the Island of Tenerife, Canary Islands, for the Period 1997–2006     

Antonio Eff-Darwich  Olivier Grassin  José Fernández 《Pure and Applied Geophysics》2008,165(6):1049-1070

Continuous monitoring of ground deformation in the volcanic island of Tenerife, Canary Islands, is based on GPS networks, since there are as yet no tiltmeter stations installed on the island. However, there is a world-class astronomical observatory on the island, the El Teide Observatory, where four tiltmeters, two aligned in the North-South and the other two in the East-West, are monitoring the movements of the solar telescope THEMIS. THEMIS (Heliographic Telescope for the Study of Solar Magnetism and Instabilites) is among the three largest solar telescopes in the world. Since THEMIS is located a few kilometers from the main volcanic structures of the island, in particular the El Teide-Pico Viejo stratovolcano, and the precision of the inclinometers is comparable to those used in geophysical studies, we carried out the analysis of the tilt measurements for the period 1997–2006. The tiltmeters at THEMIS are placed in the seventh floor of a tower, hence their sensitivity to geological processes is reduced compared to geophysical installations. However, THEMIS measurements are the only terrestrial data available in Tenerife for such a long period of observations, which include the sustained increase in seismic activity that started in 2001. In this sense, a significant change was found in the East-West tilt of approximately 35 μ-radians between the years 2000 and 2002. Some theoretical models were calculated and it was concluded that such tilt variation could not be due to dike intrusions, nor a volcanic reactivation below the El Teide-Pico Viejo volcano. The most likely explanation comes from dislocations produced by a secondary fault associated to a major submarine fault off the eastern coast of Tenerife. In any case, taking into account the nearly permanent data recording at THEMIS, they could be considered as a complement for any ground deformation monitoring system in the island.  相似文献   

Time Evolution of Deformation Using Time Series of Differential Interferograms: Application to La Palma Island (Canary Islands)     

Patricia A. Perlock  Pablo J. González  Kristy F. Tiampo  Gema Rodríguez-Velasco  Sergey Samsonov  José Fernández 《Pure and Applied Geophysics》2008,165(8):1531-1554

Differential interferometry is a very powerful tool for detecting changes in the Earth’s crust where coherence conditions are good, but is difficult to employ in some volcanic areas due to dense vegetation. We apply two differential InSAR methods using the time series associated with the interferograms to perform a phase analysis on a data set for La Palma island (Canary Islands) from the ERS-1 and ERS-2 European Space Agency (ESA) satellites for the time period 1992 to 2000. Both methods involve choosing a master image from the database and creating a series of interferograms with respect to this image. The “Coherent Pixel Time Series” (CPTS) technique chooses pixels with good average coherence, aligns the unwrapped interferograms with a stable area and then performs an inversion to calculate the linear velocity to quantify the deformation. The Coherent Target Modeling (CTM) method calculates the temporal coherence of each pixel to identify stable targets and then determines the best velocity for each pixel by using a linear fit that maximizes the temporal coherence. Using these two methods we have been able to detect deformation on La Palma Island that has been previously undetectable by conventional InSAR methods. There is a roughly circular region on the Southern part of the island that is actively deforming at ~ −4 to −8 mm/yr. This region is located near the Teneguia valcano, the host of the last known eruption on La Palma in 1971. A thorough investigation of the possible sources for this deformation revealed that it was most likely created by a subsurface thermal source.  相似文献   

The use of taxonomic distinctness indices in assessing patterns of biodiversity in modular organisms   总被引：1，自引：0，他引：1  

Stanislao Bevilacqua  Simonetta Fraschetti  Antonio Terlizzi  & Ferdinando Boero 《Marine Ecology》2009,30(2):151-163

Estimating diversity of modular organisms may be problematic due to actual difficulties in discriminating between 'individuals' and quantifying their abundances. Quantitative data, when available, are collected through methods that could preclude the application of classical diversity indices, making comparisons among studies difficult. Taxonomic distinctness indices, such as the 'Average Taxonomic Distinctness' (Δ⁺) and the 'Variation in Taxonomic Distinctness' (Λ⁺) may represent suitable tools in investigating diversity beyond the simple species number. The potential usefulness of such indices has been explored almost exclusively on unitary organisms, neglecting modular ones. In this study, we employed Δ⁺ and Λ⁺ to analyse patterns of diversity of epiphytic hydroid assemblages living on Cystoseira seaweeds at a hierarchy of spatial scales, along 800 km of rocky coast (SE Italy). ANOVA on species richness and Λ⁺ showed no significant difference in sample diversity at the investigated spatial scales. In contrast, there were significant differences at the scale of 10s of km in Δ⁺. Analyses based on simulations detected significant variations at all spatial scales in Δ⁺. Such findings underline the potential of Δ⁺ in highlighting relevant spatial scales of variation in patterns of hydroid diversity. Our results also suggest that the interplay between natural environmental variations and the complex ecological traits of modular organisms might affect taxonomic distinctness indices. We stress the need for further investigations focusing on modular organisms before any generalizations on the use of taxonomic relatedness measures in examining marine biodiversity can be made.  相似文献