The El Salvador earthquakes of January and February 2001: context, characteristics and implications for seismic risk     

J. J. Bommer  M. B. Benito  M. Ciudad-Real  A. Lemoine  M. A. Lpez-Menjívar  R. Madariaga  J. Mankelow  P. Mndez de Hasbun  W. Murphy  M. Nieto-Lovo  C. E. Rodríguez-Pineda  H. Rosa 《Soil Dynamics and Earthquake Engineering》2002,22(5)

The small Central American republic of El Salvador has experienced, on average, one destructive earthquake per decade during the last hundred years. The latest events occurred on 13 January and 13 February 2001, with magnitudes M_w 7.7 and 6.6, respectively. The two events, which were of different tectonic origin, follow the patterns of the seismicity of the region although neither event has a known precedent in the earthquake catalogue in terms of size and location. The earthquakes caused damage to thousands of traditionally built houses and triggered hundreds of landslides, which were the main causes of fatalities. The earthquakes have clearly demonstrated trends of increasing seismic risk in El Salvador due to rapid population expansion in areas of high shaking and landslide hazard, exacerbated by deforestation and uncontrolled urbanisation. The institutional mechanisms required for the control of land use and building practice are very weak and present a major obstacle to risk mitigation.  相似文献   

New unspiked K–Ar ages of volcanic rocks of the central and western sector of the Aeolian Islands: reconstruction of the volcanic stages     

Rosanna De Rosa  Herv Guillou  Roberto Mazzuoli  Guido Ventura 《Journal of Volcanology and Geothermal Research》2003,120(3-4):161-178

A geochronological study of the Filicudi, Salina, Lipari and Vulcano Islands (Aeolian Archipelago) using the unspiked potassium–argon technique provides new age data which, combined with stratigraphic correlation, better constrain the temporal evolution of volcanism. The unspiked K–Ar age of the oldest exposed lavas on Filicudi, 219±5 ka, is significantly younger than the previous estimation of 1.02 Ma. In the general context of Aeolian volcanism, this new date suggests that the volcanism of the western sector of the Aeolian Archipelago is younger than previously thought. Geochronological data point out on the rapid transition from calc–alkaline to potassic volcanism. The distribution of the K–Ar ages within the Salina–Lipari–Vulcano group shows that the volcanism started on Lipari and propagated over time northward on Salina and southward on Vulcano. Geochronological and geophysical data suggest that the onset of volcanism in the central sector of the Aeolian Arc may be due to a mantle upwelling structure located below Lipari. A change in the style of the eruptions occurred in the Salina–Lipari–Vulcano system at about 100 ka from the present. Low-energy magmatic eruptions occurred between 188 and about 100 ka. From about 100 ka to the present, higher-energy eruptions and low-energy events due to magma–water interaction also occurred. This change in the style of activity, together with the appearance of evolved products (i.e. rhyolites) during the last 50 ka, is consistent with the formation of magmatic reservoirs located at shallower depth with respect to those of the 188–100-ka period. The new geochronological data and available petrological models reveal that a change in the deep source of the primary magmas occurred in a relatively short time interval.  相似文献   

Greenhouse Gas Emissions from Hydroelectric Reservoirs in Tropical Regions   总被引：2，自引：1，他引：2  

Luiz Pinguelli Rosa  Marco Aurelio dos Santos  Bohdan Matvienko  Ednaldo Oliveira dos Santos  Elizabeth Sikar 《Climatic change》2004,66(1-2):9-21

This paper discusses emissions by power-dams in the tropics. Greenhouse gas emissions from tropical power-dams are produced underwater through biomass decomposition by bacteria. The gases produced in these dams are mainly nitrogen, carbon dioxide and methane. A methodology was established for measuring greenhouse gases emitted by various power-dams in Brazil. Experimental measurements of gas emissions by dams were made to determine accurately their emissions of methane (CH₄) and carbon dioxide (CO₂) gases through bubbles formed on the lake bottom by decomposing organic matter, as well as rising up the lake gradient by molecular diffusion.The main source of gas in power-dams reservoirs is the bacterial decomposition (aerobic and anaerobic) of autochthonous and allochthonous organic matter that basically produces CO₂ and CH₄. The types and modes of gas production and release in the tropics are reviewed.  相似文献   

Sedimentary aspects and paleoenvironmental evolution of a rift basin: Salta Group (Cretaceous–Paleogene), northwestern Argentina     

Rosa A. Marquillas  Cecilia del Papa  Ignacio F. Sabino 《International Journal of Earth Sciences》2005,94(1):94-113

The rift history of the Salta basin is related to the evolution of the Central Andes and to the activity of the Pacific margin, owing to its geographic location. Sedimentation occurred from the Neocomian to the Paleogene, with deposits reaching up to 5,000 m in thickness. Paleoenvironmental analysis reveals an evolutionary history controlled by tectonic and climatic changes. Isolated grabens characterized the early synrift stage; differential subsidence provoked distinct environments in the southern and northern subbasins. In the southern subbasins, alluvial-fan, fluvial-fan and lacustrine deposits prevail, whilst in the northern subbasins eolian and fluvial environments dominate. During the Maastrichtian, two major factors controlled the basin fill: the decrease in tectonic subsidence and a relative sea-level rise as recorded in South America. An extensive and shallow Atlantic marine ingression installed a carbonate system coincident with mainly humid conditions until the Danian. Until the Middle Eocene, the fluvial and lacustrine environmental evolution of the sag basin was controlled especially by the alternation of temperate with dry and humid periods. Paleontological records reflect these climatic changes and show their relationship to the sedimentation regime.  相似文献   

Large‐scale poroelastic fractured reservoirs modeling using the fast multipole displacement discontinuity method          下载免费PDF全文

A. Verde  A. Ghassemi 《国际地质力学数值与分析法杂志》2016,40(6):865-886

An effective approach to modeling the geomechanical behavior of the network and its permeability variation is to use a poroelastic displacement discontinuity method (DDM). However, the approach becomes rather computationally intensive for an extensive system of cracks, particularly when considering coupled diffusion/deformation processes. This is because of additional unknowns and the need for time‐marching schemes for the numerical integration. The Fast Multipole Method (FMM) is a technique that can accelerate the solution of large fracture problems with linear complexity with the number of unknowns both in memory and CPU time. Previous works combining DDM and FMM for large‐scale problems have accounted only for elastic rocks, neglecting the fluid leak‐off from the fractures into the matrix and its influence on pore pressure and stress field. In this work we develop an efficient geomechanical model for large‐scale natural fracture networks in poroelastic reservoirs with fracture flow in response to injection and production operations. Accuracy and computational performance of the proposed method with those of conventional poroelastic DDM are compared through several case studies involving up to several tens of thousands of boundary elements. The results show the effectiveness of the FMM approach to successfully evaluate field‐scale problems for the design of exploitation strategies in unconventional geothermal and petroleum reservoirs. An example considering faults reveals the impact of reservoir compartmentalization because of sealing faults for both geomechanical and flow variables under elastic and poroelastic rocks. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Phosphorus downward movement in soil highly charged with cattle manure   总被引：1，自引：0，他引：1  

Ileana Cecilia Ciapparelli  Alicia Fabrizio de Iorio  Ana Rosa García 《Environmental Earth Sciences》2016,75(7):568

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Spatial analysis approaches for the evaluation and protection of groundwater resources in large watersheds of the Canadian Shield     

Nadeau  S.  Rosa  E.  Cloutier  V.  Mayappo  D.  Paran  F.  Graillot  D. 《Hydrogeology Journal》2021,29(6):2053-2075

This study focuses on the development of two GIS-based approaches that are used jointly to evaluate the groundwater resources associated with granular aquifers in shield environments. The first approach is a multi-criteria analysis (MCA) using an analytical hierarchic process (AHP) based on geological and hydrogeological data for ranking the probability of finding readily available groundwater resources in a specific territory. The second approach relies on GIS-based geometric calculations that were developed for evaluating the extent and volume of aquifers. The approaches are applied on a 100?×?100 m grid in a 185,000-km² area corresponding to watersheds of the James Bay area in Quebec, Canada. The MCA-AHP approach revealed that the unconfined granular aquifers that present the highest aquifer potential (AP) are sparsely distributed and mostly associated with glaciofluvial formations such as the Harricana and Sakami moraines. The geometric calculations approach allowed for estimating that the total volume of groundwater stored in the unconfined granular aquifers reaches approximately 40 km³. When used jointly, the two approaches reveal that the shallow unconfined aquifers that require increased groundwater protection account for approximately 5% of the territory. In areas of confined granular aquifers, the highest APs are located in river valleys and lowlands. A sensitivity analysis conducted on the MCA-AHP approach revealed that the grid size does not significantly affect the results. Therefore, the approach was expanded northward, to a 490,000-km² territory reaching the Ungava Bay area. The proposed method could be adapted and applied in other shield areas.

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Enzymatic activity in the rhizosphere of Spartina maritima: potential contribution for phytoremediation of metals   总被引：2，自引：0，他引：2  

Reboreda R  Caçador I 《Marine environmental research》2008,65(1):77-84

Extracellular enzymatic activity (EEA) of five enzymes (peroxidase, phenol oxidase, beta-glucosidase, beta-N-acetylglucosaminidase and acid phosphatase) was analysed in sediments colonised by Spartina maritima in two salt marshes (Rosário and Pancas) of the Tagus estuary (Portugal) with different characteristics such as sediment parameters and metal contaminant levels. Our aim was a better understanding of the influence of the halophyte on microbial activity in the rhizosphere under different site conditions, and its potential consequences for metal cycling and phytoremediation in salt marshes. Acid phosphatase and beta-N-acetylglucosaminidase presented significantly higher EEA in Rosário than in Pancas, whereas the opposite occurred for peroxidase. This was mainly attributed to differences in organic matter between the two sites. A positive correlation between root biomass and EEA of hydrolases (beta-glucosidase, beta-N-acetylglucosaminidase and acid phosphatase) was found, indicating a possible influence of the halophyte in sediment microbial function. This would potentially affect metal cycling in the rhizosphere through microbial reactions.  相似文献   

Area usage estimation and spatiotemporal variability in distribution patterns of southern right whales,Eubalaena australis,of southern Brazil          下载免费PDF全文

Eduardo Pires Renault‐Braga  Karina Rejane Groch  Paulo A. de Carvalho Flores  Eduardo R. Secchi  Luciano Dalla‐Rosa 《Marine Ecology》2018,39(3)

Southern right whales—Eubalaena australis (Desmoulins, 1822)—migrate seasonally from high‐latitude feeding grounds to coastal breeding and calving grounds at lower latitudes such as the southern coast of Brazil. Understanding how these whales are distributed along the coast is important for monitoring their postwhaling recovery and defining management strategies. In this study, we applied Kernel density estimators to aerial survey data to determine main occurrence and concentration areas of right whales in southern Brazil and investigate inter‐ and intra‐annual distribution patterns between 2003 and 2012. Our results show considerable variation in area usage within and among years, and changes in the general distribution pattern of right whales in the last years of the study. Intra‐annually, higher concentration area tended to expand from July to September and decrease in November. Some areas stood out as high‐density areas for right whales: Ribanceira/Ibiraquera, Itapirubá Sul/Sol, and from Arroio to Gaivota. Some evidences also suggest preferential areas for mother–calf pairs. The higher concentration area of right whales in southern Brazil was estimated at 52,541 km² and the occurrence area was 682.69 km², which is the whole study area. As right whale distribution in the region is likely expanding due to this population's current recovery, our study provides essential information for management plan of the Right Whale Environmental Protection Area.  相似文献   

Eight luminous early-type galaxies in nearby pairs and sparse groups. I. Stellar populations spatially analysed     

D. A. Rosa  A. C. Milone  A. C. Krabbe  I. Rodrigues 《Astrophysics and Space Science》2018,363(6):131

We present a detailed spatial analysis of stellar populations based on long-slit optical spectra in a sample of eight luminous early-type galaxies selected from nearby sparse groups and pairs, three of them may have interaction with another galaxy of similar mass. We have spatially measured luminosity-weighted averages of age, [M/H], [Fe/H], and [\(\alpha /\mbox{Fe}\)] in the sample galaxies to add empirical data relative to the influence of galaxy mass, environment, interaction, and AGN feedback in their formation and evolution. The stellar population of the individual galaxies were determined through the well-established stellar population synthesis code starlight using semi-empirical simple stellar population models. Radial variations of luminosity- weighted means of age, [M/H], [Fe/H], and [\(\alpha /\mbox{Fe}\)] were quantified up to half of the effective radius of each galaxy. We found trends between representative values of age, [M/H], [\(\alpha /\mbox{Fe}\)], and the nuclear stellar velocity dispersion. There are also relations between the metallicity/age gradients and the velocity dispersion. Contributions of 1–4 Gyr old stellar populations were quantified in IC?5328 and NGC?6758 as well as 4–8 Gyr old ones in NGC?5812. Extended gas is present in IC?5328, NGC?1052, NGC?1209, and NGC?6758, and the presence of a LINER is identified in all these galaxies. The regions up to one effective radius of all galaxies are basically dominated by \(\alpha \)-enhanced metal-rich old stellar populations likely due to rapid star formation episodes that induced efficient chemical enrichment. On average, the age and [\(\alpha /\mbox{Fe}\)] gradients are null and the [M/H] gradients are negative, although discordant cases were found. We found no correlation between the stellar population properties and the LINER presence as well as between the stellar properties and environment or gravitational interaction, suggesting that the influence of progenitor mass cannot be discarded in the formation and evolution of early-type galaxies.  相似文献