B.W. Hayward,G. Murdoch,G. Maitland: Volcanoes of Auckland—the essential guide     

Gábor Kereszturi  Javier Agustin-Flores  Jan Lindsay 《Bulletin of Volcanology》2012,74(3):783-784

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Continuation of normal doubly symmetric orbits in conservative reversible systems   总被引：1，自引：1，他引：0  

Francisco Javier Muñoz-Almaraz  Emilio Freire  Jorge Galan-Vioque  Andre Vanderbauwhede 《Celestial Mechanics and Dynamical Astronomy》2007,97(1):17-47

In this paper we introduce the concept of a quasi-submersive mapping between two finite-dimensional spaces, we obtain the main properties of such mappings, and we introduce “normality conditions” under which a particular class of so-called “constrained mappings” are quasi-submersive at their zeros. Our main application is concerned with the continuation properties of normal doubly symmetric orbits in time-reversible systems with one or more first integrals. As examples we study the continuation of the figure-eight and the supereight choreographies in the N-body problem.  相似文献   

The water balance of an Amazonian micro‐catchment: the effect of interannual variability of rainfall on hydrological behaviour     

Javier Tomasella  Martin G. Hodnett  Luz Adriana Cuartas  Antonio D. Nobre  Maarten J. Waterloo  Sylvia M. Oliveira 《水文研究》2008,22(13):2133-2147

In humid tropical systems, the large intraseasonal and interannual variability of rainfall can significantly affect all components of the water balance. This variability and the lack of detailed hydrological and meteorological data in both temporal and spatial scales have created uncertainties regarding the closure of the water balance for the Amazon basin. Previous studies in Amazonian micro‐catchments suggested that both the unsaturated and groundwater system, which are not taken into consideration in basin‐wide water budgets published in the literature, play an important role in controlling the timing of runoff generation. In this paper, the components of the water balance and the variations in different storages within the system were examined using 3 years' data from a 6·58 km² micro‐catchment in central Amazonia. The role and relative importance of the various stores were examined. The results show a strong memory effect in the groundwater system that carries over seasonal climate anomalies from one year to the next and affects the hydrological response well beyond the time span of the anomaly. In addition, the deep unsaturated zone was found to play a key role in reducing most of the intraseasonal variability and also affected the groundwater recharge. This memory effect is crucial for sustaining streamflow and evaporation in years with rainfall deficiency. The memory effect caused by storage in the groundwater and unsaturated systems may also prevent the closure of annual large‐scale water balances, which assume that storage returns to a standard state each year. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Estimation of potential pollution from mine tailings in the San Pedro River (1993–2005), Mexico–US border     

Agustín Gómez-Alvarez  Diana Meza-Figueroa  Arturo I. Villalba-Atondo  Jesús Leobardo Valenzuela-García  Jorge Ramírez-Hernández  Javier Almendariz-Tapia 《Environmental Geology》2009,57(7):1469-1479

The San Pedro River (SPR) is located in northern Sonora (Mexico) and southeastern Arizona (USA). SPR is a transboundary river that develops along the Sonora (Mexico) and Arizona (USA) border, and is considered the main source of water for a variety of users (human settlements, agriculture, livestock, and industry). The SPR originates in the historic Cananea mining area, which hosts some of the most important copper mineralizations in Mexico. Acid mine drainage derived from mine tailings is currently reaching a tributary of the SPR near Cananea City, resulting in the contamination of the SPR with heavy metals and sulfates in water and sediments. This study documents the accumulation and distribution of heavy metals in surface water along a segment of the SPR from 1993 to 2005. Total concentrations of Cd, Cu, Fe, Mn, Pb, and Zn in surface waters are above maximum permissible levels in sampling sites near mine tailing deposits. Nevertheless, a significant decrease in the Fe and SO₄ ²⁻ in surface water (SO₄ ²⁻: 7,180–460.39 mg/L; Fe: 1,600–9.51 mg/L) as well as a gradual decrease in the heavy and transition metal content were observed during the period from 1994 to 2005. Approximately 2.3 km downstream of the mine tailings, the heavy metal content of the water drops quickly following an increase in pH values due to the discharging of wastewater into the river. The attenuation of the heavy metal content in surface waters is related to stream sediment precipitation (accompanied by metal coprecipitation and sorption) and water dilution. Determining the heavy metal concentration led to the conclusion that the Cananea mining area and the San Pedro River are ecosystems that are impacted by the mining industry and by untreated wastewater discharges arising from the city of Cananea (Sonora, Mexico).  相似文献   

Analysis of groundwater mining in two carbonate aquifers in Sierra de Estepa (SE Spain) based on hydrodynamic and hydrochemical data     

Sergio Martos-Rosillo  Miguel Rodríguez-Rodríguez  Francisco Moral  José Javier Cruz-Sanjulián  Juan Carlos Rubio 《Hydrogeology Journal》2009,17(7):1617-1627

The carbonate aquifers of Lora and Mingo form part of the hydrogeological unit of Sierra de Estepa (SE Spain). By means of time series analysis and a 1D numerical groundwater model, groundwater exploitation was quantified and the mean annual recharge in both systems was estimated (2001–2004). During this period, the Lora and Mingo aquifers received an average groundwater recharge of 0.29 × 10⁶ m³/year and 0.14 × 10⁶ m³/year, respectively, whereas an average of 0.34 × 10⁶ m³/year and 0.21 × 10⁶ m³/year, respectively, was extracted. These conditions led to a conspicuous lowering of the water table in both systems. In addition, the analysis of the evolution of the main hydrogeochemical parameters of the groundwater showed that the increased pumping rates produced an increase in total dissolved solids, and chloride and sodium ions in both aquifers. In the case of the Lora aquifer, the only ion that presented decreased levels was nitrate. The results show that groundwater pumping in both aquifers should not exceed the mean annual recharge of 0.29 × 10⁶ m³/year and 0.14 × 10⁶ m³/year in the Lora and Mingo aquifers, respectively. Nevertheless, it would be advisable to reduce pumping rates to below these values in order to restore piezometric levels and improve groundwater quality for different uses in the future.  相似文献   

Relics of eclogite facies assemblages in the Ceará Central Domain, NW Borborema Province, NE Brazil: Implications for the assembly of West Gondwana   总被引：1，自引：0，他引：1  

Ticiano J. Saraiva dos Santos  Maria da Glria M. Garcia  Wagner Silva Amaral  Renauld Caby  Eberhard Wernick  Michel H. Arthaud  Elton L. Dantas  M. Santosh 《Gondwana Research》2009,15(3-4):454-470

The Borborema Province, in the NE of Brazil, is a rather complex piece in the Brazil–Africa puzzle as it represents the junction of the Dahomeyide/Pharusian, Central African, Araçuai and Brasilia fold belts located between the West-African/São Luis, Congo/São Francisco and Amazonas craton. The correlation between the Dahomeyides from W-Africa (Ghana, Benin, Togo, and Mali) and the Borborema Province involves the Médio Coreaú and Central Ceará domains. The inferred continuation of the main oceanic suture zone exposed in the Dahomeyides of W Africa is buried beneath the Phanerozoic Parnaíba Basin in Brazil (northwest of the Médio Coreaú domain) where some high density gravity anomalies may represent hidden remnants of an oceanic suture. In addition to this major suture a narrow, nearly continuous strip composed of mainly mafic pods containing relics of eclogite-facies assemblages associated with partially migmatized granulite-facies metapelitic gneisses has been found further east in the NW Borborema Province. These high pressure mafic rocks, interpreted as retrograded eclogites, are located between the Transbrasiliano Lineament and the Santa Quitéria continental arc and comprise primitive to evolved arc-related rocks with either arc- or MORB-type imprints that can indicate either deep subduction of oceanic lithosphere or roots of continental and oceanic magmatic arcs. Average peak P–T conditions under eclogite-facies metamorphism (T = 770 °C and P = 17.3 kbar) were estimated using garnet–clinopyroxene thermometry and Jd content in clinopyroxene. Transition to granulite-facies conditions, as well as later widespread re-equilibration under amphibolite facies, were registered both in the basic and the metapelitic rocks and suggest a clockwise P–T path characterized by an increase in temperature followed by strong decompression. A phenomenon possibly related to the exhumation of a highly thickened crust associated with the suturing of the Médio Coreaú and Central Ceará domains, two distinct crustal blocks separated by the Transbrasiliano Lineament.  相似文献   

Recent deformation at the junction between the North Luzon block and the Central Philippines from ERS-1 Images   总被引：2，自引：0，他引：2  

M. Pubellier  F. Garcia  A. Loevenbruck and  J. Chorowicz 《Island Arc》2000,9(4):598-610

Abstract The transfer of the major part of the motion between the Philippine Sea Plate and the Sunda block is accommodated along a north-west shear wide zone partly on the Philippine Fault and partly on the Sibuyan Verde Passage Fault (SVPF) as indicated by global positioning satellite and geological data. Given the limited motion along the SVPF and the important motion along the Philippine Fault, as well as the necessity of a connection between these faults and the southern Manila Trench, a transtensional motion along the northeast-southwest Macolod Corridor (MC) may be predicted. We used synthetic aperture radar European remote sensing (SAR ERS-1) images to analyze the volcano– tectonic features of this area, because these images are sensitive to minute textural or topographic contrasts resulting from small effects of recent deformation. In addition, they allow us to determine accurately the shape of the base of volcanic edifices and to detect linear clusters of very small adjacent cones. The results presented herein allow us to extend the features recognized earlier to a larger MC. Large faults actually connect the Philippine Fault to the Sibuyan Verde Passage Fault all across the Taal Volcanic Field. In addition to extension along north-east faults, we identify an important component of left-lateral strike–slip underlined by fault scarps, dykes, alignments of volcanoes and pull-apart basins, accompanied by extension along north-south faults. A relative chronology of the fractures and volcanic edifices is proposed. When compared to the existing ages of the volcanics, an evolution scheme of the area may be proposed, according to which extension shifted from a nearly north-south opening between 5 and 2 million years to a direction close to east-west at Present. The early north-south extension existed in the Marinduque Basin and may have migrated northward and rotated to the present MC.  相似文献   

The role of benthic macrophytes and their associated macroinvertebrate community in coastal lagoon resistance to eutrophication     

Javier Lloret  Arnaldo Marín 《Marine pollution bulletin》2009,58(12):1827-1834

Eutrophication is widely recognised as one of the major menaces to coastal environments, particularly enclosed bays and lagoons. Although there is a general understanding of the consequences of eutrophication in these systems, there is a lack of sufficient knowledge concerning biotic feedbacks that influence eutrophication patterns and the resistance capacity of coastal environments.In this paper, the isotope ratios of main producers and consumers of a Mediterranean lagoon were examined in order to elucidate the fate of anthropogenic inputs from the main watercourse flowing into the lagoon.The results of the study of stable isotope data in the Mar Menor lagoon reflected that the whole benthic community plays an important role as a natural ‘filter’ that removes excess nutrients from the water column and stores them in the sediments, thereby enhancing lagoon resistance to eutrophication.  相似文献   

Seismic tomography of Central São Miguel, Azores     

Daria Zandomeneghi  Javier Almendros  Jesús M. Ibez  Gilberto Saccorotti 《Physics of the Earth and Planetary Interiors》2008,167(1-2):8-18

We determine the three-dimensional distribution of P- and S-wave velocities for Central São Miguel Island (Azores, Portugal) by tomographic inversion of local earthquake arrival times. We use P- and S-phases from 289 earthquakes recorded by a network of 20 seismometers. The model shows good resolution in the shallowest 5–6 km, as illustrated by different resolution tests. There are several velocity anomalies, interpreted as pyroclastic deposits, intrusive bodies, geothermal fields, and the effects of tectonics. A low Vp zone marks Furnas caldera, probably evidencing volcaniclastic sediments with development of intense geothermal activity. Another low Vp zone extends in correspondence of the highly fractured area between Fogo and the north coast. Conversely, strong positive anomalies are found south of Fogo and northwest of Furnas. They are interpreted in terms of high-density deposits and remnants of a plutonic intrusion. These interpretations are supported by the distribution of Vp/Vs, and are consistent with previous geological, geochemical, and geophysical data.  相似文献   

Sea Storms in the Adriatic Sea and the Western Mediterranean during the Last Millennium     

Dario Camuffo  Caterina Secco  Peter Brimblecombe  Javier Martin-Vide 《Climatic change》2000,46(1-2):209-223

Data regarding the frequency andoccurrence of sea storms in the Adriatic Sea and theWestern Mediterranean during the last millennium havebeen extracted from historical written sources. TheAdriatic Sea shows two anomalous periods of high stormfrequency: the first half of the 1500s and the secondhalf of the 1700s. In the 1500s the storms were morefrequent in autumn, while in the late 1700s theyoccurred at high frequency in winter. In the WesternMediterranean, storms had a higher frequency in thefirst half of the 1600s, with two lesser periods ofhigh frequency in the 1400s and at the end of the1700s. Although both records show a maximum frequencyof sea storms during the Spörer Minimum(1416–1534) of solar activity, sunspot series yieldno, or poor, correlation during the other periods oflowest activity, i.e., Oort Minimum (1010–1090), WolfMinimum (1282–1342), and Maunder Minimum (1645–1715),suggesting that a teleconnection between sea stormsand sunspots is improbable or masked in this region.No teleconnection was found either between the ElNiño-Southern Oscillation (ENSO) and surgesflooding Venice or the Western Mediterranean storms orbetween Venice surges and the Northern AtlanticOscillation (NAO).  相似文献