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91.
Pierre Kaufmann Gérard Trottet C. Guillermo Giménez de Castro Jean-Pierre Raulin Säm Krucker Albert Y. Shih Hugo Levato 《Solar physics》2009,255(1):131-142
The presence of a solar burst spectral component with flux density increasing with frequency in the sub-terahertz range, spectrally
separated from the well-known microwave spectral component, bring new possibilities to explore the flaring physical processes,
both observational and theoretical. The solar event of 6 December 2006, starting at about 18:30 UT, exhibited a particularly
well-defined double spectral structure, with the sub-THz spectral component detected at 212 and 405 GHz by the Solar Submilimeter
Telescope (SST) and microwaves (1 – 18 GHz) observed by the Owens Valley Solar Array (OVSA). Emissions obtained by instruments
onboard satellites are discussed with emphasis to ultra-violet (UV) obtained by the Transition Region And Coronal Explorer
(TRACE), soft X-rays from the Geostationary Operational Environmental Satellites (GOES) and X- and γ-rays from the Ramaty High Energy Solar Spectroscopic Imager (RHESSI). The sub-THz impulsive component had its closer temporal
counterparts only in the higher energy X- and γ-rays ranges. The spatial positions of the centers of emission at 212 GHz for the first flux enhancement were clearly displaced
by more than one arc-minute from positions at the following phases. The observed sub-THz fluxes and burst source plasma parameters
were difficult to be reconciled with a purely thermal emission component. We discuss possible mechanisms to explain the double
spectral components at microwaves and in the THz ranges. 相似文献
92.
Patricia Bernárdez Ricardo Prego Santiago Giralt Jaume Esteve Miguel Caetano Santiago Parra Guillermo Francés 《Marine Geology》2012
A multidisciplinary study of the elemental geochemistry and mineralogical characteristics of the marine surficial sediment in the Northern Rias (NW Iberian Peninsula) has been carried out. The linkages between the marine sediment composition and their potential sources were examined.The influence of the river-borne sediments is only detected in the innermost part of the three Rias. Regional variations of the mineral assemblages are governed by the source-rock composition of the different geological complexes and the relative source-rock contribution controlled by the continental hydrology. Mineralogical composition of the Ortigueira Ria and adjacent shelf surficial sediments are mainly made up of mafic and ultramafic rocks of the Cape Ortegal complex indicated by the high content of Mg, Mn and chrysotile and riebeckite minerals. In areas nearby Ortegal complex the imprint of heavy minerals present in the surrounding rocks has also been recorded. Barqueiro and Viveiro Rias bed-sediments are influenced by granitic and metamorphic rocks from the Ollo de Sapo complex as revealed by the high contribution of muscovite and quartz.Mining activities in the continental domain left strong imprints on marine surficial sediments. Pyrite content is high in the innermost areas of the Ortigueira Ria since this mineral is exploited in the Mera River basin, whereas high muscovite percentages characterize the Viveiro Ria owing to the abundance of granitic rocks and its exploitation in the Landro River basin. Quartz content is high nearby Cape Estaca de Bares, induced by the presence of an important excavation of this material. 相似文献
93.
William L. Bandy Franois Michaud Jacques Bourgois Thierry Calmus Jrme Dyment Carlos A. Mortera-Gutirrez Jose Ortega-Ramírez Bernard Pontoise Jean-Yves Royer Bertrand Sichler Marc Sosson Mario Rebolledo-Vieyra Florence Bigot-Cormier Oscar Díaz-Molina Angel D. Hurtado-Artunduaga Guillermo Pardo-Castro Corrine Trouillard-Perrot 《Tectonophysics》2005,398(3-4):115-140
The direction of convergence between the Rivera and North American plates becomes progressively more oblique (in a counter-clockwise sense as measured relative to the trench-normal direction) northwestward along the Jalisco subduction zone. By analogy to other subduction zones, the forces resulting from this distribution of convergence directions are expected to produce a NW moving, fore-arc sliver and a NW–SE stretching of the fore-arc area. Also, a series of roughly arc parallel strike-slip faults may form in the fore-arc area, both onshore and offshore, as is observed in the Aleutian arc.In the Jalisco subduction zone, the Jalisco block has been proposed to represent such a fore-arc sliver. However, this proposal has encountered one major problem. Namely, right-lateral strike-slip faulting within the fore-arc sliver, and between the fore-arc sliver and the North American plate, should be observed. However, evidence for the expected right-lateral strike-slip faulting is sparse. Some evidence for right-lateral strike-slip faulting along the Jalisco block–North American plate boundary (the Tepic–Zacoalco rift system) has been reported, although some disagreement exists. Right-lateral strike-slip faulting has also been reported within the interior of the Jalisco block and in the southern Colima rift, which forms the SE boundary of the Jalisco block.Threefold, multi-channel seismic reflection data were collected in the offshore area of the Jalisco subduction zone off Manzanillo in April 2002 during the FAMEX campaign of the N/O L'Atalante. These data provide additional evidence for recent strike-slip motion within the fore-arc region of the Jalisco subduction zone. This faulting offsets right-laterally a prominent horst block within the southern Colima rift, from which we conclude that the sense of motion along the faulting is dextral. These data also provide additional evidence for recent subsidence within the area offshore of Manzanillo, as has been proposed. 相似文献
94.
Ajoy Kumar Peter Minnett Guillermo Podestá Robert Evans Katherine Kilpatrick 《Journal of Earth System Science》2000,109(4):395-405
As part of the Pathfinder program developed jointly by National Aeronautics and Space Administration (NASA) and National Oceanic
and Atmospheric Administration (NOAA) a large database ofin situ sea surface temperature (SST) measurements coincident with satellite data is now available to the user community. The Pathfinder
Matchup Database (PMDB) is a multi-year, multi-satellite collection of coincident measurements from the Advanced Very High
Resolution Radiometer (AVHRR) and broadly distributed buoy data (matchups). This database allows the user community to test
and validate new SST algorithms to improve the present accuracy of surface temperature measurements from satellites. In this
paper we investigate the performance of a global Pathfinder algorithm to specific regional conditions. It is shown that for
zenith angles less than 45°, the best-expected statistical discrepancy between satellite and buoy data is about ∼ 0.5 K. In
general, the bias of the residuals (satellite — buoy) is negative in most regions, except in the North Atlantic and adjacent
seas, where the residuals are always positive. A seasonal signal in SST residuals is observed in all regions and is strongest
in the Indian Ocean. The channel-difference term used as a proxy for atmospheric water vapor correction is observed to be
unresponsive for columnar water vapor values greater than 45 mm and high zenith angles. This unresponsiveness of the channels
leads to underestimation of sea surface temperature from satellites in these conditions. 相似文献
95.
Sergey A. Silich & Guillermo Tenorio-Tagle 《Monthly notices of the Royal Astronomical Society》1998,299(1):249-266
Two-dimensional calculations of the evolution of remnants generated by the strong mechanical energy deposited by stellar clusters in dwarf galaxies ( M ∼ 109 –1010 M⊙) are presented. The evolution is followed for times longer than both the blowout time and the presumed span of energy injection generated by a coeval massive stellar cluster. The remnants are shown to end up wrapping around the central region of the host galaxy, while growing to kiloparsec-scale dimensions. Properties of the remnants such as luminosity, size, swept-up mass and expansion speed are given as functions of time for all calculated cases. The final fate of the swept-up galactic gas and of the matter processed by the central starburst is shown to be highly dependent on the properties of the low-density galactic halo. Superbubbles powered by star clusters, with properties similar to those inferred from the observations, slow down in the presence of an extended halo to expansion speeds smaller than the host galaxy escape velocity. Values of the critical luminosity required for the superbubbles to reach the edge of the galaxies with a speed comparable to the escape speed are derived analytically and numerically. The critical luminosities are larger than those in the detected sources, and thus the superbubbles in amorphous dwarf galaxies must have already undergone blowout and are presently evolving into an extended low-density halo. This will inhibit the loss of the swept-up and processed matter from the galaxy. 相似文献
96.
Léon Dejonghe Benoît Darras Guillermo Hughes Philippe Muchez James S. Scoates Dominique Weis 《Mineralium Deposita》2002,37(2):158-172
The lead isotope compositions of galena and the fluid-inclusion systematics of nine barite-bearing polymetallic (Au, Ag, Pb, Zn) deposits of the central Argentinian Patagonia (Chubut and Rio Negro provinces) have been investigated to constrain the compositions and sources of the mineralizing fluids. Most of the deposits occur as veins, with less common wall-rock disseminations and/or stockworks, and are low-sulfidation epithermal deposits hosted in Jurassic volcanic rocks. Fluid-inclusion homogenization temperatures (Th) from quartz and sphalerite from the deposits fall within the range of 100-300 °C, with the highest measured average temperatures for the most eastern deposits (Mina Angela - 298 °C; Cañadón Bagual - 343 °C). The salinities of the hydrothermal fluids at all deposits were low to moderate (⢪.4 equiv. wt% NaCl). Three groups of ore deposits can be defined on the basis of 206Pb/204Pb ratios for galena and these show a general decrease from west to east (from 18.506 to 18.000). The central Argentinian Patagonia deposits have distinctly less radiogenic lead isotope compositions than similar deposits from Peru and Chile, except for the porphyry copper deposits of central and southern Peru. Galena from the Mina Angela deposit is characterized by very low radiogenic lead isotope compositions (18.000<206Pb/204Pb<18.037 and 38.03<208Pb/204Pb<38.09) and reflects interaction with Precambrian basement. The geographic trend in lead isotope compositions of both galena and whole rocks indicates a crustal contribution which increases eastwards, also reflected in the strontium-neodymium isotope systematics of the host lavas. Finally, due to the lack of precise age determinations for the central Patagonian polymetallic deposits, a potential link with Andean porphyry copper systems remains an open question. 相似文献
97.
J.L. Macías L. Capra J.L. Arce J.M. Espíndola A. García-Palomo M.F. Sheridan 《Journal of Volcanology and Geothermal Research》2008
El Chichón volcano consists of a 2-km wide Somma crater compound cone 0.2 Ma old with peripheral domes with a central crater reactivated several times during the Holocene. The most recent eruption at El Chichón occurred from March 28 to April 4, 1982, resulting in the worst volcanic disaster during historical times in Mexico, killing more than 2000 people and destroying nine towns and small communities. The volcanic hazard map of El Chichón is based on detailed field work that documented twelve eruptions during the last 8000 years, and computer simulations. To validate the results, computer simulations were first performed over pre-1982 topography mimicking the extent of the actual deposits produced and afterwards run over post-1982 topography. These eruptions have produced pyroclastic fall, surge, flow and lahar deposits. Pyroclastic flows have different volumes and Heim coefficients varying from 0.2 (pumice flows), to 0.15 (block-and-ash flows) and 0.10 (ash flows). Simulations using FLOW3D and TITAN2D indicate that pumice flows and block-and-ash flows can fill the moat area and follow main ravines up to distances of ca. 3 km from the crater, with no effect on populations around the volcano. On the other hand, more mobile ash flows related to column-collapse events can reach up to 4 km from the vent, but will always follow the same paths and still not affect surrounding populations. The energy-cone model was used to simulate the outflow of pyroclastic surges based on the 1982 event (H/L = 0.1 and 0.2), and shows that surges may reach some towns around the volcano. 相似文献
98.
99.
Miguel Esteban Jeremy Bricker Ricardo San Carlos Arce Hiroshi Takagi NamYi Yun Warathida Chaiyapa Alexander Sjoegren Tomoya Shibayama 《Natural Hazards》2018,93(3):1507-1528
Awareness about the threats posed by different types of coastal disasters has increased throughout the world, as people are exposed to the nature of these hazards through media reports on events in distant countries. This has resulted in coastal residents being aware about the destructive power of tsunamis, despite no such events having taken place in their country in recent times. Regardless of this increased awareness, it has been hypothesized that there is still need for local governments to enact adequate policies to raise the awareness of local residents, for example, by holding regular evacuation drills. The present research presents a comparative assessment of tsunami awareness in two tourist destinations in Japan and the USA, which was derived through structured questionnaire surveys of beach users in the city of Kamakura and various coastal cities in Florida. The results show how despite relatively high level of awareness tsunamis still pose a considerable risk to each of the communities, for example, due to shortcoming in evacuation knowledge and infrastructure. 相似文献
100.
Guillermo A. González Jerson I. Reina 《Monthly notices of the Royal Astronomical Society》2006,371(4):1873-1876
An infinite family of axially symmetric thin discs of finite radius is presented. The family of discs is obtained by means of a method developed by Hunter and contains, as its first member, the Kalnajs disc. The surface densities of the discs present a maximum at the centre of the disc and then decrease smoothly to zero at the edge, in such a way that the mass distribution of the higher members of the family is more concentrated at the centre. The first member of the family has a circular velocity proportional to the radius, thus representing a uniformly rotating disc. On the other hand, the circular velocities of the other members of the family increase from a value of zero at the centre of the discs to a maximum and then decrease smoothly to a finite value at the edge of the discs, in such a way that, for the higher members of the family, the maximum value of the circular velocity is attained nearest the centre of the discs. 相似文献