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101.
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103.
José Angel Docobo Josep Maria Trigo-Rodríguez Jiri Borovicka Vakhtang S. Tamazian Vera Assis Fernandes Jordi Llorca 《Earth, Moon, and Planets》2008,102(1-4):537-542
A daylight bolide was observed over Galicia (NW Spain) and Minho (N. Portugal) on March 1, 2005 at 15 h10 min ± 3 min UTC.
We interviewed 23 eyewitnesses of the event in order to obtain the azimuth, altitude, and slope of the fireball’s trajectory.
Reports suggest an atmospheric ending height below 20 km, indicating that meteorite survival was likely. From the reconstructed
trajectory and the fireball’s duration, we obtained the approximate heliocentric orbits for the meteoroid. Assuming an entry
velocity higher than 20 km s−1 which is consistent with its estimated duration, the meteoroid originated in the asteroid belt. 相似文献
104.
Yunlong Liu Cai Liu Lei Qiu Vera Schlindwein Haijiang Zhang 《Marine Georesources & Geotechnology》2013,31(2):201-211
ABSTRACTIn this paper, we describe the results of a first pilot experiment of passive seismic monitoring near the active Longqi hydrothermal vent at the Southwest Indian Ridge during Chinese cruise DY115-30. During 102-day experiment, we recorded over 2,000 seismic events on a single ocean bottom seismometer with hydrophone close to the hydrothermal field. We classified these events into the following three classes based on their time–frequency characteristics: (1) volcano tectonic microearthquakes (VTMs); (2) regional earthquakes; (3) short-duration events (SDEs). We preliminarily located the 1,277 VTMs using a single-station location method. Our results revealed hypocenters primarily beneath the axial valley ridge which is about 10?km away from hydrothermal vent and extending to the upper mantle at a depth of 15?km. Two discrete swarms of VTMs occurred during our survey period. The SDEs show a complex frequency characteristics ascribed to clusters of monochromatic waves around different frequencies. This suggests that SDEs result from combination of harmonic waves resonating in fluid-filled pipes and cracks. 相似文献
105.
Sara Auer Ilya Bindeman Paul Wallace Vera Ponomareva Maxim Portnyagin 《Contributions to Mineralogy and Petrology》2009,157(2):209-230
Klyuchevskoy volcano, in Kamchatka’s subduction zone, is one of the most active arc volcanoes in the world and contains some
of the highest δ18O values for olivines and basalts. We present an oxygen isotope and melt inclusion study of olivine phenocrysts in conjunction
with major and trace element analyses of 14C- and tephrochronologically-dated tephra layers and lavas spanning the eruptive history of Klyuchevskoy. Whole-rock and groundmass
analyses of tephra layers and lava samples demonstrate that both high-Mg (7–12.5 wt% MgO) and high-Al (17–19 wt% Al2O3, 3–6.5 wt% MgO) basalt and basaltic andesite erupted coevally from the central vent and flank cones. Individual and bulk
olivine δ18O range from normal MORB values of 5.1‰ to values as high as 7.6‰. Likewise, tephra and lava matrix glass have high-δ18O values of 5.8–8.1‰. High-Al basalts dominate volumetrically in Klyuchevskoy’s volcanic record and are mostly high in δ18O. High-δ18O olivines and more normal-δ18O olivines occur in both high-Mg and high-Al samples. Most olivines in either high-Al or high-Mg basalts are not in oxygen
isotopic equilibrium with their host glasses, and Δ18Oolivine–glass values are out of equilibrium by up to 1.5‰. Olivines are also out of Fe–Mg equilibrium with the host glasses, but to a lesser
extent. Water concentrations in olivine-hosted melt inclusions from five tephra samples range from 0.4 to 7.1 wt%. Melt inclusion
CO2 concentrations vary from below detection (<50 ppm) to 1,900 ppm. These values indicate depths of crystallization up to ~17
km (5 kbar). The variable H2O and CO2 concentrations likely reflect crystallization of olivine and entrapment of inclusions in ascending and degassing magma. Oxygen
isotope and Fe–Mg disequilibria together with melt inclusion data indicate that olivine was mixed and recycled between high-Al
and high-Mg basaltic melts and cumulates, and Fe–Mg and δ18O re-equilibration processes were incomplete. Major and trace elements in the variably high-δ18O olivines suggest a peridotite source for the parental magmas. Voluminous, highest in the world with respect to δ18O, and hydrous basic volcanism in Klyuchevskoy and other Central Kamchatka depression volcanoes is explained by a model in
which the ascending primitive melts that resulted from the hydrous melt fluxing of mantle wedge peridotite, interacted with
the shallow high-δ18O lithospheric mantle that had been extensively hydrated during earlier times when it was part of the Kamchatka forearc. Following
accretion of the Eastern Peninsula terrains several million years ago, a trench jump eastward caused the old forearc mantle
to be beneath the presently active arc. Variable interaction of ascending flux-melting-derived melts with this older, high-δ18O lithospheric mantle has produced mafic parental magmas with a spectrum of δ18O values. Differentiation of the higher δ18O parental magmas has created the volumetrically dominant high-Al basalt series. Both basalt types incessantly rise and mix
between themselves and with variable in δ18O cumulates within dynamic Klyuchevskoy magma plumbing system, causing biannual eruptions and heterogeneous magma products.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
106.
A. E. Rosenbush 《Astrophysics》1999,42(2):140-148
The separation of novae into groups, proposed in Part 1 of this paper, is discussed: it is based on the criterion of the shape
of the light curve, plotted on “outburst amplitude-logarithm of shell radius ” scales. The observational characteristics of
novae belonging to certain groups are considered. Novae of the GQ Mus group may be characterized by x ray emission. The proposed
separation of novae into groups may be related to the structure of the shell ejected in the outburst. Novae with smooth light
curves have ellipsoidal shells without pronounced nonuniformities. Novae with temporary fading or with brightness fluctuations
in the transitional stage of the outburst have ellipsoidal shells with a nonuniform distribution of matter (equatorial and
tropical belts in novae of the DQ Her group, an equatorial belt for the RR Pic group, and a patchy structure for the CP Pup
group). Relationships among certain parameters of novae are considered: absolute stellar magnitude, outburst amplitude, shell
expansion velocity, etc. From the “depth of temporary fading in the transitional stage of the outburst-shell expansion velocity”
dependence it can be concluded that the kinetic energy of the shell may be a constant for novae of the DQ Her group.
Translated from Astrofizika, Vol. 42, No. 2, pp. 189–202, April–June, 1999. 相似文献
107.
We present results of polarimetric observations of the Galilean satellites Io, Europa, Ganymede, and Callisto at phase angles ranging from 0.19° to 2.22°. The observations in the UBVR filters were performed using a one-channel photoelectric polarimeter attached to 70-cm telescope of the Chuguev Observation Station (Ukraine) on November 19-December 7, 2000. We have observed the polarization opposition effect for Io, Europa, and Ganymede to be a sharp secondary spike of negative polarization with an amplitude of about −0.4% centered at phase angles of 0.2°-0.7° and superimposed on the regular negative polarization branch. Although these minima for Io, Europa, and Ganymede show many similarities, they also exhibit a number of distinctions. The polarization opposition effect appears to be wavelength-dependent, at least for Europa and Ganymede. No polarization opposition effect was found for Callisto. The results obtained are discussed within the framework of different mechanisms of light scattering. 相似文献
108.
Jean-Christophe Pouget David Proaño Andrea Vera Marcos Villacís Thomas Condom Marisa Escobar 《水文科学杂志》2017,62(3):431-446
La forte croissance socio-économique de Quito a conduit à d’importants projets de transferts interbassins, intensifiant la mobilisation des ressources d’altitude situées dans des zones écologiques sensibles et connaissant une fonte accélérée des glaciers. Afin d’étudier divers scénarios d’évolutions, nous proposons une modélisation du continuum climat/glacier/hydrologie/gestion des ressources en eau. Utilisant l’outil Water Evaluation and Planning (WEAP), nous avons développé : (1) une modélisation hydro-climatologique semi-distribuée avec des données mensuelles homogénéisées par vectorisation régionale ; (2) une modélisation de la production en eau des glaciers et de leur évolution interannuelle ; (3) une modélisation en unités hydrologiques distinguant différentes couvertures de sols ; et (4) une modélisation de la gestion distinguant droits, allocation et usages de l’eau. Nous présentons les résultats du calage hydrologique mensuel (1963–2006), en étudiant particulièrement l’équifinalité de diverses paramétrisations. Nous montrons la souplesse, la robustesse et les limites de la modélisation proposée, contribuant à cerner différentes incertitudes dans l’évaluation de scénarios prospectifs. 相似文献
109.
Large-eddy simulations of an evolving cloud field are used to investigate the contribution of microphysical processes to the evolution of the variance of total water and liquid water potential temperature in the boundary layer. While the first hours of such simulations show a transient behaviour and have to be analyzed with caution, the final portion of the simulation provides a quasi-equilibrium situation. This allows investigation of the budgets of the variances of total water and liquid water potential temperature and quantification of the contribution of several source and sink terms. Accretion is found to act as a strong sink for the variances, while the contributions from the processes of evaporation and autoconversion are small. A simple parametrization for the sink term connected to accretion is suggested and tested with a different set of simulations. 相似文献
110.