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61.
Holger Frey Christian Huggel Yves Bühler Daniel Buis Maria Dulce Burga Walter Choquevilca Felipe Fernandez Javier García Hernández Claudia Giráldez Edwin Loarte Paul Masias Cesar Portocarrero Luis Vicuña Marco Walser 《Landslides》2016,13(6):1493-1507
The town of Santa Teresa (Cusco Region, Peru) has been affected by several large debris-flow events in the recent past, which destroyed parts of the town and resulted in a resettlement of the municipality. Here, we present a risk analysis and a risk management strategy for debris-flows and glacier lake outbursts in the Sacsara catchment. Data scarcity and limited understanding of both physical and social processes impede a full quantitative risk assessment. Therefore, a bottom-up approach is chosen in order to establish an integrated risk management strategy that is robust against uncertainties in the risk analysis. With the Rapid Mass Movement Simulation (RAMMS) model, a reconstruction of a major event from 1998 in the Sacsara catchment is calculated, including a sensitivity analysis for various model parameters. Based on the simulation results, potential future debris-flows scenarios of different magnitudes, including outbursts of two glacier lakes, are modeled for assessing the hazard. For the local communities in the catchment, the hazard assessment is complemented by the analysis of high-resolution satellite imagery and fieldwork. Physical, social, economic, and institutional vulnerability are considered for the vulnerability assessment, and risk is eventually evaluated by crossing the local hazard maps with the vulnerability. Based on this risk analysis, a risk management strategy is developed, consisting of three complementing elements: (i) standardized risk sheets for the communities; (ii) activities with the local population and authorities to increase social and institutional preparedness; and (iii) a simple Early Warning System. By combining scientific, technical, and social aspects, this work is an example of a framework for an integrated risk management strategy in a data scarce, remote mountain catchment in a developing country. 相似文献
62.
Monica Previati Marco Palma Giorgio Bavestrello Carla Falugi Carlo Cerrano 《Marine Ecology》2010,31(4):555-565
Despite the wide distribution of zoanthids, little is known about their pattern of reproduction. Here we investigate the reproductive biology of two Mediterranean species, the common Parazoanthus axinellae (Schmidt) and the rare Savalia savaglia (Bertoloni). For both species, samples were collected during an annual cycle, from January to December 2005, in the Western Mediterranean (Ligurian Sea, Italy). Both species are gonochoric. In P. axinellae the sex‐ratio (n colonies = 30) showed a slight predominance of male colonies (M/F = 1.35), whereas in the population of S. savaglia (n colonies = 15) a predominance of females was found (M/F = 0.3). In P. axinellae the first gametocytes were visible in March, whereas in S. savaglia they became visible in May. Both species reproduce at the end of autumn when seawater temperature begins to decrease. Parazoanthus axinellae (10 m depth) spawns eggs and sperms in November, whereas S. savaglia (67 m depth) spawns in December. In P. axinellae sexes were segregated on a rocky wall, with males occurring deeper, whereas male and female colonies of S. savaglia were irregularly dispersed in the population. The maximum number of oocytes differed between the species, being higher in P. axinellae than in S. savaglia. 相似文献
63.
The Doppler orbitography and radiopositioning integrated by satellite (DORIS) system was originally developed for precise orbit determination of low Earth orbiting (LEO) satellites. Beyond that, it is highly qualified for modeling the distribution of electrons within the Earth’s ionosphere. It measures with two frequencies in L-band with a relative frequency ratio close to 5. Since the terrestrial ground beacons are distributed quite homogeneously and several LEOs are equipped with modern receivers, a good applicability for global vertical total electron content (VTEC) modeling can be expected. This paper investigates the capability of DORIS dual-frequency phase observations for deriving VTEC and the contribution of these data to global VTEC modeling. The DORIS preprocessing is performed similar to commonly used global navigation satellite systems (GNSS) preprocessing. However, the absolute DORIS VTEC level is taken from global ionospheric maps (GIM) provided by the International GNSS Service (IGS) as the DORIS data contain no absolute information. DORIS-derived VTEC values show good consistency with IGS GIMs with a RMS between 2 and 3 total electron content units (TECU) depending on solar activity which can be reduced to less than 2 TECU when using only observations with elevation angles higher than \(50^\circ \) . The combination of DORIS VTEC with data from other space-geodetic measurement techniques improves the accuracy of global VTEC models significantly. If DORIS VTEC data is used to update IGS GIMs, an improvement of up to 12 % can be achieved. The accuracy directly beneath the DORIS satellites’ ground-tracks ranges between 1.5 and 3.5 TECU assuming a precision of 2.5 TECU for altimeter-derived VTEC values which have been used for validation purposes. 相似文献
64.
With the objective of improving flood predictions, in recent years sophisticated continuous hydrologic models that include complex land‐surface sub‐models have been developed. This has produced a significant increase in parameterization; consequently, applications of distributed models to ungauged basins lacking specific data from field campaigns may become redundant. The objective of this paper is to produce a parsimonious and robust distributed hydrologic model for flood predictions in Italian alpine basins. Application is made to the Toce basin (area 1534 km2). The Toce basin was a case study of the RAPHAEL European Union research project, during which a comprehensive set of hydrologic, meteorological and physiographic data were collected, including the hydrologic analysis of the 1996–1997 period. Two major floods occurred during this period. We compare the FEST04 event model (which computes rainfall abstraction and antecedent soil moisture conditions through the simple Soil Conservation Service curve number method) and two continuous hydrologic models, SDM and TDM (which differ in soil water balance scheme, and base flow and runoff generation computations). The simple FEST04 event model demonstrated good performance in the prediction of the 1997 flood, but shows limits in the prediction of the long and moderate 1996 flood. More robust predictions are obtained with the parsimonious SDM continuous hydrologic model, which uses a simple one‐layer soil water balance model and an infiltration excess mechanism for runoff generation, and demonstrates good performance in both long‐term runoff modelling and flood predictions. Instead, the use of a more sophisticated continuous hydrologic model, the TDM, that simulates soil moisture dynamics in two layers of soil, and computes runoff and base flow using some TOPMODEL concepts, does not seem to be advantageous for this alpine basin. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
65.
Recent high-resolution observations from the Solar Dynamics Observatory (SDO) have reawakened interest in the old and fascinating phenomenon of solar tornado-like prominences. This class of prominences was first introduced by Pettit (Astrophys. J. 76, 9, 1932), who studied them over many years. Observations of tornado prominences similar to the ones seen by SDO had already been documented by Secchi (Le Soleil, 1877). High-resolution and high-cadence multiwavelength data obtained by SDO reveal that the tornado-like appearance of these prominences is mainly an illusion due to projection effects. We discuss two different cases where prominences on the limb might appear to have a tornado-like behavior. One case of apparent vortical motions in prominence spines and barbs arises from the (mostly) 2D counterstreaming plasma motion along the prominence spine and barbs together with oscillations along individual threads. The other case of apparent rotational motion is observed in a prominence cavity and results from the 3D plasma motion along the writhed magnetic fields inside and along the prominence cavity as seen projected on the limb. Thus, the “tornado” impression results either from counterstreaming and oscillations or from the projection on the plane of the sky of plasma motion along magnetic-field lines, rather than from a true vortical motion around an (apparent) vertical or horizontal axis. We discuss the link between tornado-like prominences, filament barbs, and photospheric vortices at their base. 相似文献
66.
Simone Dell��Agnello Caterina Lops Giovanni O. Delle Monache Douglas G. Currie Manuele Martini Roberto Vittori Angioletta Coradini Cesare Dionisio Marco Garattini Alessandro Boni Claudio Cantone Riccardo March Giovanni Bellettini Roberto Tauraso Mauro Maiello Luca Porcelli Simone Berardi Nicola Intaglietta 《Experimental Astronomy》2011,32(1):19-35
MAGIA is a mission approved by the Italian Space Agency (ASI) for Phase A study. Using a single large-diameter laser retroreflector, a large laser retroreflector array and an atomic clock onboard MAGIA we propose to perform several fundamental physics and absolute positioning metrology experiments: VESPUCCI, an improved test of the gravitational redshift in the Earth?CMoon system predicted by General Relativity; MoonLIGHT-P, a precursor test of a second generation Lunar Laser Ranging (LLR) payload for precision gravity and lunar science measurements under development for NASA, ASI and robotic missions of the proposed International Lunar Network (ILN); Selenocenter (the center of mass of the Moon), the determination of the position of the Moon center of mass with respect to the International Terrestrial Reference Frame/System (ITRF/ITRS); this will be compared to the one from Apollo and Lunokhod retroreflectors on the surface; MapRef, the absolute referencing of MAGIA??s lunar altimetry, gravity and geochemical maps with respect to the ITRF/ITRS. The absolute positioning of MAGIA will be achieved thanks to: (1) the laboratory characterization of the retroreflector performance at INFN-LNF; (2) the precision tracking by the International Laser Ranging Service (ILRS), which gives two fundamental contributions to the ITRF/ITRS, i.e. the metrological definition of the geocenter (the Earth center of mass) and of the scale of length; (3) the radio science and accelerometer payloads; (4) support by the ASI Space Geodesy Center in Matera, Italy. Future ILN geodetic nodes equipped with MoonLIGHT and the Apollo/Lunokhod retroreflectors will become the first realization of the International Moon Reference Frame (IMRF), the lunar analog of the ITRF. 相似文献
67.
Marisa?Giuffrida Francois?Holtz Francesco?Vetere Marco?ViccaroEmail author 《Contributions to Mineralogy and Petrology》2017,172(11-12):90
Changes in magmatic assemblages and crystal stability as a response of CO2-flushing in basaltic systems have rarely been directly addressed experimentally, making the role of CO2 in magma dynamics still controversial and object of scientific debate. We conducted a series of experiments to understand the response of magmas from Etna volcano to CO2 flushing. We performed a first experiment at 300 MPa to synthesize a starting material composed of crystals of some hundreds of µm and melt pools. This material is representative of an initial magmatic assemblage composed of plagioclase, clinopyroxene and a water-undersaturated melt with 1.6 wt% H2O. In a second step, the initial assemblage was equilibrated at 300 and 100 MPa with fluids having different XCO 2 fl (CO2/(H2O + CO2)). At low XCO 2 fl (< 0.2 to 0.4), plagioclase is completely dissolved and clinopyroxene show dissolution textures. For relatively high XCO 2 fl (0.9 at 300 MPa), the flushing of a CO2-rich fluid phase leads to an increase of the amount of clinopyroxene and a decrease of the abundance of plagioclase at 300 MPa. This decrease of plagioclase proportion is associated with a change in An content. Our experiments demonstrate that flushing basaltic systems with fluids may drastically affect crystal textures and phase equilibria depending on proportions of H2O and CO2 in the fluid phase. Since texture and crystal proportions are among the most important parameters governing the rheology of magmas, fluid flushing will also influence magma ascent to the Earth’s surface. The experimental results open new perspectives to decipher the textural and compositional record of minerals observed in volcanic rocks from Mt. Etna, and at the same time offer the basis for interpreting the information preserved in minerals from other basaltic volcanoes erupting magmas enriched in CO2. 相似文献
68.
Vittorio Scribano Marco Viccaro Renato Cristofolini Luisa Ottolini 《Mineralogy and Petrology》2009,95(3-4):235-250
Three types of ultramafic xenoliths from the Hyblean area (Sicily) show prime evidence for mantle metasomatism, namely: 1) Spinel-facies depleted harzburgite veined by phlogopite-bearing clinopyroxenite; 2) Amphibole-bearing harzburgite; and 3) Al-spinel websterite. (2) and (3) exhibit glassy pockets having respectively mugearitic and basanitic compositions, but a little amount of glass with low Ca and very low alkalis in (2). Glasses generally show trace element distributions consistent with the partial melting of pargasite-dominated mineral assemblages. Abundant Ca-Mg-carbonate globules immersed in these glassy pockets testify to immiscibility between silicate and carbonatite melts. Silicate melts and hydrous-silicate supercritical fluids, which underwent phase separation during fluxing throughout the semi-brittle lithospheric mantle, may account for such metasomatizing processes. The nature and abundance of some fluid-mobile elements in glasses and hydrous minerals (especially the Ca-poor glass, with B?=?59 ppm, Li?=?27 ppm, Ba?=?700 ppm and phlogopite, with Ba?=?8,465 ppm, Sr?=?260 ppm, F?=?5,700 ppm) suggest that some hydrous fluids may derive from hydrothermally altered oceanic crust. Conversely, metasomatizing silicate melts probably have a deep-seated origin. These results confirm previous suggestions on the key role of mantle metasomatism in the origin of some alkaline Hyblean magmas. 相似文献
69.
Catherine Heymans Ludovic Van Waerbeke David Bacon Joel Berge Gary Bernstein Emmanuel Bertin Sarah Bridle Michael L. Brown Douglas Clowe Håkon Dahle Thomas Erben Meghan Gray Marco Hetterscheidt Henk Hoekstra Patrick Hudelot Mike Jarvis Konrad Kuijken Vera Margoniner Richard Massey Yannick Mellier Reiko Nakajima Alexandre Refregier Jason Rhodes Tim Schrabback David Wittman 《Monthly notices of the Royal Astronomical Society》2006,368(3):1323-1339
70.
Abstract— We review the physical principles on which asteroid thermal models are based and their application in the derivation of asteroid sizes and albedos. In particular, the use of simple thermal models to derive reliable diameters and albedos of near‐Earth asteroids is discussed. 相似文献