Perceptions of environmental change and migration decisions     

Vally Koubi  Sebastian Stoll  Gabriele Spilker 《Climatic change》2016,135(3-4):439-451

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Self-sustained oscillations at Volcán de Colima (México) inferred by Independent Component Analysis   总被引：2，自引：1，他引：1  

E. De Lauro  S. De Martino  M. Palo  J. M. Ibañez 《Bulletin of Volcanology》2012,74(1):279-292

We have analyzed Long-Period (LP) seismic events of Volcán de Colima (Mexico) recorded by four three-component broad-band seismometers during January 2006. Frequency-domain analysis shows spectra mainly peaked in the range 0.3–2 Hz and characterized by a monotonic decreasing envelope, as those produced in a cylindrically-symmetric self-oscillating cavity interacting with a confined jet. Independent Component Analysis, a time-series decomposition method, extracts two or three nonlinear oscillation modes depending on the station, with the fundamental one peaked at 0.4–0.5 Hz. These decomposed waves have a well defined spectral content and are self-sustained oscillations with low dimensionality, as shown by dynamic system reconstruction methods. Moreover, they show radial polarization in near field and transverse polarization in far field in North-West South-East direction. Finally, we hypothesize a branched plumbing system with two principal conduits having alignments orthogonal to one another.  相似文献   

An example of flow differentiation: clinopyroxenite of the Predazzo igneous complex (north Italy)     

Federico Lucchini  Lauro Morten 《Lithos》1977,10(1):39-47

Chemical, modal and mineralogic data and textural observations suggest that the small mafic-ultramafic body at Predazzo, consisting of olivine-bearing gabbro, clinopyroxenite and quartz-bearing gabbro, is the result of a flow differentiation mechanism acting on a mush formed of 60% solid plus 40% liquid. Such a mechanism was capable of producing the concentration of the early formed crystals ($\text{cpx}\text{+}\text{mt}$) towards the center of the body (clinopyroxenite) with segregation of two portions enriched in liquid toward the margins (olivine- and quartz-bearing gabbros).  相似文献   

A cosmological hydrodynamic code based on the piecewise parabolic method     

Claudio Gheller  Ornella Pantano  & Lauro Moscardini 《Monthly notices of the Royal Astronomical Society》1998,295(3):519-533

We present a hydrodynamical code for cosmological simulations which uses the piecewise parabolic method (PPM) to follow the dynamics of the gas component and an N -body particle–mesh algorithm for the evolution of the collisionless component. The gravitational interaction between the two components is regulated by the Poisson equation which is solved by a standard fast Fourier transform (FFT) procedure. In order to simulate cosmological flows we have introduced several modifications to the original PPM scheme which we describe in detail. Various tests of the code are presented including adiabatic expansion, single and multiple pancake formation and three-dimensional cosmological simulations with initial conditions based on the cold dark matter scenario.  相似文献   

Geodetic control on recent tectonic movements in the central Mediterranean area     

R. Devoti  C. Ferraro  E. Gueguen  R. Lanotte  V. Luceri  A. Nardi  R. Pacione  P. Rutigliano  C. Sciarretta  F. Vespe 《Tectonophysics》2002,346(3-4)

During the Neogene and Quaternary, the western Mediterranean geodynamics was apparently dominated by the nearly eastward migration of the Apenninic arc and the associated opening (spreading) of the back-arc basin (Tyrrhenian Sea). However, during the last 5 My, the collision of the arc with the Apulian platform led to a dramatic change in the tectonic setting of the area. As geological processes require a long period of time to register the displacements of the different blocks, it is indispensable to take into account the present-day motion given by space geodesy data analysis in order to better constrain the geological models.Geodetic motions were derived from Global Positioning System (GPS), Satellite Laser Ranging (SLR) and Very Long Baseline Interferometry (VLBI) observations collected from different networks. All the geodetic solutions have been computed and combined at the Centre of Space Geodesy (CGS), at Matera, Italy.The geodetic results show a NNE motion of the Adriatic plate with a small component of counter-clockwise rotation, in good agreement with the geological and geophysical observations.In the southern Tyrrhenian area, the lengthening of the Matera–Cagliari baseline should imply that convergence cannot be considered as the driving mechanism for the Apenninic subduction process. The estimated motion of Noto is in quite good agreement with the estimated motion of the African plate.  相似文献   

Crustal zircons and mantle sulfides: Archean to Triassic events in the lithosphere beneath south-eastern Sicily     

Giovanna T. Sapienza  William L. Griffin  Suzanne Y. O''Reilly  Lauro Morten   《Lithos》2007,96(3-4):503-523

Three types of zircon coexist in an unusual lower crustal xenolith from the Valle Guffari diatreme (Hyblean Plateau, Sicily): igneous Type 1 (near-euhedral, weakly zoned; Ce/Ce > 1); partially recrystallised Type 2 (ovoid, structureless; weak Ce anomaly); hydrothermal Type 3 (sugary, spongy-textured, probably related to F-rich aqueous fluids). U–Pb dating by LAM-ICPMS, supported by in situ Hf-isotope analysis, suggests that both Type 1 and Type 2 zircons were originally Archean (ca 2.7 Ga), though many of these grains have experienced severe Pb loss. The U–Pb ages of the hydrothermal zircons cluster around 246 Ma, interpreted as the timing of the hydrothermal event. Their ε_Hf (+ 8.5 to − 1.2) indicates the mixing of old crustal components and material from a juvenile source.

In situ Os-isotope analyses of sulfides hosted in peridotite xenoliths from Valle Guffari show Paleoproterozoic–Archean T_RD minimum ages, corresponding to the age of the oldest zircon grains in the crustal xenolith. Other peaks of T_RD ages suggest that multiple metasomatic events have affected the lithospheric mantle.

These observations suggest that the lower crust and the upper part of the lithospheric mantle beneath the Hyblean Plateau represent the northernmost portion of the African Plate. These two units have coexisted since at least late Archean time, and have remained linked through several episodes of crustal modification, including the Permo-Triassic hydrothermal event, which was probably related to the onset of rifting in the Ionian Basin.  相似文献   

A physically-based method for removing pits in digital elevation models   总被引：1，自引：0，他引：1  

Salvatore Grimaldi  Fernando Nardi  Francesco Di Benedetto  Erkan Istanbulluoglu  Rafael L. Bras 《Advances in water resources》2007

Spurious pits in digital elevation models (DEMs) are traditionally removed by filling depressions, often creating flat regions that lead to inaccurate estimation of landscape flow directions. In this study, a physical approach based on a simple landscape evolution model is proposed for DEM pit removal. This method, an alternative to traditional geometrical procedures, enforces more realistic slopes and flow directions on topography. The procedure is compared with the method most commonly used in the literature and distributed with commercial GIS software where, generally, elevations of a depression are increased up to the lowest value among neighbouring cells. Several tests are performed and parameters sensitivity is carried out in order to demonstrate the performance of the proposed model as compared to traditional methods.  相似文献   

Time structure of the extensive air shower front     

G. Agnetta  M. Ambrosio  C. Aramo  G. C. Barbarino  J. Beaman  B. Biondo  D. Campana  O. Catalano  L. Colesanti  G. D''Ali  A. Erlykin  F. Guarino  A. Lauro  J. Lloyd-Evans  A. Mangano  G. Osteria  A. A. Watson 《Astroparticle Physics》1997,6(3-4):301-312

The GREX/COVER_PLASTEX experiment has measured the temporal and spatial fine structure of the EAS disc at sea level in a new and original way, using resistive plate counter detectors for direct measurements of the arrival time of each particle crossing the detector. Data were taken at EAS core distances up to 100 m for shower size N > 10⁵ (PeV energy range). Arrival times of shower particles were measured with nanosecond accuracy. More than 450000 air shower events have been included in this analysis.  相似文献   

Promotion of graphite formation by tectonic stress – a laboratory experiment     

Georg Nover  Johannes B. Stoll  Jutta von der Gönna 《Geophysical Journal International》2005,160(3):1059-1067

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CO₂ in the Weddell Gyre and Antarctic Circumpolar Current: austral autumn and early winter     

Mario Hoppema  Michel H. C. Stoll  Hein J. W. de Baar   《Marine Chemistry》2000,72(2-4)

Quasi-continuous fugacity of CO₂ (fCO₂) data were collected in the eastern Weddell Gyre and southern Antarctic Circumpolar Current (ACC) of the Southern Ocean during austral autumn 1996. Full depth Total CO₂ (TCO₂) sections are presented for austral autumn and winter (1992) cruises. Pronounced fCO₂ gradients were observed at the Southern Ocean fronts. In the Weddell Gyre, fCO₂ regimes appeared to coincide with surface and subsurface hydrographic regimes. The southern ACC was supersaturated with respect to CO₂, as was part of the northern Weddell Gyre. The southern Weddell Gyre was markedly undersaturated. The great potential of autumn cooling for generating undersaturation and CO₂ uptake from the atmosphere was demonstrated. In the northeastern Weddell Gyre, upwelling of CO₂- and salt-rich deep water was shown to play a role as the horizontal fCO₂ distribution closely resembled that of the surface salinity. The total uptake of atmospheric CO₂ by the Weddell Gyre in autumn (45 days) was calculated to be 7·10¹² g C. The deep TCO₂ distribution noticeably reflected the different water masses in the region. A new deep TCO₂ maximum was detected in the ACC, which apparently characterizes the boundary between the equatorward flowing Antarctic Bottom Water (AABW) and the Circumpolar Deep Water (CDW). East of the Weddell Gyre, the AABW stratum is much thicker (>2000 m) than more to the west, on the prime meridian (<300 m).  相似文献