scholarly journals Some geophysical constraints to dynamic processes in the Southwestern Mediterranean

1996 ◽  
Vol 39 (6) ◽  
Author(s):  
V. Pasquale ◽  
M. Verdoya ◽  
P. Chiozzi
Keyword(s):  
Heat Flux ◽  
Continental Crust ◽  
Gravitational Collapse ◽  
Seismic Activity ◽  
Thermal State ◽  
Dynamic Processes ◽  
Oceanic Spreading ◽  
Evolutionary Scheme ◽  
Alboran Basin ◽  
Tectonic Framework

The total tectonic subsidence, thermal state and seismotectonic regime have been analysed to better constrain the dynamic processes which originated the basins of the Southwestern Mediterranean. It is argued that backarc extension and oceanic spreading are the possible and main processes which took place within a compressional framework, driven by the interaction between the African and European plates. As inferred by both subsidence and heat-flux data, in the central part of the Algerian-Balearic basin the crust is oceanic, 20 Ma old on average, originated by a spreading phase, which also affected the Ligurian-Provençal basin. The Alboran basin, which is underlain by stretched continental crust, shows an intermediate seismic activity and a few deep events, explainable by a gravitational collapse of cold lithosphere. After a review of the most recent geodynamical hypotheses, an evolutionary scheme is attempted envisaging the lateral continental escape of the Gibraltar arc. Within a convergent tectonic framework, some lithospheric material could translate almost perpendicular to the convergence direction, and undergo a lateral subduction process, secondary to the main boundary between plates.

The effect of geothermal heat flux on the deglacial evolution of the Greenland ice sheet

2021 ◽  
Author(s):  
Parviz Ajourlou ◽  
François PH Lapointe ◽  
Glenn A Milne ◽  
Yasmina Martos
Keyword(s):  
Boundary Condition ◽  
Heat Flux ◽  
Thermal State ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Sampling Procedure ◽  
Geophysical Research ◽  
Geothermal Heat ◽  
Input Field ◽  
Uncertainty Estimates

<p>Geothermal heat flux (GHF) is known to be an important control on the basal thermal state of an ice sheet which, in turn, is a key factor in governing how the ice sheet will evolve in response to a given climate forcing. In recent years, several studies have estimated GHF beneath the Greenland ice sheet using different approaches (e.g. Rezvanbehbahani et al., Geophysical Research Letters, 2017; Martos et al., Geophysical Research Letters, 2018; Greve, Polar Data Journal, 2019). Comparing these different estimates indicates poor agreement and thus large uncertainty in our knowledge of this important boundary condition for modelling the ice sheet. The primary aim of this study is to quantify the influence of this uncertainty on modelling the past evolution of the ice sheet with a focus on the most recent deglaciation. We build on past work that considered three GHF models (Rogozhina et al., 2011) by considering over 100 different realizations of this input field. We use the uncertainty estimates from Martos et al. (Geophysical Research Letters, 2018) to generate GHF realisations via a statistical sampling procedure. A sensitivity analysis using these realisations and the Parallel Ice Sheet Model (PISM, Bueler and Brown, Journal of Geophysical Research, 2009) indicates that uncertainty in GHF has a dramatic impact on both the volume and spatial distribution of ice since the last glacial maximum, indicating that more precise constraints on this boundary condition are required to improve our understanding of past ice sheet evolution and, consequently, reduce uncertainty in future projections.</p>

scholarly journals Problems of irradiance characteristics measurement of solar simulators for ground spacecraft tests

2020 ◽  
Vol 4 (3) ◽  
pp. 129-140
Author(s):  
A. A. Shevchuk ◽  
O. V. Pastushenko ◽  
V. V. Dvirniy ◽  
G. V. Dvirniy ◽  
A. A. Filatov
Keyword(s):  
Heat Flux ◽  
Direct Measurement ◽  
Thermal State ◽  
Solar Spectrum ◽  
Experimental Tests ◽  
Thermal Vacuum ◽  
Solar Simulator ◽  
Vacuum Chambers ◽  
Mismatch Correction ◽  
Photoelectric Converters

The reliability of both spacecraft as a whole and of their systems is confirmed at the stage of complex ground-based experimental tests, including complex thermal vacuum tests. The thermal state of the test object in thermal vacuum chambers is obtaining, in particular, using a solar simulator. Radiometers based on silicon photoelectric converters are most often used to control the irradiance of a solar simulator under conditions of thermal vacuum tests. At the same time, an analysis of the features of silicon photoelectric converters shows that their direct measurement with the accuracy required for ground-based tests of spacecraft is impossible; their output is nonlinear, depends on the received spectrum, their own temperature and has long-term instability. The achieved measurement accuracy directly depends on the number and accuracy of the tools used and the methods of the necessary correction, of which the mismatch correction between the solar simulator spectrum and the solar spectrum is the most difficult and laborious. At the same time, spectrally nonselective heat flux radiometers are free from the above disadvantages. In the course of the experiment we carried out, the significant dependence of the accuracy of measuring the irradiance with radiometers based on silicon photoelectric converters on the received spectrum was confirmed. The conclusion is made that direct measurement by heat flux radiometers of the irradiance of the solar simulator is most justified under the conditions of thermal vacuum tests.

Dynamics of viscous dissipative collapse with casual approach in string inspired Gauss–Bonnet gravity

2019 ◽  
Vol 34 (10) ◽  
pp. 1950074
Author(s):  
M. Tahir ◽  
G. Abbas
Keyword(s):  
Heat Flux ◽  
Gravitational Collapse ◽  
Bulk Viscosity ◽  
Transport Equations ◽  
Coupling Coefficients ◽  
Dynamical Equations ◽  
Bonnet Gravity ◽  
Viscous Heat ◽  
Theory Of Gravity

In this work, we have studied the effects of dissipative viscous/heat gravitational collapse on the dynamics of collapsing source in 5D Einstein–Gauss–Bonnet theory using full casual approach. For this purpose, the dynamical equations have been formulated by using Misner–Sharp approach in 5D Einstein–Gauss–Bonnet theory of gravity. Using the Müller–Israel–Stewart theory, the dynamical equations have coupled with casual transport equations for the heat flux, the bulk and shear bulk viscosity to determine the effects of heat flux including thermodynamics viscous/heat coupling coefficients. The applications of this work to certain astrophysical situations are discussed.

scholarly journals RADIATING SPHERICAL COLLAPSE WITH HEAT FLOW

2003 ◽  
Vol 12 (04) ◽  
pp. 667-676 ◽  
Author(s):  
M. GOVENDER ◽  
K. S. GOVINDER ◽  
S. D. MAHARAJ ◽  
R. SHARMA ◽  
S. MUKHERJEE ◽  
...  
Keyword(s):  
Heat Flux ◽  
Simple Model ◽  
Gravitational Collapse ◽  
Temporal Evolution ◽  
Junction Conditions ◽  
X Ray ◽  
Spherical Collapse ◽  
Radial Heat ◽  
Cold Star ◽  
Radial Heat Flux

We present here a simple model of radiative gravitational collapse with radial heat flux which describes qualitatively the stages close to the formation of a superdense cold star. Starting with a static general solution for a cold star, the model can generate solutions for the earlier evolutionary stages. The temporal evolution of the model is specified by solving the junction conditions appropriate for radiating gravitational collapse. The results will be useful in constructing models for the evolution of X-ray pulsars, like Her X-1.

The late extension in the inner western Alps: a synthesis along the south-Pelvoux transect

2006 ◽  
Vol 177 (6) ◽  
pp. 299-310 ◽  
Author(s):  
Pierre Tricart ◽  
Jean-Marc Lardeaux ◽  
Stéphane Schwartz ◽  
Christian Sue
Keyword(s):  
Gravitational Collapse ◽  
Seismic Activity ◽  
Western Alps ◽  
Normal Faulting ◽  
The West ◽  
Internal Part ◽  
Orogenic Wedge ◽  
External Domain ◽  
Radial Spreading ◽  
Oriented Parallel

Abstract During the Oligocene, in the central western Alps, tectonic accretion of the external domain to the internal orogenic wedge along the Briançonnais frontal thrust (BFT) was followed by backfolding, resulting in the Alpine fanning structure. The Briançonnais fan axis was rapidly exhumed by erosion. This growing wedge at the scale of the entire Alpine structure was a short-lived situation that ended with the onset of extension in its internal part, before the end Oligocene. To the east, in the Queyras Piedmont Schistes lustrés, extension in ductile then brittle conditions accommodated the tectonic denudation of the Dora-Maira crystalline massif below the Monviso ophiolites, themselves exhumed below the Queyras Schistes lustrés. Consistently, the final cooling of these Schistes lustrés becomes younger eastwards during the Miocene. To the west, inversion of the BFT was directly associated with dense normal faulting in the Briançonnais-Piedmont nappe stack. Local reactivation of thrust surfaces resulted in spectacular trains of tilted blocks oriented parallel and normal to the orogen. When considered at the scale of the entire internal zones, the brittle extension developed during the Neogene globally displays a multitrend character. It is a close to radial spreading that strongly suggests the gravitational collapse of an overthickened crust. Extensional movement along the BFT and multitrend normal faulting in its hangingwall continue at present, resulting in shallow depth seismic activity. From the Neogene onwards, the Alpine structure underwent contrasting tectonic regimes. Extension limited the growth of the internal wedge or accompanied its thinning at least in its upper part. Concurrently the external wedge continued growing through successive folding-thrusting phases.

scholarly journals How old is the ice beneath Dome A, Antarctica?

2014 ◽  
Vol 8 (1) ◽  
pp. 289-305 ◽  
Author(s):  
B. Sun ◽  
J. C. Moore ◽  
T. Zwinger ◽  
Z. Liyun ◽  
D. Steinhage ◽  
...  
Keyword(s):  
Heat Flux ◽  
Thermal State ◽  
Ice Core ◽  
Three Dimensional ◽  
Glacial Cycle ◽  
Dome A ◽  
Geothermal Heat ◽  
Surface Conditions ◽  
Kunlun Station ◽  
Ice Fabrics

Abstract. Chinese scientists will start to drill a deep ice core at Kunlun station near Dome A in the near future. Recent work has predicted that Dome A is a location where ice older than 1 million years can be found. We model flow, temperature and the age of the ice by applying a three-dimensional, thermo-mechanically coupled full-Stokes model to a 70 km × 70 km domain around Kunlun station, using isotropic non-linear rheology and different prescribed anisotropic ice fabrics that vary the evolution from isotropic to single maximum at 1/3 or 2/3 depths. The variation in fabric is about as important as the uncertainties in geothermal heat flux in determining the vertical advection which in consequence controls both the basal temperature and the age profile. We find strongly variable basal ages across the domain since the ice varies greatly in thickness and any basal melting effectively removes very old ice in the deepest parts of the subglacial valleys. Comparison with dated radar isochrones in the upper one third of the ice sheet cannot sufficiently constrain the age of the deeper ice, with uncertainties as large as 500 000 yr in the basal age. We also assess basal age and thermal state sensitivities to geothermal heat flux and surface conditions. Despite expectations of modest changes in surface height over a glacial cycle at Dome A, even small variations in the evolution of surface conditions cause large variation in basal conditions which is consistent with basal accretion features seen in radar surveys.

scholarly journals Rifting and thermal evolution of the Northwestern Mediterranean

1995 ◽  
Vol 38 (1) ◽  
Author(s):  
V. Pasquale ◽  
M. Verdoya ◽  
P. Chiozzi
Keyword(s):  
Heat Flux ◽  
Continental Crust ◽  
Thermal Model ◽  
Thermal Evolution ◽  
Continental Margins ◽  
Sea Floor ◽  
Thermal Features ◽  
Significant Extension ◽  
Transitional Crust ◽  
Northwestern Mediterranean

The structural setting of the Northwestern Mediterranean stems from tectonothermal processes which reflect on the nature of the crust. The Oligocene to Present evolution is here analysed with a thermal model which takes into account the significant extension of the continentallithosphere before the onset of sea-floor spread- ing in the bathyal zone. Subsidence data were used to set the boundaries of the oceanic realm which was com- pared with previous reconstructions inferred from other geophysical evidence. The thermal features of the transitional crust that lies between the oceanic crust and the stretched continental margins were also outlined. The Ligurian-Proven~al basin is a marginaI basin, whereas only the continental crust is expected in the Valen- cia trough. An evolutionary sketch of the study area that accounts for the observed subsidence and heat flux is proposed.

scholarly journals A perturbative approach to the time-dependent Karmarkar condition

2021 ◽  
Vol 81 (2) ◽  
Author(s):  
Megandhren Govender ◽  
Wesley Govender ◽  
Kevin P Reddy ◽  
Sunil D Maharaj
Keyword(s):  
Boundary Condition ◽  
Heat Flux ◽  
Gravitational Collapse ◽  
Time Dependent ◽  
Perturbative Approach ◽  
Radial Heat ◽  
Radiating Star ◽  
Static Regime ◽  
Radial Heat Flux ◽  
Static Core

AbstractIn this work we employ a perturbative approach to study the gravitational collapse of a shear-free radiating star. The collapse proceeds from an initial static core satisfying the time-independent Karmarkar condition and degenerates into a quasi-static regime with the generation of energy in the form of a radial heat flux. The time-dependent Karmarkar condition is solved together with the boundary condition to yield the full gravitational behaviour of the star. Our model is subjected to rigorous regularity, causality and stability tests.

Gravitational Collapse with Heat Flux and Gravitational Waves

2013 ◽  
Vol 52 (10) ◽  
pp. 3598-3603 ◽  
Author(s):  
Zahid Ahmad ◽  
Qazi Zahoor Ahmed ◽  
Abdul Sami Awan
Keyword(s):  
Heat Flux ◽  
Gravitational Waves ◽  
Gravitational Collapse
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