Transform/oblique rift system : what have we learned from numerical modelling and what's next ?

2020 ◽  
Author(s):  
Laetitia Le Pourhiet ◽  
Anthony Jourdon
Keyword(s):  
Numerical Modelling ◽  
Large Scale ◽  
Initial Conditions ◽  
Strike Slip ◽  
Rift System ◽  
New Concepts ◽  
Long Time ◽  
3D Numerical Modelling ◽  
Transform Margin ◽  
Conjugate Margins

<p>For very long time, transform margins have been treated and described  based on oceanic transform fault concepts. Their was no change in kinematics nor structures with time and thermally speaking, it was hypothesed that the margin was reheated as the mid-oceanic ridge translated passively along the margin.  In the last 10 years, 3D numerical modelling has been made available and numbers of studies have challenged this view. It is time to review the concepts that have emerge. Interrestingly, many modelling contributions have tackled the obliquity at very different scales, with initial conditions varying from simple flat layered homogeneous lithosphere to subduction of opposite vergence. Moreover some contributions have focus on rheological aspect and other on inheritance at different scale and different physical coupling have been used. Some models were targeting at reproducing the oceanic transform concepts, other at exploring how large scale structure can emerge.  I will therefore try to review  the state of art in numerical modelling of transform margin and oblique extensional system based on my own work and literature review. I will try to emphize the important differences and similarities used in the different modelling. Using different models with different boundary conditions and scale I will try to introduce a new conceptual model of transform margin which captures important characteristics like the delay in continental break-up highlighted by the tracing of sediments and water-depth as well as the obliquity between syn-rift and post-rift subsidence.  Some models of oblique extension have also been producing new type of strike slip ocean continent transition which somehow could be interpreted as steep transform margins but appears to be mainly strike slip and have no conjugate margins. To conclude, all these 3D numerical modelling  allow us today to present a very different view of transform margins than 10 years ago. Some of the new concepts that have emerged  mendate to re assess our interpretation of exisiting datasets.</p>

scholarly journals The fate of random initial vorticity distributions for two-dimensional Euler equations on a sphere

2015 ◽  
Vol 786 ◽  
pp. 1-4 ◽  
Author(s):  
Paul K. Newton
Keyword(s):  
Numerical Simulations ◽  
Euler Equations ◽  
Large Scale ◽  
Initial Conditions ◽  
Infinite Family ◽  
Small Scale ◽  
Two Dimensional ◽  
Random Initial Conditions ◽  
Long Time ◽  
Initial Vorticity

The paper by Dritschel et al. (J. Fluid Mech., vol. 783, 2015, pp. 1–22) describes the long-time behaviour of inviscid two-dimensional fluid dynamics on the surface of a sphere. At issue is whether the flow settles down to an equilibrium or whether, for generic (random) initial conditions, the long-time solution is periodic, quasi-periodic or chaotic. While it might be surprising that this issue is not settled in the literature, it is important to keep in mind that the Euler equations form a dissipationless Hamiltonian system, hence the set of equations only redistributes the initial vorticity, generating smaller and smaller scales, while keeping kinetic energy, angular impulse and an infinite family of vorticity moments (Casimirs) intact. While special solutions that never settle down to an equilibrium state can be constructed using point vortices, vortex patches and other distributions, the fate of random initial conditions is a trickier problem. Previous statistical theories indicate that the long-time state should be a stationary large-scale distribution of vorticity. By carrying out careful numerical simulations using two different methods, the authors make a compelling case that the generic long-time state resembles a large-scale oscillating quadrupolar vorticity field, surrounded by persistent small-scale vortices. While numerical simulations can never conclusively settle this issue, the results might help guide future theories that seek to prove the existence of such an interesting dynamical long-time state.

scholarly journals 3D NUMERICAL MODELLING OF THE SEISMIC RESPONSE OF THE THESSALONIKI URBAN AREA: THE CASE OF THE 1978 VOLVI EARTHQUAKE

2017 ◽  
Vol 50 (3) ◽  
pp. 1433
Author(s):  
C. Smerzini ◽  
K. Pitilakis ◽  
K. Hashemi
Keyword(s):  
Numerical Modelling ◽  
Urban Area ◽  
Ground Motion ◽  
Large Scale ◽  
Spectral Element ◽  
Seismic Wave Propagation ◽  
Earthquake Ground Motion ◽  
Ground Shaking ◽  
3D Numerical Modelling ◽  
Wide Scale

This study aims at showing the numerical modelling of earthquake ground motion in the Thessaloniki urban area, using a 3D spectral element approach. The availability of detailed geotechnical/geophysical data together with the seismological information regarding the relevant fault sources allowed us to construct a large-scale 3D numerical model suitable for generating physics based ground shaking scenarios within the city of Thessaloniki up to maximum frequencies of about 2 Hz. Results of the numerical simulation of the destructive MW6.5 1978 Volvi earthquake are addressed, showing that realistic estimates can be obtained. Shaking maps in terms of ground motion parameters such as PGV are used to discuss the main seismic wave propagation effects at a wide scale.

On non-self-similar regimes in homogeneous isotropic turbulence decay

2012 ◽  
Vol 711 ◽  
pp. 364-393 ◽  
Author(s):  
Marcello Meldi ◽  
Pierre Sagaut
Keyword(s):  
Energy Spectrum ◽  
Large Scale ◽  
Isotropic Turbulence ◽  
Initial Conditions ◽  
Self Similarity ◽  
Velocity Correlation ◽  
Turbulence Decay ◽  
Long Time ◽  
Self Similar ◽  
Decay Exponent

AbstractBoth theoretical analysis and eddy-damped quasi-normal Markovian (EDQNM) simulations are carried out to investigate the different decay regimes of an initially non-self-similar isotropic turbulence. Breakdown of self-similarity is due to the consideration of a composite three-range energy spectrum, with two different slopes at scales larger than the integral length scale. It is shown that, depending on the initial conditions, the solution can bifurcate towards a true self-similar decay regime, or sustain a non-self-similar state over an arbitrarily long time. It is observed that these non-self-similar regimes cannot be detected, restricting the observation to time exponents of global quantities such as kinetic energy or dissipation. The actual reason is that the decay is controlled by large scales close to the energy spectrum peak. This theoretical prediction is assessed by a detailed analysis of triadic energy transfers, which show that the largest scales have a negligible impact on the total transfers. Therefore, it is concluded that details of the energy spectrum near the peak, which may be related to the turbulence production mechanisms, are important. Since these mechanisms are certainly not universal, this may at least partially explain the significant discrepancies that exist between experimental data and theoretical predictions. Another conclusion is that classical self-similarity theories, which connect the asymptotic behaviour of either the energy spectrum $E(k\ensuremath{\rightarrow} 0)$ or the velocity correlation function $f(r\ensuremath{\rightarrow} + \infty )$ and the turbulence decay exponent, are not particularly relevant when the large-scale spectrum shape exhibits more than one range.

scholarly journals A model for simulating the deposition of water-lain sediments in dryland environments

2004 ◽  
Vol 8 (2) ◽  
pp. 122-134 ◽  
Author(s):  
M. A. Bunch ◽  
R. Mackay ◽  
J. H. Tellam ◽  
P. Turner
Keyword(s):  
Land Surface ◽  
Large Scale ◽  
Initial Conditions ◽  
Sedimentary Facies ◽  
Storm Event ◽  
Storm Events ◽  
Near Surface ◽  
Radial Profiles ◽  
Long Time ◽  
The Uk

Abstract. A numerical process-imitating model, the Discrete Storm Event Sedimentation Simulator (DSESS), has been developed to represent the climatic and hydraulic conditions of drylands in modelling their geomorphological development and sedimentary facies distributions. The ultimate aim is to provide insights into the lateral variability of permeability in the Triassic Sandstone aquifers of the UK for the study of solute movement. DSESS employs discrete storm-flood automata, released across a cellular landscape, to model sediment transport: erosion, migration and deposition. Sediment classes with different grain sizes can be modelled. Empirical process-based equations are used to quantify the movement of the automata, their erosion potential, sediment-carrying capacity and interaction with the underlying sediments. The approach emphasises the sequence of dryland storm events and associated floods rather than their timing. Flood events are assumed to be discrete in time. Preliminary tests carried out with DSESS using simple systems and idealised initial conditions produce lithological and land surface features characteristic of dryland settings and indicate the potential of the model for large-scale, long-time modelling of sedimentary facies development. Markedly different results are observed across the range of tests carried out in response to the non-linear interactions between the different elements of the landscape and the floodwaters simulated with DSESS. Simulations show that sediment accumulations develop concave upward radial profiles, plano-convex cross-profiles and possess a general lateral grading of sediment with distance from source. The internal grain size architecture shows evidence of both persistent and rapidly changing flow conditions, with both lateral and longitudinal stepping of coarse bodies produced by ‘scour and fill’ events and random avulsions. Armoured layers form so that near-surface sediments have increased likelihood of preservation. Future developments will include representation of aeolian deposition, mass wasting and hyper-concentrated (debris) flows. Keywords: avulsion, channel, deposition, drylands, erosion, gravel armouring, modelling, sheet-flood, transport capacity

Role of kinematic thermomechanical modelling on constraining asymmetric continental break up

2021 ◽  
Author(s):  
Paul Perron ◽  
Laetitia Le Pourhiet ◽  
Anthony Jourdon ◽  
Tristan Cornu ◽  
Claude Gout
Keyword(s):  
Numerical Modelling ◽  
Cross Sections ◽  
Initial Conditions ◽  
Numerical Models ◽  
Mechanical Coupling ◽  
Lithospheric Thickness ◽  
Rifted Margins ◽  
Major Player ◽  
Long Time ◽  
Rifted Margin

<p>For a long time, the complexity of the lithosphere was ignored by numerical modelling because the inherited structural and compositional complexity of the “real” lithosphere is indeed mainly unknown to geologists so modeler preferred to understand first order parameters such as rate of extension, lithospheric thickness, mechanical coupling or decoupling at the Moho. These models were not representative of any particular region but they were helpful. As a wider community of geologist became interested in numerical modelling, a growing number of numerical models have attempted to account for a major player in structural geology: inheritance. However, the complexity of “real” Earth has been simplified and “idealized” where inherited “anomalies” (e.g. fault, pluton, craton) or a combination of them has been added without really knowing the exact initial conditions which are the unknown of the problem. Yet another approach has been to add a lot of them in a more or less random mater or to replace them by initial noise in the parameters. None of these approaches actually fulfil the need for end-users community to have predictive models.</p><p>Realizing that structural inheritance is some kind of kinematic forcing in the solution of the models but also that it is not possible to anticipate and identify all the geological structures that can be inherited in rifted margin lithospheres, we have developed a new approach, through the integration of a new kinematic module to pTatin2D thermomechanical code, permitting to understand the kinematics of deformation of the continental lithosphere and asthenosphere through time leading to the establishment of rifted margins. The method is settled and validated by fitting the architecture (i.e. basement, Moho, LAB, Tmax) and by solving the kinematics of a random unknow 2D cross section extracted from 3D thermomechanical rifted margin model.</p><p>This new tool aims to help geologists to better constrain and draw on their 2D geological cross sections the position of the Moho, the Lithosphere-Asthenosphere boundary (LAB), the temperature isotherms and the heat flux.</p><p>Key words: Kinematic thermomechanical modelling, asymmetric rifted margin architecture, modelling method.</p>

Universal mechanism for saturation of vorticity growth in fully developed fluid turbulence

2013 ◽  
Vol 728 ◽  
Author(s):  
Chakradhar Thantanapally ◽  
Dhiraj V. Patil ◽  
Sauro Succi ◽  
Santosh Ansumali
Keyword(s):  
Coherent Structures ◽  
Large Scale ◽  
Blow Up ◽  
Initial Conditions ◽  
Inviscid Flows ◽  
Collective Dynamics ◽  
Fluid Turbulence ◽  
Show Evidence ◽  
Long Time ◽  
Decaying Turbulence

AbstractNumerical results from large-scale, long-time, simulations of decaying homogeneous turbulence are reported, which indicate that blow-up of inviscid flows is tamed by the emergence of collective dynamics of coherent structures. The simulations also suggest that this collective dynamics might lead to universal behaviour during the transient evolution of turbulence. In particular, simulations with three different initial conditions show evidence of a ${k}^{- 3} \log k$ spectrum in the transient stage, before the Kolmogorov ${k}^{- 5/ 3} $ asymptotic regime is attained. Such a universal transient might serve as a spectral funnel to the time-asymptotic Kolmogorov spectrum, which is invariably observed in the late stage of all three simulations presented in this work. The present work is entirely based on simulation evidence. However, the statistical analysis of the coherent structures suggests an analogy with population dynamics, which might be conducive to new mathematical models of transient decaying turbulence.

scholarly journals A stochastic view of isotropic turbulence decay

2011 ◽  
Vol 668 ◽  
pp. 351-362 ◽  
Author(s):  
MARCELLO MELDI ◽  
PIERRE SAGAUT ◽  
DIDIER LUCOR
Keyword(s):  
Reynolds Number ◽  
High Reynolds Number ◽  
Large Scale ◽  
Isotropic Turbulence ◽  
Initial Conditions ◽  
Response Surfaces ◽  
Turbulence Decay ◽  
Initial Spectrum ◽  
Long Time ◽  
High Reynolds

A stochastic eddy-damped quasi-normal Markovian (EDQNM) approach is used to investigate self-similar decaying isotropic turbulence at a high Reynolds number (400 ≤ Reλ ≤ 104). The realistic energy spectrum functional form recently proposed by Meyers & Menevau (Phys. Fluids, vol. 20, 2008, p. 065109) is generalized by considering some of the model constants as random parameters, since they escape measure in most experimental set-ups. The induced uncertainty on the solution is investigated, building response surfaces for decay power-law exponents of usual physical quantities. Large-scale uncertainties are considered, the emphasis being put on Saffman and Batchelor turbulences. The sensitivity of the solution to initial spectrum uncertainties is quantified through probability density functions of the decay exponents. It is observed that the initial spectrum shape at very large scales governs the long-time evolution, even at a high Reynolds number, a parameter which is not explicitly taken into account in many theoretical works. Therefore, a universal asymptotic behaviour in which kinetic energy decays as t−1 is not detected. However, this decay law is observed at finite Reynolds numbers with low probability for some initial conditions.

TO THE QUESTION OF RESPONSIBILITY FOR TORTURE IN THE RUSSIAN FEDERATION

2020 ◽  
Vol 10 (2) ◽  
pp. 103-106
Author(s):  
ASTEMIR ZHURTOV ◽  
Keyword(s):  
Human Rights ◽  
Russian Federation ◽  
Large Scale ◽  
Human Life ◽  
International Standards ◽  
World Community ◽  
The World ◽  
Long Time ◽  
Protection Of Human Rights ◽  
The Russian Federation

Cruel and inhumane acts that harm human life and health, as well as humiliate the dignity, are prohibited in most countries of the world, and Russia is no exception in this issue. The article presents an analysis of the institution of responsibility for torture in the Russian Federation. The author comes to the conclusion that the current criminal law of Russia superficially and fragmentally regulates liability for torture, in connection with which the author formulated the proposals to define such act as an independent crime. In the frame of modern globalization, the world community pays special attention to the protection of human rights, in connection with which large-scale international standards have been created a long time ago. The Universal Declaration of Human Rights and other international acts enshrine prohibitions of cruel and inhumane acts that harm human life and health, as well as degrade the dignity.Considering the historical experience of the past, these standards focus on the prohibition of any kind of torture, regardless of the purpose of their implementation.

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