Émergence de la complexité dans un modèle simple de comportement mécanique des roches     

David Amitrano 《Comptes Rendus Geoscience》2004,336(6):505-512

We propose a mechanical model for the behaviour of rocks based on progressive damage at the elementary scale and elastic interaction. It allows us to simulate several experimental observations: mechanical behaviour ranging from brittle to ductile, fractal structure of the damage, power-law distribution of the damage avalanches. These macroscopic properties are not incorporated at the elementary scale, but are the results of the interaction between elements. This emerging complexity permits us to consider the strain rock process as a complex system characterized by non-linear dynamics. To cite this article: D. Amitrano, C. R. Geoscience 336 (2004).  相似文献   

Three-dimensional forward and backward modelling of diapirism: numerical approach and its applicability to the evolution of salt structures in the Pricaspian basin     

Alik Ismail-Zadeh  Igor Tsepelev  Chistopher Talbot  Alexander Korotkii   《Tectonophysics》2004,387(1-4):81-103

Numerical studies of ductile deformations induced by salt movements have, until now, been restricted to two-dimensional (2D) modelling of diapirism. This paper suggests a numerical approach to model the evolution of three-dimensional (3D) salt structures toward increasing maturity. This approach is also used here to restore the evolution of salt structures through successive earlier stages. The numerical methodology is applied to study several model examples. We analyse a model of salt diapirs that develop from an initial random perturbation of the interface between salt and its overburden and restore the evolved salt diapirs to their initial stages. We show that the average restoration errors are less than 1%. An evolutionary model of a 2D salt wall loaded by a 2D pile of sediments predicts a decomposition of the salt wall into 3D diapiric structures when the overburden of salt is supplied by 3D synkinematic wedge of sediments. We model salt extrusion feeding a gravity current over the depositional surface and estimate an average rate of extrusion and horizontal velocity of salt spreading. Faulting of the overburden to salt overhangs initiates new secondary diapirs, and we analyse the growth of these secondary diapirs. We also study how lateral flow effects the evolution of salt diapirs. The shape of a salt diapir can be very different if the rate of horizontal flow is much greater than the initial rate of diapiric growth solely due to gravity. We discuss the applicability of the results of the models to the evolution of Late Permian salt structures in the Pricaspian basin (Russia and Kazakhstan). These structures are distinguishable into a variety of styles representing different stages of growth: salt pillows, diapirs, giant salt massifs, 2D diapiric walls and 3D stocks complicated by large overhangs. The different sizes, shapes and maturities of salt structures in different parts of the Pricaspian basin reflect areal differences in salt thickness and loading history. Our results suggest that the numerical methodology can be employed to analyse the evolution of all salt structures that have upbuilt through younger ductile overburdens.  相似文献   

Mixed-grid and staggered-grid finite-difference methods for frequency-domain acoustic wave modelling   总被引：3，自引：0，他引：3  

Bernhard Hustedt  Stéphane Operto  Jean Virieux 《Geophysical Journal International》2004,157(3):1269-1296

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Spectral element modelling of three-dimensional wave propagation in a self-gravitating Earth with an arbitrarily stratified outer core     

Emmanuel Chaljub  Bernard Valette 《Geophysical Journal International》2004,158(1):131-141

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Wave propagation across fluid–solid interfaces: a grid method approach     

Jianfeng Zhang 《Geophysical Journal International》2004,159(1):240-252

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Numerical modelling method for wave propagation in a linear viscoelastic medium with singular memory   总被引：1，自引：0，他引：1  

Jian-Fei Lu  Andrzej Hanyga 《Geophysical Journal International》2004,159(2):688-702

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Effects of spatially structured vegetation patterns on hillslope erosion in a semiarid Mediterranean environment: a simulation study   总被引：1，自引：0，他引：1  

Matthias Boer  Juan Puigdefbregas 《地球表面变化过程与地形》2005,30(2):149-167

A general trend of decreasing soil loss rates with increasing vegetation cover fraction is widely accepted. Field observations and experimental work, however, show that the form of the cover‐erosion function can vary considerably, in particular for low cover conditions that prevail on arid and semiarid hillslopes. In this paper the structured spatial distribution of the vegetation cover and associated soil attributes is proposed as one of the possible causes of variation in cover–erosion relationships, in particular in dryland environments where patchy vegetation covers are common. A simulation approach was used to test the hypothesis that hillslope discharge and soil loss could be affected by variation in the spatial correlation structure of coupled vegetation cover and soil patterns alone. The Limburg Soil Erosion Model (LISEM) was parameterized and verified for a small catchment with discontinuous vegetation cover at Rambla Honda, SE Spain. Using the same parameter sets LISEM was subsequently used to simulate water and sediment fluxes on 1 ha hypothetical hillslopes with simulated spatial distributions of vegetation and soil parameters. Storms of constant rainfall intensity in the range of 30–70 mm h^?1 and 10–30 min duration were applied. To quantify the effect of the spatial correlation structure of the vegetation and soil patterns, predicted discharge and soil loss rates from hillslopes with spatially structured distributions of vegetation and soil parameters were compared with those from hillslopes with spatially uniform distributions. The results showed that the spatial organization of bare and vegetated surfaces alone can have a substantial impact on predicted storm discharge and erosion. In general, water and sediment yields from hillslopes with spatially structured distributions of vegetation and soil parameters were greater than from identical hillslopes with spatially uniform distributions. Within a storm the effect of spatially structured vegetation and soil patterns was observed to be highly dynamic, and to depend on rainfall intensity and slope gradient. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

The role of the seismic trigger in the Calitri landslide (Italy): historical reconstruction and dynamic analysis   总被引：2，自引：0，他引：2  

Salvatore Martino  Gabriele Scarascia Mugnozza 《Soil Dynamics and Earthquake Engineering》2005,25(12):933-950

The study covered by this paper was focused on the historical case of the Calitri landslide, which was repeatedly reactivated by earthquakes, as reported since 1694. The town of Calitri (Southern Italy) is located on a ridge whose southern slope, from its top to the Ofanto river valley floor, has been historically affected by major landsliding. The last record of recurrence of the Calitri landslide leads back to the 1980 Irpinia earthquake, which caused significant damage to the town and had pervasive and visible ground effects. Based on a detailed historical reconstruction of landsliding and seismicity at Calitri, the study analysed the current static and dynamic stability of the landsliding slope by means of a finite-difference numerical analysis, taking into account the various factors of landslide initiation and kinematics. The results of the numerical analysis: (i) were consistent with the roto-translational mechanism observed upon the latest reactivation of the landslide; (ii) demonstrated that excess pore pressure redistribution caused a lag between the seismic trigger and the initiation of landsliding; and (iii) showed the impact of seismic input frequency on propagation and depth of slope instability.  相似文献   

The impact of epistemic uncertainty on an earthquake loss model     

Helen Crowley  Julian J. Bommer  Rui Pinho  Juliet Bird 《地震工程与结构动力学》2005,34(14):1653-1685

Models capable of estimating losses in future earthquakes are of fundamental importance for emergency planners, for the insurance and reinsurance industries, and for code drafters. Constructing a loss model for a city, region or country involves compiling databases of earthquake activity, ground conditions, attenuation equations, building stock and infrastructure exposure, and vulnerability characteristics of the exposed inventory, all of which have large associated uncertainties. Many of these uncertainties can be classified as epistemic, implying—at least in theory—that they can be reduced by acquiring additional data or improved understanding of the physical processes. The effort and cost involved in refining the definition of each component of a loss model can be very large, for which reason it is useful to identify the relative impact on the calculated losses due to variations in these components. A mechanically sound displacement‐based approach to loss estimation is applied to a test case of buildings along the northern side of the Sea of Marmara in Turkey. Systematic variations of the parameters defining the demand (ground motion) and the capacity (vulnerability) are used to identify the relative impacts on the resulting losses, from which it is found that the influence of the epistemic uncertainty in the capacity is larger than that of the demand for a single earthquake scenario. Thus, the importance of earthquake loss models which allow the capacity parameters to be customized to the study area under consideration is highlighted. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

3-D modelling and analysis of Dst C-responses in the North Pacific Ocean region, revisited     

Alexei Kuvshinov  Hisashi Utada  Dmitry Avdeev  Takao Koyama 《Geophysical Journal International》2005,160(2):505-526

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