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The morphological impact of storms on coastal accumulations varies considerably in space along the coast of western France. At some locations, the storm produces erosion, whereas at others, impacts may vary from erosion to accumulation, or no effect. This is explained by the variability of incident waves. Wave amplitude variability, cross-checked with wave direction variability, is presented on a phase diagram and shows that the response of the coast is not linked to the absolute values reached during the storm, but to changes in wave patterns that take place during the event. The morphology of the bottom (skerries, banks) is greatly forcing these changes because of the high tidal range and the complicated and fast-changing patterns of refraction. Locations with a flat seafloor have an almost predictable response to storms. Places with a complex submarine morphology have a response characterized by high variability. The variability of the wave pattern during a half tidal cycle storm (from low tide at 1 m to high tide at 13 m in 6 h) is a microscale equivalent of the variability of wave patterns changing during sea level rise in the Holocene (from −7 to 0 m in 6 ka). This fact explains why, during the late Holocene, the same locations (1) have displayed a very chaotic response to sea level rise and (2) are displaying, today, a highly variable response to storms. In that respect, seafloor morphology is a mesoscale to macroscale control on beach/barrier behaviour. 相似文献
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Louise Wedderkopp Bjerrum Kuvvet Atakan Mathilde Bøttger Sørensen 《Bulletin of Earthquake Engineering》2010,8(6):1569-1601
The M
w = 8.0 Wenchuan earthquake of May 12, 2008, caused destruction over a wide area. The earthquake cost more than 69,000 lives
and the damage is reported to have left more than 5 million people homeless. It is estimated that 5.36 million buildings were
destroyed and 21 million buildings were damaged in Sichuan and the nearby provinces. Economic losses due to the event are
estimated to be 124 billion USD. From a field reconnaissance trip conducted in October 2008, it is evident that the combination
of several factors, including mountainous landscape, strong ground shaking, extensive landslides and rock-falls, has exacerbated
the human and economic consequences of this earthquake. Extensive damage occurred over a wide area due to the shear size of
the earthquake rupture combined with poor quality building construction. In order to investigate the ground shaking during
the earthquake, we have conducted a strong ground motion simulation study, applying a hybrid broadband frequency technique.
The preliminary results show large spatial variation in the ground shaking, with the strongest ground motions along the fault
plane. The simulation results have been calibrated against the recorded ground motion from several near-field stations in
the area, and acceleration values of the order of 1 g are obtained, similar to what was recorded during the event. Comparison
with the damage distribution observed in the field confirms that the effect of fault rupture complexity on the resulting ground
motion distribution also controls to a large extent the damage distribution. The applied simulation technique provides a promising
platform for predictive studies. 相似文献
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Violaine Combier Satish C. Singh Mathilde Cannat Javier Escartin 《Earth and Planetary Science Letters》2008,272(1-2):19-28
We study the relationships between the seafloor structures and the axial magma chamber geometry in the 9°N overlapping spreading center (OSC) area on the fast spreading East Pacific Rise (EPR). Our observations are based on a new high resolution bathymetric map of the 9°N OSC area derived from picks of the seafloor arrival on 3D seismic data, and on previously published data that constrain the presence and distribution of melt below the 9°N OSC. Differences in the orientation of structures between the seafloor and the magma chamber indicate a sharp change in principal stress directions with depth, suggesting that the brittle crust above the melt sill is decoupled from the melt sill itself and the ductile crust underlying it. The stress-field within the brittle upper crust results from a local interaction of the two overlapping spreading centers, whereas the stress-field in the crust below the melt sill corresponds to the regional stress-field imposed by plate separation. Given this mechanical structure of the crust, the melt sill shape and location appear to be controlled by the following factors: the location of the deep melt source below the melt sill, the ambient stress-field at the depth of the melt sill, and the stress-field in the brittle upper crust above the melt sill, which thermally shapes the roof of the melt sill through repeated eruptions. 相似文献
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Oil exploration requires quantitative determination of structural geometry in sedimentary basins. This leads to back-and-forth use of geological methods, e.g. cross-section balancing and geophysical techniques, such as tomography, and the synthesis becomes tedious, especially in three dimensions. This suggests that they should be as much as possible quantitatively integrated into a single consistent framework. For this integration, we propose using inversion techniques, i.e. multicriteria optimization. We locally model a geological structure as a ( geometric) foliation , the leaves of which represent deposition isochrons. We consider a geological structure as a set of foliations joined along faults and unconformities. We propose five kinds of geological data to constrain structural geometry quantitatively: dip measurements that may be available along wells, developability and smoothness of deposition isochrons, the directions of fold axes, and layer parallelism. Using concepts of differential geometry, we formulate these data in terms of least-squares criteria. To solve the canonical non-uniqueness problem raised by the inversion of parametric representations of geometrical objects such as foliations (many parametrizations describe the same object), we introduce the additional criterion method which consists of adding an unphysical objective function to the physical objective function, so as to make the solution unique. Assuming well trajectories and borehole correlations to be known, we optimize, with respect to these criteria, several simple structures comprising one foliation, including a field example. 相似文献
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ABSTRACTSkempton coefficient B is commonly used to evaluate the saturation of a sample before the shearing stage in a triaxial test. For unsaturated soils, measuring the degree of saturation Sr at the end of the consolidation stage is very difficult whereas measuring Skempton coefficient B is very simple. Using this coefficient to obtain Sr of a sample in a triaxial apparatus without complex procedures might be an improvement, especially as regards testing procedures for unsaturated soils. Different authors have proposed a relationship between these two parameters based on the hypothesis that a variation of B coefficient with Sr is mostly due to the compressibility of air in the pores. However, the presence of air as a fluid phase gives rise to suction after the equilibrium is reached inside the sample leading to an increase in stiffness. Based on this observation, this article presents a new relationship that enables Sr to be evaluated with a given Skempton coefficient taking into account not only the initial void ratio and the isotropic elastic modulus but also the suction and the elastoplastic behaviour of the soil. The results of the proposed approach are then confronted with the original relationship and compared to experimental data. 相似文献
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Jean-Pierre Rivet Farrokh Vakili Olivier Lai David Vernet Mathilde Fouché William Guerin Guillaume Labeyrie Robin Kaiser 《Experimental Astronomy》2018,46(3):531-542
More than sixty years after the first intensity correlation experiments by Hanbury Brown and Twiss, there is renewed interest for intensity interferometry techniques for high angular resolution studies of celestial sources. We report on a successful attempt to measure the bunching peak in the intensity correlation function for bright stellar sources with 1 meter telescopes (I2C project). We propose further improvements of our preliminary experiments of spatial interferometry between two 1 m telescopes, and discuss the possibility to export our method to existing large arrays of telescopes. 相似文献