Ground motion prediction equations based on shallow crustal earthquakes in Georgia and the surrounding Caucasus          下载免费PDF全文

Jorjiashvili Nato  Shengelia Ia  Godoladze Tea  Gunia Irakli  Akubardia Dimitri 《地震科学（英文版）》2022,35(6):497-509

Strong ground motions caused by earthquakes with magnitudes ranging from 3.5 to 6.9 and hypocentral distances of up to 300 km were recorded by local broadband stations and three-component accelerograms within Georgia’s enhanced digital seismic network. Such data mixing is particularly effective in areas where strong ground motion data are lacking. The data were used to produce models based on ground-motion prediction equations (GMPEs), one benefit of which is that they take into consideration information from waveforms across a wide range of frequencies. In this study, models were developed to predict ground motions for peak ground acceleration and 5%-damped pseudo-absolute-acceleration spectra for periods between 0.01 and 10 s. Short-period ground motions decayed faster than long-period motions, though decay was still in the order of approximately 1/r. Faulting mechanisms and local soil conditions greatly influence GMPEs. The spectral acceleration (SA) of thrust faults was higher than that for either strike-slip or normal faults but the influence of strike-slip faulting on SA was slightly greater than that for normal faults. Soft soils also caused significantly more amplification than rocky sites.  相似文献   

Quantifying land degradation in the Zoige Basin,NE Tibetan Plateau using satellite remote sensing data   总被引：3，自引：0，他引：3  

Kai-feng Yu  Frank Lehmkuhl  Dimitri Falk 《山地科学学报》2017,14(1):77-93

Considerable efforts have been dedicated to desertification research in the arid and semi-arid drylands of central Asia. However, there are few quantitative studies in conjunction with proper qualitative evaluation concerning land degradation and aeolian activity in the alpine realm. In this study, spectral information from two Landsat-5 TM scenes (04.08.1994 and 28.07.2009, respectively) was combined with reference information obtained in the field to run supervised classifications of eight landscape types for both time steps. Subsequently, the temporal and spatial patterns of the alpine wetlands/grasslands evolutions in the Zoige Basin were quantified and assessed based on these two classification maps. The most conspicuous change is the sharp increase of ~627 km² degraded meadow. Concerning other land-covers, shallow wetland increases ~107 km² and aeolian sediments (mobile dunes and sand sheets) have an increase of ~30 km². Considering the deterioration, an obvious decrease of ~440 km² degraded wetland can be observed. Likewise, decrease of deep wetland (~78 km²), humid meadow (~80 km²) and undisturbed meadow (~88 km²) were determined. These entire evolution matrixes undoubtedly hint a deteriorating tendency of the Zoige Basin ecosystem, which is characterized by significantly declined proportion of intact wetlands, meadow, rangeland and a considerable increase of degraded meadow and larger areas of mobile dunes. In particular, not only temporal alteration of the land-cover categories, the spatial and topographical characteristics of the land degradation also deserves more attention. In the alpine rangelands, the higher terraces of the river channels along with their slopes are more liable to the degradation and desertification. This tendency has significantly impeded the nomadic and agriculture activities. The set of anthropozoogenic factors encompassing enclosures, overgrazing and trampling, rodent damaging and exceedingly ditching in the wetlands are assumed to be the main controlling mechanisms for the landscape degradation. A suite of strict protection policies is urgent and indispensable for self-regulation and restoration of the alpine meadow ecosystem. Controlling the size of livestock, less ditching in the rangeland, and the launching of a more strict nature reserve management by adjacent Ruoergai, Maqu and Hongyuan Counties would be practical and efficacious in achieving these objectives.  相似文献   

Towards a seismic design method for plane steel frames using equivalent modal damping ratios     

George A. Papagiannopoulos  Dimitri E. Beskos 《Soil Dynamics and Earthquake Engineering》2010

A method for seismic design of plane steel moment resisting frames based on the use of equivalent modal damping ratios is developed. The method determines the design base shear of the structure through spectrum analysis using rationally obtained equivalent modal damping ratios instead of the crude strength reduction (behavior) factor. An equivalent linear structure, which retains the mass and initial stiffness of the original non-linear structure and takes into account geometrical non-linearity and inelasticity in the form of equivalent, time-invariant, modal damping ratios is established. The equivalent damping ratios for the first few significant modes are numerically computed by first iteratively forming a frequency response transfer function modulus until it satisfies certain smoothness criteria and then by solving a set of non-linear algebraic equations. Thus, design equations providing equivalent damping ratios as functions of period and allowable deformation and damage are constructed using extensive numerical data coming from plane steel moment resisting frames excited by various seismic motions. These equations can be used in conjunction with a design spectrum, appropriately constructed for high damping values, and modal synthesis tools to calculate the seismic design forces of the structure. The proposed method is illustrated by numerical examples. It is concluded that unlike the usual approach of seismic codes employing a single common value of the strength reduction factor value for all modes, the proposed approach working with deformation and damage dependent equivalent modal damping ratios leads to more accurate and deformation and damage controlled results.  相似文献   

A medieval settlement caught in the sand: Optical dating of sand-drifting at Pulle (N Belgium)     

Cilia Derese  Dimitri Vandenberghe  Nele Eggermont  Jan Bastiaens  Rica Annaert  Peter Van den haute 《Quaternary Geochronology》2010,5(2-3):336-341

Close to the village of Pulle (N Belgium), six trenches were opened for archaeological research. This resulted in the discovery of a dense spread of traces of human settlement. Only a relatively small number of artefacts was found, but these allowed attributing the traces to habitation during the Iron Age and Early Middle Ages. In one of the trenches, the level with the archaeological finds was covered by a drift-sand dune. The accumulation of these aeolian sediments presumably put an end to the human occupation. Hence, dating these sediments might provide essential information as to the chronology of the occupational history of the site.Quartz-based optical dating was applied to constrain the timing of sand-drifting at Pulle. All samples showed satisfactory luminescence characteristics and yielded an internally consistent set of optical ages. Within analytical uncertainty, the age results show no increase with depth and do not allow differentiating between distinct phases of sand-drifting. An average age of 1.2 ± 0.1 ka was obtained, which is interpreted as an upper age limit for human occupation at the site. The results also illustrate (the limit on) the time resolution that can be achieved through conventional quartz single-aliquot optical dating techniques; considering these limitations, we conclude that the sand-drifting at Pulle occurred during a single, fairly short event in the Early Middle Ages.  相似文献   

Multi-view dense matching supported by triangular meshes     

Dimitri Bulatov  Peter WernerusChristian Heipke 《ISPRS Journal of Photogrammetry and Remote Sensing》2011,66(6):907-918

We present a new procedure to compute dense 3D point clouds from a sequential set of images. This procedure is considered as a second step of a three-step algorithm for 3D reconstruction from image sequences, whose first step consists of image orientation and the last step is shape reconstruction. We assume that the camera matrices as well as a sparse set of 3D points are available and we strive for obtaining a dense and reliable 3D point cloud. Three novel ideas are presented: (1) for sparse tracking and triangulation, the search space for correspondences is reduced to a line segment by means of known camera matrices and disparity ranges are provided by triangular meshes from the already available points; (2) triangular meshes from extended sets of points are used for dense matching, because these meshes help to reconstruct points in weakly textured areas and present a natural way to obtain subpixel accuracy; (3) two non-local optimization methods, namely, 1D dynamic programming along horizontal lines and semi-global optimization were employed for refinement of local results obtained from an arbitrary number of images. All methods were extensively tested on a benchmark data set and an infrared video sequence. Both visual and quantitative results demonstrate the effectiveness of our algorithm.  相似文献   

Outward migration of extrasolar planets to large orbital radii     

Dimitri Veras  Philip J. Armitage 《Monthly notices of the Royal Astronomical Society》2004,347(2):613-624

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The dynamics of two massive planets on inclined orbits     

Dimitri Veras  Philip J. Armitage 《Icarus》2004,172(2):349-371

The significant orbital eccentricities of most giant extrasolar planets may have their origin in the gravitational dynamics of initially unstable multiple planet systems. In this work, we explore the dynamics of two close planets on inclined orbits through both analytical techniques and extensive numerical scattering experiments. We derive a criterion for two equal mass planets on circular inclined orbits to achieve Hill stability, and conclude that significant radial migration and eccentricity pumping of both planets occurs predominantly by 2:1 and 5:3 mean motion resonant interactions. Using Laplace-Lagrange secular theory, we obtain analytical secular solutions for the orbital inclinations and longitudes of ascending nodes, and use those solutions to distinguish between the secular and resonant dynamics which arise in numerical simulations. We also illustrate how encounter maps, typically used to trace the motion of massless particles, may be modified to reproduce the gross instability seen by the numerical integrations. Such a correlation suggests promising future use of such maps to model the dynamics of more coplanar massive planet systems.  相似文献   

A resonant-term-based model including a nascent disk,precession, and oblateness: application to GJ 876     

Dimitri Veras 《Celestial Mechanics and Dynamical Astronomy》2007,99(3):197-243

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Adaptive POD-Galerkin Technique for Reservoir Simulation and Optimization     

Voloskov  Dmitry  Pissarenko  Dimitri 《Mathematical Geosciences》2021,53(8):1951-1975

Mathematical Geosciences - This paper introduces a novel method using an adaptive functional basis for reduced order models based on proper orthogonal decomposition (POD). The method is intended to...  相似文献