Modeling regional initiation of rainfall-induced shallow landslides in the eastern Umbria Region of central Italy   总被引：3，自引：6，他引：3  

Diana Salciarini  Jonathan W. Godt  William Z. Savage  Pietro Conversini  Rex L. Baum  John A. Michael 《Landslides》2006,3(3):181-194

We model the rainfall-induced initiation of shallow landslides over a broad region using a deterministic approach, the Transient Rainfall Infiltration and Grid-based Slope-stability (TRIGRS) model that couples an infinite-slope stability analysis with a one-dimensional analytical solution for transient pore pressure response to rainfall infiltration. This model permits the evaluation of regional shallow landslide susceptibility in a Geographic Information System framework, and we use it to analyze susceptibility to shallow landslides in an area in the eastern Umbria Region of central Italy. As shown on a landslide inventory map produced by the Italian National Research Council, the area has been affected in the past by shallow landslides, many of which have transformed into debris flows. Input data for the TRIGRS model include time-varying rainfall, topographic slope, colluvial thickness, initial water table depth, and material strength and hydraulic properties. Because of a paucity of input data, we focus on parametric analyses to calibrate and test the model and show the effect of variation in material properties and initial water table conditions on the distribution of simulated instability in the study area in response to realistic rainfall. Comparing the results with the shallow landslide inventory map, we find more than 80% agreement between predicted shallow landslide susceptibility and the inventory, despite the paucity of input data.  相似文献   

Transient dynamic response of fluid-saturated soil under a moving cyclic loading     

Yu-Jia Hu  Yuan-Yuan Zhu  Chang-Jun Cheng 《Soil Dynamics and Earthquake Engineering》2011

Based on the Theory of Porous Media (TPM), a mathematical model of a two-dimensional incompressible fluid-saturated elastic soil is established, and the periodic boundary conditions are presented to analyze the transient dynamic response of this soil under a moving cyclic loading. The differential quadrature method (DQM) and the second-order backward difference scheme are applied to discretize the governing equations on the spatial and temporal domains, respectively. As application, a typical two-dimensional wave-induced transient problem with a seabed of finite thickness is analyzed, and the numerical results are compared with the analytical results presented in the present work. In addition, a transient dynamic response of fluid-saturated soil under limit moving vehicle loadings is studied. The effects of the velocity of vehicle and the volume fraction on the settlement and the pore water pressure are studied.  相似文献   

Computational issues and applications of line-elements to model subsurface flow governed by the modified Helmholtz equation     

Mark Bakker  Kristopher L. Kuhlman 《Advances in water resources》2011,34(9):1186-1194

Two new approaches are presented for the accurate computation of the potential due to line elements that satisfy the modified Helmholtz equation with complex parameters. The first approach is based on fundamental solutions in elliptical coordinates and results in products of Mathieu functions. The second approach is based on the integration of modified Bessel functions. Both approaches allow evaluation of the potential at any distance from the element. The computational approaches are applied to model transient flow with the Laplace transform analytic element method. The Laplace domain solution is computed using a combination of point elements and the presented line elements. The time domain solution is obtained through a numerical inversion. Two applications are presented to transient flow fields, which could not be modeled with the Laplace transform analytic element method prior to this work. The first application concerns transient single-aquifer flow to wells near impermeable walls modeled with line-doublets. The second application concerns transient two-aquifer flow to a well near a stream modeled with line-sinks.  相似文献   

Singular value decomposition as a denoising tool for airborne time domain electromagnetic data   总被引：1，自引：0，他引：1  

P.-A. Reninger  G. Martelet  J. Deparis  J. Perrin  Y. Chen 《Journal of Applied Geophysics》2011,75(2):264-276

Airborne time domain electromagnetic (TDEM) surveys are increasingly carried out in anthropized areas as part of environmental studies. In such areas, noise arises mainly from either natural sources, such as spherics, or cultural sources, such as couplings with man-made installations. This results in various distortions on the measured decays, which make the EM noise spectrum complex and may lead to erroneous inversion and subsequent misinterpretations. Thresholding and stacking standard techniques, commonly used to filter TDEM data, are less efficient in such environment, requiring a time-consuming and subjective manual editing. The aim of this study was therefore to propose an alternative fast and efficient user-assisted filtering approach. This was achieved using the singular value decomposition (SVD). The SVD method uses the principal component analysis to extract into components the dominant shapes from a series of raw input curves. EM decays can then be reconstructed with particular components only. To do so, we had to adapt and implement the SVD, firstly, to separate clearly and so identify easily the components containing the geological signal, and then to denoise properly TDEM data.The reconstructed decays were used to detect noisy gates on their corresponding measured decays. This denoising step allowed rejecting efficiently mainly spikes and oscillations. Then, we focused on couplings with man-made installations, which may result in artifacts on the inverted models. An analysis of the map of weights of the selected “noisy components” highlighted high correlations with man-made installations localized by the flight video. We had therefore a tool to cull most likely decays biased by capacitive coupling noises. Finally, rejection of decays affected by galvanic coupling noises was also possible locating them through the analysis of specific SVD components. This SVD procedure was applied on airborne TDEM data surveyed by SkyTEM Aps. over an anthropized area, on behalf of the French geological survey (BRGM), near Courtenay in Région Centre, France. The established denoising procedure provides accurate denoising tools and makes, at least, the manual cleaning less time consuming and less subjective.  相似文献   

Microstructural evolution during strain localization in dolomite aggregates     

《Journal of Structural Geology》2014

Dolomite aggregates deformed by dislocation creep over a wide range of conditions (T = 700–1000 °C, effective pressure of 900 MPa, strain rates of 10⁻⁷ – 10⁻⁴/s) strain weaken by up to 75% of the peak differential stress. Microstructural study of samples shortened to different finite strains beyond the peak differential stress shows that strain becomes highly localized within shear zones by high-temperature creep processes, with no contribution of brittle cracking. At low strains (8%), dolomite deforms homogeneously by recrystallization-accommodated dislocation creep. At progressively higher sample strains, deformation is localized into narrow shear zones made up of very fine (∼3 μm) recrystallized grains and relict porphyroclasts (20–100 μm). Finely-recrystallized dolomite grains in the shear zones are largely dislocation free and localized shear is facilitated by diffusion creep. In contrast, original dolomite grains and porphyroclasts in shear zones have high dislocation densities and do not deform after shear zone formation. Calculated strain rates in the shear zones are two to three orders of magnitude faster than the imposed bulk strain rate of the samples and these strain rates are consistent with predictions of the diffusion creep flow law for fine-grained dolomite.  相似文献   

长江中下游地区冬季极端降水事件与天气尺度瞬变波活动的可能联系   总被引：6，自引：2，他引：4  

陈海山  朱月佳  刘蕾 《大气科学》2013,37(4):801-814

利用ERA40、NCEP/NCAR逐日再分析资料和长江中下游地区85站逐日降水资料,从大气内部天气尺度瞬变波的角度对长江中下游地区极端降水事件进行了成因分析。研究发现瞬变波活动与极端降水的发生关系密切;冬季在两支急流并存的欧亚大陆上空存在南北两支瞬变波活跃带。南支瞬变波在冬季极端降水频发、少发年存在较明显的差异。总体而言,极端降水频发年,瞬变波活动活跃,欧亚大陆上空的瞬变波持续时间长、传播连续、强度偏强;极端降水少发年,则反之。从逐日变化来看,南支瞬变波的强度和能量传播过程与极端降水的发生频次均具有一定的对应关系。北支瞬变波的传播及瞬变波对水汽的输送和极端降水的发生也有一定促进作 用。这些结果均表明,冬季极端降水的发生与天气尺度瞬变波的活动联系紧密,天气尺度瞬变波的异常活动及传播可能是极端降水发生的重要条件,研究可为极端降水的成因研究提供新的思路。  相似文献   

The Asymmetric Atmospheric Response to the Decadal Variability of Kuroshio Extension during Winter     

Jianqi ZHANG  Chongyin LI  Xin LI  Chao ZHANG  Jingjing CHEN 《大气科学进展》2021,38(5):785-799

The Kuroshio extension(KE)exhibits interdecadal variability,oscillating from a stable state to an unstable state.In this paper,ERA-Interim reanalysis data are used to discuss the possible reasons for the asymmetric response of the atmosphere to symmetric sea surface temperature anomaly(SSTA)during periods of differential KE states.The analysis has the following results:the SSTA presents a nearly symmetrical distribution with opposite signs during the KE stable and unstable periods.During the KE stable period,the storm track is located north of 40°N and is significantly enhanced in the northeast Pacific Ocean.The atmospheric response is similar to the West Pacific/North Pacific Oscillation teleconnection(WP/NPO like pattern)and presents a barotropic structure.The inversion results of the potential vorticity equation show that the feedback of transient eddy vorticity manifests a WP/NPO like pattern and presents a barotropic structure,which is the main reason for bringing about the response of the WP/NPO like pattern.The magnitude of the feedbacks of both diabatic heating and transient eddy heating is small,which can offset one another.During the KE unstable period,the main body of the storm track is located to the south of 40°N,and there is no significant response signal in the atmosphere,except near the west coast of North America.Compared with the KE stable period,the asymmetry of response of the transient eddy vorticity is the main reason for the asymmetric response of the atmosphere.  相似文献   

瞬变电磁法在哈密三岔口西矿段隐伏斑岩型铜矿床的应用     

屈栓柱  谢晓辉  李美英 《新疆地质》2013,(2)

激发极化法是寻找斑岩型矿床的重要手段之一,限于勘查深度较浅和碳质及无用金属硫化物干扰等原因,不能对隐伏矿体进行定位和评价.以新疆哈密三岔口西矿段隐伏斑岩型铜钼矿为例,在分析区域成矿地质背景、前人激电工作成果和岩石物性特征基础上,结合典型斑岩型成矿模式,提出应用瞬变电磁法圈定控矿岩体、岩体顶部及边部的中高电磁感应变化率(中高阻梯级带)部位为成矿有利部位的思路.通过后期钻探验证,发现了规模较大的隐伏斑岩型铜钼矿体,取得较好找矿效果.  相似文献   

Algorithms for Lunar Flash Video Search, Measurement, and Archiving     

Wesley Swift  Robert Suggs  Bill Cooke 《Earth, Moon, and Planets》2008,102(1-4):299-303

Lunar meteoroid impact flashes provide a method to estimate the flux of the large meteoroid flux and thus their hazard to spacecraft. Although meteoroid impacts on the Moon have been detected using video methods for over a decade, the difficulty of manually searching hours of video for the rare, extremely brief impact flashes has discouraged the technique’s systematic implementation. A prototype has been developed for the purpose of automatically searching lunar video records for impact flashes, eliminating false detections, editing the returned possible flashes, and archiving and documenting the results. Several utilities for measurement, analysis, and location of the flashes on the moon included in the program are demonstrated. Application of the program to a year’s worth of lunar observations is discussed along with examples of impact flashes.  相似文献   

Experimental and numerical analyses of vibrations induced by high-speed trains on the Córdoba–Málaga line     

P. Galvín  J. Domínguez 《Soil Dynamics and Earthquake Engineering》2009

This paper has two main purposes. One is to present and analyse soil and structural vibration data obtained experimentally during certification testing of the high-speed train line between Córdoba and Málaga (Spain) that was opened on December 2007. The second is to show the capabilities of a three-dimensional boundary element method (BEM)/finite element method (FEM) numerical approach for the analysis of train induced vibrations. The model can represent local soil conditions, discontinuities such as underpasses, as well as structures placed next to the rail track. Vibrations in those structures can be computed taking into account, in a rigorous way, dynamic soil–structure interaction and local soil properties. Experimental and numerical results at several points near the track are compared. Results for an overhead contact support structure are also evaluated. The comparison of numerically predicted and recorded results shows that the model is reliable for predicting the amplitude of vibrations produced in the soil and nearby structures by high-speed trains.  相似文献