Was a dacite dome implicated in the 9,500 <Emphasis Type="SmallCaps">b.p.</Emphasis> collapse of Mt Ruapehu? A palaeomagnetic investigation     

Elizabeth?McClellandEmail author  Patrick?S.?Erwin 《Bulletin of Volcanology》2003,65(4):294-305

Constraining the process by which volcanoes become unstable is difficult. Several models have been proposed to explain the driving forces which cause volcanic edifices to catastrophically collapse. These include models for destabilisation of volcanic flanks by wedging due to dyke intrusion and the weakening of mechanical properties by pressurisation of pore fluids. It is not known which, if any, of the models are relevant to particular sector collapse events. Recent developments in the palaeomagnetic estimation of emplacement temperatures of volcaniclastic rocks have shown that even relatively low emplacement temperatures can be recorded by volcaniclastics with high fidelity. We have carried out a palaeomagnetic study of emplacement temperatures to investigate the role of igneous activity in the initiation of the 9,500 b.p. Murimotu sector collapse of Mt Ruapehu, New Zealand. This debris avalanche deposit has three fades which are stratigraphically superimposed, and the lowermost fades contains three lithological assemblages representing different segments of the edifice which were transported with little internal mixing within the flow. We have determined that some of the dacite-bearing assemblage 1, fades 1 was hot (∼350 °C) during transport and emplacement, whereas none of the other lithological assemblages of fades contained hot material. Our interpretation is that a dacite dome was active on the ancient Ruapehu edifice immediately prior to the Murimotu sector collapse. The partially cooled carapace of the dome and material shed from this part was incorporated into the avalanche deposit, along with cold lavas and volcaniclastics. We have not found evidence for incorporation of material at or close to magmatic temperatures, at least in the sampled locations. Our palaeomagnetic work allows us to develop a comprehensive, new palaeomagnetic classification of volcaniclastics. Published online: 25 January 2003 Editorial responsibility: D. Dingwell  相似文献   

A nonlinear elastic solution for 1-D subsidence due to aquifer storage and recovery applications   总被引：2，自引：1，他引：1  

Jiang?LiEmail author 《Hydrogeology Journal》2003,11(6):646-658

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Influence of rainfall on the deformation and stability of a slope in overconsolidated clays: a case study   总被引：2，自引：0，他引：2  

E.?E.?AlonsoEmail author  A.?Gens  C.?H.?Delahaye 《Hydrogeology Journal》2003,11(1):174-192

The behaviour of an instrumented unstable slope in a profile of weathered overconsolidated clay has been analysed. Available field investigation data and laboratory tests were integrated in a coupled hydromechanical model of the slope. Particular attention was given to the unsaturated soil conditions above the water table and to the influence of the rainfall record. Recorded pore-water pressures helped to identify the hydrogeological conditions of the slope. The coupled model was used to compute slope deformations and the variation of safety with time. Actual rainfall records were also integrated into the analysis. Comparison of measurements and calculations illustrate the nature of the slope instability and the complex relationships between mechanical and hydraulic factors. Electronic Publication  相似文献   

"96.1"高原暴雪过程三维条件性对称不稳定的数值研究   总被引：37，自引：22，他引：15  

王文  程麟生 《高原气象》2002,21(3):225-232

利用“96．1”青藏高原东北部暴雪过程的较成功的中尺度模拟的输出资料,用非纬向非平行基流中的对称不稳定模式,对“96．1”暴雪发生发展过程的动力学机制进行了三维基流中二维非线性对称不稳定数值模拟试验。结果表明,ψ场和ω场的三维配置与切变线的演变过程相当一致,说明用三维基流中二维非线性对称不稳定可能能较好地描述SI在切变线东伸南移过程中所起的作用。  相似文献   

A laboratory simulation of mesoscale flow interaction with the Alps     

E. Ferrero  A. Longhetto  L. Briatore  G. Chabert d&#x;Hieres  H. Didelle  C. Giraud  P. Gleizon 《Dynamics of Atmospheres and Oceans》2002,35(1):308

A series of laboratory experiments, aimed at the simulation of some aspects of Alpine lee cyclogenesis has been carried out in the rotating tank of the Coriolis Laboratory of LEGI-IMG in Grenoble. Dynamic and thermodynamic processes, typical of baroclinic development triggered by the orography, were simulated. The background flow simulating the basic state of the atmosphere consisted of a stream of intermediate density fluid introduced at the interface between two fluid layers. The structure of the intermediate current was established by mixing fluid obtained from the upper layer of fresh water with fluid removed from the heavier salty layer below.The dynamical similarity parameters are the Rossby (Ro), Burger (Bu) and Ekman (Ek) numbers, although this last, owing to its small values, need not be matched between model and prototype, since viscous effects are not important for small time scales. The flow in both the prototype and laboratory simulation is characterized by hydrostatics; this requires (Ro²δ²/Bu)1 (where δ=H/L is the aspect ratio of the obstacle) which is clearly satisfied, in the atmosphere and oceans, and for the laboratory experiment.A range of experiments for various Rossby and Burger numbers were conducted which delimited the region of parameter space for which background flows akin to that found to the northwest of the Alps prior to baroclinic cyclogenesis events, were observed.One such experiment was carried out by placing a model of the Alps at the appropriate place in the flow field. The subsequent motion in the laboratory was observed and dye tracer motions were used to obtain the approximate particle trajectories. The density field was also analyzed to provide the geopotential field of the simulated atmosphere. Using standard transformations from the similarity analysis, the laboratory observations were related to the prototype atmosphere. The flow and the geopotential fields gave results compatible with the particular atmospheric event presented.  相似文献   

A study on the nonlinear stability of fronts in the ocean on a sloping continental shelf     

Li Yang  Mu Mu  Wu Yonghui 《大气科学进展》2000,17(2):275-284

1.IntroductionArnol'd(1965,1969)variationalprincipleandapriorestimatemethodisessentiallyageneralizationofLyapunovstabilitymethodforfinite--dimensionaldynamicalsystemsininfinite--dimensionalones,andhestudiedthenonlinearstabilityof2--dimensionalincompressibleidealfluidmotionbyuseofthismethod,andestablishedtwotheoremswhichareArnol,d'sfirsttheoremandArnol'd'ssecondtheorem.Eversincethe1980's,manyscientistshavebeenworkingonthissubject,Holmetal.(1985);MclntyreandShepherd(1987);Zeng(1989);Muetal.(1…  相似文献   

Static and dynamic response of massive caisson foundations with soil and interface nonlinearities—validation and results     

Nikos Gerolymos  George Gazetas   《Soil Dynamics and Earthquake Engineering》2006,26(5):377-394

The static, cyclic, and dynamic response of a massive caisson foundation embedded in nonlinear layered or inhomogeneous soil and loaded at its top is investigated. The caisson is supported against horizontal displacement and rotation by four types of inelastic springs and dashpots, described with the BWGG model that was developed in the preceding companion paper [Gerolymos N, Gazetas G. Development of winkler model for static and dynamic response of caisson foundations with soil and interface nonlinearities. Soil Dyn Earthq Eng, submitted companion paper]. The prediction of the model is satisfactorily compared with results from 3D-finite element analysis. Some experimental corroboration of the method is provided with the help of a 1/3-scale lateral load test that had been conducted in the field by EPRI. An illustrative example of a caisson embedded in linearly-inhomogeneous clay and subjected to static and dynamic loading is analysed. Characteristic results are presented highlighting the role of soil inelasticity and its interplay with the two dominant interface nonlinearities: separation (gapping) of the caisson shaft from the surrounding soil, and uplifting of the base from the underlying soil.  相似文献   

“96·8”华北暴雨数值模拟与稳定性分析   总被引：3，自引：3，他引：3  

边清河  丁治英  董金虎 《气象》2006,32(8):17-22

分析1996年8月发生在华北地区的台风暴雨过程的环流形势，发现：副热带高压与台风低压之间的气压梯度很大，宽广的偏南急流源源不断地向北输送水汽和能量，而太行山一带正处于汇合区，构成十分有利的暴雨天气形势。应用MM5数值预报方法对1996年8月4—5日的降雨天气过程进行数值模拟，并依据天气学原理和位涡理论对此过程的稳定性进行分析认为：（1）MM5数值预报模式较好地模拟出了台风暴雨的物理过程。（2）此次降雨的不稳定层结有南高北低现象，同时有对称不稳定和对流不稳定存在；条件性对称不稳定可使环流加速，对降水有一定的增幅作用。  相似文献   

2005年3月22日华南飑线的综合分析   总被引：8，自引：1，他引：8  

罗建英  廖胜石  梁岱云  马艺  寿绍文 《气象》2006,32(10):70-75

2005年3月22日华南地区发生了一次飑线天气过程。利用常规观测、雷达回波、自动气象站资料及NCEP1°×1°的逐6小时资料,从天气形势、雷达回波、物理量场等多角度综合诊断分析了该飑线过程。结果表明:该过程具有低层增温、增湿,中高层降温、低湿的特征。飑线发生在快速东移的高空槽前上干冷、下暖湿的不稳定区域,华南地区700hPa低空急流的爆发及低层急流核向东传输对不稳定能量的突然释放有很大的触发作用。飑线系统在低空增温、增湿与对流层中层干侵入的相互作用下形成,产生大范围的雷雨大风、冰雹等强对流天气。  相似文献   

地-气耦合动力系统的研究     

莫嘉琪  王辉  林万涛 《气象学报》2006,64(3):400-404

研究了一类地-气耦合系统的非线性模型,目的是创建一个地-气振子模型的非线性方程的渐近求解方法,利用变分迭代方法,构造了对应问题解的近似展开式。即首先引入一组泛函和计算出它们的变分,并算出Lagrange乘子,其次,决定变分迭代,最后得到原地-气振子模型非线性问题解的一致收敛的近似展开式。  相似文献