Large-scale failures on domes and stratocones situated on caldera ring faults: sand-box modeling of natural examples from Kamchatka, Russia     

Alexander Belousov  Thomas R. Walter  Valentin R. Troll 《Bulletin of Volcanology》2005,67(5):457-468

Edifices of stratocones and domes are often situated eccentrically above shallow silicic magma reservoirs. Evacuation of such reservoirs forms collapse calderas commonly surrounded by remnants of one or several volcanic cones that appear variously affected and destabilized. We studied morphologies of six calderas in Kamchatka, Russia, with diameters of 4 to 12 km. Edifices affected by caldera subsidence have residual heights of 250–800 m, and typical amphitheater-like depressions opening toward the calderas. The amphitheaters closely resemble horseshoe-shaped craters formed by large-scale flank failures of volcanoes with development of debris avalanches. Where caldera boundaries intersect such cones, the caldera margins have notable outward embayments. We therefore hypothesize that in the process of caldera formation, these eccentrically situated edifices were partly displaced and destabilized, causing large-scale landslides. The landslide masses are then transformed into debris avalanches and emplaced inside the developing caldera basins. To test this hypothesis, we carried out sand-box analogue experiments, in which caldera formation (modeled by evacuation of a rubber balloon) was simulated. The deformation of volcanic cones was studied by placing sand-cones in the vicinity of the expected caldera rim. At the initial stage of the modeled subsidence, the propagating ring fault of the caldera bifurcates within the affected cone into two faults, the outermost of which is notably curved outward off the caldera center. The two faults dissect the cone into three parts: (1) a stable outer part, (2) a highly unstable and subsiding intracaldera part, and (3) a subsiding graben structure between parts (1) and (2). Further progression of the caldera subsidence is likely to cause failure of parts (2) and (3) with failed material sliding into the caldera basin and with formation of an amphitheater-like depression oriented toward the developing caldera. The mass of material which is liable to slide into the caldera basin, and the shape of the resulted amphitheater are a function of the relative position of the caldera ring fault and the base of the cone. A cone situated mostly outside the ring fault is affected to a minor degree by caldera subsidence and collapses with formation of a narrow amphitheater deeply incised into the cone, having a small opening angle. Accordingly, the caldera exhibits a prominent outward embayment. By contrast, collapse of a cone initially situated mostly inside the caldera results in a broad amphitheater with a large opening angle, i.e. the embayment of the caldera rim is negligible. The relationships between the relative position of an edifice above the caldera fault and the opening angle of the formed amphitheater are similar for the modeled and the natural cases of caldera/cone interactions. Thus, our experiments support the hypothesis that volcanic edifices affected by caldera subsidence can experience large-scale failures with formation of indicative amphitheaters oriented toward the caldera basins. More generally, the scalloped appearance of boundaries of calderas in contact with pre-caldera topographic highs can be explained by the gravitational influence of topography on the process of caldera formation.Editorial responsibility: J. Stix  相似文献   

Interpretation from large-scale shake table tests on piles undergoing lateral spreading in liquefied soils   总被引：2，自引：0，他引：2  

M. Cubrinovski  T. Kokusho  K. Ishihara 《Soil Dynamics and Earthquake Engineering》2006,26(2-4):275-286

Results from a benchmark test on full-scale piles are used to investigate the response of piles to lateral spreading. In the experiment, two single piles, a relatively flexible pile that moves together with the surrounding soil and a relatively stiff pile that does not follow the ground movement have been subjected to large post-liquefaction ground displacement simulating piles in laterally spreading soils. The observed response of the piles is first presented and then the results are used to examine the lateral loads on the pile from a non-liquefied soil at the ground surface and to evaluate the stiffness characteristics of the spreading soils. The measured ultimate lateral pressure from the crust soil on the stiff pile was about 4.5 times the Rankine passive pressure. The back-calculated stiffness of the liquefied soil was found to be in the range between 1/30 and 1/80 of the initial stiffness of the soil showing gradual decrease in the course of lateral spreading.  相似文献   

某大型商业建筑消防设计     

王培玲 《中国勘察设计》2007,(9):105-107

大型商业建筑投资规模大,人员密集,一旦发生火灾,损失巨大,因此消防设计要慎之又慎。本文根据某大型商业建筑的特点,介绍了关于给排水和暖通专业的消防设计。  相似文献   

Investigation of Low-Frequency Perturbations Induced by a Steep Obstacle     

D. Cava  S. Schipa  U. Giostra 《Boundary-Layer Meteorology》2005,115(1):27-45

Flow perturbation due to the orographic forcing at the top of a steep ridge has been investigated. Spectral and wavelet analyses of longitudinal and vertical wind velocity components highlight the presence of low-frequency perturbations produced by topography. Wavelet kurtosis reveals the intermittent character of these perturbations. The application of a multi-resolution data filter allows the detection of the topographically forced structures and the consequent statistical characterisation. The detected topographically forced structures remain active only for a 15% of the time on average. Nevertheless, they appear very efficient in the momentum transport, accounting for about 50% of the downward momentum flux produced in the low frequency range. Quadrant analysis highlights how topographical forcing produces the weakening of ejections and the strengthening of sweeps at the top of the ridge.  相似文献   

大尺度环境场对热带气旋影响的动力分析   总被引：15，自引：3，他引：15  

雷小途  陈联寿 《气象学报》2001,59(4):429-439

文中基于正压大气运动的基本方程组 ,把大气运动场分解为大尺度环境场和热带气旋环流 ,采用动力分析的方法 ,分析了有 /无大尺度环境场作用的热带气旋运动特征。结果表明 :无环境场时 ,热带气旋的运动遵循位涡守恒原理、热带气旋的定常运动满足相当地转风平衡关系 (f 平面近似 ) ,其等位涡线和等压能线均与流线重合 ;有环境场时 ,热带气旋的运动不再遵循位涡守恒原理、其定常运动的等位涡线和等压能线也均与流线不再重合 ,但热带气旋的定常运动满足准相当地转风平衡关系 (f 平面近似 )、等相当压能线与流线重合。最后还能过建立有 /无大尺度环境场作用的热带气旋强度变化及移动速度的方程式 ,定性地分析了大尺度环境场对热带气旋强度变化及移动的影响。  相似文献   

西部大开发与铁路建设   总被引：3，自引：3，他引：3  

何振宁 《工程地质学报》2001,9(4):429-434

西部大开发将给我国中西部地区带来前所未的机遇, 而铁路建设正是遇到新的挑战。本文针对西部地区特殊的地质条件与地质环境, 详细探讨了在西部地区进行铁路建设可能遇到的问题, 为西部地区铁路建设提供了必要参考。  相似文献   

一次梅雨暴过程中潜热的计算分析   总被引：4，自引：0，他引：4       下载免费PDF全文

抽彩军  寿绍文等 《气象科学》2002,22(4):468-473

本文针对1991年7月5日20时-6日20时一次江淮梅雨过程，计算了潜热的释放，并揭示出潜热具有以下特点：（1）在整个梅雨锋暴雨过程中有大量凝结潜热释放，且在梅雨锋暴雨的强盛时期潜热释放最多。（2）在此次梅雨锋暴雨过程中对流凝结潜热的释放明显大于大尺度稳定凝结潜热的释放，且主要集中在650hPa-550hPa，它的强弱变化与实际降水强度变化成正比。  相似文献   

Solar origin of geomagnetic storms and prediction of storms with the use of neural networks     

H. Lundstedt 《Surveys in Geophysics》1996,17(5):561-573

This review deals with how the changes of the large-scale solar magnetic fields are related to the occurrence of solar phenomena, which are associated with geomagnetic storms. The review also describes how artificial neural networks have been used to forecast geomagnetic storms either from daily solar input data or from hourly solar wind data. With solar data as input predictions 1–3 days or a month in advance are possible, while using solar wind data as input predictions about an hour in advance are possible. The predictions one hour ahead of the geomagnetic storm indexD _st from only solar wind input data have reached such high accuracy, that they are of practical use in combination with real-time solar wind observations at L1. However, the predictions days and a month ahead need to be much improved in order to be of real practical use.  相似文献   

A new parallel PM code for very large-scale cosmological simulations     

Tom MacFarland  H. M. P. Couchman  F. R. Pearce  Jakob Pichlmeier   《New Astronomy》1998,3(8):687-705

We have developed a parallel Particle–Particle, Particle–Mesh (P³M) simulation code for the Cray T3E parallel supercomputer that is well suited to studying the time evolution of systems of particles interacting via gravity and gas forces in cosmological contexts. The parallel code is based upon the public-domain serial Adaptive P³M-SPH (http://coho.astro.uwo.ca/pub/hydra/hydra.html) code of Couchman et al. (1995)[ApJ, 452, 797]. The algorithm resolves gravitational forces into a long-range component computed by discretizing the mass distribution and solving Poisson's equation on a grid using an FFT convolution method, and a short-range component computed by direct force summation for sufficiently close particle pairs. The code consists primarily of a particle–particle computation parallelized by domain decomposition over blocks of neighbour-cells, a more regular mesh calculation distributed in planes along one dimension, and several transformations between the two distributions. The load balancing of the P³M code is static, since this greatly aids the ongoing implementation of parallel adaptive refinements of the particle and mesh systems. Great care was taken throughout to make optimal use of the available memory, so that a version of the current implementation has been used to simulate systems of up to 10⁹ particles with a 1024³ mesh for the long-range force computation. These are the largest Cosmological N-body simulations of which we are aware. We discuss these memory optimizations as well as those motivated by computational performance. Performance results are very encouraging, and, even without refinements, the code has been used effectively for simulations in which the particle distribution becomes highly clustered as well as for other non-uniform systems of astrophysical interest.  相似文献   

The carbon cost of agricultural production in the global land rush     

《Global Environmental Change》2023

Increases in the number of large-scale land transactions (LSLTs), commonly known as ‘land grabbing’ or ‘global land rush,’ have occurred throughout the lower- and middle-income world over the past two decades. Despite substantial and continuing concerns about the negative socio-environmental impacts of LSLTs, trade-off analysis on boosting crop yield and minimizing climate-related effects remains limited. Our study makes use of a global dataset on LSLTs for agricultural production to estimate potential carbon emissions based on different scenarios of land cover change and fertilizer use, as well as potential value of agricultural production on transacted land. We show that, if fully implemented on ∼ 38 M ha of transacted land, 2.51 GtC will be emitted during land conversion, with another 24.2 MtC/year emitted from fertilizer use, assuming farming technology of investors’ origin is adopted on transacted land. Comparison of different combinations of forest protection policies and agricultural intensification levels reveals that enforcing strict deforestation regulation while promoting fertilizer use rate improves the carbon efficiency of agricultural production. Additionally, positive spillovers of investors’ farming technology on existing arable lands of host countries can potentially double their crop yield. Our analyses thus suggest that fostering agricultural intensification and technology spillovers under strict regulation on land allocation to investors to protect forests would allow for boosting agricultural yield while minimizing carbon emissions.  相似文献