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91.
92.
在分析1995年云南孟连西73级地震的前震序列时,发现跟踪最大前震62级的余震序列中,有一组较大震级的地震呈现出随时间的增长不断线性递增的特点,这种特点在云南其他震例中也曾多次出现过。利用修正的大森公式n(t)=k/(t+c)p拟合该序列,在获得的参数重新构造的频度-线性化时间坐标中,这一组地震显示出与海城前震序列随时间变化震级出现非线性增强的共同特征。采用表征物质加速应变而失稳的方程d(∑M01/2)/dt=c/(tm-t)n,对孟连西前震序列多方面进行跟踪定量分析,预测主震的发生时间平均比实发时间仅推迟26min,震级相差017级。 相似文献
93.
Historic maps, photographs, and channel cross-sections show that the channel of the Carmel River underwent massive bank erosion, channel migration, and aggradation in a major flood in 1911, then narrowed and incised by 1939. The channel was stable until 1978 and 1980, when bank erosion affected some reaches but not others. The narrowing and incision were in response to a lack of major floods after 1914 and construction in 1921 of a dam that cut off sediment supply from the most actively eroding half of the basin. Localized erosion in 1978 and 1980 occurred during low magnitude events along reaches whose bank strength had been reduced by devegetation. These events illustrate that the stability of a fluvial system can be disrupted either by application of a large erosive force in a high magnitude event (the 1911 flood) or in a low magnitude event, by reducing the resistance to erosion (bank devegetation). The Carmel River is a potentially unstable system. Its discharge and slope characteristics place it near the threshold between meandering and braided. On the Lower Carmel, the presence of bank vegetation can make the difference between a narrow, stable meandering channel and a wide shifting channel with braided reaches. 相似文献
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塔里木盆地阿克库勒凸起于奇地区哈拉哈塘组油气成藏机制 总被引:2,自引:0,他引:2
于奇地区是塔里木盆地塔河油区外围重要的油气勘探地区。研究结果表明:区内哈拉哈塘组油源主要来自阿克库勒凸起南部寒武系—下奥陶统烃源岩,油源充足,具有一定的勘探潜力;原油总体具有油质较轻、含硫量较低但含蜡量较高的特点;天然气属于典型的伴生气;圈闭类型主要为低幅度的构造圈闭,油气分布主要受低幅度背斜和断层所控制;区内储层至少发生了3次油气注入成藏期,即侏罗纪—白垩纪、古近纪古新世晚期—始新世和古近纪渐新世早期—新近纪中新世;成藏机制可归结为油气多期充注和多期次生成藏,燕山期为圈闭的形成与油气藏初步建立阶段,喜山期为圈闭的定型与油气藏重建阶段,成藏模式为它源-双向排烃-多期次生成藏或古生新储-双向排烃-多期次生成藏。 相似文献
97.
A. M. Korotkii T. A. Grebennikova L. P. Karaulova N. I. Belyanina 《Russian Journal of Pacific Geology》2007,1(4):352-365
In the Ussuri-Khanka depression of Primorye, the Quaternary alluvial-lacustrine and lacustrine sedimentogenesis progressed under conditions of transgressive accumulation in response to the depression tectonic subsidence and recurrent climatic fluctuations. The alluvial dams and irregular accumulation are proved to have been the leading factors of lakes’ formation within the depression. As is shown, fluctuations of the water level in limnic reservoirs depended on the climatic changes. New data considered in this work confirm the lacustrine genesis of a greater part of the Middle Pleistocene-Holocene sedimentary succession in the Khanka depression. Two transgressive phases, when the water level in the lakes rose by 1.5–2.0 m above the present one, are established for the Subboreal. The general conclusion is that the mesorhythmic structure of the sedimentary succession in the Ussuri-Khanka depression reflects the influence of climatic fluctuations in the Late Cenozoic. 相似文献
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采用虚拟激励法计算了大跨度钢管混凝土拱桥在纵向、竖向、横向、三维多点激励作用下的均方响应,在此基础上探讨了各方向激励及三维激励的多点输入效应对钢管混凝土拱桥地震响应特性的影响。结果表明纵向和竖向激励的多点输入效应对结构响应有明显影响,而横向激励的多点输入效应可忽略。 相似文献
100.
Recent seismic events have caused damage or collapse of invaluable historical buildings, further proving the vulnerability of unreinforced masonry (URM) structures to earthquakes. This study aims to understand failure of masonry arches—typical components of URM historic structures—subjected to horizontal ground acceleration impulses. An analytical model is developed to describe the dynamic behaviour of the arch and is used to predict the combinations of impulse magnitudes and durations which lead to its collapse. The model considers impact of the rigid blocks through several cycles of motion, illustrating that failure can occur at lower ground accelerations than previously believed. The resulting failure domains are of potential use for design and assessment purposes. Predictions of the analytical model are compared with results of numerical modelling by the distinct element method, and the good agreement between results validates the analytical model and at the same time confirms the potential of the distinct element framework as a method of evaluating complex URM structures under dynamic loading. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献