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1.
新疆和中亚五国山河相连,都是“一带一路”建设的重要支点,但也是滑坡、泥石流等斜坡灾害的高发区,且两地的地质灾害发育有着明显的共性。本文对新疆和中亚地区的斜坡灾害研究现状进行综述,分析了两地斜坡灾害形成机理、发育规律,即中高山地分布集中,受降雨和冰雪融水影响很大,黄土滑坡发育。新疆的斜坡灾害研究多围绕公路、水利等工程设施;中亚地区的斜坡灾害研究以自然灾害居多,且在很大程度上受地震作用控制。最后,分析了新疆及中亚地区斜坡灾害研究的发展趋势,建议建立现代化的灾害监测预警系统,加强“一带一路”沿线国家地质灾害研究的国际合作。 相似文献
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对滇西南1970年以来所有M≥4.6级地震前的空间活动图像进行研究,用地震频度作为参数描述地震前区域的地震活动增强与平静现象,用空区、条带描述地震的孕震过程,得到以下认识:①地震频度增加是滇西南地区5级以上地震前的共性特征;②滇西南地区M≥4.6级地震前出现空区的比例随着地震震级的增加而有所增加,4.6~4.9级地震前只有60%的地震出现空区,5.0~5.9级地震前有90.9%的地震出现空区,而6.0级以上地震前全部出现空区;③空区平均持续时间也随着震级的加大而增加,空区平均持续时间为13.58个月,最短为3个月,最长为37个月;④主震位置(27/33)多发生在空区边缘(含长轴端12次、短轴端8次)。震前出现条带的规律则不明显。 相似文献
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哈萨克斯坦卡帕尔-阿拉善4号井氦气(He)含量映震特征 总被引:1,自引:0,他引:1
介绍了哈萨克斯坦卡帕尔-阿拉善4号井的水文地球化学环境,分析其17年氦气(He)含量变化映震特征,氦气(He)变化的地震前兆异常表现为:上升(或下降)幅度、速率变化超出正常范围,具有较好的重复性,测值遵循的是,背景值-趋势性上升(或突升),趋势性下降(或突降)-恢复至背景值的变化过程。将该井氦气(He)观测数据经过滤波、差分处理后,以3倍均方差作为异常识别标准,结果表明:氦气(He)对监测点周围300km范围5级地震、400km范围6级地震的对映率分别为100%、66.7%,是较好的地震前兆手段之一。 相似文献
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The Chi-Chi 1999 (ML = 7.3) earthquake generated a large number of aftershocks in the vicinity of the rupture plane. The spatial-temporal distribution of these aftershocks was recorded with high precision and thus provided a unique possibility to study whether the correlation between aftershocks and stress changes are primary due to coseismically induced stress changes (static), or whether stress relaxation processes (viscoelastic) in the lower crust contribute significantly to this correlation. From our analysis of a 3D finite element model simulating the viscoelastic stress changes due to the coseismic displacement and tectonic loading we found that the aftershocks are highly correlated with the stress variations (static and viscoelastic) caused by the main shock. Although we found that the correlation between seismicity rate changes and viscoelastic stress fluctuation is slightly better than that of the static stress changes, these differences can only be identified well in the lower crust. As a result, it is reasonable to conclude that static stress changes are the key mechanism for triggering early and shallow aftershocks in the upper crust. It is reasonable to infer that the viscoelastic relaxation in the lower crust does affect the occurrence of early aftershocks in the deep crust, but it does not significantly affect the shallow aftershocks. However, the stress changes induced from the lower crust gradually transfer to the upper crust and may influence the occurrence of aftershocks after a longer time period (>four Maxwell times). 相似文献
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Adem Dogangun Ramazan Acar Halil Sezen Ramazan Livaoglu 《Bulletin of Earthquake Engineering》2008,6(3):505-517
Almost all historical minarets in Turkey were constructed using cut stone, masonry blocks or combination of these two materials.
The structural and geometrical properties of each masonry minaret, or slender tower structure, depend on many factors including
the structural knowledge and applications at the time of construction, experience of the architect or engineer, seismicity
of the region, and availability of construction materials in that area. Recent earthquakes in Turkey have shown that most
masonry minarets in high seismic regions are vulnerable to structural damage and collapse. In this study, in order to investigate
the dynamic behavior of historical unreinforced masonry minarets, three representative minarets with 20, 25, and 30 m height
were modeled and analyzed using two ground motions recorded during the 1999 Kocaeli and Duzce, Turkey earthquakes. The modal
analyses of the models have shown that the structural periods and the overall structural response are influenced by the minaret
height and spectral characteristics of the input motion. The dynamic displacement and axial stress time histories are computed
at the critical points on the minarets. During recent earthquakes, most minaret failures occurred above the base of the structure.
Consistent with the observed response, the largest stresses were calculated at the same location. 相似文献
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A simple modal damping identification model developed by the present authors for classically damped linear building frames is extended here to the non-classically damped case. The modal damping values are obtained with the aid of the frequency domain modulus of the roof-to-basement transfer function and the resonant frequencies of the structure (peaks of the transfer function) as well as the modal participation factors and mode shapes of the undamped structure. The assumption is made that the modulus of the transfer function of the non-classically damped structure matches the one of the classically damped structure in a discrete manner, i.e., at the resonant frequencies of that function modulus. This proposed approximate identification method is applied to a number of plane building frames with and without pronounced non-classical damping under different with respect to their frequency content earthquakes and its limitations and range of applicability are assessed with respect to the accuracy of both the identified damping ratios and that of the seismic structural response obtained by classical mode superposition and use of those identified modal damping ratios. 相似文献
10.
A review of considerations on seismic safety of embankments and earth and rock-fill dams 总被引:2,自引:0,他引:2
M. Yener Ozkan 《Soil Dynamics and Earthquake Engineering》1998,17(7-8):439-458
An attempt has been made to summarise the methods of approach used in assessing the dynamic behaviour and safety of earth and rock-fill dams under seismic shaking until about the present time, from the soil engineer's point of view. Shortcomings of the pseudo-static method, procedures to estimate the permanent deformations, liquefaction effects, and experience gained from the previous events have been reviewed. Observing that the most important cause of instability is the occurence liquefaction during ground motions, cyclic approach and steady-state approach in assessing the liquefaction potential have been addressed and recent practical approaches of analysis and design have been referred. It has been found noteworthy to recall that incidence of failure or serious damage to well-engineered dams has not been experienced, even under strong ground shaking. 相似文献