军队参与国际重大自然灾害救援行动工作机制建设的思考

向遭受严重自然灾害的国家或地区提供人道主义紧急支援,是各国军队在和平时期的重要使命。目前中国军队还没有成建制地出国参加过重大自然灾害的国际救援。本文介绍了联合国重大自然灾害国际救援行动协调工作机制、联合国框架下的军队资源参与灾害救援的工作机制。结合印尼地震海啸、海地地震等灾害中各国军队救援的情况,对我国军队将来参与国际重大自然灾害救援,在法律、预案和工作机制准备方面进行了分析,并提出了建议。     

Seepage driving effect on deformations of San Fernando dams

In the process of flow deformation of an earth dam, the seepage force inside the dam plays a role as a driving force. The seepage force acts just like the gravitational force in terms of pushing soils away from their original locations after liquefaction is triggered. This paper draws attention to this seepage driving effect by presenting a set of fully coupled finite element analyses on the well-known San Fernando dams, with the objective of evaluating the impact of this seepage effect. The results indicate that while this effect is always there, its practical significance depends on a number of factors. In the case of the upper San Fernando dam, which experienced a significant, but restricted, downstream movement during the 1971 earthquake, the seepage driving effect was indeed significant. On the contrary, for the lower dam, which failed and slid into the upstream reservoir during the same earthquake, this seepage effect was relatively less pronounced. The detailed results of the analyses reveal the likely mechanisms of failure and deformation of the two dams and the likely cause behind the difference between their responses during the earthquake.     

SPATIAL AND TEMPORAL DISTRIBUTION OF SLIP RATE DEFICIT ACROSS HAIYUAN-LIUPAN SHAN FAULT ZONE CONSTRAINED BY GPS DATA

As the northeast boundary of the Tibetan plateau, the Haiyuan-Liupan Shan fault zone has separated the intensely tectonic deformed Tibetan plateau from the stable blocks of Ordos and Alxa since Cenozoic era. It is an active fault with high seismic risk in the west of mainland China. Using geology and geodetic techniques, previous studies have obtained the long-term slip rate across the Haiyuan-Liupan Shan fault zone. However, the detailed locking result and slip rate deficit across this fault zone are scarce. After the 2008 Wenchuan M_S8.0 earthquake, the tectonic stress field of Longmen Shan Fault and its vicinity was changed, which suggests that the crustal movement and potential seismic risk of Haiyuan-Liupan Shan fault zone should be investigated necessarily. Utilizing GPS horizontal velocities observed before and after Wenchuan earthquake(1999~2007 and 2009~2014), the spatial and temporal distributions of locking and slip rate deficit across the Haiyuan-Liupan Shan fault zone are inferred. In our model, we assume that the crustal deformation is caused by block rotation, horizontal strain rate within block and locking on block-bounding faults. The inversion results suggest that the Haiyuan fault zone has a left-lateral strike-slip rate deficit, the northern section of Liupan Shan has a thrust dip-slip rate deficit, while the southern section has a normal dip-slip rate deficit. The locking depths of Maomao Shan and west section of Laohu Shan are 25km during two periods, and the maximum left-lateral slip rate deficit is 6mm/a. The locking depths of east section of Laohu Shan and Haiyuan segment are shallow, and creep slip dominates them presently, which indicates that these sections are in the postseismic relaxation process of the 1920 Haiyuan earthquake. The Liupan Shan Fault has a locking depth of 35km with a maximum dip-slip rate deficit of 2mm/a. After the Wenchuan earthquake, the high slip rate deficit across Liupan Shan Fault migrated from its middle to northern section, and the range decreased, while its southern section had a normal-slip rate deficit. Our results show that the Maomao Shan Fault and west section of Laohu Shan Fault could accumulate strain rapidly and these sections are within the Tianzhu seismic gap. Although the Liupan Shan Fault accumulates strain slowly, a long time has been passed since last large earthquake, and it has accumulated high strain energy possibly. Therefore, the potential seismic risks of these segments are significantly high compared to other segments along the Haiyuan-Liupan Shan fault zone.     

PRESENT KINEMATICS CHARACTERISTICS OF THE NORTHERN YUMUSHAN ACTIVE FAULT AND ITS RESPONSE TO THE NORTHEASTWARD GROWTH OF THE TIBETAN PLATEAU

Qilian Shan and Hexi Corridor, located in the north of Tibetan plateau, are the margin of Tibetan plateau's tectonic deformation and pushing. Its internal deformations and activities can greatly conserve the extension process and characteristics of the Plateau. The research of Qilian Shan and Hexi Corridor consequentially plays a significant role in understanding tectonic deformation mechanism of Tibetan plateau. The northern Yumushan Fault, located in the middle of the northern Qilian Shan thrust belt, is a significant component of Qilian Shan thrust belt which divides Yumushan and intramontane basins in Hexi Corridor. Carrying out the research of Yumushan Fault will help explain the kinematics characteristics of the northern Yumushan active fault and its response to the northeastward growth of the Tibetan plateau.Because of limited technology conditions of the time, different research emphases and some other reasons, previous research results differ dramatically. This paper summarizes the last 20 years researches from the perspectives of fault slip rates, paleao-earthquake characteristics and tectonic deformation. Using aerial-photo morphological analysis, field investigation, optical simulated luminescence(OSL)dating of alluvial surfaces and topographic profiles, we calculate the vertical slip rate and strike-slip rate at the typical site in the northern Yumushan Fault, which is(0.55±0.15)mm/a and(0.95±0.11), respectively. On the controversial problems, namely "the Luotuo(Camel)city scarp" and the 180 A.D. Biaoshi earthquake, we use aerial-photo analysis, particular field investigation and typical profile dating. We concluded that "Luotuo city scarp" is the ruin of ancient diversion works rather than the fault scarp of the 180 A.D. Biaoshi earthquake. Combining the topographic profiles of the mountain range with fault characteristics, we believe Yumu Shan is a part of Qilian Shan. The uplift of Yumu Shan is the result of Qilian Shan and Yumu Shan itself pushing northwards. Topographic profile along the crest of the Yumu Shan illustrates the decrease from its center to the tips, which is similar to the vertical slip rates and the height of fault scarp. These show that Yumu Shan is controlled by fault extension and grows laterally and vertically. At present, fault activities are still concentrated near the north foot of Yumu Shan, and the mountain ranges continue to rise since late Cenozoic.     

Research on wind-induced responses of a large-scale membrane structure

The wind-induced responses of a large-scale membrane structure, Expo Boulevard, are evaluated in this study. To obtain the wind pressure distribution on the roof surface, a wind tunnel test is performed. A brief analysis of wind pressure on the membrane roof is conducted first and then an analysis of the wind-induced responses of the structure is carried out using a numerical integral method in the time domain. In the process of calculation, the geometrical nonlinearity is taken into account. Results indicate that mean, RSM and peak values of the structure responses increase nonlinearly while the approaching flow velocity increases. Strong nonlinear characteristics are observed in the displacement responses, whereas the responses of nodal stress and cable axial force show minimal nonlinear properties when the membrane structure is subjected to wind loads. Different values of the damping ratio only have a minimal impact on the RSM response of the structure because the background component is a dominant part of the total dynamic response and the resonant component is too small. As the damping ratio increases from 0.02 to 0.05, the RMS responses of vertical displacement, nodal stress and cable axial force decrease by 8.1%, 6.7% and 17.9%, respectively. Since the mean component plays a significant role in the wind-induced response, the values of the gust response factor are not high for Expo Boulevard.     

石泉井水位异常与九寨沟7.0级地震关联性探讨

选取2014—2020年共计7年的石泉流体井水位整点值数据,结合小波分析方法及区域构造分析,研究石泉井水位长期异常变化的可能原因。结果表明,石泉水位异常活跃主要发生在2017年8月8日九寨沟地震之后,利用小波分析提取高频异常信息效果较好,九寨沟7.0级地震后的区域断裂活动加强或九寨沟地震造成的断裂周边含水层渗透性发生变化可能为导致石泉井水位长期异常的直接原因,未来月河断裂石泉段附近断层活动性值得进一步关注。     

太湖春季浮游植物群落对不同形态氮的吸收

为研究太湖春季浮游植物群落氮吸收特征及其与浮游植物群落结构和环境因子的关系,于2010年5月中旬采集太湖6个点位水样,利用15N稳定同位素示踪技术,测定太湖浮游植物群落对硝态氮,铵态氮和尿素的吸收,结果表明:太湖浮游植物群落对铵态氮的吸收速率均值最高,占几种氮总吸收量p(DN)的62.8%,各点位值在0.181 -1....     

2016年2月11日新疆新源5.0级地震发震构造及房屋震害特点

2016年2月11日新疆新源县发生MS5.0地震,极震区烈度为Ⅵ度。综合现场调查及地震等震线分布情况,初步判定本次地震的发震构造为阿吾拉勒山南缘断裂。对灾区乡镇的房屋进行调查,发现部分土木结构房屋未进行过抗震设计,在本次地震中破坏较为严重;部分砖木结构房屋地基未按照规范施工,在震动荷载作用下出现不均匀沉降,致使房屋墙体被拉裂、倾斜。数月前灾区发生过强降雨、冻融灾害,加之多次地震灾害叠加,造成本次地震房屋破坏率高、房屋破坏程度重。     

龙潭水库诱发地震震源参数分析

利用广西龙滩水库地震台网记录的数字地震波资料,用波谱分析方法计算了龙滩水库库区ML2．5—4．5级共计95个地震的震源参数。并对震源参数进行分析,结果表明：库区视应力的范围在0-3．5巴之间,2007年7月17日库区最大4．5级地震的视应力最大,为3．07巴。视应力随震级的增大呈幂函数增大趋势,两者的拟合关系为：σap...     

利用InSAR技术研究滇西南镇康—永德地区现今地壳形变特征

基于12景ALOS PALSAR卫星影像,利用InSAR的前沿技术,提取了2007~2010年滇西南镇康—永德一带的平均地壳形变速率和形变时间序列,并结合不同时段的水准和GPS监测结果,从三维角度研究了该区域现今的地壳运动特征。研究结果表明,水准资料显示的镇康—永德一带异常隆起区位于南汀河断裂带附近,范围沿北东—南西方向呈近椭圆形展布。这一地壳形变异常区在数十年尺度上表现为隆升(速率约2~3 mm/a),表明区域具备中强地震孕育的地壳形变背景。而在2007~2013的数年尺度上表现为大幅垂向形变波动,可能反映区域近年来地壳垂直运动比较活跃,应加强跟踪与监视。