层状岩质边坡的屈曲破坏分析

本文根据多层层状结构岩质边坡的屈曲破坏模式，建立了相应的力学模型，从理论上对这种形式的破坏机理进行了研究，得出了相应力学模型的挠曲曲线的理论解。对具体工程实例的应用表明，本文的研究成果不仅能解决具体工程问题，而且有助于深入理解该类边坡的屈曲破坏机理。     

Soil bentonite wall protects foundation from thrust faulting: analyses and experiment

When seismic thrust faults emerge on the ground surface,they are particularly damaging to buildings,bridges and lifelines that lie on the rupture path.To protect a structure founded on a rigid raft,a thick diaphragm-type soil bentonite wall(SBW) is installed in front of and near the foundation,at sufficient depth to intercept the propagating fault rupture.Extensive numerical analyses,verified against reduced–scale(1 g) split box physical model tests,reveal that such a wall,thanks to its high deformability and low shear resistance,"absorbs" the compressive thrust of the fault and forces the rupture to deviate upwards along its length.As a consequence,the foundation is left essentially intact.The effectiveness of SBW is demonstrated to depend on the exact location of the emerging fault and the magnitude of the fault offset.When the latter is large,the unprotected foundation experiences intolerable rigid-body rotation even if the foundation structural distress is not substantial.     

A comparative study of the design spectra defined by Eurocode 8, UBC, IBC and Turkish Earthquake Code on R/C sample buildings

Earthquake codes have been revised and updated depending on the improvements in the representation of ground motions, soils and structures. These revisions have been more frequently seen in recent years. One of the key changes in earthquake codes has been performed on the design spectra. In this paper, the design spectra recommended by Turkish Earthquake Code and three other well known codes (Uniform Building Code, Eurocode 8, and International Building Code) are considered for comparison. The main purpose of this study is to investigate the differences caused by the use of different codes in the dynamic analysis and seismic verification of given types of buildings located at code defined different sites. The differences in expressions and some important points for elastic and inelastic spectra defined by the codes are briefly illustrated in tables and figures. Periods, base shears, lateral displacements and interstory drifts for the analyzed buildings located at code defined ground type are comparatively presented.     

祁连山东段庄浪河流域地貌特征及其构造指示意义

晚新生代以来,青藏高原北东向扩展,致使祁连山地区遭受了强烈的构造隆升,造就了祁连山地区复杂的构造格局和急剧变化的构造地貌,其典型水系流域地貌特征揭示了该地区的新构造活动和地貌演化过程。庄浪河流域位于祁连山东段,作为青藏高原北东向扩展的前缘地区,庄浪河流域的地貌参数对构造活动非常敏感,提取庄浪河流域的地貌信息,有助于揭示祁连山东段庄浪河流域地貌对构造活动的响应,及系统探讨该区地貌发育特征及其所蕴含的构造意义。庄浪河流域内及边缘发育有庄浪河断裂、天祝盆地南缘断裂、疙瘩沟隐伏断裂以及金强河-毛毛山-老虎山断裂。晚新生代以来,这些断裂仍在活动,并且控制着流域内的构造变形、山体隆升和河流水系地貌发育。本研究采用ALOS DEM 12.5 m数据,基于ArcGIS空间分析技术,通过高程条带剖面、河流坡降指标体系（K,SL,SL/K）和Hack剖面、面积-高程积分值（HI）和积分曲线（HC）等方法,对庄浪河流域地貌特征进行了初步分析。结果表明,庄浪河地区地形起伏由北西向南东递减,构造活动存在东西分异的规律;庄浪河流域内部K值、SL、SL/K、HI值西侧高于东侧,Hack剖面西侧相比东侧上凸更明显;H...     

Landslide susceptibility mapping using geological data, a DEM from ASTER images and an Artificial Neural Network (ANN)

An efficient and accurate method of generating landslide susceptibility maps is very important to mitigate the loss of properties and lives caused by this type of geological hazard. This study focuses on the development of an accurate and efficient method of data integration, processing and generation of a landslide susceptibility map using an ANN and data from ASTER images. The method contains two major phases. The first phase is the data integration and analysis, and the second is the Artificial Neural Network training and mapping. The data integration and analysis phase involve GIS based statistical analysis relating landslide occurrence to geological and DEM (digital elevation model) derived geomorphological parameters. The parameters include slope, aspect, elevation, geology, density of geological boundaries and distance to the boundaries. This phase determines the geological and geomorphological factors that are significantly correlated with landslide occurrence. The second phase further relates the landslide susceptibility index to the important geological and geomorphological parameters identified in the first phase through ANN training. The trained ANN is then used to generate a landslide susceptibility map. Landslide data from the 2004 Niigata earthquake and a DEM derived from ASTER images were used. The area provided enough landslide data to check the efficiency and accuracy of the developed method. Based on the initial results of the experiment, the developed method is more than 90% accurate in determining the probability of landslide occurrence in a particular area.     

Seismicity re-evaluation of the northern Red Sea

The Aqaba subnetwork of five vertical short-period stations of the seismological observatory of King Saud University was installed in late 1986 along the eastern side of the Gulf of Aqaba, northern Red Sea. During the first six years (1986 August to 1992 July) of the subnetwork operation, 400 microearthquakes were detected. Of these, 93 events were recorded by most of the subnet stations and were located. Their epicentres lie in the northern part of the Red Sea between latitudes 25.5 N and 27.5 N and longitudes 33.5 E and 36 E along the axial depression of the Red Sea where the large intrusions (deeps) are located. Magnitudes of the locatable events ranged from 2.1 to 4.8. Two intensive swarms of about 200 microearthquakes occurred in February and June of 1992. The February swarm is the first intensive sequence observed in the surveying area since the establishment of the KSU network. Frequency-magnitude analysis of the recorded events for the period 1986-1992 yielded 3.543 for a and 0.658 for b . These relatively higher b values (0.658) are a good indication of the crustal heterogeneity under the spreading zone of the northern Red Sea. USGS and KSU data together show 3.41 for a and 0.49 for b . This study, together with historical data, confirms that the area is very seismically active and that the activity is mainly of swarm type, and may be attributed to the subsurface magmatic activity and spreading centres that are usually associated with strike-slip and normal faulting, respectively.     

2020年古冶MS5.1地震序列微震检测及活动性研究

2020年7月12日河北省古冶(39.78°N, 118.44°E)发生M_S5.1地震, 震源深度10 km.本文通过对其周边500 km范围内的84个固定台站连续观测地震数据, 采用基于图形处理器的模板匹配定位识别技术(GPU-M&L)对地震前后(2020年6月1日至2020年8月31日)共三个月的连续数据进行了微震检测和地震活动性分析.我们首先从台网目录的362个古冶地震序列事件中挑选了信噪比较高的118个地震作为模板, 通过模板扫描和检测, 获得共1017个地震, 约为台网目录的2.8倍, 然后运用双差定位方法(hypoDD)对669个地震事件进行了重定位.最后我们对古冶地震的事件序列进行时空分布、震源机制解以及b值空间分布等分析.结果显示古冶M_S5.1地震前, 震中区周边地震活动性显著, 地震前后地震序列分布优势方向为NE向, 震源深度方向近直立分布; 发震断裂为唐山—古冶断裂或其延伸部分, 与1976年唐山M_S7.8地震同为唐山断裂带, 发震断层走向基本一致.据此, 我们推测古冶M_S5.1地震是1976年唐山M_S7.8地震后余震区应力调整所触发.