模糊综合评判与聚类分析方法在水准观测网点稳定性分析中的应用

本文采用模糊综合评判和模糊聚类分析的方法对潍坊水准观测网点的稳定性进行了综合评判。根据对四个因素的单一评定,确定出隶属函数。并将水准网点的活动水平分为三类。通过综合评判得到评价集的稳定因素,进而用聚类分析方法分离出这些稳定点。     

应用模糊综合评判方法研究大同—阳高6.1级地震的发展趋势

利用模糊综合评判方法对1970年1月至1989年10月发生在山西境内大于3.0级的地震序列进行了处理。选取4个地震预报因子,给出了M_L∈〔4.0,5.0〕和M_L∈〔5.5,6.5〕两个震级区间的识别方程,据此方程的外推结果,提出大同—阳高地震序列在1989年11月和12月两月内可能出现起伏,但发生地震的最大震级为M_L∈〔4.0,6.0〕,实践证明,该结论与事实相符。     

组合式刚塑带加筋土强度的理论分析与试验验证

根据试验结果和理论研究,推导得到水平向与环向组合式刚塑带加筋土的强度表达式,并考虑筋材强度的发挥和筋土比例,随后进行详细讨论分析。研究表明,组合式刚塑带加筋土的黏聚力有很大的提高,如果环内含有草根,则形成二次加筋作用,其强度会进一步提高。用文中所推导出的强度公式得到的计算曲线与试验曲线吻合较好,最大误差在5.1%以内,同时加筋材料强度的发挥在1%~7.5%。最后对加筋土强度指标进行分析,研究发现组合式刚塑带加筋土的黏聚力增大了2.75~5.35倍,内摩擦角最大提高了21.7%;而水平向刚塑带加筋土、环向刚塑带加筋土的黏聚力分别增大了0.5~2.767倍、0.732~3.417倍,而它们内摩擦角则增加不多,最大增加了2.2°。综合考虑认为,“4环+3水平”组合加筋形式的加筋效果最好,其次是“2环+4水平”组合加筋形式。在实践中,可参照以上两种加筋形式进行边坡、地基加固修复等。     

水泥聚苯模壳格构式混凝土墙体抗震性能的芯孔尺寸影响试验研究

为研究芯孔尺寸对传统型水泥聚苯模壳(EPSC)格构式混凝土墙体抗震性能的影响,对2个传统型EPSC格构式混凝土墙体原型试件进行低周往复荷载试验,2个试件芯孔直径分别为160 mm和120 mm;对比分析了2个试件的破坏特征和承载力、滞回曲线、骨架曲线、刚度退化等抗震性能。结果表明:芯孔直径大的复合墙体具有更优良的抗震性能;芯孔直径增加,复合墙体的承载力、抗侧刚度和耗能能力均有不同程度的提高。     

Evaluation of the response modification coefficient and collapse potential of special concentrically braced frames

Special concentrically braced frames (SCBFs) are commonly used for seismic design of buildings. Their large elastic stiffness and strength efficiently sustains the seismic demands during smaller, more frequent earthquakes. During large, infrequent earthquakes, SCBFs exhibit highly nonlinear behavior due to brace buckling and yielding and the inelastic behavior induced by secondary deformation of the framing system. These response modes reduce the system demands relative to an elastic system without supplemental damping using a response modification coefficient, commonly termed the R factor. More recently, procedures put forth in FEMAP695 have been made to quantify the R factor through a formalized procedure that accounts for collapse potential. The primary objective of the research in this paper was to evaluate the approach for SCBFs. An improved model for SCBFs that permits simulation of brace fracture was used to conduct response history analyses. A series of three‐story, nine‐story and 20‐story SCBFs were designed and evaluated. Initially, the FEMAP695 method was conducted to estimate collapse and the corresponding R factor. An alternate procedure for scaling the multiple acceleration records to the seismic design hazard was also evaluated. The results show significant variation between the two methods. Of the three variations of buildings studied, the largest vulnerability was identified for the three‐story building. To achieve a consistent margin of safety against collapse, a significantly lower R factor is required for the low‐rise SCBFs (three‐story), whereas the mid‐rise and high‐rise SCBFs (nine‐story and 20‐story) may continue to use the current value of 6, as provided in ASCE‐07. Copyright © 2013 John Wiley & Sons, Ltd.     

含剪力墙钢筋混凝土结构抗震能力的评估方法及应用

根据我国现行抗震设计规范、混凝土结构设计规范以及目前既有建筑结构抗震能力研究成果,借鉴强度与延性评估理论,探讨了一种适合我国工程实际的既有含剪力墙钢筋混凝土结构的抗震能力评估方法。应用自行编制的评估程序EAC-RCSW应用于一工程实例,表明该方法可定量评估含剪力墙钢筋混凝土结构的抗震能力。     

大别山库区降水预报性能评估及应用对策

对降水预报进行性能评估及应用对策研究可以更好地发挥降水预报在水库调度中的决策支持作用.基于大别山库区近10 a汛期(2007—2016年5月1日—9月30日)24~168 h共7个预见期降水预报和地面降水观测资料,采用正确率、TS评分、概率统计、ROC曲线以及CTS等方法评估大别山库区降水预报性能,并以响洪甸水库为重点研究区域分析降水预报在水库调度中的应用对策.结果表明:1)大别山库区各量级的降水预报都有正预报技巧;24~72 h预见期降水预报的TS评分较高且空报率、漏报率也较低,具有较高的预报性能;但96 h及以上预见期降水预报性能明显下降,中雨以上量级空报率、漏报率较大,特别是对大暴雨及其以上量级的降水预报性能显著下降.2)大别山库区预报降水量级与实况降水量级基本符合,预报降水量级大于等于实况降水量级的概率超过75%;虽然降水预报量级上呈现出过度预报的现象,但降水过程预报对水库调度仍有较好的应用价值,应用时要考虑到降水预报量级可能存在偏差.3)转折性天气预报96 h及以上预见期CTS评分较低,但72 h以内预见期的性能明显改进,尤其是24 h预见期CTS评分也提高到了38.2%;水库调度可从长预见期的降水预报获取降水过程及其可能发生转折的信息,根据短预见期的降水预报进行调度方案调整.     

Investigation of the relationship between optical auroral forms and HF radar E region backscatter

The SuperDARN HF radars have been employed in the past to investigate the spectral characteristics of coherent backscatter from L-shell aligned features in the auroral E region. The present study employs all-sky camera observations of the aurora from Husafell, Iceland, and the two SuperDARN radars located on Iceland, Þykkvibær and Stokkseyri, to determine the optical signature of such backscatter features. It is shown that, especially during quiet geomagnetic conditions, the backscatter region is closely associated with east-west aligned diffuse auroral features, and that the two move in tandem with each other. This association between optical and radar aurora has repercussions for the instability mechanisms responsible for generating the E region irregularities from which radars scatter. This is discussed and compared with previous studies investigating the relationship between optical and VHF radar aurora. In addition, although it is known that E region backscatter is commonly observed by SuperDARN radars, the present study demonstrates for the first time that multiple radars can observe the same feature to extend over at least 3 h of magnetic local time, allowing precipitation features to be mapped over large portions of the auroral zone.     

Evaluation of the exact conditional spectrum and generalized conditional intensity measure methods for ground motion selection

Two existing, contemporary ground motion selection and modification procedures – (i) exact conditional spectrum (CS‐exact) and (ii) generalized conditional intensity measure (GCIM) – are evaluated in their ability to accurately estimate seismic demand hazard curves (SDHCs) of a given structure at a specified site. The amount of effort involved in implementing these procedures to compute a single SDHC is studied, and a case study is chosen where rigorous benchmark SDHCs can be determined for evaluation purposes. By comparing estimates from ground motion selection and modification procedures with the benchmark, we conclude that estimates from CS‐exact are unbiased in many of the cases considered. The estimates from GCIM are even more accurate, as they are unbiased for most – but not all – of the cases where estimates from CS‐exact are biased. We find that it is possible to obtain biased SDHCs from GCIM, even after employing a very diverse collection of intensity measures to select ground motions and implementing its bias‐checking feature, because it is usually difficult to identify intensity measures that are truly ‘sufficient’ for the response of a complex, multi‐degree‐of‐freedom system. Copyright © 2015 John Wiley & Sons, Ltd.     

鄂尔多斯西缘北段的地壳结构和块体间变形关系

本文对喜马拉雅计划二期部分台站的远震波形数据进行接收函数提取,利用接收函数共转换点叠加方法获得阿拉善地块、鄂尔多斯地块以及银川—河套盆地下方0~80 km深度的速度间断面结构.结果表明：鄂尔多斯地块成层性好,地壳厚度为38~42 km,康拉德界面为18~22 km,阿拉善地区的Moho面深度为38~45 km.河套盆地地壳厚度约52 km,银川断陷盆地和贺兰山下方的Moho面最深为~55 km.鄂尔多斯西缘构造边界下方Moho面变化明显,且黄河断裂为深大断裂直接切割莫霍界面.根据本文的间断面成像结果我们进一步确定阿拉善地块与鄂尔多斯地块分属不同的大地构造单元.与此同时,我们推测贺兰山以西70~80 km范围内和鄂尔多斯地块西缘北段存在地壳增厚变形的可能.

     

孟加拉湾西南季风与南海热带季风的气候特征比较

本文运用NCAR/NCEP再分析数据和APHRO_MA_V1003R1降水数据,对比分析了孟加拉湾西南季风和南海热带季风的气候特征异同以及对降水分布的影响,得到如下结论:(1)孟加拉湾西南季风比南海热带季风爆发更早、强度更强、持续时间更久、向北推进更北.(2)孟加拉湾西南季风建立过程缓慢,主要是索马里越赤道西南气流的逐渐加强和热带印度洋ITCZ(赤道辐合带)的逐渐北移;而南海热带季风建立过程迅速,主要是东亚大槽的一次替换过程伴随西太平洋副热带高压的突然东撤和热带西太平洋ITCZ的突然北跳.(3)孟加拉湾西南风纬向分量较强,季风建立前后主要变化在于偏西风的强度;而南海西南风经向分量较强,季风建立后风向突然逆转,东南风由于副高东撤而迅速被西南风取代.(4)孟加拉湾西南季风撤退较快,而南海季风则撤退较慢.(5)根据季风进程将夏季风期划分为季风发展期(5月)、强盛期(6-8月)和减退期(9-10月).其间对流活跃区的发展和推进、季风槽的位置以及对应降水区域均有明显差异.(6)在夏季风期,孟加拉湾和南海经度上分别存在着由ITCZ北抬引起的、在季风槽对流活跃区上升而在南北两侧下沉的、南北对称分布的季风经向次级环流.由于孟加拉湾和青藏高原强大热源的存在,孟加拉湾上升区南北跨度比南海的更大;孟加拉湾经圈环流更加稳定,而南海经圈环流的南北摆动更明显;孟加拉湾上升中心区比南海的偏北;在季风减退期,由于南海ITCZ撤退较慢,其上升区比孟加拉湾上升区偏北.     

南北地震带与华北地块强震间的相关迁移

地震震源机制解和地应力实测结果表明, 我国大陆地区存在近似于辐射状的区域应力场, 其辐射中心位于青藏地块东部. 本文首先定义我国大陆应力场近似辐射中心(35°N、 100°E)为动力源点, 在此基础上计算了1900年以来我国大陆东部地区(30°N—44°N、 104°E—125°E)所发生的34次M_S≥6.0地震震中到动力源点的距离与地震发生时间的关系. 结果表明, 20世纪南北地震带中北段发生M_S≥7.0地震后, 华北地块陆续发生了一系列M_S≥6.0地震, 且有随时间从南北地震带附近大体向东迁移的规律. 据此说明, 华北地块的地震主要受控于印度板块作用下青藏地块向我国大陆东部挤压的影响, 在其作用下产生了华北地块M_S≥6.0地震的系列东向迁移活动. 总体来看有4组明显的地震迁移活动, 每组地震“序列”的迁移视速度约为80 km/a. 华北地块首发M_S≥6.0地震距南北地震带中北段最近一次M_S≥7.0地震的时间间隔约为1个月至11.8年, 且60%的M_S≥6.0地震发震地点在(39°N±1.5°)区域内. 据此推测, 2008年汶川M_S8.0和2013年芦山M_S7.0地震后, 华北地块近年存在发生M_S≥6.0地震的可能, 晋冀蒙交界和环渤海及其附近地区值得重点关注.      

Research on the Relationship between Active Faults and Earthquakes in the Junction Area of the China North-South Seismic Belt and Central Orogenic Belt Based on GIS

Research on the relationship between faults and seismicity in the junction area of China's north-south seismic belt and central orogenic belt based on the Geography Information System (GIS) has been done.For each of the 16 faults in this area,we build a 25km buffer zone and use overlay analysis to investigate the seismicity and its characteristics on each fault.The results unveil the main seismic faults as follows:the western segment of the northern-edge of the west Qinling fault,the southwestern segment of the Lixian-Luojiabao fault,the southeastern segment of the Lintan-Dangchang fault,the southwestern segment of the Wenxian fault,the Huya fault,and the Xueshan fault.The most active faults are the Huya and Xueshan faults,then the Tazang fault,the Lixian-Luojiabao fault and the northern piedmont of the Guanggaishan-Dieshan fault.The research zone can be divided into four areas according to focal depth,which gets deeper from north to south.The profile of focal depth indicates the geometry and mechanical property of faults,and further reveals the movement model of eastward extrusion of the Tibetan plateau and southeastward escape of masses,thus providing basis for the protection against earthquakes and hazard mitigation in this area.