2015年4月25日尼泊尔廓尔喀M_S8.1级地震强地面运动

2015年4月25日尼泊尔廓尔喀地区发生MS8.1级地震,本文分析了加德满都强震台站的强地震动记录特征,其水平向地震动表现为明显的脉冲地震动,脉冲周期约为6.0s,反映了近场地震动的方向性效应;处于深厚沉积层上的加德满都谷地对地震动有一定的放大作用,且主震的场地峰值频率向低频段偏移,出现明显的场地非线性反应;采用随机有限断层方法模拟的空间地震动分布与宏观地震烈度图符合较好,可以为分析宏观震害提供参考;通过与尼泊尔设计反应谱对比,得出在短周期与长周期段,加德满都台站的水平向地震动的反应谱远高于设计反应谱,说明即使严格按照尼泊尔建筑抗震规范设计施工的建筑结构也难以抵御此次地震的破坏。     

地震台智能电源Android平台控制系统

针对无人值守地震台因供电故障造成的观测数据质量问题,现阶段GPRS在地震台站的应用大多以手机短信呈现,无良好的可视化操作界面,设计开发一种底层基于STM32单片机,以GPRS为数据传输方式,Android手机APP为监控界面的智能电源控制系统。通过在河北省地震局石家庄中心台下属的深州郭家庄地震台进行应用,证明该电源控制系统能够保证观测设备的稳定运行,并为设备维护提供了保障和依据。     

祁连山西段测震指标异常综合应用

通过对1980年以来至今14个指标的全时间扫描,并使用祁连山西段地区Ms5．0地震进行对应。结果表明,选取A值、AC值、A（b）值、b值、Mf值和地震活动度S值进行同步异常分析,能显著提高祁连山西段地区的有震报震率,但有漏报。对目前地区异常集中区进行时间扫描,结果显示,祁连山西段地区出现同步异常,认为2012年或稍长时期有发生Ms≥5．0中强震的可能。     

自流井水温固体潮效应及其应变响应能力

井水温度观测是一项重要的地震前兆观测手段,旨在捕捉地震孕育过程中的应力-应变信息。水温固体潮效应作为地壳应力-应变信息的真实反映和地震前兆观测的干扰因素,具有重要的研究意义。本文首先依据对自流井中热状态的分析,认为自流井水温固体潮效应可能主要存在两种机制,即热传导机制和热对流机制;据此,推导出热传导机制中水温与固体潮体应变变化的定量关系;最后以流量相对较大的本溪自流井为例进行分析。结果表明,本溪井水温固体潮效应是热传导机制和热对流机制共同作用的结果,其中,热传导机制起主要作用。     

THREE KINDS OF TIME DISTRIBUTION FUNCTIONS OF REMARKABLE EARTHQUAKES IN SEISMIC SEQUENCES

ＴＨＲＥＥＫＩＮＤＳＯＦＴＩＭＥＤＩＳＴＲＩＢＵＴＩＯＮＦＵＮＣＴＩＯＮＳＯＦＲＥＭＡＲＫＡＢＬＥＥＡＲＴＨＱＵＡＫＥＳＩＮＳＥＩＳＭＩＣＳＥＱＵＥＮＣＥＳＤｉａｏＳｈｏｕｚｈｏｎｇＷａｎｇＨｏｎｇｗｅｉＣｈａｏＨｏｎｇｔａｉＨｕａＡｉｊｕｎ（Ｓｅｉ...     

The control of wind strength on the barchan to parabolic dune transition

The evolution of barchan-to-parabolic dunes can be driven by vegetation establishment, which may be linked to climate change and/or human activity. However, little is known of the impact of changes in wind strength on vegetation development and the resulting impacts on the evolution of dune morphology and sedimentological characteristics. To address this issue, we studied the morphology and grain-size characteristics of barchan, barchan-to-parabolic and parabolic dunes in the Mu Us Desert in north China, which was combined with an analysis of changes in normalized difference vegetation index (NDVI) and climatic variables during 1982–2018. The results reveal a trend of increasing growing-season NDVI which was related to a significant decrease in drift potential (DP). Therefore, we suggest that the initiation of dune transformation was caused by the reduced wind strength which favored the establishment and development of vegetation. To reveal the response of sedimentological reorganization during the processes of dune transformation, grain-size characteristics along the longitudinal profile of the three different types of dunes were examined. The decreasing wind strength led to the transport of fine sands on the upper part of the windward face of the dunes, resulting in a progressive coarsening of the grain-size distribution (GSD) and a reduction in dune height at the crest area. No distinct trend in sorting and mean grain-size was observed on the windward slope of the barchan-to-parabolic dune, indicating that the sand in transit had little influence on the GSD. Conversely, progressive sorting and coarsening of the sand occurred towards the crest of the parabolic dune. This indicates that vegetation development limited the transport of sand from upwind of the dune, and affected a shift in the dune source material to the underlying source deposits, or to reworked pre-existing aeolian deposits, and resulted in the trapping of sand in the crest area. © 2020 John Wiley & Sons, Ltd.     

新型装配式混凝土框架连接节点抗震性能试验

为推广装配式混凝土框架结构的应用,提出3种不同的新型装配式钢筋混凝土框架中节点连接形式,进行低周往复荷载试验。对比各试件的破坏形态、滞回性能、刚度退化、累积耗能和节点剪切变形等抗震指标。研究结果表明:采用方钢管连接的装配式混凝土节点呈现梁端弯曲破坏,采用工字钢连接或对拉螺栓连接的节点呈现节点核心区剪切破坏。采用方钢管的连接形式既能改善节点核心区的破坏形态,又能提高其承载能力、变形能力、耗能能力和梁端转动能力,同时显著改善节点的滞回特性,减小核心区的剪切变形。在弹塑性和塑性变形阶段,采用方钢管连接形式的装配式混凝土节点的抗震性能优于工字钢连接和对拉螺栓连接的节点。此外,采用工字钢连接形式比对拉螺栓连接形式的节点具有更高的承载能力、耗能能力和较小的核心区剪切变形。     

地下水测年方法及其在地震监测中的应用展望

对地下水动力学特征的观测与研究,是地震前兆监测的重要方法之一。地下水动力学研究中,利用地下水测年方法,可以对地下水的补给、径流特征及更新能力作出定性和定量的分析。本文介绍了近年来国际上常用的地下水测年方法,总结了前人在该领域的主要研究进展,重点分析了地下水更新能力与地震前兆信息的关系、地下水运动规律与地震构造活动的关系以及地下水浅层补给与异常干扰排除的方法等。已有的研究成果表明,地下水年龄的测定与分析方法对于了解监测点映震能力、评价构造活动与地震活动程度,以及在观测资料异常变化的现场核实等方面,可以发挥重要作用。     

Characteristics of strong motions and damage implications of M S6.5 Ludian earthquake on August 3, 2014

The Ludian County of Yunnan Province in southwestern China was struck by an MS6.5 earthquake on August 3, 2014, which was another destructive event following the MS8.0 Wenchuan earthquake in 2008, MS7.1 Yushu earthquake in 2010, and MS7.0 Lushan earthquake in 2013. National Strong-Motion Observation Network System of China collected 74 strong motion recordings,which the maximum peak ground acceleration recorded by the 053 LLT station in Longtoushan Town was 949 cm/s2 in E–W component. The observed PGAs and spectral ordinates were compared with ground-motion prediction equation in China and the NGA-West2 developed by Pacific Earthquake Engineering Researcher Center. This earthquake is considered as the first case for testing applicability of NGA-West2 in China. Results indicate that the observed PGAs and the 5 % damped pseudo-response spectral accelerations are significantly lower than the predicted ones. The field survey around some typical strong motion stations verified that the earthquake damage was consistent with the official isoseismal by China Earthquake Administration.     

高层隔震结构扭转分析

为研究高层隔震结构在地震作用下的扭转效应,用Etabs软件建立1个高层抗震结构和4个具有不同扭转特性的高层隔震结构的空间模型进行地震响应分析,以验证此原则上部结构质量中心与隔震层刚度中心的重合与否对结构扭转效应的影响程度,而后考察偏心高层隔震结构在偶然偏心地震作用下结构的扭转效应。结果表明:由于地震作用的减小,扭转效应要远小于原抗震结构,且隔震本身对于结构扭转效应的抑制效果要好于上述原则;扭转效应的减震率大于平动效应的减震率。布置在隔震层平面外围的铅芯橡胶隔震支座对隔震层的扭转有一定的控制作用。