Experimental analysis of seismic torsional ground motion recorded by the LSST‐Lotung array

The purpose of this study was to perform an experimental analysis of the amplitude of full‐scale spatial variability of seismic motions with regard to earthquake engineering. The LSST‐Lotung array in Taiwan provides a good set of records for this type of study. Of interest are the free‐field torsional seismic components induced by the spatial variability of seismic motions. In this study, three events have been considered: LSST‐06, LSST‐07 and LSST‐16. In time domain analysis, the experimental results obtained show that when the separation distance increases, the induced torsion decreases, and the normalized differential motion parameter increases. Also, the results show that the stronger the event, in terms of maximum PGA, the larger the induced torsional amplitude and the smaller the induced normalized differential motion parameter. Copyright © 2002 John Wiley & Sons, Ltd.     

上海地震台阵的设计方法

从台阵波数响应特性、子台选址与测试、场地背景噪声分析和记录信号评价等方面，综合对上海地震台阵进行设计，确定了台阵子台的布局点位。本文还介绍了规则台阵与不规则台阵中的几种不同子台布局的台阵波数响应图，并由此得出，采用不规则的子台布局同样可得到性能较好的地震台阵；台阵的子台越多，其响应特性的主峰就越尖锐。     

Crustal thickness, discontinuity depth, and upper mantle structure beneath southern Africa: constraints from body wave conversions

The technique of receiver function analysis is applied to the study of crustal and upper mantle structures beneath the Kaapvaal craton in southern Africa and its surroundings. Seismic data were recorded by the seismic array of 82 sites deployed from April 1997 to April 1999 across southern Africa, as well as a dense array of 32 sites near Kimberley, in operation from December 1998 to June 1999. Arrival times for phases converted at the Moho are used to determine crustal thickness. The Moho depth in the south–western section of the craton was found to vary between 37 and 40 km, except for one station that recorded a depth of 43 km (SA23). Farther north along the western block of the craton (into Botswana) the depth increases up to 43 km. The depth increases even further in the north–eastern section of the craton, where results vary from 40 to 52 km. Just north of the Kaapvaal craton, in the neighbouring Zimbabwe craton, the crustal thickness drops significantly. The results obtained there varied from 36 to 40 km. For the Kimberley area, using the dense array, the Moho depth was found to be 37.3 km. Arrivals of the Ps and Ppps phases were used to determine the Poisson’s ratio in the region. This was found to be 0.26±0.01. Arrivals of phases from the 410 and 660 km mantle discontinuities are used to interpret the relative positions of these discontinuities, as well as for comparison of mantle temperatures and seismic velocities in the region with global averages. In the Kimberley area the 410 and 660 km discontinuities were found at their expected depth, implying that mantle temperatures in the region are close to the global average. The seismic velocities above the ‘410’ were found up to 5% faster than the averages from the global iasp91 model, which is fast even by Precambrian standards. In other sections of the Kaapvaal craton, the velocities are also faster than global averages, but not as fast as beneath Kimberley. In these sections, the ‘410’ is also slightly elevated, while the ‘660’ is depressed, which implies a slightly lower mantle temperature relative to the global average. Beneath the Kaapvaal craton we find evidence suggesting the presence of a zone with a reduced wavespeed gradient at an upper bound of approximately 300 km, which may mark the lower chemical boundary of the craton.     

三线阵CCD摄影测量理论在月球探测中的应用

月球是目前世界各国进行深空探测的首选星球,月球探测卫星属于传输型卫星。本文利用三线阵CCD摄影测量理论对月球摄影测量处理进行了可行性分析,指出其关键技术并提出解决方案,最后通过模拟实验进行验证.研究结果表明:三线阵CCD摄影测量理论可以较好地解决我国月球探测中的某些难题,完全可以应用于月球摄影测量中。     

利用PMC方法评估地震台阵的地震检测能力——以西昌流动地震台阵为例

为实现对高密度、宽频带流动地震台阵地震检测能力的实时、不同深度评估,本研究采用"基于概率的完整性震级"(PMC)方法,以西昌流动地震台阵为例,对2013-01-13—2014-05-14期间平均的地震检测能力、不同震源深度检测能力,以及某一时刻的实时地震检测能力进行了评估.结果表明,PMC方法可识别地震观测资料处理中人为因素对地震检测能力的影响,不同震源深度下地震的检测能力存在差异,其中H=7.5km时,"网内"的完整性震级MP可达ML0.8,而在H=15.0km和25.0km时,"网内"的MP分别为ML1.0和ML1.4.在示例的2014-01-14时刻,非正常运行的台站造成地震检测能力的变化可被清晰识别出.此外,与MAXC和EMR等其它常用方法的对比表明,这些方法可能过高估计了地震台阵的检测能力.     

高密度电法在上海地区的应用

结合工程实例,主要介绍了高密度电法在上海地区的综合应用,并分析了高密度电法的各种装置形式的优缺点。     

2022年6月19日广东佛山龙卷的双极化相控阵雷达特征

利用X波段双极化相控阵雷达等多源观测资料,分析了2022年6月19日早晨广东佛山超级单体龙卷的环境条件和对流风暴的结构及演变特征。龙卷母体风暴是在强西南季风天气背景下的一条东北-西南向飑线南端发展起来的。环境条件具备较大对流有效位能、低抬升凝结高度和强垂直风切变等有利于超级单体龙卷发生发展的热力和动力条件;低空风暴相对螺旋度、超级单体复合指数和强龙卷指数的显著增强对超级单体龙卷的发生有较好指示意义。具有高时空分辨率的佛山南海X波段双极化相控阵雷达探测到了龙卷母体微型超级单体的发展过程和龙卷涡旋的演变特征：对流单体在前侧低层入流的加强下逐渐形成钩状回波和反射率弱回波空洞;中气旋首先在2.5km附近高度形成后向低层伸展,随着后侧下沉气流的加强,低层涡旋旋转增强,当低层中气旋旋转速度超过22m·s-1(强中气旋)且直径紧缩至1.5km以内时,龙卷即将触地,龙卷涡旋特征(TVS)和龙卷碎片特征(TDS)出现是龙卷触地的主要特征,龙卷发生在反射率弱回波空洞、TVS和TDS附近。     

地震短临跟踪黑龙江地磁台阵的架设

介绍了黑龙江省地震局短临跟踪项目中的地磁台阵及运行情况,在该地区选定大庆,富裕,泰来,望奎和肇源5个观测点形成地磁台阵,利用GM4-LDG型流动磁通门磁力仪对地磁场三分量进行测量,并利用GPRS和CDMA无线网络技术,实现数据远程无线传输与仪器监控。