青藏高原西北地区与南北地震带地震活动性研究

通过研究青藏高原地区地震的发震时间和空间分布规律，发现青藏高原西北地区70%的6级以上地震发生在青藏高原地震活动高潮时期，以青藏高原西北地区地震的发震时间为基准，以一年的时间窗口去检测南北地震带发生的地震，发现青藏高原西北地区与南北地震带中强震发震时间接近，具有很强的关联。青藏高原西北地区发生的地震与南北地震带南、北、中段的地震活动相关性各不相同，地震活动频次上呈现出与南北地震带北段相关性最弱，与南段相关性最强，但在震级上表现出与南北地震带北段和中段强震活动关系密切，与滇缅构造转换区的中震联系紧密，图像信息方法为两个地区地震活动相关性提供了证据。研究同时发现以海原地震为起始地震时南北地震带的强震具有由北向南往复迁移的特征，南北地震带中段和滇缅构造转换区的地震迁移次数更多，表明两个地区地震活动确实联系紧密。这项研究对于南北地震带的地震危险性评价和"源线模式"地震预测方法具有重要的意义。     

地震序列中重复地震的累积滑动量对后续中强地震的前兆意义——以辽宁海城-岫岩地区4个显著地震序列为例

海城-岫岩地区是辽宁地震多发区,地震序列频发,具有区域地震窗口效应。在该地区一些显著的地震序列中,发现同一台站记录中有多个具有高度相似波形的地震,即重复地震序列。这些地震发震位置非常接近,破裂区域基本重合,因此可能反映孕震断层的一些活动特征。本文利用波形互相关方法对辽宁海城-岫岩地区4个显著地震序列进行重复地震识别,研究发现地震序列中重复地震的累积滑动量数值大小似乎与后续中强震在距离上有一定相关性,其中岫岩MS5.4地震前的前震序列产生的累积滑动量最大,并在主震前出现明显的滑动加速现象。     

地震序列中重复地震的累积滑动量对后续中强地震的前兆意义——以辽宁海城-岫岩地区4个显著地震序列为例

海城-岫岩地区是辽宁地震多发区,地震序列频发,具有区域地震窗口效应。在该地区一些显著的地震序列中发现同一台站记录中有多个具有高度相似波形的地震,即重复地震序列。这些地震发震位置非常接近,破裂区域基本重合,因此可能反映孕震断层的一些活动特征。本文利用波形互相关方法对辽宁海城-岫岩地区4个显著地震序列进行重复地震识别,研究发现地震序列中重复地震的累积滑动量数值大小似乎与后续中强震在距离上有一定相关性,其中岫岩MS5.4地震前的前震序列产生的累积滑动量最大,并在主震前出现明显的滑动加速现象。     

利用地磁低点位移预测发震时间

四川及邻区是未来大震的重点监测地区，为了震情监视分析与预测，对四川地区出现的地磁“低点位移”与四川及邻区的中强地震对应进行了系统研究，认为地磁“低点位移”现象是客观存在的，“低点位移”作为一种地磁异常现象，与地震发生有较好的相关性。     

蒙甘宁青地区近百年来中强地震之间的相关性分析

根据全国强地震目录,选取1900年至2010年发生在内蒙古、甘肃、宁夏和青海交界地区的历史及现代中强地震作为研究对象,分析其时空分布特点,试图论证上述地区中强地震之间的相关性。研究结果表明,蒙甘宁青地区中强地震之间整体上存在一定的相关性,而在划定的不同时空范围内,这种相关性表现不一。     

安徽中西部地区地震异常研究

试图通过分析安徽中西部地区１９７０年以来出现的１６次群体性地震学异常,寻找“有异常无地震”的力源,研究结果表明“有异常无地震”的现象与华东及附近海域的中强城具有一定的相关性,当该区发生ＭＬ≥５．０以上地震时,安徽中西部地区出现群体性地震学异常。这一现象表明,安徽中西部地区是华东及附近海域不均匀应力场发展演化过程中的一个应力集中点,也是地震学异常的敏感区,深入研究它与震中区地震活动之间的关系,对识别     

华北地区与日本海沟地震的相关性分析

据板块运动及构造动力的因果关系研究了我国华北地区６级以上与日本海沟地区７级以上地震活动的关系，结果表明，两个地区群体地震活动在时间轴上的不均匀分布及起伏具有一定的同步性，且华北地区的群体地震活动的开始时间晚于日本海沟地区。     

辽宁地区1509年4月21日和1552年10月27日地震考证

辽宁是历史地震资料比较缺乏的地区,深入研究历史疑难地震,尤其是确认一些破坏性地震,对补充已有的地震目录和开展地震预测及工程场地地震安全性评价有重要作用。在历史地震研究中认真考查,论证已有的地震史料是最主要的手段和方法。但是若能在此基础上,利用现代地震资料,按"地震重复"发生理论反推一些历史上可能存在的破坏性地震,也可以认为是对历史地震研究方法的一种补充。按照这一思路,本文在进一步分析地震史料的基础上,通过与现代地震活动图像和大地震震害现象的对比,确认辽宁地区1509年4月21日的地震是一次破坏性地震,并对1552年10月27日的地震做了讨论。     

陕西地区5级左右地震的震兆研究

本文根据历史及现今地震资料研究了陕西地区５级左右地震发生的时空规律及其相关现象，从而为陕西今后的震情判断提供依据。主要结果如下：Ｍｓ≥５地震发生的平均时间间隔为５８年，４－５级地震丛的发生间隔为１０－４０年；Ｍｓ≥５地震的活动有以９为倍数的韵律特征，并有集中在７－９月发生的现象；５级左右的地震一般都分布在渭河盒地北缘断裂或秦岭山间断裂带上；４级以上地震发生前，在震中附近一定范围内小震活跃。     

山西大同-阳高地震活动背景

通过对大同盆地历史地震活动及大同盆地历史地震活动与华北地震区、山西地震带强震活动的关系的研究，得出山西大同-阳高1989年6．1级地震活动是这一地区历史地震的延续，是华北北部中强地震活动的重要组成部分，具有广义前震的重要意义，其后对应发生的河北张北6．2级地震。标志着华北地震区的地震活动期已进入尾声。     

震级-频度关系小震端分布特征的一种可能的解释

通过震级-频度关系资料和地震台站分布资料的分析,发现震级-频度关系曲线在震级较小的一端的分布特征反映了地震能量分形和地震台站状况交互作用的结果,从而在地震序列分析中,考虑不同历史时期地震台站的状况及其影响,是一项必不可少的工作.     

对大灰厂台形变异常的再认识

按照文献[1]的思路和方法,利用历史观测数据,通过建立大灰厂台形变资料动态预估方程,对唐山地震前后两次形变异常重新作了分析。结果表明,1975年前后和1980年前后的两次形变异常情况类似,且具有较好的预估关系,其它年份的资料也有重复的特点。其特点与地震孕育引起的地壳形变关系不大。因此把1975年形变异常作为唐山地震的前兆信息依据不足,两次异常都是由于干扰因素影响所致。     

The large earthquake of 8 August 1303 in Crete: seismic scenario and tsunami in the Mediterranean area

By conducting a historical review of this large seismic event in the Mediterranean, it has been possible to identify both the epicentral area and the area in which its effects were principally felt. Ever since the nineteenth century, the seismological tradition has offered a variety of partial interpretations of the earthquake, depending on whether the main sources used were Arabic, Greek or Latin texts. Our systematic research has involved the analysis not only of Arab, Byzantine and Italian chronicle sources, but also and in particular of a large number of never previously used official and public authority documents, preserved in Venice in the State Archive, in the Marciana National Library and in the Library of the Museo Civico Correr. As a result, it has been possible to establish not only chronological parameters for the earthquake (they were previously uncertain) but also its overall effects (epicentral area in Crete, Imax XI MCS). Sources containing information in 41 affected localities and areas were identified. The earthquake also gave rise to a large tsunami, which scholars have seen as having certain interesting elements in common with that of 21 July 365, whose epicentre was also in Crete. As regards methodology, this research made it clear that knowledge of large historical earthquakes in the Mediterranean is dependent upon developing specialised research and going beyond the territorial limits of current national catalogues.     

A Multidisciplinary Study of the DPRK Nuclear Tests

The Democratic People Republic of Korea announced two underground nuclear tests carried out in their territory respectively on October 9th, 2006 and May 25th, 2009. The scarce information on the precise location and the size of those explosions has stimulated various kinds of studies, mostly based on seismological observations, by several national agencies concerned with the Nuclear Test Ban Treaty verification. We analysed the available seismological data collected through a global high-quality network for the two tests. After picking up the arrival times at the various stations, a standard location program has been applied to the observed data. If we use all the available data for each single event, due to the different magnitude and different number of available stations, the locations appear quite different. On the contrary, if we use only the common stations, they happen to be only few km apart from each other and within their respective error ellipses. A more accurate relative location has been carried out by the application of algorithms such as double difference joint hypocenter determination (DDJHD) and waveform alignment. The epicentral distance between the two events obtained by these methods is 2 km, with the 2006 event shifted to the ESE with respect to that of 2009. We then used a dataset of VHR TerraSAR-X satellite images to detect possible surface effects of the underground tests. This is the first ever case where these highly performing SAR data have been used to such aim. We applied InSAR processing technique to fully exploit the capabilities of SAR data to measure very short displacements over large areas. Two interferograms have been computed, one co-event and one post-event, to remove possible residual topographic signals. A clear displacement pattern has been highlighted over a mountainous area within the investigated region, measuring a maximum displacement of about 45 mm overall the relief. Hypothesizing that the 2009 nuclear test had been carried out close to the area where the displacement has been observed through the DInSAR technique, its relation with the epicenter location obtained through seismological processing has been discussed as a possible alternative hypothesis with respect to the preferred solutions reported by the nuclear explosion database (NEDB). The distance of about 10 km between the two places can be considered acceptable in light of the possible systematic location shifts commonly observed in the seismological practice over a global scale. The difference between the m _b magnitudes of the two tests could reflect differences in geological conditions of the two test sites, even if the yield of the two explosions had been the same.     

Response spectral relationships for rock sites derived from the component attenuation model

The seismological model was developed initially from the fundamental relationship between earthquake ground motion properties and the seismic moment generated at the source of the earthquake. Following two decades of continuous seismological research in the United States, seismological models which realistically account for both the source and path effects on the seismic shear waves have been developed and their accuracy rigorously verified (particularly in the long and medium period ranges). An important finding from the seismological research by Atkinson and Boore and their co‐investigators is the similarity of the average frequency characteristics of seismic waves generated at the source between the seemingly very different seismic environments of Eastern and Western North America (ENA and WNA, respectively). A generic definition of the average source properties of earthquakes has therefore been postulated, referred to herein as the generic source model. Further, the generic ‘hard rock’ crustal model which is characteristic of ENA and the generic ‘rock’ crustal model characteristic of WNA have been developed to combine with the generic source model, hence enabling simulations to be made of the important path‐related modifications to ground motions arising from different types of crustal rock materials. It has been found that the anelastic contribution to whole path attenuation is consistent between the ENA and WNA models, for earthquake ground motions (response spectral velocities and displacements) in the near and medium fields, indicating that differences in the ENA and WNA motions arise principally from the other forms of path‐related modifications, namely the mid‐crust amplification and the combined effect of the upper‐crust amplification and attenuation, both of which are significant only for the generic WNA ‘rock’ earthquake ground motions. This paper aims to demonstrate the effective utilization of the latest seismological model, comprising the generic source and crustal models, to develop a response spectral attenuation model for direct engineering applications. The developed attenuation model also comprises a source factor and several crustal (wave‐path modification) component factors, and thus has also been termed herein the component attenuation model (CAM). Generic attenuation relationships in CAM, which embrace both ENA and WNA conditions, have been developed using stochastic simulations. The crustal classification of a region outside North America can be based upon regional seismological and geological information. CAM is particularly useful for areas where local strong motion data are lacking for satisfactory empirical modelling. In the companion paper entitled ‘response spectrum modelling for rock sites in low and moderate seismicity regions combining velocity, displacement and acceleration predictions’, the CAM procedure has been incorporated into a response spectrum model which can be used to effectively define the seismic hazard of bedrock sites in low and moderate seismicity regions. This paper and the companion paper constitute the basis of a long‐term objective of the authors, to develop and effectively utilize the seismological model for engineering applications worldwide.     

Seismological services of the Australian Bureau of Mineral Resources,Geology and Geophysics

The Bureau of Mineral Resources, Geology and Geophysics provides seismological services which complement those provided by several other agencies.The services comprise the operation of 20 seismograph stations in continental Australia, and the operation of regional data centres for earthquakes and strong earth-motion data. The ambit of the data centres includes BMR stations in Antarctica and Papua New Guinea, and foreign stations in Papua New Guinea and the Solomon Islands. Most of the data are lodged at World Data Centres, and the remainder are available from the BMR national centre.The combined Australian network has provided data at a regional level only for about the last twenty years. These have however, been sufficient to show that although seismicity is low it is not insignificant, and that there are several areas where damaging earthquakes can be expected to recur at 50-year intervals; about 500 Australian earthquakes are located annually.Complete national location capability does not extend below Richter magnitude 4, and it is unlikely that significant improvements can be expected in the near future. In most of the areas where earthquake risk is important from a civil standpoint the detection capability is about magnitude 3. For the other more remote areas advanced techniques based on unattended seismometers and satellite telemetry will probably be needed to attain the same capability.     

A seismogram digitization and database management system

IntroductionSeismograms contain seismic wave data recorded by instruments. They are the main information source for seismological studies. Now we are developing seismological stations with digital records, which can offer seismic wave data with better quality than before. But the paper analog seismograms accumulated in the past decades still have great room for application. They are important original data for studying earthquakes. Lots of valuable information are contained in them. Due to a…     

中国现代地震科技文献分布特征

本文基于文献计量学方法,研究了我国自公元1900年以来,尤其是近35年以来的现代地震科技文献的基本特征.其中包括:文献增长速率、文献分散与集中规律、分枝学科文献分布以及地震事件对文献产出量影响等.笔者得到以下几点有意义的结论:1.70年代之后,我国地震科技文献产出量每年以32%的速率增长;2.地震学各分枝学科文献分布量和年增长量是不平衡的;3.地震文献分布服从布拉德福(Bradford)的文献离散率,和加菲尔德(Garfield)的文献集中律;4.地震文献量的增长,明显受到地震事件的影响.      

大地电场日变化特征

利用后土桥等地震台的大地电场分钟值资料,分析了各方向的日变形态和特征。结果发现,一般各方向日变与地磁场日变近似,出现双峰单谷。而后土桥地震台有别于其他地震台,东西向以半日波为主,出现双峰双谷。     

甘肃省地震数据资料处理实用软件研制

介绍了一套应用软件系统。该系统的应用能使甘肃与全国各省交换的地震前兆资料以及省内各手段、各测项所需的资料自动检索、转发和查错处理。这样，既减少了人工环节，降低了操作人员的劳动强度，提高了工作效率，更重要的是保证了资料的可靠性