Tsunami Hazard in the Eastern Mediterranean: Strong Earthquakes and Tsunamis in the Corinth Gulf,Central Greece

The exhaustive review of a long number of historical documents, books, reports,scientific and press reports, instrumental recordings, previous catalogues andpersonal field observations, concluded with the production of a completely newtsunami catalogue for the Corinth Gulf, Central Greece, which is arranged in theformat adopted by the GITEC group for the new European Tsunami Catalogue.The catalogue is presented in three sections: the Quick-Look Table, the Quick-LookAccounts File and the References File. An Appendix explains why some particularsea disturbances were not included in the new catalogue although they were consideredas tsunami events by previous researchers. Past history clearly shows that most tsunamis in the Corinth Gulf are produced by strong (Ms 5.5) offshore and near shore earthquakes. However, seismic or aseismic sliding of coastal and submarine sediments is a significant factor in tsunamigenesis. Calculations based on the random model indicate that the probability for at least one tsunami occurrence of intensity TI 2 TI 3 and TI 4 within 50 years equals 0.851, 0.747 and 0.606, respectively. From the intensity–frequency relationship the mean return period of tsunami intensity TI 2, TI 3 and TI 4 equals to 16, 40 and 103 years. The tsunami geographicaldistribution, however, is non-random with a clear trend for the tsunamigenesis todecrease drastically from west to east within the Corinth Gulf. In fact, the probabilityfor a strong earthquake to cause a tsunami of TI 3 in the Corinth Gulf consideredas an entity is 0.35, while in the western part of the Gulf it goes up to 0.55. Therefore, the rapid and accurate determination of the earthquake focal parameters is of great importance in an algorithm of a real-time tsunami warning system in the Corinth Gulf.     

Effects on the Ionosphere Due to Phenomena Occurring Below it

The terrestrial thermosphere and ionosphere form the most variable part of theEarth's atmosphere. Because our society depends on technological systems thatcan be affected by thermospheric and ionospheric phenomena, understanding,monitoring and ultimately forecasting the changes of the thermosphere–ionosphere system are of crucial importance to communications, navigation and the exploration of near-Earth space. The reason for the extreme variability of the thermosphere–ionosphere system isits rapid response to external forcing from various sources, i.e., thesolar ionizing flux, energetic charged particles and electric fields imposed via the interaction between the solar wind, magnetosphere and ionosphere, as well as coupling from below (meteorological influences) by the upward propagating, broad spectrum,internal atmospheric waves (planetary waves, tides, gravity waves) generated in thestratosphere and troposphere. Thunderstorms, typhoons, hurricanes, tornadoes andeven seismological events may also have observable consequences in the ionosphere.The release of trace gases due to human activity have the potential to cause changes inthe lower and the upper atmosphere.A brief overview is presented concerning the discoveries and experimentalresults that have confirmed that the ionosphere is subject to meteorologicalcontrol (especially for geomagnetic quiet conditions and for middle latitudes).D-region aeronomy, the winter anomaly of radiowave absorption, wave-liketravelling ionospheric disturbances, the non-zonality and regional peculiaritiesof lower thermospheric winds, sporadic-E occurrence and structure, spread-Fevents, the variability of ionospheric electron density profiles and Total ElectronContent, the variability of foF2, etc., should all be considered in connection withtropospheric and stratospheric processes. Ionospheric weather, as a part of spaceweather, (i.e., hour-to-hour and day-to-day variability of the ionospheric parameters)awaits explanation and prediction within the framework of the climatological, seasonal,and solar-cycle variations.     

Application of Fisher method to discriminating earthquakes and explosions using criterion m b/ M S

We try to give a quantitative and global discrimination function by studying m _b/M _S data using Fisher method that is a kind of pattern recognition methods. The reliability of the function is also analyzed. The results show that this criterion works well and has a global feature, which can be used as first-level filtering criterions in event identification. The quantitative and linear discrimination function makes it possible to identify events automatically and achieve the goal to react the events quickly and effectively. Contribution No.05FE3018, Institute of Geophysics, China Earthquake Administrtion.     

数字地震台网短信通系统的设计与应用

从现代移动通信短信息业务SMS出发，思考数字地震观测技术的应用新领域。介绍了DsnSMMS系统的设计方案、系统结构和主要功能。分析了OCX短信控件、系统软件、地震信息处理程序、台网实时监控程序的开发，各模块实现的功能。通过系统软件开发和短信收发设备的集成，实现了地震信息的快速群发、触发报警及台网运行状态的监控，并可以采用移动设备远程控制台网软硬件。从无锡市数字地震台网的实际应用表明，该系统智能化的交互操作与远程监控取得了良好的效果。     

Smaller source earthquakes and improved measuring techniques allow the largest earthquakes in Iceland to be stress forecast (with hindsight)

A group of three earthquakes in 2000 June in SW Iceland included the two largest earthquakes in Iceland in the past 30 yr. Previously, temporal changes in shear-wave splitting had not been recognized before these earthquakes as there were too few small earthquakes to provide adequate shear-wave data, and they were not stress forecast, even with hindsight. These large earthquakes were subject to a special investigation by the European Community funded PREPARED Project during which the seismic catalogue was extended to include smaller magnitude earthquakes. This more detailed data set, together with a semi-automatic programme for measuring the parameters of shear-wave splitting greatly increased the number of time-delay measurements.
The new measurements displayed the typical temporal variations before larger earthquakes as seen elsewhere: a long-term increase in time delays, interpreted as stress accumulation before the earthquake; and a decrease, interpreted as crack coalescence, immediately prior to the earthquake. The logarithms of the durations of both the implied accumulation of stress and the crack coalescence have the same self-similar relationships to earthquake magnitude as found elsewhere in Iceland. This means that, in principle, the time and magnitude of the larger earthquakes could have been stress forecast in real time had the smaller source earthquakes of the extended catalogue and the improved measuring procedures been available at the time.     

断层之间的相互作用及其地震地质意义

从断层间相互作用产生的同震库仑应力改变入手,提出了断层间相互作用的触震与缓震效应,探讨了断层间的相互作用对断层活动性、断层未来地震潜势及余震活动分布图像的影响.从断层间相互作用的角度分析了大陆强震准周期丛集复发行为的可能的物理机制.认为断层间的相互作用具有重大的地震地质意义,在进行断层活动习性和断层地震危险性定量评价及余震分布图像预测时,应该充分考虑断层间相互作用的影响.     

永登5.8级地震序列及有关问题讨论

对永登５．８ 级地震序列及近１０ 年来永登—兰州地区的小震活动进行了研究,结果表明：永登５．８ 级地震为孤立型,震前近１０ 年震区一直有小震活动,主震是在小震活动经历了一个增多—加剧—平静的过程后才发生的。历史地震活动资料及地质构造表明,永登地区存在中强地震孕育的背景     

1997年1月21日～4月16日新疆伽师强震群综述

１９９７年１月２１日～４月１６日,新疆伽师相继发生了７次Ｍ≥６的地震,造成了破坏与伤亡。该文就伽师强震群进行了综述,包括：地震类型和地震参数;震源机制;伽师地震的临震预报;地震现场工作等。     

地震科技信息的优化管理与数据库的建立和应用

天津市地震局从贯彻执行国家地震局预测预防司的有关文件做起,结合其地震科技信息工作的特点,从优化管理入手,借助现代化的工具和手段,建立了文献管理数据库,并在实践中加以应用,以增强服务功能,更好地为防震减灾服务。     

GPS授时技术在地震观测中的应用

在地震观测中，时间基准测量的精度非常重要。我们利用全球定位系统（ＧＰＳ）设计完成了数字地震记录仪的实时在线授时系统，提高了时间服务精度。本文详细介绍了利用ＧＰＳ授时的基本原理，给出了我们研制的数字地震仪中授时系统设计的理论计算和具体的同步算法和程序以及硬件设计框图。