A Study of Seismicity and Earthquake Hazard at the Proposed Kalabsha Dam Site,Aswan, Egypt

High and Aswan Dams Authority (HADA) proposed a plan aiming at constructing a rockfill dam in the Kalabsha area, about 60 km south of Aswan High Dam. The aim of this dam is to restrain the overflow of water to the Kalabsha Valley for keeping one billion cubic meters from being lost due to seepage and evaporation. The safety of dams during earthquakes is extremely important because failure of such a structure may have disastrous consequences on life and property. Therefore, different factors were considered as part of a site assessment. Five seismic source zones, close enough to the site to give rise to potentially damaging earthquake ground motions, were identified. Seven active faults that have the potential for producing significant earthquakes and that pass through or near the dam site were also identified. The earthquake loading represented by ground motions at the site was evaluated. Probabilistic seismic hazard procedures were used for assessing the earthquake loading at six individual sites using Area-and Line-Source Models (ASM & LSM). The ASM is based on current observed seismicity, whereas the LSM is based on geological slip rates. The output represents the expected acceleration amplitude with 90 percent probability of not being exceeded in exposure times of 20, 50, and 100 years. The results from the two models appear to be different, the expected ground motions from ASM were twice as high as expected from LSM. This difference is due to the load of the Aswan reservoir (Nasser Lake) triggering earthquakes on those parts of the faults that lie under the lake at Kalabsha area. The hazard at the selected sites is given by the hazard curve that is represented by the relationship between the peak ground acceleration and its annual exceedance probability. By comparing the curves for the six individual sites for the same source model, it can be concluded that the potential ground acceleration level for all the sites is almost the same. Considering the mean results from the two models, the annual exceedance probability of the expected ground acceleration from ASM is approximately ten times higher than the annual exceedance probability from LSM.Since ASM is based on current seismicity, it is more appropriate forrepresenting the actual hazard for the dam site.     

巨大灾害后的脆弱性：台湾集集地震后中部地区土地利用与覆盖变迁

自2004年底的南亚大海啸、美国遭受飓风侵袭以来，人类社会如何采取应对措施以降低灾害的冲击成为国际科学界的一个重要议题。台湾在几年前也遭遇巨大的地震灾害，1999年9月21日凌晨，震中发源于台湾中部、芮氏规模7.3级的巨大地震，造成全台湾2 000多人死亡，8 000多人受伤，除了造成直接的经济社会损失外，也造成山区土石松滑、地层松动与山崩，直接改变了地表的覆盖状况。在后续几年台风所带来的强风豪雨下，丰沛的降雨量使原本因地震而松滑的土石大量滑落，造成严重的土石流灾害，河床也因土石泥沙的堆积而被提升，形成严重的洪患。这些自然环境的变化不仅再次改变地表的覆盖，也使重建后的小区面临极大的灾害风险。此次冲击促使当地居民重新思考人地关系之意义，通过重建过程凝聚小区意识，发展有别于过去的土地利用形态。因此为检验当地居民对灾害的暴露程度、敏感性与适应能力，本研究采用近年来在国际环境灾害研究课题备受重视的脆弱性研究途径，并利用野外调查以及遥测与地理信息系统分析呈现地震后的土地覆盖变化。希望通过分析人与环境系统的变化，以及人类社群的社会内部固有特质，归纳出重要机制以发展降低脆弱性的策略。 研究结果显示，灾害是人与环境耦合系统(coupled system)共同形成的结果，非单一的独立事件，也不是不可避免的；且地方的脆弱性具有演化与多元化的特性，同一地方下不同族群与个体对灾害的脆弱性皆不同，因此灾害研究必须更关注于灾害发生的机制，相关的政策与策略也必须建立在更小的社会与空间单元上。     

The importance of hydrogeological and hydrological investigations in the residential area: a case study in Burdur,Turkey

Water resources in residential areas are negatively affected by floods. In addition, many aquifers are contaminated as a result of urbanization. Great damage caused during earthquakes are partly attributed to the residential pattern which ignores the potential effect of groundwater. Hydrogeological and hydrological surveys must be carried out in the residential areas to determine the interaction between water and residential development of all types.Recent hydrogeological and hydrological investigations regarding the impact of urbanization were made for the city of Burdur (Turkey). To evaluate the effect of earthquakes on groundwater, groundwater isohypse and groundwater isopach maps were prepared showing most of the buildings within the Burdur city boundaries, which are in the areas where groundwater depth is less than 10 m. This is considered a critical depth for liquefaction during an earthquake. Lowering of the groundwater table has to be considered as one of the alternatives in reducing earthquake hazards. The chemical makeup of groundwater was also determined to consider its relationship to contamination and possible effects upon the foundations. Streams flowing across the Burdur residential area formed a flooding risk. Results of the peak flow analysis can be used to design improvements for the city. Maps of the best residential development areas have been prepared by using hydrological and hydrogeological results.     

Earthquake hazard in Jordan

An estimate of the maximum macroseismic intensities and ground accelerations which might be expected for the Hashemite Kingdom of Jordan is made. The inferred maximum magnitudes lie in the range of 6.1 to 7.3 although the possibility that larger earthquakes can occur with long recurrence times cannot be precluded. Peak horizontal accelerations in the range of 0.4 to 0.5 g can be expected in Jordan. Probabilistic estimates indicate that the odds are about even (50-50) that an earthquake with a magnitude of at least 6 will occur within 80 years.     

闽台地震速报技术研究

本文通过系统地分析台网正式运行以来记录到主要的网内、网缘、网外地震的各种震相特征和定位参数 ,总结研究各区的震相特征、台站记录状况和震级的误差 ,力争提高台网地震速报的速度和精度。     

Outgoing long wave radiation variability from IR satellite data prior to major earthquakes

Our analysis of the continuous outgoing long wave earth radiation (OLR) indicates anomalous variations prior to a number of medium to large earthquakes. The most recent analysis of OLR is from the M9.0 Sumatra Andaman Islands mega trust event. We compared the reference fields for December 2001 to 2004 and found OLR anomalous values, > 80 W/m², (2σ) within the epicentral area on Dec 21, 2004, 5 days before the event. We used the NOAA/IR daily (one degree) and monthly (two and half degree) gridded data to differentiate between the global and seasonal variability and the transient local anomalies. The cause of such anomalies is not fully understood; one possible explanation is the existence of thermal outgoing radiation as a result of near ground air ionization and latent heat change due to change of air humidity and temperature. This phenomenon is hypothesized to be part of a relationship between tectonic stresses, electrochemical and thermodynamic processes in the atmosphere and increasing mid IR flux, all part of a family of electromagnetic (EM) phenomena related to earthquake activity. The time scale of the observed variations is a few weeks before the onset of the seismic event. In comparison with several years of data, the observed time-series preceding the earthquake had unusually high OLR. The OLR anomaly corresponds to a large area of ground coverage and coincides with the main epicentral zone. The significance of these observations is explored using data from most recent East Asian earthquake swarm of December 2004 and three other earthquakes.     

2008年汶川地震(Ms8.0)非对称同震破碎带的确定:来自WFSD-1随钻流体的证据

地震过程中相当可观的一部分能量消耗于裂隙的活化与形成,来自汶川地震断裂带科学钻探一号孔(WFSD-1)的随钻流体表明,地震新形成的裂隙对应有较强的流体异常,它们为流体的入侵提供了良好的通道。随钻流体呈非对称性分布于主滑移面的两侧,主要的流体异常带集中在主滑移带下方须家河组顶部120 m范围内,该带中气体的含量以及变动的频率明显高于上部相同的宽度范围以及下部沉积岩层,来自地球物理测井的资料同样显示这一带破碎严重并伴随有大量水的侵入,暗示汶川地震形成的裂隙具有非对称性分布的特征。这一特征可能同时受控于断裂上盘彭灌杂岩与下盘须家河组岩层的力学性质差异以及地震破裂过程中形成的非对称性应力分布。     

造山带与岩石圈演化动力学研究述评

本文综述指出：深部过程，可能导致放射性元素在地幔或下地壳的某些部位聚结而产生强烈的核反应，致使下地壳加热和上地壳的快速抬升和伸展垮塌，产生地震、火山作用、岩浆作用，形成山脉。通过对来自地球内部的α─粒子辐射监测，有可能对毁灭性地震作出预报。     

A statistical procedure for the analysis of seismotectonically induced hydrochemical signals: A case study from the Eastern Carpathians, Romania

Changes in the stress field of an aquifer system induced by seismotectonic activity may change the mixing ratio of groundwaters with different compositions in a well, leading to hydrochemical signals which in principle could be related to discrete earthquake events. Due to the complexity of the interactions and the multitude of involved factors the identification of such relationships is a difficult task. In this study we present an empiric statistical approach suitable to analyse if there is an interdependency between changes in the chemical composition of monitoring wells and the regional seismotectonic activity of a considered area. To allow a rigorous comparison with hydrochemistry the regional earthquake time series was aggregated into an univariate time series. This was realized by expressing each earthquake in form of a parameter “e”, taking into consideration both energetic (magnitude of a seismic event) and spatial parameters (position of epi/hypocentrum relative to the monitoring site). The earthquake and the hydrochemical time-series were synchronised aggregating the e-parameters into “earthquake activity” functions E, which takes into account the time of sampling relative to the earthquakes which occurred in the considered area. For the definition of the aggregation functions a variety of different “e” parameters were considered. The set of earthquake functions E was grouped by means of factor analysis to select a limited number of significant and representative earthquake functions E to be used further on in the relation analysis with the multivariate hydrochemical data set. From the hydrochemical data a restricted number of hydrochemical factors were extracted. Factor scores allow to represent and analyse the variation of the hydrochemical factors as a function of time. Finally, regression analysis was used to detect those hydrochemical factors which significantly correlate with the aggregated earthquake functions.This methodological approach was tested with a hydrochemical data set collected from a deep well monitored for two years in the seismically active Vrancea region, Romania. Three of the hydrochemical factors were found to correlate significantly with the considered earthquake activities. A screening with different time combinations revealed that correlations are strongest when the cumulative seismicity over several weeks was considered. The case study also showed that the character of the interdependency depends sometimes on the geometrical distribution of the earthquake foci. By using aggregated earthquake information it was possible to detect interrelationships which couldn't have been identified by analysing only relations between single geochemical signals and single earthquake events. Further on, the approach allows to determine the influence of different seismotectonic patterns on the hydrochemical composition of the sampled well. The method is suitable to be used as a decision instrument in assessing if a monitoring site is suitable or not to be included in a monitoring net within a complex earthquake prediction strategy.     

上海村镇民房抗震对策分析

本文采用类比法和定量化方法对上海宝山区村镇民房震害损失进行了预测。在此基础上,对上海已有的和新建的民房提出抗震对策和措施。