与建筑物地震预期损失相关的结构地震反应预计方法研究

采用经济损失作为建筑结构抗震性能参数的方法可以用来预计建筑物在特定地震作用下的年平均预期损失。这种方法可以使用以构件为基础的方法来预计建筑物的经济损失,如何正确预计建筑物在不同地震作用下的结构反应至关重要。

南京地区地球物理场与地震构造稳定性

岩石圈的不均衡状态是地球物理场存在差异的原因,对区域地球物理场进行分析,可以了解岩石圈的不均衡及其构造活动的背景.本文在对南京地区地震地质环境分析的基础上,通过重力异常、地热场、深部速度结构、天然地震层析成像等地球物理资料进行系统分析,研究它们与本区地震构造稳定性的关系;分析研究地震活动,从现今地壳运动速度场与地壳形变观测资料研究本区大范围构造应力状况;最后结合该区域新生代演化史和第四纪沉积与活断层研究成果的综合分析,得出本区地震构造相对稳定,不存在发生特大地震的构造条件,研究区未来可能发生的破坏性地震强度为中等或中等以下.

汶川地震砖房震害的启示

汶川地震中砖房震害严重。但震害也表明,只要按现行规范及其依据的理论进行设计与施工,即使在超预期的强震作用下,砖房仍有相当好的抗震能力,足以在较高地震烈度下使用。

Non-Structural Mitigation Programs For Sediment-Related Disasters after the Chichi Earthquake in Taiwan

Following the Chichi Earthquake （ML=7.3） in 1999, sediment-related disasters, such as landslides and debris flows, have become more frequent in Taiwan. Because engineering structures cannot be fully and rapidly emplaeed, the government has initiated non-structural hazard mitigation programs. Initially, community debris flow evacuation drills were promoted in 2000. Typhoon Toraji caused numerous debris flow events in July 2001, and some communities evacuated according to the drills, significantly reducing the numbers of possible casualties. Based on that result, the government expanded the program for evacuation drills. Secondly, the early warning system created after the Chichi Earthquake will prevent many potential future casualties. Rainfall threshold values for debris flow warnings in different areas are determined from information received from local weather stations and modified for local geomorphologic situations. Real- time information is gradually being integrated to create a debris flow disaster warning system, the goal of which is to provide warnings to zones in which debris flows are likely. The warning system was launched in 2005 and has two levels of alarms： yellow and red. The final, red alarm triggers enforced evacuation. Overall, the decrease in casualties from debris flows during the decade after the Chichi Earthquake is not the result of a decrease in number or severity of sediment related disasters, but is more directly related to the gradually improved early warning and evacuation system. However, the compound hazards resulting from Typhoon Morakotin 2009 remind us of the ongoing need for improving the existing mitigation system.

Abnormally large short-term and impending earthquake geomagnetic anomaly implies a possibility of earthquake pre-warning

The study found that strong magnetic anomalies repeatedly took place before big earthquakes. Based on geomagnetic record analysis results,we discussed a possible pattern of the magnetic anomalies prior to earthquake. In meizoseismal area or epicenter,in a time period of 36 h to about 10 min before earthquake,the exceptional big geomagnetic change increases with the magnitude of earthquake. We calculated that,in a place of 1 km from the epicenter,the magnetic anomaly before destructive earthquakes of Ms 6～9 can reach to 102～104 nT(the magnitude of earth magnetic field is 104 nT) ,rather than the magnitude of 10 nT from seismomagnetic effect theories since 1960s. From this we speculated the abnormal magnetic ULF near epicenter before earthquake seems to be an "intermittent magnetic eruption". Accordingly,we proposed that geomagnetic induction earthquake alarm can be a new pre-warning method to surmount hardship in solving the puzzledom of earthquake imminent prediction.

New Evidence of Late Quaternary Activity on the Xinyi-Wuhe Segment of the Tancheng-Lujiang Fault Zone

The Tancheng-Lujiang fault zone has great influence in eastern China. Studies have shown obvious signs of neotectonic activities on the Xinyi-Wuhe segment of the Tancheng-Lujiang fault zone. In this study,on the basis of the previous work,many seismological surveys are made along the Tancheng-Lujiang fault zone and trenches are excavated in key sites.Combined with the analysis of the seismic activities along the fault,the fault movement features and future seismic risk are discussed. Much first-hand information obtained in the paper can provide an important reference value for the study of large earthquake recurrence rules and the mid and long-term earthquake prediction on the Xinyi-Wuhe segment of the Tancheng-Lujiang fault zone.

Discussion on Earthquake Forecasting and Early Warning

Through analysis of natural and social attributes of earthquake forecasting,the relationship between the natural and social attributes of earthquake forecasting(early warning)has been discussed.Regarding the natural attributes of earthquake forecasting,it only attempts to forecast the magnitude,location and occurrence time of future earthquake based on the analysis of observational data and relevant theories and taking into consideration the present understanding of seismogeny and earthquake generation.It need not consider the consequences an earthquake forecast involves,and its purpose is to check out the level of scientific understanding of earthquakes.In respect of the social aspect of earthquake forecasting,people also focus on the consequence that the forecasting involves,in addition to its natural aspect,such as the uncertainty of earthquake prediction itself,the impact of earthquake prediction,and the earthquake resistant capability of structures(buildings),lifeline works,etc.In a word,it highlights the risk of earthquake forecasting and tries to mitigate the earthquake hazard as much as possible.In this paper,the authors also discuss the scientific and social challenges faced in earthquake prediction and analyze preliminarily the meanings and content of earthquake early warning.

Short-term Earthquake Prediction in the Sichuan-Yunnan Region Using the Method of Modulated Earthquakes

By scanning modulated or un-modulated earthquakes spatio-temporally in the region of Sichuan-Yunnan,short-term non-stationary seismic precursory patterns were extracted with significant difference and the characteristic of non-stationary short-term seismic anomalies were analyzed as well as prediction efficiency of modulated small earthquakes before a strong earthquake. Besides,small earthquake modulation ratios near the region of the epicenter were calculated and sorted by time. The results indicated that there were significant effects using the modulated earthquake method to predict earthquakes greater than MS6. 0 in a short time. Before the MS8. 0 Wenchuan earthquake,there were obvious short-term precursory seismicity gap patterns of modulated small earthquakes.

Quantitative Seismicity Analysis for the Risk of Historical Large Earthquake Rupture Zone:Application to the Mid-North Segment of the North-South Seismic Belt

Although seismic gap theory plays an important role in the med-and long-term earthquake prediction,the potential risk of the non-seismic gap in historical earthquake rupture areas will need to be simultaneously taken into account in the study of med-and long-term earthquake prediction,due to the temporally clustering or non-linear behavior of large earthquake recurrence.In order to explore technical methods which can be based on observational data,and identify historical earthquake rupture zones( including the seismic gap in historical and prehistoric earthquake rupture zones),we select eight historical large earthquake rupture zones with different elapsed times on the mid-north segment of the North-South Seismic Belt to make quantitative analysis on the characteristics of modern seismicity of these zones and preliminarily explore the seismicity method for determining the urgency degree of potential earthquake hazards.The results mainly show that the pvalue,which reflects the attenuation of earthquake sequence,and the a-value,which reflects the seismicity rate,are strongly related to the elapsed time of the latest earthquake in the rupture zone.However,the corresponding relationships in some rupture areas are not clear perhaps due to the complex fault structure and faulting behavior.The b-value,which represents the state of tectonic stress accumulation,does not easily reflect the elapsed time information of different evolution stages.The b-value temporal scanning shows a steady evolution over time in most of the rupture zones,but in the rupture zone of the Wudu M8.0 earthquake of 1879,the b-value shows significant fluctuations with a decreasing trend for 20 years.By comparative analysis,we conclude that the rupture zones of the 1933 M7.5 Maoxian earthquake and the 1976 M7.2 Songpan-Pingwu earthquake are still in the decaying period of earthquake sequences,and thus do not have the background for recurrence of M7.0 earthquakes.The low b-value Maqu segment,which is located at the north margin of the rupture zone of the 842A.D.M7.0 Diebu earthquake,is more dangerous than the Diebu segment.The continuous decline of the b-value in the 1879 M8.0 Wudu earthquake rupture zone may also indicate a new round of seismogenic process.

Recent Developments of Earthquake Early Warning in California,USA

In this paper we outline the science,engineering,and societal considerations of the prototype Earthquake Early Warning System( EEWS) in California and detail the development and testing of methodologies in the last 10 years in America. Also,we give a brief introduction of Earthquake Early Warning( EEW) in China,and based on the summary of EEW in California we make an analysis of the perspectives,misconceptions,and challenges that China may have.