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利用福建水氡台网 1 990年以来的水氡资料 ,针对 6次福建及其东南沿海大于 4 5级地震 ,7次台湾及其近海大于 6 8级地震进行分析研究 ,认为地震前异常存在加速性、同步性 ,形态的多样性 ,空间分布的不确定性。运用“九五”攻关软件 ,给出上述两区域地震异常特征的共性和个性 ,并对映震效能进行R值评分 相似文献
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本文计算了福建自1992年至2004年以来的地倾斜EW和NS两分量的固体潮潮汐因子,并进行动态组合,绘制组合动态三种特征量:ΔγEW ΔγNS(表征扩容)、ΔγEW-ΔγNS(表征剪切应变)、ΔγEW/ΔγNS(表征介质各向异性)的时序曲线图,并进行固体潮特征分析,寻找中、强地震发生前远场块体和近场块体地倾斜突变性形变异常与之对应关系。结果表明:在福建沿海,海潮是决定倾斜固体潮特征的主要因素;福建发生5级上的中强地震、台湾发生7级以上强烈地震时,福建地倾斜固体潮潮汐因子及其动态组合特征存在明显的渐进式突变性形变异常现象,异常量和异常持续时间与震级和震中距有较好的对应关系。 相似文献
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[地震活动概况] 我国地震活动自1994年呈现出大陆地区7级强震连发、地震活动水平连续4年保持较高活动水平和增强趋势,1998年则显示出第五个活跃期的中强以上地震活跃状态,6级以上地震频度仍然很高,但释放能量比1997年有明显降低,反映出处在地震活跃期之中相对较弱的活跃状态。东部沿海地区地震活动水平也有明显减弱,没有5级地震发生。同样,福建地区地震活动也表现出在经历了1997年相对活跃后的又一次显著减弱态势,显现出地震活动强弱交替起伏变化的特征。 相似文献
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2005年度闽台地区的地震活动水平均较上一年度有所减弱,而台湾海峡南部的地震活动水平与上一年度相比则有较明显的增强。一、福建及其近海地区地震活动据福建地震台网测定,2005年1月至12月福建及其近海地区共发生ML2.0级以上地震49次(图1),其中2.0-2.9级44次,3.0-3.9级5次,最大地震为8月9日晋江海域ML3.6级。3级以上地震均发生在沿海一带(表1)。与上一年度该区域ML2.0级以上地震89次、最大震级ML4.5级相比较,2005年度福建及其近海地区的地震频次和强度均出现了较明显的减弱。图12005年度闽台地区地震震中分布图(ML≥2.0)表12005年度福建… 相似文献
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文中利用福建水氡台网1990年以来的水氡资料,针对6次福建及其东南沿海大于4·5级地震,7次台湾及其近海大于6·8级地震进行分析研究,认为地震前异常存在加速性、同步性,形态的多样性,空间分布的不确定性。经过分析,给出上述两区域地震异常特征的共性和特性。 相似文献
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根据福建数字遥测地震台网测定 ,2 0 0 3年 1月至 2 0 0 3年 1 2月 ,福建及其邻近地区共发生 2 0级以上地震 72次 ,其中 2 0～ 2 9级 65次 ,3 0～ 3 9级 7次 ,最大地震为 3月 1 8日漳平 3 6级 ;台湾海峡地区共发生 2 0级以上地震 2 6次 ,其中 2 0～ 2 9级 1 7次 ,3 0 相似文献
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1999年福建及台湾地区地震活动综述 总被引：1，自引：0，他引：1
一、地震活动概况1999年福建及其沿海地区地震活动在经历了1998年和今年上半年的相对平静之后,今年下半年地震活动显著增强,相继发生惠安海域48级地震、福州38级震群和水口库区32级震群活动,地震活动继续呈现强弱交替起伏变化的特征,显示该区地震活动仍呈较强态势。东南沿海地震带目前处于二十世纪以来第Ⅴ个地震活跃幕的后期阶段,估计中强地震活跃态势仍将持续一段时间。二、地震频度和强度据福建数字遥测地震台网测定,1999年福建及其沿海地区共发生ＭＬ≥20级地震132次,其中20≤ＭＬ≤29级地震123次;30≤ＭＬ≤39级地震16次;40≤ＭＬ≤49… 相似文献
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本文通过对东南沿海地震带地震活动幕的划分,并综合分析近年来的地震活动特征,认为该带自1998年后已进入20世纪以来第V地震活动幕的平静幕时段。文章还分析了九江—瑞昌地区地震对福建乃至华南地区地震的影响,结果表明,两区域地震无明显的相关性,这可能是由于九江—瑞昌地区处于华北和华南大陆板块内的一级地块交界处,发震动力背景与福建并不相同。福建及其邻近地区的地震主要还是受菲律宾海板块沿NW方向与欧亚板块的相互推挤作用,并遵循其强弱交替的幕式活动为主。目前处于第V活动幕的平静幕时段,本时段将持续至2008年前后,按平静时段的活动特征,今后1-2年福建内陆发生M≥4级地震的可能性小,沿海地区有可能发生4-5级,而台湾海峡中、东部有M≥5级地震活动。 相似文献
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福建减灾十年(1989-1999)正处在我省地震活动十分活跃的时期,共发生4.0级以上地震16次,其中有6次地震造成了地震灾害,使我省经济损失达2.6亿元,人员伤亡412人,并对当地的社会生活和经济建设产生了消极影响。文章分析了本省地震活动特点与灾害特征,分析了造成本省地震灾害的主要因素和地震灾害不十分严重的原因。 在福建减灾十年中,省地震部门坚持以预防为主,依靠科技进步,发挥政府减灾职能,走综合防震减灾道路;认真抓好观测数据高质量产出,各类信息处理与综合分析,震后快速应急三个环节;积极实施全省综合防御地震灾害体系建设,闽南地区综合防震减灾示范工程已经在全国综合防震减灾工作中起到示范作用,福建数字遥测地震台网工程成为中国大陆第一个正式投入观测的全省数字化地震台网;同时加快了法制建设步伐,坚持不懈地进行地震知识的科普宣传教育,努力提高全民防震减灾意识。这些措施对减轻福建十年地震灾害取得显著收益。 为了减轻我省下世纪地震灾害,提出几个值得重视的向题,防患于未然。全省地震前兆台网必须彻底改造,建设高灵敏度、高精度的数字化前兆台网,引入新的观测系统,以期捕捉未来中强以上地震的前兆信息;关注未来城市地震灾害向题,应该开展城市地震灾害环境调查与研究;加强管理,对地震烈度 相似文献
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海啸作为五大海洋自然灾害之一,严重威胁着人类生命财产安全。近些年来,国内外学者对地震海啸进行了大量研究,主要针对海啸的生成、传播、爬高和淹没的数值模拟,以及古海啸沉积物进行研究,但是对于海啸地震震源机制的研究还比较欠缺,尤其是缺乏对震级小于6.5的海啸地震的研究。针对我国的地震海啸研究现状,强调震级小于6.5地震引发海啸的问题不容忽视。本文归纳整理了全球766次地震海啸,利用三角图分类基本法则对海啸地震震源机制解进行分类,并对其中341个发生在1976年后的海啸地震进行震源机制解分析,对其中633次海啸浪高进行统计学方法分析研究。本文认为逆冲型、正断型、走滑型和奇异型机制地震均能引发海啸,逆冲型地震引发的海啸占比最大,震级小于6.5级地震引发的海啸的浪高也有高达10 m的情况,也能产生巨大破坏性。逆冲型、正断型、奇异型地震可直接引起海底地形垂向变化,进而引发海啸,而走滑型地震引发海啸则可能有两种原因,一种是走滑型地震并非纯走滑型而是带有正断或逆冲分量从而引发海啸,另外一种是走滑型地震引发海底滑坡导致海底地形变化进而产生海啸。从海啸地震震源深度分析,能产生海啸的地震震源深度97%以上都是浅源地震,主要集中在30 km深度以内,但是也有中深源地震海啸。本文综合海啸地震的震源特点、我国地理位置以及以往海啸发生的情况,认为未来我国沿海地区威胁性的地震海啸主要集中在马尼拉海沟和台湾海峡区域,在今后海啸预警方面需要格外重视这些区域,通过建立完善海啸预警系统来减少损失。 相似文献
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从断层中心论向块体中心论转变--论活动块体在地震活动中的作用 总被引：37，自引：2，他引：35
讨论活动块体在地震活动中的作用。板缘地震在空间上呈线性分布,而中国大陆地震在空间上呈片状分布。大陆强震往往涉及两个以上方向断层的活动,且强震往往沿块体边界迁移或在其两侧断层上对迁。一些强震前后由中小地震震源机制解反映的Ｐ轴方向往往发生近９０°的转向,这种现象难以用区域应力方向变化来解释,但可从块体活动角度出发,用块体两个边界断层的先后错动来解释。地震前异常的远程效应、震后烈度异常分布图像以及地震序列特点等也显示了活动块体的作用。不同地区由地震活动性推测的块体活动方式有所差别,其原因可能和区域主压应力轴与块体两个边界断层走向的夹角不同有关。据此认为,在分析中国地震活动时要把视角从以活动断层为中心转变为以活动块体为中心 相似文献
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Application of a modified pattern informatics method to forecasting the locations of future large earthquakes in the central Japan 总被引：2，自引：0，他引：2
We propose a modification of the Pattern Informatics (PI) method that has been developed for forecasting the locations of future large earthquakes. This forecast is based on analyzing the space–time patterns of past earthquakes to find possible locations where future large earthquakes are expected to occur. A characteristic of our modification is that the effect of errors in the locations of past earthquakes on the output forecast is reduced. We apply the modified and original methods to seismicity in the central part of Japan and compared the forecast performances. We also invoke the Relative Intensity (RI) of seismic activity and randomized catalogs to constitute null hypotheses. We do statistical tests using the Molchan and Relative Operating Characteristic (ROC) diagrams and the log-likelihoods and show that the forecast for using the modified PI method is generally better than the competing original-PI forecast and the forecasts from the null hypotheses. Using the bootstrap technique with Monte-Carlo simulations, we further confirm that earthquake sequences simulated based on the modified-PI forecast can be statistically the same as the real earthquake sequence so that the forecast is acceptable. The main and innovative science in this paper is the modification of the PI method and the demonstration of its applicability, showing a considerable promise as an intermediate-term earthquake forecasting tool. 相似文献
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As urban poverty in the Third World worsens, an increasing proportion of World Food Programme (WFP) food aid is being used to support poor urban dwellers. WFP food aid has typically been used in three main ways in urban areas: as free relief after disasters (such as floods or earthquakes) have struck urban centres; as part of institutional feeding projects; and as support to urban renewal. While there have been some creative approaches to using food aid to help overcome urban poverty, the benefits have usually only been temporary. It has proved difficult to design food aid interventions for the urban poor that help to overcome the causes of poverty in sustainable ways. The challenge is to use food aid to help make permanent as well as temporary improvements in the lives and livelihoods of the poor. 相似文献
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Evaluating inelastic displacement demand of structures exposed to seismic hazard is required for the design of new buildings as well as for seismic risk assessment of existing structures. Most of the buildings are designed to withstand strong earthquakes by responding in the nonlinear range. Having special parts of the structure designed to develop a stable hysteretic behaviour allows the structure to deform in order to accommodate the displacement demand imposed by strong ground motions. This paper is centred on finding a correspondence between the maximum elastic and inelastic displacement responses of the single degree of freedom (SDOF) systems subjected to earthquakes generated by Vrancea seismic source. Vrancea intermediate-depth earthquakes are responsible for the seismic hazard throughout Romanian territory. They have distinctive features, such as large displacement demand and large predominant periods, which makes Romania a special seismic environment. Using a database of Romanian and Japanese strong ground motions generated by intermediate-depth earthquakes and performing nonlinear dynamic analysis on the SDOF oscillators following the Takeda model, this study estimates the inelastic to elastic displacement ratio of reinforced concrete systems. Soil conditions, epicentral distance and magnitude influence on inelastic response is analysed using constant ductility response spectra. The main findings of the study are: the local increase of the inelastic to elastic displacement ratio for type C soil (Eurocode 8 classification) for large magnitude earthquakes and the significant effect of soil conditions on the inelastic response of the SDOF systems. The inelastic amplification was evaluated using a functional form depending on system ductility, soil conditions and earthquake magnitude.
相似文献16.
Amit Shiuly R. B. Sahu Saroj Mandal Narayan Roy 《Journal of the Geological Society of India》2018,91(4):400-410
Kolkata, capital of West Bengal, India, presently congested with moderate to high rise buildings, has undergone low to moderate damages due to past earthquakes. The city is situated on the world’s largest delta island with soft thick alluvial soil layer. In this study, an attempt has been made to study ground response due to a number of past earthquakes, 1897 Shillong earthquake, 1964 Calcutta earthquake and 2011 Sikkim earthquake, for the purpose of preliminary microzonation of the Kolkata city. For this, synthetic ground motions have been generated at bedrock level by stochastic method. By using 1D wave propagation technique, the synthetic ground motion has been computed at surface level for 144 borehole locations in the city. Contours of PGA, PGV and PGD parameters in the city have been drawn for these three earthquakes. Response spectra for these three earthquakes have also been computed and an optimum response spectrum has been determined. A good correlation has been obtained with predicted ground motion at surface level of the city with the reported intensity and damages occurred in buildings of Kolkata during past earthquakes. The scenario of simulated ground motion for the past three earthquakes depicts that Kolkata city is very much prone to damages even due to moderate far and near source earthquakes. 相似文献
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Jyh-Woei Lin 《Arabian Journal of Geosciences》2011,4(3-4):575-593
The goal of this research is to examine one-dimensional total electron content (TEC) data using principal component analysis (PCA) to search for total electron content (TEC) anomalies associated with large earthquakes in 24 h prior to nucleation. The characteristics of principal eigenvalues generated for TEC prior to 24 earthquakes of magnitude scale M?≥?5.0 and 6 lesser earthquakes of magnitude scale M?<?5 that occurred in Taiwan from 01 January 2000 to 31 December 2001 are examined. In an earlier paper, I was able to confirm the statistical findings of Liu et al. (J Geophys Res 111, 2006) that sparse earthquake-associated TEC anomalies existed in 5 days prior to the 12 large earthquakes they examined (Lin, Terr Atm Ocean Sci, 2010). In this paper, I wish to examine the subtlety of principal component analysis in detecting earthquake-associated TEC anomalies by examining if such precursors can be detected in 24 h prior to large earthquakes. Of the earthquakes examined, TEC anomalies given by clear extreme principal eigenvalues were evident within 24 h of nucleation for 21 of the 24 earthquakes of M?≥?5.0. After making allowance for the general status of background TEC, it is clear that these extreme principal eigenvalues are representative of earthquake-associated anomalies. For the smaller earthquakes (M?<?5), it was not possible to differentiate earthquake-associated anomalies from background effects on TEC status. These new findings confirm the validity of PCA in searching for earthquake-associated TEC anomalies and show that it is subtle enough to detect TEC anomalies within 24 h leading to a large earthquake. If this approach continues to prove successful, it could theoretically be used in real-time prediction of large earthquakes through early detection of earthquake-associated TEC anomalies. 相似文献
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中国大陆科学钻探主孔0-2000米流体地球化学异常与地震的关系 总被引：3，自引：1，他引：3
CCSD流体中He、N2、Ar是记录地震的敏感载体，可能记录了本地一些中小地震及远强震的异常信息。与远强震对应的流体异常幅度大，一般始于远强震前数天，且He、He／Ar、N2／Ar多为负异常，Ar多为正异常；而本地中小地震大多造成主孔流体组分的小幅度波动变化。远强震可能改变了CCSD钻探区的地下流体循环，地震期间监测到泥浆中相对富Ar贫N2和He的地下流体贡献增加，震后，地震引起的附加流体贡献逐渐消失。CCSD的流体组分和比值可能记录了区内地壳应力变化，反映了远强震期间区域构造活动乃至地球深部构造活动产生的场兆、源兆信息，地壳屈曲的假设可以加深CCSD流体作为远强震敏感载体的理解。远强震期间CCSD流体异常也可能是记录了震前长周期波传播至CCSD主孔时激发的流体变化，反映了震源区的应力变化。 相似文献
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This study presents a way to handle historical earthquakes whose parameters are based on sparse documentary materials. It is recommended that discrete earthquake scenarios should be constructed in such cases. Scenarios are possible sets of parameters for a past earthquake, reconstructed on the basis of the macroseismic data available. A probability value is to be attached to each of them using expert judgment. This means that uncertainties associated with historical earthquakes become discrete instead of continuous. Assigning a probability value to each scenario and including alternative solutions in the catalogue makes decision-making more transparent. The current state of the art of the research on a given historical earthquake is documented. It is illustrated how seismic histories of a given place are altered when different scenarios of historical key earthquakes are taken into account. The seismic histories consequently have different probabilities. The choice of an appropriate seismic history could be governed by the need: For example, for a high-risk facility, the high-intensity histories have to be considered. Different earthquake scenarios included in the catalogue would permit to evaluate also the uncertainty of the activity rate and to construct the final logic tree. 相似文献
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Comparison of historical and of post-seismic triangulation data is used to model vertical crustal movements in the vicinity of the Kapareli Fault (or the Alkynonides earthquakes North Fault), one of the two antithetic normal faults which reactivated during the 1981, Gulf of Corinth (Ms = 6.7) earthquakes. This fault is characterized by a much smaller geomorphological signature than the South (or Perachora) fault of the same seismic sequence. Analysis of geodetic data on the basis of polynomial filtering and elastic dislocation modelling, as well as analysis of structural and coastal change data permits us to conclude that the upper bound in the uncertainty level of most of the available elevation changes is 20–30 cm, usually lower than the corresponding dislocation signal. In addition, the available geodetic data have a systematic pattern and are consistent with structural data. For this reason they permit more precise constraints on the geometry and the role of the Kapareli Fault (or the Alkyonides earthquakes North Fault): its total length is estimated about 17 km, about 50% longer than its surface trace; about 30–40 cm subsidence of its hanging wall, as well as at least 15 cm maximum uplift of its footwall is also inferred. This new evidence suggests that although in the long-term the Kapareli fault may represent a rather secondary, antithetic fault to the Alkyonides earthquakes South (Perachora) fault, during the 1981 earthquakes it probably had a more important structural role. 相似文献