滇西北强震活动特征及短期震兆研究

根据历史地震资料研究了滇西北强震活动韵律特征及最近10多年来6.0级以上强震前震中附近中小地震活动空间演化图像。对1986年以来滇西北5.0级以上中强震前该地区M≥3.0和M≥4.0地震的活跃和平静异常以及3级以上震群进行了清理和配套性研究,定量地给出了滇西北强震短期震兆指标。得到以下主要结果:滇西北6.0级以上强震前,在全省4.0级以上地震平静异常阶段或3.0级以上地震活跃阶段,震中附近3级地震比较活跃,并形成明显的条带、围空、密集等地震活动有序分布异常图像;滇西北6.0级以上地震短期异常综合预报量Y≥0.56。短期震兆模型可分为两种:①滇西北3.0级以上地震活跃异常和3～4级震群活动同时出现;②滇西北4级以上地震出现平静异常后又出现3.0级以上地震平静异常。     

四川六级以上地震前地震活动条带的特征

本文比较了地震带、地震活动成带转移和强震前地震活动条带的概念。对于1970年下半年以来,四川及邻近地区发生的6级以上强震前的背景性地震活动条带和弱震密集条带,进行了清理和研究。背景性地震活动条带指强震前十几个月到几年出现的由4级以上地震组成的地震活动条带。弱震密集条带是强震前几个月出现的,由微弱地震组成的地震活动条带。 3次7级以上地震和盐源、宁蒗6.9级地震前出现了背景性地震活动条带。其中炉霍7.9级和松潘—平武7.2级地震前出现两条互相近乎垂直的背景性条带。永善7.1级和盐源—宁蒗6.9级地震前只有一条背景性条带。8次6级以上地震中有7次震前出现了弱震密集条带。强震往往发生在两条地震活动条带的交汇部位附近或一条地震活动条带的端部或空段。 本文对于7个弱震密集条带的震例作了各时空参数与未来强震震级的统计分析。弱震密集条带的面积S、持续时间ΔT与震级M分别在信度α=0.05和0.10的情况下,通过线性相关检验,用最小二乘法求得的直线关系为: M=3.40lgS—3.91±1.3   M=1.84lgΔT+6.01±1.3 式中ΔT的单位是月,S的单位是103公里2。 最后,本文初步探讨了震前地震活动条带与构造、强震震源机制的关系及其在地震预报中的作用。      

2001年昆仑山口西8.1级特大地震孕育过程及中强地震活动图像演化

通过在百年时间域、45°×35°空间域对2001年昆仑山口西8.1级特大地震的孕震过程和中强地震活动图像演化进行时空扫描研究,认为该地震存在清晰的长期、中期、短期和临震几个孕育阶段,给出了各阶段清晰有序的地震活动图像,并找出划分各孕育阶段的标志性地震.同时指出8.1级特大地震的特殊性和预测预报的困难性.     

中国大陆强震前地震活动图像演化特征研究

将1966年以来中国大陆发生的75次6.5级以上地震分为52组, 按华北-东北、 西南、 青藏块体、 新疆不同构造区域, 分别对其6.5级以上强震前4级、 5级以上地震活动图像进行了全时空扫描, 选取震前特征图像, 按构造区域进行分析、 总结, 研究强震前中等地震活动图像演变的基本特征, 及其震前图像演化的共性和差异性。 研究结果表明: 强震前不同级别中等地震活动出现二个阶段异常图像转化具有普适性。 5级地震图像后期在时间和空间上配套出现的4级地震的异常图像, 可能是强震孕育过程中由中期向短期过渡的一种标志。     

大震的孕育规律与预报初探

大地震的孕育与发生,是构造变动的一部份,是受区域应力场控制的。本文正是通过对区域地震活动图象的研究,探索大震可能发生的危险地点;并通过其变化规律,探讨大震孕育的周期。笔者根据对川滇地区两千年的历史地震资料及1965年至1982年底的十八年地方台网资料的研究,初步确定了以 NW50°、NE40°的地震密集条带构成的网状图象。7级大震,90%以上发生在条带内,80%以上发生在网状结构的“结点”区。通过对1970—1976年五次7级大震的综合对比研究,初步确定,大地震的孕育周期:6—5年、4—3年为中长期阶段,2—1年为中短期阶段。而大震前,震源结点区及其相应的共轭条带上,多有中强震发生。从而可为大地震的长、中、短期预报,为中强震的中、短期以至临震预报提供趋势意见。     

伽师地震前后喀什台地磁短周期变化特征

在地震孕育过程中,由于应力的集中、积累,导致岩石介质磁性发生变化,即产生震磁效应。研究表明地磁短周期变化与地震发生前后出现的地磁扰动关系密切,不同频率的电磁感应场,携有不同频率电磁波穿透深度地层的介质信息。对地磁扰动场信息进行提取,计算,分析,可以获得与其相关的地震前后地磁场的变化特征。1997年1月21至4月16日,新疆伽师地区(76.6°～77.2°E,39.3°～39.8°N)发生了强震群活动,6级以上地震7次,5级以上地震4次。随后在5月17日,6月24日又分别发生两次5级地震。该震群活动6级地震时间间隔短、分布范围小,仅在3个月的时间内,连…     

四川及邻区强震前地震活动频度的变化特征

对发生在四川及邻区的17次6级以上强震事件的震前中小地震活动进行了分析,发现在这些主震前均出现了区域性、中期或短期的中小地震活动增强或平静的过程。这种过程可用四川地区3．5～5．9级地震的月频次变化来进行量化,并可作为预测四川及其邻区6级以上强震的一项指标。经反复试验,本文提出判别地震月频次异常的标准,给出将异常用于强地震预报的规则,同时,对该项指标的预测效能进行了内符检验：结果表明：月频次异常指标对于研究区具有较好的中期预测效能及一定的中短期预测效能。     

新疆及周边地区强震成组活动及其预测研究

系统分析了1900年以来新疆及周边6级以上地震成组活动基本特征。 结果表明, 新疆及周边地区6级以上地震成组活动明显, 并具有持续时间短、 地震强度大、 频度高的特点。 新疆及周边地区7级以上地震有95％发生在地震成组活动期间, 地震成组活动是该区域发生7级以上强震的中期预测指标之一。 地震成组活动一般出现在低活动水平背景下, 而且成组地震活动在空间上相对集中分布, 在地震活动期间强震存在由新疆西南向北东迁移的特点, 其中天山地震带尤其是南天山西段为强震主要的活动区域。 地震成组活动伴随地震条带图像的出现; 在地震成组活动前或活动中新疆地区前兆测项异常明显增加, 具有群体异常的起伏变化过程。     

川滇及邻区强震地区震前的地震活动特征

对中国大陆西部的川、滇及邻区,1970年以来8次MS≥7.0级强震的震源地区,震前的中强地震活动及时空图像进行了分析.结果表明:强震前在震源地区MS≥4.8级的中强地震活动, 在地表特定的断裂构造带上成团丛集活动,其中早期和中期阶段出现的中强地震位置,是未来强震的震中地区.震级-时间关系的时序特征显示,强震前的早期、中期和短期的三个阶段,中强地震震级随时间逐渐增大,并逐步增长,直到强震发生,地震活动的间隔时间Δt-t 曲线则由大变小衰减至发生强震.在强震前,早期阶段的中强地震小于中期阶段出现的中强地震,中期阶段的较大中强地震,可成为强震前一次具有信号震标志的较大地震.同时,强震前孕震期与临震期的持续时间有一个线性比值关系,比值为0.21～0.27.根据比值关系以及强震地区震前中期阶段和短期阶段出现的地震事件,可作为强震预测的一种震兆指标.     

四川地区地震活动条带预报效能的研究

根据国家地震局(87)震发科字第105号文,我们承担条带预报方法的研究任务。强震前的地震活动条带是有别于地震带、地震活动成带转移的一种震兆。笔者曾对四川及邻近地区8次6级以上地震前的地震活动条带进行了清理和研究。主要结果是:(1)强震前的地震活动条带可分为两种:背景性条带和弱震密集条带。前者由4级以上地震组成,出现时间早,持续时间长,可用于中期预报。后者使用资料的震级下限低,出     

Changes in sediment transport in the Kuye River in the Loess Plateau in China

In this paper, the changes in sediment transport over 51 years from 1955 to 2006 in the Kuye River in the Loess Plateau in China are assessed. Key factors affecting sediment yield and sediment transport, such as precipitation depth, discharge, and human activities are studied. To investigate the changes in sediment yield in this watershed, a trend analysis on sediment concentration, precipitation depth, and discharge is conducted. Precipitation depths at 2 Climate Stations （CSs）, as well as discharge and sediment transport at 3 Gauging Stations （GSs） are used to assess the features of sediment transport in the Kuye River. The rtmoff modulus （defined as the annual average discharge per unit area, L/（s·km^2）） and the sediment transport modulus （defined as the annual suspended sediment transport per unit area, t/（yr km^2）） are introduced in this study to assess the changes in runoff and sediment yield for this watershed. The results show that the highest average monthly discharge during the study period in the Kuye River is 66.23 m^3/s in August with an average monthly sediment concentration of 88.9 kg/m^3. However, the highest average monthly sediment concentration during the study period in the Kuye River is 125.34 kg/m^3 and occurs in July, which has an average discharge of 42.6 m^3/s that is much less than the average monthly discharge in August. It is found that both the runoff modulus and sediment transport modulus at Wenjiachuan GS on the Kuye River has a clear downward trend. During the summer season from July to August, the sediment transport modulus at Wenjiachuan GS is much higher than those at Toudaoguai and Longmen GSs on the Yellow River. The easily erodible loess in the Kuye River watershed and the sparse vegetation are responsible for the extremely high sediment yield from the Kuye River watershed. The analyses of the grain size distribution of suspended load in the Kuye River are presented. The average monthly median grain size of suspended load in the Kuye River is largest in February and then decreases until June. In July, the average monthly median grain size of suspended load approaches another peak and decreases until September. Then, the median grain size of suspended load starts to increase until February of the following year. However, the average monthly median grain size of suspended load in the Yellow River at Toudaoguai and Longmen GSs is the smallest between early summer and late fall The median grain size in the Yellow River starts to increase in November and approaches the largest size in January.     

Variations in trace gas concentrations in different environments in India

Observations of trace gases (SO₂, NH₃, NO₂ and O₃) were made during the period 1981 to 1984 at 6 different locations representative of urban industrial, urban, nonurban, thermal power plant and marine environment. Diurnal variations of the trace gases were studied in an urban environment. Except in the urban industrial environment, the concentration of NH₃ was found in the range of background values. Also, the average concentrations of NO₂ and O₃ at the different environments were in the order of background values. However, the concentrations of SO₂ were substantially higher by about 7 times, in urban industrial and thermal power plant environments. The diurnal variations of SO₂, NH₃ and NO₂ showed anitphase relationship with surface temperature at the urban environment station which is relatively free of industrial pollution. Discussion is centred on trace gas variations in different environments in India together with the values reported for various countries in the world.     

TritiogenicHe in groundwater in Takaoka

³He/⁴He ratios up to 3.5 times the ratio of atmospheric He were found in groundwater samples. The³He enrichment can be attributed to radiogenic³He produced by in-situ beta-decay of³H. This shows that tritiogenic³He is accumulating in confined waters. From tritiogenic³He and³H concentrations, ages of groundwaters can be calculated. Detection of tritiogenic³He gives a tool to trace a tritium contamination which occurred in the past and cannot be assessed only by the³H counting method.     

2008年云南地震灾害概况

列出了2008年云南省破坏性地震目录.在此基础上,结合云南省地震局的地震灾害评估资料,总结了2008年云南地震灾害的主要数据和特性.最后列出1990～2008年云南地震灾害的相应数据,并进行了简要对比.     

Applied volcanology in geothermal exploration in Iceland

In an active spreading area like Iceland, where the regional geothermal gradient is in the range 50–150°C/km, it is normally not a problem to find high enough temperature with deep drilling, but the difficulties arise with finding permeable layers at depth within the strata. Various volcanological methods can be applied in the search for aquifers and geothermal reservoir rocks. The flow pattern (as deduced from deuterium studies) indicates that the thermal water flows preferentially along high porosity stratiform horizons and dyke swarms from the recharge areas in the highlands to the hot spring areas in the lowlands. The primary porosity of the volcanic strata is dependent on the chemical composition and the mode of eruption of the volcanic units. Both the reservoir rocks and the flow channels forming the geothermal plumbing system are thought to vary from the Tertiary to the Quaternary provinces due to environmental conditions at the eruptive sites.     

2007年中国大陆地震灾害损失述评

在列出2007年中国5级以上地震目录的基础上,结合有关省(自治区、直辖市)地震局的地震灾害评估资料,总结出2007年中国大陆地震灾害的主要数据和特性。最后列出1990—2007年中国大陆地震灾害的相应数据,并进行了简要的比较。     

Projected changes in flood indices in selected catchments in Poland in the 21st century

The aim of this study is to estimate likely changes in flood indices under a future climate and to assess the uncertainty in these estimates for selected catchments in Poland. Precipitation and temperature time series from climate simulations from the EURO-CORDEX initiative for the periods 1971–2000, 2021–2050 and 2071–2100 following the RCP4.5 and RCP8.5 emission scenarios have been used to produce hydrological simulations based on the HBV hydrological model. As the climate model outputs for Poland are highly biased, post processing in the form of bias correction was first performed so that the climate time series could be applied in hydrological simulations at a catchment-scale. The results indicate that bias correction significantly improves flow simulations and estimated flood indices based on comparisons with simulations from observed climate data for the control period. The estimated changes in the mean annual flood and in flood quantiles under a future climate indicate a large spread in the estimates both within and between the catchments. An ANOVA analysis was used to assess the relative contributions of the 2 emission scenarios, the 7 climate models and the 4 bias correction methods to the total spread in the projected changes in extreme river flow indices for each catchment. The analysis indicates that the differences between climate models generally make the largest contribution to the spread in the ensemble of the three factors considered. The results for bias corrected data show small differences between the four bias correction methods considered, and, in contrast with the results for uncorrected simulations, project increases in flood indices for most catchments under a future climate.     

冬季亚洲中强震与夏季我国东部主雨带的准同纬性

根据1954～2003年50年亚洲中强震与我国地温资料,分析了冬季震中纬度—震涡中心纬度—冬季我国东部强地热涡中心纬度—夏季我国东部主雨带纬度4者之间的相互关系,发现冬季中强震与夏季主雨带之间具有较好的准同纬性. 这是每年汛期降水预报的一个指标. 文中也讨论了应用此预报指标时的一些特例.     

Advances in ground motion studies in China

This paper briefly summarizes the works in the processing of strong ground motion data, the factors affecting strong ground motion, the modeling of strong ground motion and the calculating of broad-band response spectrum which have been done recent years by engineering seismologists and seismologists of China. In addition, we think back to the international cooperation in strong ground motion of the recent years and make some expectations for the future.