西藏玛尼7.5级震与云南的远场前兆异常

远场前兆,是一种场兆,它是地壳构造活动的反映,往往也是强震连发的异常表现,它显示区域构造应力场的增强作用。１９９６年２月３日丽江７．０级大震后,云南省的前兆异常突出。前兆异常分布广,异常种类也多;有新的趋势性异常出现,持续多年的继承性异常也很多,有些前兆异常幅度类似于孟连、武定、丽江三次强震前的异常图象。１９９７年７～９月,这些趋势性异常或继承性异常出现转折与恢复,一些短期异常也趋于结束。如果说云     

1995—1996年云南孟连西,武定,丽江三次强震前的地震活动背景性异常

分析了１９９５￣１９９６年发生的云南孟连西７．５级、武定以北６．５级和丽江以北７．０级三次强震前云南及邻近地区出现的地震活动背景性异常,包括地震空区、条带、小震群活动、地震窗口、诱发地震、强震原地复发以及迁移等特征。对地震活动期的分析表明,１９８８年澜沧－耿马地震后云南地区处于强震活动高潮期,１９９３年区内发生５．０￣６．３级地震７次,达到发生７级以上强震的预报指标。这些地震活动背景异常为这３次强     

1999年河源2次4～5级地震的中短期前兆异常及其思考

对1999年广东省河源市两次4．5级地震前出现的前兆异常进行分析后认为,这些异常既反映了河源两次地震前局部应力场的变化,也反映了华南构造块体应力场的增强,是台湾集集7．6级强震群前大范围内地壳活动增强的表现。由于前兆异常的空间分布与块体内深大活动断裂构造的局部应力集中有关,因此,由前兆异常的多少和分布来判断未来强震的发生地点将是困难的。     

哈萨克斯坦卡帕尔-阿拉善4号井前兆异常特征分析

选取距卡帕尔-阿拉善4号井300 km范围内的3次5级地震,400 km内的3次6级地震,约600 km内1次7级地震、1次6级强震群作为震例资料,分析了这些地震前卡帕尔-阿拉善4号井前兆异常特征。结果表明:①对于5级地震,50.0%测项出现前兆异常,水化学、水动态异常各占50.0%。这些异常的58.3%表现为中期异常,41.7%表现为短期异常,无单独临震异常,也无叠加临震异常。异常变化幅度大而明显,且以趋势性上升或下降为主。硅酸和硫酸根在同一地震前异常时间与异常形态相似。②对于6级地震,33.3%测项出现前兆异常,其中水化学异常占38.9%,水动态异常占16.7%。出现的异常57.1%为中期异常,28.6%为短期异常,14.3%为临震异常。异常形态多为脉冲突跳,而仅有少数为趋势性高值异常。各异常项目之间有一定的同步性。③对于7级地震或6级强震群,37.5%测项出现前兆异常。出现的异常83.3%为中期异常,16.7%为短期异常。异常幅度大而明显,异常形态以单值突跳或趋势性为主。     

云南地区断层形变速率异常及强震预测指标

运用云南地区1997～2002年的跨断层短水准短基线资料,研究了姚安Ms6．5、永胜Ms6．0级地震的形变前兆异常特点。以断层运动速率与基准值之比定义异常参数R值,定量分析了云南地区1998～2002年的形变异常及其与区域强震的关系,提出强震预测指标。结果表明,R值出现异常后的3～20个月内,区域内都有6级以上强震发生。     

昆仑山口西8.1级地震前兆场异常的综合演化特征

从综合的角度系统分析了2001年11月14日青海昆仑山口西8．1级地震前青海地区前兆场异常的演化特征，从时、空、强3个方面总结了趋势性异常、短临异常的演变过程，并提出趋势性异常属于远场大震异常，其异常形态多数继承了兴海6．6级地震前的异常特征，临震异常具有从震中向外围迁移的特性。     

地电前兆异常特征及澜沧—耿马7.6级等地震预报问题

深入研究了全国地电台网内M_s≥5.0的45次地电前兆震例,用统计方法按大震、强震、中强地震分别研究其地电前兆特征。 通过研究得到:大震地电阻率异常范围,其半径超过200km,在700km以内,异常时间在12—20个月内发震的概率最高,为97.8％;强震地电阻率异常范围大多在300km以内,趋势异常的时间在12个月以内发震的概率最高,为86.5％;中强地震地电阻率异常范围,半径一般在200km以内,趋势异常时间在180天之内发震的概率最高,为95.0％。大震、强震、中强地震地电趋势异常时间似乎存在着20个月、12个月、6个月三个不同的异常时间段。 临震异常类型一般可分为加速型、转向型和波动型三类。对7级和7级以上大震能观测到临震异常前兆的震例只有33.3％、强震和中强地震能观测到临震异常前兆的震例均为50.0％。出现临震异常后1—20天发震的概率最高,达94.4％。 1988年11月以来,西部地区先后发生澜沧-耿马7.6、巴塘6.7、天祝6.2级地震。震前都曾依据地电前兆短临异常特征,作过某种程度的监测预报工作,取得了较好的短临预报效果。     

1995—1996年云南地区三次强震前地震活动的短期异常

在地震学参量年度异常的背景＾（３）,阐述了１９９５￣１９９６年云南地区发生的孟连、武定、丽江三次强震前的地震活动短期异常,包括地震平静、小震群、窗口地震、调制地震、地震波参数以及４级左右地震向震中迁移等。结果表明,这些异常特征表现突出,其演化进程显示了强震孕育的阶段性。     

2010年4月14日玉树7.1级地震前异常特征及强震动力学关系探讨

系统地分析了2010年4月14日玉树7.1级地震的地震活动性异常、前兆异常以及震前动物反常行为.研究表明,玉树7.1级地震前异常并不丰富,但觉察到的异常突出.其中中长期异常有6级、5级和4级的平静区;前兆观测有玉树表层水温、德令哈表层水温和平安电磁波等显著异常;同时震前1周还存在数量较多的动物宏观异常现象;主震前130min发生了一次4.7级地震.结合1996年以来巴颜喀拉地块边界的强震震源机制解,探讨了玉树地震孕育的动力学过程.结果表明,1996年喀喇昆仑山口7.1级、1997年玛尼7.5级和2010年玉树7.1级地震是同一动力学过程下的强震事件,且中长期存在的不同震级档平静区演化可能与上述动力学过程有关.还对强震原地复发、前震识别和玉树地震中的前兆观测等科学问题进行了讨论.     

前兆异常与强震时空点的研究

本文研究了云南三次７ 级以上强震前的小震活动, 前兆异常总台项频数变化, 地下水时空特征。得出在大震前３ ～６ 个月前兆异常台项总频数的升高现象与３０ ～３９ 级小震向震中区收缩的时间大致同步, 可能是大震前的异常从短期向短期临震过渡的时间标志。震前１ ～３ 个月出现的前兆台项总频数异常峰值和水位、水氡的场兆现象则是异常进入短期临震的时间; 峰值回落是震源区进入临震状态的时间。     

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.     

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.     

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.     

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.     

Copper in natural waters in Transbaikalia

Cu concentrations in surface (river and lake) and subsurface waters are determined. The geographic pattern of Cu distribution in natural water is identified. This pattern is controlled by the difference between its concentrations in drained rocks and soils and the geochemical redox conditions of its migration. Territories with low, medium, and elevated Cu concentrations in natural waters are identified. The concentrations of Cu in natural waters of the region are found to be generally lower than the Clarke values.     

Changes in thermal extremes in Poland

Changes in thermal extremes of the climate of Poland in 1951–2010 are examined. Warm extremes have become more frequent, while cold extremes have become less frequent. In the warming climate of Poland, the increase in the number of extremely warm days in a year and the decrease in the number of extremely cold days in a year have been observed. Also the increase of the maximum number of consecutive hot days in a year and the decrease of the maximum number of consecutive very cold and extremely cold days in a year have been observed. However, the trends are not of ubiquitous statistic significance, as the natural variability is strong.     

Hydrological changes in the Ganges system in Bangladesh in the post-Farakka period

Abstract

The basin area of the Ganges River in Bangladesh is extremely dependent on a regular water supply from upstream to meet requirements for agriculture, fisheries, navigation, salinity control, and domestic and industrial sectors. In 1975, India commissioned a barrage on the Ganges River at Farakka to divert a significant portion of the dry season flow in order to make the Calcutta Port navigable. Statistical analyses of discharge and water level data have been carried out to determine if significant changes have occurred in the hydrology of the Ganges system in Bangladesh in the post-Farakka period. Siltation of the Gorai River (an offtake of the Ganges River) has also been examined using the stage-discharge relationship and regression analysis. The analyses show that the diversion has caused considerable hydrological changes in the Ganges system in Bangladesh. The water supply in the dry season has been reduced substantially, while siltation of the Gorai River has increased significantly.     

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.