北部湾6.1,6.2级地震的前兆异常

通过对北部湾６．１，６．１级地震前的震兆分析，认为地震是在区域地震活动出现中期异常背景的情况下发生的，前兆观测的趋势异常较为突出，但短临异常极少，地震活动性和前兆观测手段的趋势异常变化具有稳定性和准同步性，反映了震前区域应力场的变化。     

华北北部场源前兆观测资料分析（一）

１９７６年唐山地震前，在距震很远的地区内都观测到一些前兆趋势变化，如重力、重力位二次微商Ｗ△、水氡、地电阻率、水位和油井出油量等变化。作者认为这些变化不是由震源体直接引起的，而是在区域应力场的作用下，在某些活动断层附近，浅层岩，尤其是含水砂岩层和含油层受挤压出现的一些与地震有拳异常现象，其特征是：（１）异常范围大，可能在距震源很远的地方发生，但就同一种方法的多个观测点来说却又是局部的，即只有其中部     

华北北部场源前兆观测资料分析(一)──场源前兆特征与机制

1976年唐山地震前，在距震源很远的地区内都观测到一些前兆趋势变化，如重力、重力位二次徽商W△、水氧、地电阻率、水位和油井出油量等变化。作者认为这些变化不是由震源体直接引起的，而是在区域应力场的作用下，在某些活动断层附近，浅层岩，尤其是含水砂岩层和含油层受挤压出现的一些与地震有关的异常现象。其特征是：（1）异常范围大，可能在距震源很远的地方发生，但就同一种方法的多个观测点来说却又是局部的，即只有其中部分测点才能观测到异常，不少测点观测不到异常。（2）异常发生的时间大致相同。有些异常有同步变化的特征，如同时上升或同时下降。（3）临震前多数异常有恢复的趋势。这些特征与引起异常的机理有关。作者还从理论上计算了这种趋势异常量级，重力变化100×10-6cm／s2左右，重力位二次微商变化（1～2）×10－9／s2，地电阻率变化2％～3％，Rn变化7．4～11．1Bq／L，这样的变化量在活动断层附近的一些台站可能观测到。作者还研究了干旱降雨对某些前兆的影响，其影响量级可以被一些方法观测到，因此在确定是否是地震异常时，必须注意利用综合分析的方法排除干旱降雨的影响，减少异常的多解性。     

东营凹陷陡坡带油井前兆异常及其动力学成因讨论

分析了东营凹陷陡坡带断裂体系 ,研究了东营凹陷陡坡带油井前兆异常与地震活动的关系 ,探讨了油井前兆异常的动力学成因。孕震过程是应力场变化和调整的过程 ,应力场变化导致孔隙压力变化 ,使得油井产生前兆异常。特定的地质环境是油井前兆异常的基础 ,应力转化为孔隙压力是油井前兆异常的前提。油井前兆异常是正异常还是负异常 ,取决于油井所处的地质环境在孕震过程中地应力是增加还是减小 ,前兆异常幅度取决于孔隙压力的变化幅度     

24小时拟合检验方法的应用

地震前兆观测中有许多方法都能观测出固体潮汐的变化,如重力、倾斜、应变、地下水位等。固体潮汐的观测资料除用于地球结构、地球物理性能等的研究之外,主要用于地震预报、是地震前兆观测中能够预知其正常背景的手段。知道了正常变化范围,就能区分出异常变化。从中再找出地震前兆的异常变化。 固体潮观测的各手段进行地震预报时,普遍应用潮波的观测振幅与理论振幅的比值的变化和漂移     

地应力地磁场与地震

通过地表重力异常和磁异常的对比，可以找到两者之间的一些因果关系。这种关系在整个地磁场与应力场的历史变化中又得到了进一步的验证。这种因果关系是：地球的初始磁场可能是由晶体的压电效应产生的，地磁场的变化反映了地球应力场的变化。     

长期性前兆异常的探讨

对长期性前兆异常进行研究的结果表明:①长期性前兆异常的开始和结束及其发展变化一般与地震活动幕的起止和强震活动有关;②近年出现的长期性前兆异常的开始时间一般是先东后西,呈现出一定程度的有序性,与强震依次由东向西发生一致。长期性前兆异常展示了区域应力场的演化、扩展、转移的图像,以及地震间的相联系和相互影响,并有可能判定地震幕的起止和预测后续地震。 因此,该结果为研究和判定地震趋势提出了一种可能的途径。     

强震水化学前兆场特征

研究了唐山、松潘两次７级以上强震的水化学前兆场特征。结果表明，两次强震水化学前兆场有相似的特征。在震源区，水化趋势性异常和短临突变异常所占的比例大，远离震源区所占的比例小，且有逐渐减小的趋势；在震源区，水化趋势性异常起始的时间早，远离震源区异常起始的时间晚，趋势异常的形态均为逐渐升高。水化学前兆场的形成与区域应力场有关，但与震源应力场关系密切，可能起主导作用的是震源应力场。     

流动重力资料对汶川M_S8.0地震的中期预测

通过对中国地壳运动观测网络重力观测资料的系统整理和分析,结合一定的孕震理论和前兆机制理论,研究了网络重力观测前兆手段的异常特征,并给出了1～2年尺度的地震趋势预测意见.     

大同—阳高6.1级地震前兆场分析

通过对１９８９年大同－－阳高６．１级地震异常的清理,发现６４项前兆异常,９项测震学异常,前兆异常主要在距震中１００ｋｍ￣３００ｋｍ范围内,异常的演化具有明显的阶段性、早期趋势异常和临震异常均出现在震中附近地区、异常的空间展布不对称性等。分析了前兆场的时空强特征、前兆异常机理、孕震过程及场源关系。指出,大同－－阳高地震是受华北区域应力场控制,在ＮＥＥ向主压应力作用下,ＮＮＥ向断层发生右旋走滑错动,Ｎ     

SCIENCE CHINA Earth Sciences SUBJECT INDEX TO VOLUME 57(2014)

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Distribution of throughfall and stemflow in multi‐strata agroforestry,perennial monoculture,fallow and primary forest in central Amazonia,Brazil

The partitioning of rain water into throughfall, stemflow and interception loss when passing through plant canopies depends on properties of the respective plant species, such as leaf area and branch angles. In heterogeneous vegetation, such as tropical forest or polycultural systems, the presence of different plant species may consequently result in a mosaic of situations with respect to quantity and quality of water inputs into the soil. As these processes influence not only the water availability for the plants, but also water infiltration and nutrient leaching, the understanding of plant effects on the repartitioning of rain water may help in the optimization of land use systems and management practices. We measured throughfall and stemflow in a perennial polyculture (multi‐strata agroforestry), monocultures of peach palm (Bactris gasipaes) for fruit and for palmito, a monoculture of cupuaçu (Theobroma grandiflorum), spontaneous fallow and primary forest during one year in central Amazonia, Brazil. The effect on rain water partitioning was measured separately for four useful tree species in the polyculture and for two tree species in the primary forest. Throughfall at two stem distances, and stemflow, differed significantly between tree species, resulting in pronounced spatial patterns of water input into the soil in the polyculture system. For two tree species, peach palm for fruit (Bactris gasipaes) and Brazil nut trees (Bertholletia excelsa), the water input into the soil near the stem was significantly higher than the open‐area rainfall. This could lead to increased nutrient leaching when fertilizer is applied close to the stem of these trees. In the primary forest, such spatial patterns could also be detected, with significantly higher water input near a palm (Oenocarpus bacaba) than near a dicotyledonous tree species (Eschweilera sp.). Interception losses were 6·4% in the polyculture, 13·9 and 12·3% in the peach palm monocultures for fruit and for palmito, respectively, 0·5% in the cupuaçu monoculture and 3·1% in the fallow. With more than 20% of the open‐area rainfall, the highest stemflow contributions to the water input into the soil were measured in the palm monocultures and in the fallow. Copyright © 1999 John Wiley & Sons, Ltd.     

A Monte Carlo study of rainfall forecasting with a stochastic model

A procedure for short-term rainfall forecasting in real-time is developed and a study of the role of sampling on forecast ability is conducted. Ground level rainfall fields are forecasted using a stochastic space-time rainfall model in state-space form. Updating of the rainfall field in real-time is accomplished using a distributed parameter Kalman filter to optimally combine measurement information and forecast model estimates. The influence of sampling density on forecast accuracy is evaluated using a series of a simulated rainfall events generated with the same stochastic rainfall model. Sampling was conducted at five different network spatial densities. The results quantify the influence of sampling network density on real-time rainfall field forecasting. Statistical analyses of the rainfall field residuals illustrate improvement in one hour lead time forecasts at higher measurement densities.     

Anthropogenic Eutrophication and Red Tide Outbreak in Lacustrine Systems of the Kashmir Himalaya

Red tide, a recurrent phenomenon has become conspicuous in several Kashmir lake ecosystems since 1991. The responsible organism (Euglena pedunculata), a rare flagellate rediscovered in the Kashmir Himalaya (Khan 1993) caused first and unprecedented red tide outbreak, constituting a maximum of 96% of resident numerical phytoplankton density in Dal Lake. At present, conflicting hypotheses exist on the generation of causal assemblage(s) imparting redness to waters: Jeeji Bai (1991) linked its origin to acid precipitation – a fallout of burning oil‐fields during the Gulf War – whilst Khan (1993) holds local factor(s) responsible. Field/experimental studies support the latter contention that the influx of untreated sewage, in unison with warm temperatures, high levels of PhAR, iron and interruption to hydrological flow‐pattern together with absence/or reduction in grazing activity created conducive environmental milieu for red tide outbreak. Dal Lake “red tide” drifted the bloom‐inoculum to other waters, including Lake Wular, where additional ecological niches were carved out, threatening the aesthetic value and biological diversity of Kashmir lakes. Ecological monitoring indicates frequent seasonal red tide occurrence in Dal Lake (including summer‐autumn event of 1998) which testifies its unabated eutrophication status. Further studies are needed on ecological adaptability and biogeographic distribution of this rare and unique red tide‐causing flagellate.