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１９７５￣１９９１年间,广东河源市新丰江水库区发生了５次ＭＬ４．７￣５．１级地震。距震中１０ｋｍ以内的河源黄子洞地电台记录到了震前不同程度的地电阻率异常变化。采用距平法消除年变干扰后异常延续时间一般为３个月左右,电阻率异常下降幅度在１％左右。利用《指南》中的震兆异常信度分析法确认其异常信度后,利用模糊信息处理法对异常判定地震三要素进行了计算,结果与实际基本符合。 相似文献
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南北带北段地壳上地幔密度与磁性结构 总被引：1，自引：0，他引：1
利用对应分析约束下的重磁联合反演方法,计算了南北带北段４条地震测深剖面的地壳上地幔的密度和磁化率物性参数。结果表明：①自上而下区内存在中新生界地层与下伏地层（０．１４￣０．３０ｇ／ｃｍ＾３）、中上地壳与下地壳（０．１０￣０．２０ｇ／ｃｍ＾３）和下地壳与上地幔顶部之间（０．３０￣０．４０ｇ／ｃｍ＾３）３个密度分界面;②区内磁性参数随深度增加而增大,浅部中新生界地层几乎无磁性,中上地壳磁化率一般为１０ 相似文献
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本文分析了我国１９００年以来Ｍ＿ｓ≥７．０级地震前与断层面总面积有关的参量ΣＥ￣（２／３）随时间的变化，探讨了运用ΣＥ￣（２／３）－ｔ曲线进行中期地震预报的可能性。通过分析某一地区历史地震的Ｅ￣（２／３）（ｔ）曲线，可以认识这一地区在过去若干年内地震的活动情况，并由此判断该区未来几年到几十年内地震活动的总状态；还可以根据Ｅ￣（２／３）（ｔ）曲线外推估计一个地区目前地震活动的可能强度。本文对Ｅ￣（２／３）（ｔ）曲线的基本形态作了粗略的分类，并试图对一个地区历史地震系列的Ｅ￣（２／３）（ｔ）曲线，用灾变论的观点确定该曲线的灾变条件和时间，以建立一种可应用的地震预报方法。 相似文献
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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 总被引：2，自引：2，他引：0
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 相似文献
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目的：研究CT导向胸部病灶穿刺活检的方法及应用价值，材料与方法：83例中，脑内病变70例，纵膈病变10例，胸壁及胸膜病变3例，穿刺针为肺活检针，共穿93针，结果：穿刺成功率为100％，取材病理检验效果，理想占80．7％，可行占13．3％，总可靠率为94．－％，不可靠6．0％，结论：精确的定位，熟练的技术及病人的良好配合可提高穿刺成功率和取材的可靠性。 相似文献
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本文清理了吉林省地震前兆台网在省内中等地震,邻区中强以上地震、西太平洋地震带大震前记录到的１４次前兆异常。通过震例统计,筛选出省内前兆映震敏感测点和敏感测项。根据映震范围曲线求出最低映震震级为３．０左右,线性区内最大映震距离为６００￣８００ｋｍ。对５级地震的反映距离为２００￣３００ｋｍ。 相似文献
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采用一种新的统计检验方法对ＶＡＮ方法在１９８７￣１９８９年间预报成功率和随机采样地震目录获得的成功率之间进行了对比（成功率是把成功预报的次数与所发出的预报总次数的比值）。与以往的检验不同，这次检验所采样的分布是从１９６０￣１９８５年间的历史地震空间和震级的分布所得出的。ＶＡＮ方法预报成功率以延时２２天为计达６７．９％，而在ＮＥＩＣ人武部目录上随机极样中仅为３７．２％，可达到上述指标（６７．９％）， 相似文献
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Gtz Schroth Luciana Ferreira Da Silva Marc‐Andree Wolf Wenceslau Geraldes Teixeira Wolfgang Zech 《水文研究》1999,13(10):1423-1436
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. 相似文献
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M. N. French R. L. Bras W. F. Krajewski 《Stochastic Environmental Research and Risk Assessment (SERRA)》1992,6(1):27-45
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. 相似文献
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M. A. Kahn 《洁净——土壤、空气、水》2000,28(2):95-101
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. 相似文献
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