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由跨断层形变测量反映的华北地块近期断裂活动特征 总被引：3，自引：0，他引：3
通过对华北地块不同构造部位、不同地震活动时段的跨断层测量资料研究表明，华北地块对于NE走向断裂作用为主的构造单元(包括地块和边界带)的强震活跃时段的断层运动速率明显小于强震不活跃时段；对于NW走向断裂作用为主的构造单元，其强震活跃时段的断层运动速率明显大于强震不活跃时段；对于NE、NW走向断裂共同作用的构造单元，断层运动速率变化特征类似于NW走向断裂作用为主的构造单元。结果还表明，华北地块现今强震活动主要受NW走向断裂的控制。 相似文献
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基于Coulomb3.3软件,通过研究地震累加与单震的库仑应力变化对后续地震的触发关系,对北祁连山东段及邻区自1561年以来的9次强震静态库仑应力变化进行了研究。结果表明：对于叠加现象来说,后一地震事件除了门源地震落在应力影区外,先前地震活动对后续地震都产生了明显的触发作用,库仑应力变化在0.1~4.066 bar之间;而对于单独事件的应力变化,断层距较小的地震之间相互触发的影响较大。根据库仑应力变化和年应力累积量的比值,得出地震在没有先前地震作用下还需要的应力累积时间。最后根据大震后区域断裂库伦应力变化及断裂强震活动历史等特征,对本区未来强震地震危险性进行分析,得出本区未来地震危险区位于云雾山断裂以及天祝-景泰—古浪一带的金强河断裂上。 相似文献
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把环境应力增高，作为将要发生强震的前兆。根据陈培善导出的利用地震波资料直接计算环境剪应力τ＿０值的公式，计算了１９８７─１９９１年全国范围内的环境剪应力值，并据此预测了１９９２年以后３年内可能发生６级以上地震的５个强震危险区。实际验证结果是：从１９９２年５月至今，中国境内共发生Ｍ≥６．０的地震７次，６次均落在预先划定的危险区内。根据进一步的研究，计算了１９９２─１９９３年全国环境应力值，结合１９９１年以前的资料，对未来１９９３年１１月─１９９６年３年内可能发生强震的危险区进行了预测，提出了６个值得注意的强震危险区。 相似文献
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鲜水河断裂带乾宁——康定段的几何结构比较复杂，由雅拉河、色拉哈——康定、折多塘和磨西4条次级断裂组成，历史上曾发生过1725，1786和1955年3次7级以上强震．本文在断错地貌和年代学（14C 和TL）研究结果的基础上，确定的鲜水河断裂带乾宁——康定段各分支断裂晚第四纪以来的平均水平滑动速率分别为:雅拉河断裂:（2.00.2）mm/a；色拉哈——康定断裂:（5.50.6）mm/a；折多塘断裂:（3.60.3）mm/a；磨西断裂:（9.90.6）mm/a．
历史地震地表破裂、同震位错和古地震资料研究结果表明，雅拉河断裂具有上千年的强震复发间隔，色拉哈——康定和折多塘断裂强震复发的平均间隔在230～350ａ，未来百年均不存在强震复发的可能性；磨西断裂强震复发间隔在300ａ左右，上一次的1786年7级地震距今已达213ａ，未来百年正处于新一轮的强震复发背景之中． 相似文献
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小江断裂带及周边地区强震危险性分析 总被引：2，自引：1，他引：1
根据历史地震资料及现今区域台网中小地震观测资料,对小江断裂带及周边地区的历史地震活动特征,特别是小江断裂带不同段落的现今断层活动习性进行了研究,依据b值,结合其它地震活动性参数,勾画出了该区未来强震的潜在危险区:①石屏一建水断裂段6.8级地震重现期为88～193年,目前已平静121年;小江断裂带的宜良-嵩明段6.8级地震蕈现期是108～225年,目前已平静175年.②小江断裂东川段具有中等偏大应力水平,属于中小地震活动频繁的地段;小江断裂华宁段具有较低应力水平,属于以小震活动为主的地段;通海-峨山断裂具有中等应力水平,属于中小地震活动频繁地段.③石屏-建水断裂和小江断裂宜良-嵩明段存在较低的6值和较小强震复发周期,具有较高应力水平,属于潜在地震震级偏大的区域,是未来发生7级以上大震的潜在危险区. 相似文献
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“八五”地震预报理论及方法攻关进展之二──大地电磁测量中期预测青海６．０级地震成功在“八五”地震预报深入攻关中，专门设置了一个中期预报方法的研究课题，即近期（１－３年）重点强震危险区判定指标的研究。其目的意义是在特定的危险区确定后，寻找能够指示１－３... 相似文献
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截直断裂是发育在大型的走滑或斜滑断裂带末端的分支断裂，断裂带长期反复活动，在其末端，因地壳应力消散或减弱，断裂走向发生急剧转折之后，在转折点附近产生了截直断裂，截直断裂的性状可以归纳为如下几点：（１）发育于接近主干断裂末端的转折点附近，其走向与主干断裂的总体走向一致，性状与主干断裂相似；（２）切割的地层或控制的沉积较的裂为新；（３）断裂的长度较小，断面较主干断裂为陡，（４）形成的时代为主干断裂发育 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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