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将遗传算法应用于地震矩张量解的反演问题．采用数字化台网P波波形资料及台湾台网P波初动方向资料,研究了1994年9月16日台湾海峡7.3级地震及其邻近地区(北纬21～26,东经115～120)ML5.8共5个地震的矩张量解及震源参数．在5个地震中,1994年9月16日台湾海峡7.3级地震是我国东南沿海地区自1918年南澳7.3级地震以来最大的一次地震．结果表明:这次7.3级地震的矩张量解以双力偶成分为主,是断层面接近NW走向的正断层．断层面的走向与大震前地震的条带分布走向及余震分布显示的破裂图象较相像．震源机制的张应力轴接近水平,近NE走向;压应力轴几乎垂直,近NWW走向．似乎表明,这次地震是受菲律宾板块向欧亚板块北西向挤压的力源控制．但从P轴接近竖直而T轴接近水平看,这是一次强烈拉张性的正断层．其它4个强震震源机制解与7.3级大震相互差别较大．这些地震震源机制解的复杂性表明了海峡地震序列发展过程是比较复杂的． 相似文献
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采用宽频带Ｐ波波形资料，利用全局反演方法，推断了１９９４年９月１６日发生在台湾海峡的一次强烈地震的地震矩张量；并采用随机加权方法进行误差分析．结果表明，这次地震的矩张量解以双力偶成分为主，是断层面为ＥＷ走向的正倾错动．震源机制的张应力轴接近水平，ＳＮ走向；压应力轴几乎竖直．地震矩值为０．９８×１０１９Ｎｍ．震源过程的持续时间仅有４ｓ，震源时间函数显示了均匀的单一破裂事件．通过对台湾东南到吕宋岛以北地震带的震源性质分析，探讨了该地区产生ＳＮ向水平拉张应力状态的原因． 相似文献
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地震矩张量反演在地震观测报告中的应用 总被引：3，自引：0，他引：3
针对我国地震工作的实际需要,从１９９５年起,《中国地震台网目录和地震矩张量解》刊登了国内较大地震和全球大震的地震矩张量解和震源机制解。同时在《中国地震年报》上也刊登国内及邻区较大地震的地震长张量解和震源机制解。为了方便用户使用,本文对有关参数进行了说明。 相似文献
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帕米尔地区地震活动及震源机制解的分布特征 总被引：2，自引：0，他引：2
帕米尔地区存在一个明显的ＮＥ－ＳＷ向中，深源地震带，中，深源地震震源机制分布具有明显的区域特征，兴都库什地区震源断错以倾滑逆断层为主，Ｔ轴仰角几乎垂直，帕米尔弧形构造东侧分布的地震以走滑性质为主，Ｐ轴仰角接近水平，当深度为１００～２００ｋｍ时在弧形构造南侧形成了一个明显的北东向的正断层分布。中，深源地震主压应力方向随深度增加由ＮＷ向逐渐变为ＮＥ向，主压应力Ｐ轴仰角平缓。 相似文献
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台湾海峡7.3级地震序列特征 总被引：1，自引：0，他引：1
根据粤闽台网和汕头地震遥测台网资料，讨论了１９９４年９月１６日台湾海峡南部７．３级地震的序列特征及震源机制等问题，分析认为，此次地震为大陆地壳下部破裂的产物，与北东向断裂活动有关。 相似文献
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利用ＣＤＳＮ及ＧＤＳＮ数字化Ｐ波波形资料,用遗传算法反演１９９６年包头西ＭＳ＝６．４地震的地震矩张量解。结果表明该地震矩张量解以双力偶成分为主,是断层面接近南北走向的左旋走滑错动,断裂面走向与大震后５天内余震的分布带走向基本一致。压应力轴与张应力转接近水平,前者近北西西走向,后者近北北东走向。 相似文献
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本文使用新疆区域数字地震台站记录的宽频带长周期数字波形资料,在时间域反演了2008年10月5日新疆乌恰6.8级地震的强余震及其周围先后发生的52次中等强度地震的矩张量解,结合Harvard大学在该区域的地震矩张量结果,研究了帕米尔东北缘的应力场分区特征.研究结果显示,位于印度板块向欧亚板块推挤的前缘及向北凸出的弧型构造的最北缘的卡兹克阿尔特弧形活动褶皱-逆断裂带,以逆冲推覆活动为主,并有部分走滑类型的地震,基本不存在正断层类型的地震;该弧型构造近东西走向的顶部(文中的西区)与其北西走向的东侧(文中的东区)的局部应力场最大主压应力方向不同,分别为NW、NNE方向,显示出在承受印度板块向欧亚板块俯冲作用的同时,东区也更多的受到了塔里木块体顺时针旋转作用的影响.位于帕米尔陆内俯冲和变形作用强烈、碰撞造成深源地震带东段的南区,地震以走滑错动为主, 逆断、正断层都有,显示出相对复杂的应力状态.位于帕米尔高原内部的西区和南区的应力场最大主压应力方向一致,由北向南,由最大主压应力轴接近水平,过渡为最大主张应力轴接近水平,一定程度揭示了板块俯冲的状态.结合南区和西区的地震深度差异及机制解中断层面的倾角,推测在中帕米尔的东部,由北向南的板块俯冲至150~170km深度,俯冲角度为60°左右. 相似文献
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传统地震目录中增加矩震级及震源机制解的必要性分析 总被引：1，自引：0，他引：1
本文梳理了我国地震目录的产出现状,对于我国近几年应急机构和区域台网产出的震源机制解、矩震级进行了比较研究。结果表明:中国地震局地球物理研究所和地震预测研究所对于国内陆地地区6级以上地震的地震矩张量解的产出率为100%,5级以上地震的地震矩张量解产出率为81%。这两个研究所给出的3种矩张量结果和GCMT给出的矩张量结果较为一致,类型统计一致率分别达到71%、86%和66%,其中P、T轴空间夹角优势分布在15°左右。产出的矩震级和GCMT解得到的矩震级相差不大,偏差在0.1以内的比率分别为46%、86%和71%,偏差在0.3以内的比率分别为85%、100%和97%。结果表明对于我国内陆地区的5级以上地震,这两个研究所产出率较高、结果较为一致。而由各台网据震源参数得出的5级左右地震的矩震级和GCMT求解的矩震级比较起来明显偏小。由此探讨了在传统地震目录中增加震源机制解及矩震级的必要性。 相似文献
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本研究将利用余震分布和区域应力场确定大震断层面参数的方法应用于2010年玉树MS7.1级地震发震断层面参数的确定,获得了本次地震断层面参数为:走向294.6°,倾角78.0°,滑动角7.5°,属于左旋走滑型地震和甘孜—玉树断裂带的性质相一致.主震前后应力场反演结果表明该区域的应力场为:中间主应力轴近直立,最大和最小主应力轴近水平,且发现玉树地震前后震源区应力场存在偏转现象,最大主压应力轴由震前的NEE向逆时针旋转至震后的NNE向,震后最大主压应力轴与断层走向近垂直,表明主震对震源区应力释放较为充分. 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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