成都断陷区活动断裂带基本特征及其潜在地震能力的判定

成都断陷是龙门山前缘重要的第四纪构造盆地，龙门山前山断裂和龙泉山西坡断裂对断陷盆地的形成和演化有重要的控制作用。晚第四纪时成都断陷遭受北西－南东向的挤压，使断陷盆地边缘和内部的北东，北北东向断裂具逆冲运动性质，并导致龙门山前山断裂，龙泉山西坡断裂和蒲江－新津－成都－德阳断裂上中，强地震的发生，研究表明，上述３条断裂均具有发生中强地震的潜在能力。     

中小地震应变能密度等值图像在龙门山地震带边界调整中的应用

地震区、带的划分直接影响地震活动性参数的选取和地震危险性分析的结果,它是地震区划中一项重要的工作.龙门山地震带位于南北地震带中部,地震活动相当强烈.目前编制的五代图,根据最新研究的资料,对龙门山地震带与长江中游地震带、巴颜喀拉山地震带东南边界以及柴达木-阿尔金地震带的边界做了相应改动,将成都盆地、龙日坝断裂划归龙门山地震带,将日月山断裂划归柴达木-阿尔金地震带.     

龙门山和成都地震构造区的划分

新编制的地震动参数区划图采用了潜在震源区三级划分方案,以体现背景地震活动空间分布的不均匀性,并在地震构造区内归纳出统一的地震构造模型。本文根据西南地区潜在震源区三级划分的成果,分析了龙门山地震统计区内的龙门山和成都地震构造区的基本特征,历史地震活动强度及频度,主要活动构造的构造变形样式,建立了地震构造区的发震构造模型,确定了构造区的本地地震及划分构造源的地震构造标志。同时,提出了确定背景源空间分布函数的简单方法。     

汶川8.0级地震前上报的宏观异常现象及分析

清理了汶川8.0级地震前四川省地震局收到的每周、月度各单位或个人上报的各类异常资料.这些宏观异常现象主要包括居民生活用井水质变化、泉水变化,气象、动、植物异常现象等.2002～2003年宏观异常现象集中分布在凉山州,多数沿安宁河-则木河构造带以及川滇交界西侧分布;2004～2008年5月宏观异常现象散布在龙门山、龙泉山、鲜水河-安宁河-则木河构造带以及川滇交界地区.四川地区宏观异常项数在2002年4～6月,2003年6～8月间为最为集中出现的两个时段,之后零星出现.对震前龙门山构造带附近出现的宏观现象进行分析后,我们看不出与地震间的必然联系,难以作为预测未来大地震的依据.     

龙门山断裂带地壳速度结构和震源位置的精确修定

结合使用人工地震折射测线和天然地震观测资料，给出了龙门山断裂带P波和S波的地壳平均速度模型．以此模型为基础，修定了沿龙门山断裂带分布的202个地震，给出了震源位置误差小于1.5 km的精确解．以到时曲线为准，将修定后的震源参数与四川台网常规定位的震源参数进行了比较，到时数据相对于时距曲线极小的分散，证明定位后的震源位置的精度得到了相当的改善．所获得的震源分布表明，地震活动主要发生在沿龙门山主中央断裂．绝大多数地震分布在3～22 km深度范围的上地壳中．结果证明，本文所提供的速度模型和采用的定位方法是适合龙门山断裂带地震定位使用的；配合日本东北大学提供的实时处理系统，对提高四川台网的定位精度是十分有效的．      

龙门山和成都地震构造区的划分

新编制的地震动参数区划图采用了潜在震源区三级划分方案,以体现背景地震活动空间分布的不均匀性,并在地震构造区内归纳出统一的地震构造模型.本文根据西南地区潜在震源区三级划分的成果,分析了龙门山地震统计区内的龙门山和成都地震构造区的基本特征,历史地震活动强度及频度,主要活动构造的构造变形样式,建立了地震构造区的发震构造模型,确定了构造区的本底地震及划分构造源的地震构造标志.同时,提出了确定背景源空间分布函数的简单方法.     

龙门山后山断裂汶川M_S8.0地震地表破裂带

2008年汶川Ms8．0地震发生之后,多方研究者开展了汶川震区地表破裂实地调查。已发表的调查结果论证汶川地震地表破裂带沿龙门山构造带中央断裂和前山断裂分布。本文作者近期沿龙门山后山活动断裂开展了踏勘性调查。调查结果表明,除龙门山中央断裂带和前山断裂带出现汶川地震的地表破裂带之外,位于龙门山构造带后山断裂（汶川-茂县断裂）存在另一条长约100km、     

汶川M_S8.0级地震发震构造大震复发间隔估算

汶川Ms8．0级地震发生在青藏高原东缘著名的龙门山断裂带上,造成了中央断裂和前山断裂共约330kin的地震地表破裂带。初步研究表明,龙门山断裂带上大震复发可能属特征地震模式。结合龙门山断裂带的地震地质情况和汶川地震地表破裂带的基本参数综合分析,本文从地质学、地震学和GPS数据分析三个方面评估了龙门山断裂带的大震复发周期。结果表明,上述三种方法获得的龙门山断裂带Ms8．0级地震的复发间隔分别为：3185a、170（02264a和4310a,平均为3000a左右：Ms7．5级地震的平均复发间隔为1000a左右;Ms7．0级地震的平均复发间隔为500a左右。这些结果与其他学者的研究结果相比,相差不多,基本反映了龙门山断裂带的地震能量水平和累积速度。     

四川龙门山活动断裂带典型地段晚第四纪强震多期活动证据

断错地貌调查和探槽开挖是获取活动断裂多期活动重要的线索．介绍了龙门山中央断裂带北川县城及平武县平通镇的断层沟槽调查及龙门山前山断裂带绵竹县汉旺镇台地前缘探槽开挖获得的认识．调查结果表明,北川断层沟槽包括汶川地震在内至少存在3次断层活动事件;平通断层沟槽包括汶川地震在内至少存在两次以上断层活动事件;汉旺探槽揭示了2-3次古地震事件．在上述3个地点中,北川断层沟槽和汉旺探槽在汶川地震前的一次强震时间接近,分别为大于5．8ka和小于6．63ka,接近为6ka．由此也获取了在汶川地震前龙门山活动断裂带的一次强震活动中,中央断裂带和前山断裂带同时活动的证据．     

汶川8．0级地震前龙门山断裂带的近场“闭锁”

由于地貌和交通条件的限制,在跨龙门山断裂带区域只有短水准监测场地。多年持续监测的七盘沟和耿达场地跨龙门山后山断裂,灌县和双河场地跨龙门山前山断裂等4个短水准场地,而在龙门山中央断裂上没有监测场地。根据跨龙门山后山和前山断裂的4个短水准场地监测资料计算分析,在2008年5月12日汶川8．0级地震前,测量成果显示：龙门山后山断裂的近场速率为0．03mm／a,     

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.