Inter- and intra-annual trend analysis of water level and flow in the middle and lower reaches of the Ganjiang River,China

ABSTRACT

The Ganjiang River is the largest tributary of Poyang Lake in China, and its hydrological regime variation greatly affects the utilization of regional water resources and the ecological environment of the lake. In this study, a novel trend analysis method, the Moving Average over Shifting Horizon (MASH), was applied to investigate the inter- and intra-annual trends of flow and water level from 1976 to 2016 at the Xiajiang and the Waizhou hydrological stations in the Ganjiang River. The Significant Change Rate Method (SCRM) was proposed to determine the MASH averaging parameters. The trend analysis results show a statistically significant decrease in water level series throughout the year and the relationship of flow and water level have changed greatly at the Waizhou station. The sediment load reduction, large-scale sand mining and water level decrease of Poyang Lake are identified as the main causes for the water level decrease.     

东昆仑阿拉克湖地区第四纪水系演化过程及其趋势

根据第四系沉积物的沉积时代、沉积类型及盆山耦合与迁移规律,将东昆仑阿拉克湖地区第四纪水系变迁划分了4个阶段：早更新世小型内陆盆地无序水系阶段;中更新世冰川水系与东流水系阶段;晚更新世柴达木盆地内陆水系向南溯源侵蚀阶段;全新世黄河外泄水系形成与发展阶段。根据研究区及相邻地区黄河水系和柴达木盆地内陆水系的溯源侵蚀发展历史及趋势分析,认为研究区未来水系发展趋势不一定是加鲁河袭夺鄂陵湖、扎陵湖两湖及黄河水系,而可能是黄河加快下蚀作用和溯源侵蚀,鄂陵湖和扎陵湖将逐渐消失成为河流,黄河水系最终将袭夺柴达木内陆盆地水系。     

Study of Influence of Regional Geodynamic Background on Strata Behaviors in China's Tongxin Mine

Strata behaviors are mainly affected by regional geodynamic background. The influence of rock mass stress and energy distribution on strata behaviors in the Tongxin mine is studied in terms of regional tectonic movement, seismic activity and tectonic stress field. The results show that the extrusion lifting movement of Kouquan fault adjacent to the Tongxin mine results in the stress concentration in the rock of the Carboniferous coal bed and accumulation of a large amount of elastic energy and forms structural background of Tongxin mine. Due to various seismic activities in the mine area, the strain energy is known to reach much higher levels, up to 0.5×10⁸ J^1/2. Since the stratigraphic structure is sensitive to the mining operation, the strain energy could cause strong strata behaviors. A special geological structure model of the Tongxin mine is established based on the geodynamic division method. The distribution of regional structure stress field is determined by the rock mass stress analysis system. Based on this model, Tongxin mine is divided into five areas with high stress, eight areas with low stress and eight areas with gradient stress. The strong strata behaviors mostly occur in high stress areas. These results could provide guidance to predict the strength of regional or mine pressure and control strata behavior in different areas.     

Assessment of the natural and anthropogenic sources of chemical elements in alluvial soils from the Drava River using multivariate statistical methods

The objectives of this study are as follows: (a) an assessment of the geochemical background signature of the Drava Valley before the industrial revolution; (b) an evaluation of anthropogenic geochemical influences on the alluvial plains and river terraces in the valley; and (c) a determination of the spatial distribution of trace elements in the alluvial soils of the Drava River downstream of the Austrian–Slovenian border to the confluence of Mura and Drava Rivers.     

伽师强震群震源特征及震源机制力学成因分析

应用改进的主地震相对定位法对17年伽师强震群3级以上地震进行了精确定位,根据较强地震的空间分布和震源机制解推断出伽师震群的发震构造为北北西向的雁行断裂.根据伽师震群地震的2177个P波初动方向记录,计算了伽师震群的平均震源机制解.基于Silver的震源模型,由震源谱推断了伽师震群主要地震的破裂方向,破裂尺度及应力降.文中最后用右阶雁行断裂的数值模型计算了伽师震群的发震构造所产生的扰动应力场的空间分布图像,用其解释了序列地震震源机制的多样性和低应力降现象,并认为特定的雁行发震构造与强震的多发性有关.     

基于碎屑锆石特征的雅鲁藏布江山南宽谷风成沙丘物源示踪

雅鲁藏布江河谷（尤其是"一江两河"区域）风沙化较为严重,制约了当地社会经济的可持续发展,追踪河谷风沙来源对当地风沙治理意义重大。本研究聚焦于拉萨贡嘎机场附近的山南宽谷风沙地貌,采集2个河沙、3个风成沙丘和1个坡积物样品,以及引用前人研究的2个河沙样品。基于碎屑锆石U-Pb年龄及微量元素地球化学特征,进行沙源示踪研究,旨在为当地风沙治理提供科学依据。对360颗锆石进行LA-ICP-MS U-Pb定年,获得322个谐和年龄。分析结果表明,河沙、风成沙丘及坡积物样品碎屑锆石U-Pb年龄分布特征高度相似,主要峰值与冈底斯岩浆弧新生代的两期岩浆活动一一对应;非矩阵多维标度统计技术（MDS）分析也证实了样品与冈底斯岩浆弧有良好的亲缘性;地球化学判别图解显示锆石具有亏损轻稀土元素、富集重稀土元素、明显正Ce异常和明显负Eu异常的特征,亦指示其岩浆成因,表明冈底斯岩浆弧为沙丘、河沙与坡积物中碎屑锆石的主要来源。依据不同类型样品碎屑锆石年龄对比以及锆石年龄相似程度对比,结果发现：1）雅鲁藏布江地区风沙地貌主要是由于枯水季河床水位下降,导致河岸和河漫滩出露地表,就地起沙吹扬到山坡上所形成;2）研究区河沙并非主要从上游搬运而来,更多是拉萨河搬运汇入的泥沙。依据沙源分析结果,欲解决河谷风沙化问题,首要应在河岸和河漫滩种植适宜当地气候的耐旱植物固定河床上的泥沙,这是最直接有效的手段。     

1605年海南岛琼州大地震及其发震构造的初步探讨

琼北地区铺前−清澜断裂是一条关系到1605年琼山7½级大地震发震构造判断的重要断裂。为准确厘定该断裂的最新活动特征,针对琼北地区第四纪玄武岩盖层和巨厚海相砂沉积等地质条件,采用大吨位震源的浅层人工地震勘探和小间距钻孔联合地质剖面探测相结合的方法,分别在海口江东三江镇岐山头村和东寨村展开探测。结果表明：(1) 铺前−清澜断裂断错了多个标志地层,最浅断错至全新统烟墩组淤泥层,上断点埋深10 m左右,钻探所揭示的断层面明显具有走滑兼具逆冲性质,是一条具有一定宽度、多分支、多期次活动的大规模断裂带;(2)钻孔联合地质剖面所揭示的地层深度范围内,被断错地层的位移量随着深度增加而加大,铺前−清澜断裂自8 346~7 153 a cal BP以来有过活动,全新世累计垂直位移量4~5 m,垂直位移速率为0.53~0.63 mm/a,推断其为1605年琼山大地震的发震断裂。本研究取得的铺前−清澜断裂全新世活动的新证据,为国土空间规划和区域地震危险性评价提供了科学依据。

     

Contrasting origins of Cenozoic silicic volcanic rocks from the western Cordillera of the United States

Two fundamentally different types of silicic volcanic rocks formed during the Cenozoic of the western Cordillera of the United States. Large volumes of dacite and rhyolite, mostly ignimbrites, erupted in the Oligocene in what is now the Great Basin and contrast with rhyolites erupted along the Snake River Plain during the Late Cenozoic. The Great Basin dacites and rhyolites are generally calc-alkaline, magnesian, oxidized, wet, cool (<850°C), Sr-and Al-rich, and Fe-poor. These silicic rocks are interpreted to have been derived from mafic parent magmas generated by dehydration of oceanic lithosphere and melting in the mantle wedge above a subduction zone. Plagioclase fractionation was minimized by the high water fugacity and oxide precipitation was enhanced by high oxygen fugacity. This resulted in the formation of Si-, Al-, and Sr-rich differentiates with low Fe/Mg ratios, relatively low temperatures, and declining densities. Magma mixing, large proportions of crustal assimilation, and polybaric crystal fractionation were all important processes in generating this Oligocene suite. In contrast, most of the rhyolites of the Snake River Plain are alkaline to calc-alkaline, ferroan, reduced, dry, hot (830–1,050°C), Sr-and Al-poor, and Nb-and Fe-rich. They are part of a distinctly bimodal sequence with tholeiitic basalt. These characteristics were largely imposed by their derivation from parental basalt (with low fH₂O and low fO₂) which formed by partial melting in or above a mantle plume. The differences in intensive parameters caused early precipitation of plagioclase and retarded crystallization of Fe–Ti oxides. Fractionation led to higher density magmas and mid-crustal entrapment. Renewed intrusion of mafic magma caused partial melting of the intrusive complex. Varying degrees of partial melting, fractionation, and minor assimilation of older crust led to the array of rhyolite compositions. Only very small volumes of distinctive rhyolite were derived by fractional crystallization of Fe-rich intermediate magmas like those of the Craters of the Moon-Cedar Butte trend. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

2006年6月10日浙江飑线FY-2C卫星云图特征

利用国际卫星云气候计划（International Satellite Cloud Climate Program,简称ISCCP）提供的1998—2007年共10 a的深对流路径跟踪资料,统计分析了影响江淮地区对流系统（Convection system,简称CS）的时空分布及其参数特征。结果表明：影响江淮地区的CS主要集中在春夏两季,大多生成于江淮本地及我国中西部地区,呈现以江淮地区为中心的带状分布特征,越靠近江淮区域CS分布越为密集。依据源地不同,将影响江淮地区的CS分为5类,受气候条件与地形地貌的共同作用,各源地CS参数特征差异显著,总体来说CS的水平尺度越大,其生命史、对流云团(Convective clusters,简称CC)数目及水平云温度梯度也越大。其中江淮中心区域（MID）区域CS水平尺度、生命史和CC数目的平均值均为最小;东南（SE）区域CS生命周期以中长周期为主,水平尺度、最大对流比和云温度梯度的平均值最大。梅雨期内江淮地区对流活动频繁,CS的水平尺度大、生命史长、CC数目多。