Seismic imaging,crustal stress and GPS data analyses: Implications for the generation of the 2008 Wenchuan Earthquake (M7.9), China     

Zhi Wang  Jian Wang  Zhiliang Chen  Yuping Liu  Runqiu Huang  Shunping Pei  Qingzhi Zhang  Wenqing Tang 《Gondwana Research》2011,19(1):202-212

Seismic imaging together with global positioning system (GPS) and crustal stress data analyses show that the Mw7.9 2008 Wenchuan earthquake occurred within a distinct area of high crustal stress (～ 17.5 MPa) and high Poisson's ratio (7–10%) anomalies centered on the Longmen-Shan (Shan means Mountain in Chinese) tectonic fault belt. Low P-wave and S-wave velocities in the southwest (SW) segment contrast with high-velocity anomalies in the central portion (CP) and northeast (NE) segment within the uppermost ～ 15 km depths along the tectonic fault belt, though a presumably ductile zone with low-velocity anomalies separates the CP and NE segment. The rupture initiated near the southwestern end of the CP at a zone of high Poisson's ratio (σ) which extends down into the lower crust. These low-velocity and high-σ anomalies immediately below the source hypocenter, together with the high crustal stress, indicate the presence of high-pressure fluids from the lower crust, which might have reduced the mechanical strength of the fractured rock matrix and triggered the earthquake. Our study suggests that the structural heterogeneity and high crustal stress played an important role in the nucleation of the Wenchuan earthquake and its rupture process.  相似文献   

Factors affecting the internal loading of phosphorus from calcareous sediments of Baiyangdian Lake in North China     

Li Ming Dong  Zhi Feng Yang  Xin Hui Liu 《Environmental Earth Sciences》2011,64(6):1617-1624

Phosphorus (P) is the limiting macronutrient for primary production in most lakes. Sediment characteristics are strongly correlated to the internal P loading in lakes. This study investigated speciation of P, Fe, Al, and Ca in sediments of six sampling sites with varying trophic status in Baiyangdian Lake of North China during the period of July 2008 and March 2009. The results of sequential extraction experiments of the top sediments showed that total extractable P ranged approximately from 13 to 28 μmol g⁻¹ for all sampling sites and the rank order of P-fractions was HCl–P > NaOH₈₅–P > NaOH₂₅–P > BD–P > NH₄Cl–P. BD–P and BD–Fe had a consistent change with seasons. Their concentrations were both much higher in early spring and mid-autumn. BD–Fe, Al extracted with NaOH at 25°C and 85°C affected corresponding P concentration in sediments, while high concentration of extractable Ca from sediments showed no direct effects. According to the Kopáček et al. model of the molar ratios of Al:Fe and [NaOH₂₅–Al]:[NH₄Cl–P + BD–P], there was potential P release from sediments twice a year for some hypereutrophic sites in early spring and mid-autumn, especially in the former season.  相似文献   

大菱鲆（Scophthalmus maximus）大规模家系选育优良家系的生长发育规律   总被引：3，自引：1，他引：2       下载免费PDF全文

王新安  马爱军  黄智慧  刘庆明  郭黎  杨志  曲江波 《海洋与湖沼》2011,42(2):266-273

运用Logistic、Gompertz和von Bertalanffy3种生长模型分别对大菱鲆的5个优良家系E♂1×E♀2、F♂4×N♀3、F♂2×E♀4、E♂2×F♀1、F♂1×F♀4及对照组群体的生长曲线进行了拟合和比较分析。结果表明,家系E♂1×E♀2、F♂2×E♀4和E♂2×F♀1的最优拟合模型为Gompert...  相似文献   

北海珍珠养殖区与非养殖区海域水体氮含量的分布及其与环境因子的关系     

韦蔓新  何本茂  黎广钊  王欣  李智 《台湾海峡》2011,30(2):181-188

根据2008年9月和2009年4月对广西北海海域珍珠养殖区和非养殖区水体各形态氮含量的调查资料,采用对比手法研究其氮循环特征及其与环境因子的关系.结果表明：研究海域水体各种形态氮含量无论在季节上还是区域上,均突出地体现了养殖生物的释放作用和陆源排污的影响作用.氮的含量变化随着区域和季节不同而显示出特有的规律.春季,正值珠贝插核期的养殖区水体中的氮含量较低,并在不同区域随生物链作用呈现出很好的规律性,各形态氮含量与环境因子之间呈相关的几率较高,其中DON含量与pH值以及DIN含量与SS和TOC含量之间的负相关性均达到了非常显著水平（p〈0.01）,但水环境是以耗氧过程影响为主.秋季,随着养殖珠贝进入养成期,在其摄食和排泄压力大幅度增加的同时,以主要存在形态出现的TN、DN、DON含量亦大幅度上升,但作为浮游植物直接吸收的DIN含量却在明显上升的情况下仍然远低于一类海水水质标准值,只有NH4-N含量与水温呈显著负相关（p〈0.05）,水环境却以增氧状态出现.而非养殖区水体的氮含量无论是春季还是秋季,只是从TN、PN、DN含量的分布上体现了与养殖区的一致性,其余形态氮含量的分布则多与养殖区的相反;各形态氮含量与环境因子之间的相关性则秋季较春季密切,尤其DN、NH4-N与SS含量的负相关性,DIN含量与pH值的正相关性非常显著（p〈0.01）.从春秋季整个海区氮含量的变化情况（春季TN、DN、DON、DIN含量的变化范围分别为10.66~16.96、6.82~12.85、4.43~11.63、0.69~2.81 mol/dm3,平均值分别为13.46、8.86、7.11、1.75 mol/dm3;秋季TN、DN、DON、DIN含量的变化范围分别为14.07~28.01、12.22~23.01、11.01~21.59、1.08~3.11 mol/dm3,平均值分别为20.54、17.00、15.34、1.65 mol/dm3）可见,研究海域无论养殖区还是非养殖区氮循环状况良好,生物链作用在其中起着重要的作用.这对于研究海域生态环境的可持续发展极为有利.  相似文献   

Impact of Model Bias Correction on a Hybrid Data Assimilation System     

Xia  Yu  Chen  Jing  Zhi  Xiefei  Chen  Lianglyu  Zhao  Yang  Liu  Xueqing 《Acta Meteorologica Sinica》2020,34(2):400-412

Journal of Meteorological Research - Hybrid data assimilation combines a conventional 3-D or 4-D variational system with background error covariance (BEC) generated from ensemble forecast systems....  相似文献   

北京“7·16”暴雨诱发地质灾害成因分析     

许凤雯  狄靖月  李宇梅  王志  包红军  刘海知 《气象》2020,46(5):705-715

从2018年7月16日北京暴雨过程雨情和地质灾害灾情出发,介绍了此次过程的地质灾害气象预警及检验;并基于北京区域地质灾害易发度信息,结合多源融合定量降水估测(QPE)驱动CREST水文模型模拟径流量与土壤湿度特征、过程雨强特征,分析了北京本次地质灾害气象成因。结果表明,北京北部和西部处于地质灾害中、高易发区,区(县)小时累计面雨量达到50 mm以上易发生灾害,降水持续24 h后是地质灾害的高发时段,灾害常发生于雨强较大峰值后的15 h内;基于雨强-降水持续时间推求的地质灾害致灾临界雨量阈值对北京地区地质灾害气象预警有一定的借鉴意义;基于水文模型的北京区域径流量、坡面径流深、土壤湿度等水文过程要素模拟对预警也有较好的指导意义。  相似文献   

2020年安徽梅雨异常特征及预测前兆信号分析     

田红  程智  谢五三  戴娟 《湖北气象》2020,39(6):564-570

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地闪资料在LAPS云分析中的应用研究     

苏传程  师春香  谷军霞  毛文书  朱智  刘军建  孙帅 《气象研究与应用》2020,(1):54-60

为进一步研究闪电活动特征,利用ADTD闪电定位资料、静止气象卫星葵花八号等气象资料,对2016年7月20日一次强对流天气过程中的闪电活动进行分析,探讨闪电活动与LAPS云分析场的关系,探索地闪资料在LAPS云分析中的应用。结果表明,地闪活动集中区域对应着强降水区,降水峰值与闪电活动峰值为重合的现象;大部分闪电发生处于对流云系影响范围之内且对应了中高层次的云顶性质;在LAPS云分析场中地闪活动频繁的区域,云柱更为厚实且出现了更为强烈的上升运动,水汽也更为充沛,闪电活动与积雨云的对应关系不仅可以反向验证卫星反演的云分类产品,也可以对LAPS三维云场进行订正和调整,并作为多源数据融合云分析的补充资料。  相似文献   

Changes in daily climate extremes in the arid area of northwestern China   总被引：3，自引：0，他引：3  

Huaijun Wang  Yaning Chen  Shi Xun  Dongmei Lai  Yuting Fan  Zhi Li 《Theoretical and Applied Climatology》2013,112(1-2):15-28

There has been a paucity of information on trends in daily climate and climate extremes, especially for the arid region. We analyzed the changes in the indices of climate extremes, on the basis of daily maximum and minimum air temperature and precipitation at 59 meteorological stations in the arid region of northwest China over the period 1960–2003. Twelve indices of extreme temperature and six indices of extreme precipitation are examined. Temperature extremes show a warming trend with a large proportion of stations having statistically significant trends for all temperature indices. The regional occurrence of extreme cool days and nights has decreased by ?0.93 and ?2.36 days/decade, respectively. Over the same period, the occurrence of extreme warm days and nights has increased by 1.25 and 2.10 days/decade, respectively. The number of frost days and ice days shows a statistically significant decrease at the rate of ?3.24 and ?2.75 days/decade, respectively. The extreme temperature indices also show the increasing trend, with larger values for the index describing variations in the lowest minimum temperature. The trends of Min Tmin (Tmax) and Max Tmin (Tmax) are 0.85 (0.61) and 0.32 (0.17)?°C/decade. Most precipitation indices exhibit increasing trends across the region. On average, regional maximum 1-day precipitation, annual total wet-day precipitation, and number of heavy precipitation days and very wet days show insignificant increases. Insignificant decreasing trends are also found for consecutive dry days. The rank-sum statistic value of most temperature indices exhibits consistent or statistically significant trends across the region. The regional medians after 1986 of Min Tmin (Tmax), Max Tmin (Tmax), warm days (nights), and warm spell duration indicator show statistically more larger than medians before 1986, but the frost days, ice days, cool days (nights), and diurnal temperature range reversed. The medians of precipitation indices show insignificant change except for consecutive dry days before and after 1986.  相似文献   

皖江城市带县域经济发展差异演变特征分析   总被引：1，自引：0，他引：1  

汪志  焦华富  郇恒飞 《地理与地理信息科学》2011,27(1):53-58

采用传统的统计分析方法与ESDA方法,以县域为研究单元,以人均GDP为测度指标,选取1997-2009年数据,从时空视角分析皖江城市带县域经济发展的演变特征。从时间角度看,皖江城市带县域经济发展呈现总体差异持续扩大、发展速度不均衡化趋势;从空间角度看,全局Moran′s I指数显示,皖江城市带县域经济发展总体空间集聚效应较弱,局部Moran散点图则进一步揭示了各地级市对周边县域经济的带动作用不明显,存在较强的极化效应,仅合肥、芜湖、马鞍山地区产生空间扩散效应,但扩散的强度和范围较小。结合县域经济发展存在的问题,提出统筹县域经济协调发展建议,从而更好地为皖江城市带承接产业转移示范区建设提供理论指导。  相似文献