1980 - 2015年南迦巴瓦峰地区冰川变化及其对气候变化的响应   总被引：6，自引：5，他引：1  

吴坤鹏  刘时银  郭万钦 《冰川冻土》2020,42(4):1115-1125

基于地形图和Landsat TM/OLI遥感影像等数据， 利用目视解译和波段比值法提取1980年、 2000年和2015年南迦巴瓦峰地区冰川空间分布数据， 分析研究区近35年冰川变化， 探讨冰川对气候变化的响应。结果表明： 1980 - 2015年， 南迦巴瓦峰地区冰川面积持续减小并呈加速退缩的趋势， 近35年共减少了（75.23±4.67） km²， 占1980年冰川总面积的（25.2±1.6）%， 年平均面积减小率为（0.73±0.05）%。研究区东南坡冰川面积变化速率大于西北坡， 在不同流域、 海拔及朝向上， 冰川变化差异较大。南迦巴瓦峰地区冰川表碛十分发育， 表碛覆盖冰川面积变化率小于裸露冰川， 表碛覆盖对冰川消融具有抑制作用。南迦巴瓦峰地区在气温显著升高的背景下， 虽然降水量有所增加， 但冰川对气温更加敏感， 因气温升高引起冰川消融所带来的物质损失超过降水增加对冰川的补给， 导致南迦巴瓦峰地区冰川普遍萎缩。  相似文献   

变荷载下双层地基一维非线性固结近似解析解     

江留慧  李传勋  杨怡青  张锐 《岩土力学》2020,41(5):1583-1590

目前考虑土体非线性压缩及渗透特性的双层地基非线性固结解均假定土体固结系数保持不变，能反映固结系数变化的双层地基非线性固结解还很鲜见。引入经典的e- 和e- 非线性关系描述土体的非线性压缩、渗透特性，在假定双层地基上、下土层压缩指数与渗透指数比值 相等且不等于1的基础上，得到变荷载下考虑土体固结系数变化的双层地基一维非线性固结近似解。该解答在 1条件下可退化为已有的 1时双层地基一维非线性固结解。基于此解探讨了双层地基上、下土层参数的相对比值对非线性固结性状的影响。结果表明：单面排水条件下 越小，下层土与上层土的相对压缩性越低、相对渗透性越高，则双层地基非线性固结速率越快；减小 值，增加双层地基中压缩性小、渗透性高的土层的厚度，会加快地基的固结速率。  相似文献   

短期重现性地磁日变化感应电流集中分布与地震关系初步研究     

冯志生  姜楚峰  冯丽丽  李军辉  戴勇  黄颂  姚丽  章鑫  袁桂平  倪晓寅  戴苗  李鸿宇 《中国地震》2020,36(3):502-516

通过分析台站之间地磁垂直分量日变化相关性,研究中国大陆南北带地区90°E～110°E,2009～2018年地磁日变化感应电流线状集中分布现象与M_S≥6.0地震关系。统计发现,我国每月平均出现约2次感应电流集中分布现象,且10天左右内有原地重复出现现象——感应电流集中分布重叠异常,原地重现的集中分布感应电流日期间隔一般在10天左右以内,原地重现日期一般不连续,重现次数一般仅有2次。研究发现,我国南北带2009～2018年共出现重叠异常23次,20次重叠异常出现后18个月内重叠段发生M_S≥6.0地震,对应率高达87%,地震基本发生在重叠段端部250km以内,重叠段发生2次M_S≥6.0地震的比例较低,约35%;重叠段2个端部均发生M_S≥6.0地震的比例极小,仅约9%。部分重叠段走向与已经发现的上地幔和地壳高导带埋深走向基本一致,推测重叠异常发生在上地幔和地壳高导带附近,是来自上地幔和地壳内高导带附近的地震异常信息。目前已知,中国大陆强地震主要发生在上地幔高导层的隆起区一带及其壳内高导层发育地区,深部电性测深结果表明,大震易于发生在电导率急剧变化的梯度带,但这些地区何时发生地震还未得知,本文发现的重叠异常解释了这些地区1～2年内是否发生地震这一问题。  相似文献   

2017年四川九寨沟M_S7.0地震前区域重力场变化          下载免费PDF全文

祝意青  梁伟锋  赵云峰  刘芳  隗寿春  徐云马 《地球物理学报》2017,60(10):4124-4131

利用南北地震带2014-2017年期间的流动重力观测资料，系统分析了区域重力场变化及其与2017年8月8日四川九寨沟7.0级地震发生的关系.结果表明：①区域重力场异常变化与北西西向塔藏断裂和南北向岷江断裂带在空间上关系密切，反映了沿控震断裂在2013-2017年期间发生了引起地表重力变化效应的地壳变形和构造活动.②九寨沟地震前，测区内出现了大空间范围的区域性重力异常，而震源区附近产生了局部重力异常，沿塔藏断裂带形成了重力变化高梯度带，其中，甘肃玛曲、迭部、青海河南蒙古族自治县、四川若尔盖、九寨沟一带重力差异变化达100×10^-8m·s^-2以上；这些可能反映九寨沟地震前，区域及震源区附近均产生与该地震孕育、发生有关的构造运动或应力增强作用.③九寨沟地震震中位于重力差异运动剧烈的鞍部等值线附近，与断裂走向基本一致的重力变化高梯度带零值线上，这一观测事实进一步佐证了重力场动态变化图像对强震地点预测具有重要的指示意义.  相似文献   

Effect of grain‐scale pressure variations on garnet growth: a numerical approach          下载免费PDF全文

X. Zhong  J.C. Vrijmoed  L. Tajčmanová 《Journal of Metamorphic Geology》2017,35(1):19-33

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Modelling spatial variations in dissolved oxygen in fine‐grained streams under uncertainty          下载免费PDF全文

Vahid Zahraeifard  Zhiqiang Deng  Ronald Malone 《水文研究》2015,29(2):212-224

This paper presents a novel triple‐layer model, called VART DO‐3L, for simulation of spatial variations in dissolved oxygen (DO) in fine‐grained streams, characterized by a fluid mud (fluff or flocculent) layer (an advection‐dominated storage zone) as the interface between overlying stream water and relatively consolidated streambed sediment (a diffusion‐dominated storage zone). A global sensitivity analysis is conducted to investigate the sensitivity of VART DO‐3L model input parameters. Results of the sensitivity analysis indicate that the most sensitive parameter is the relative size of the advection‐dominated storage zones (A_s/A), followed by a lumped reaction term (R) for the flocculent layer, biological reaction rate (μ_o) in diffusive layer and biochemical oxygen demand concentration (L) in water column. In order to address uncertainty in model input parameters, Monte Carlo simulations are performed to sample parameter values and to produce various parameter combinations or cases. The VART DO‐3L model is applied to the Lower Amite River in Louisiana, USA, to simulate vertical and longitudinal variations in DO under the cases. In terms of longitudinal variation, the DO level decreases from 7.9 mg l at the Denham Springs station to about 2.89 mg l^?1 at the Port Vincent station. In terms of vertical variation, the DO level drops rapidly from the overlying water column to the advection‐dominated storage zone and further to the diffusive layer. The DO level (C_F) in the advective layer (flocculent layer) can reach as high as 40% of DO concentration (C) in the water column. The VART DO‐3L model may be applied to similar rivers for simulation of spatial variations in DO level. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

Soil property variation mapping through data mining of soil category maps          下载免费PDF全文

Fei Du  A‐Xing Zhu  Lawrence Band  Jing Liu 《水文研究》2015,29(11):2491-2503

Spatial information on soil properties is an important input to hydrological models. In current hydrological modelling practices, soil property information is often derived from soil category maps by the linking method in which a representative soil property value is linked to each soil polygon. Limited by the area‐class nature of soil category maps, the derived soil property variation is discontinuous and less detailed than high resolution digital terrain or remote sensing data. This research proposed dmSoil, a data‐mining‐based approach to derive continuous and spatially detailed soil property information from soil category maps. First, the soil–environment relationships are extracted through data mining of a soil map. The similarity of the soil at each location to different soil types in the soil map is then estimated using the mined relationships. Prediction of soil property values at each location is made by combining the similarities of the soil at that location to different soil types and the representative soil property values of these soil types. The new approach was applied in the Raffelson Watershed and Pleasant Valley in the Driftless Area of Wisconsin, United States to map soil A horizon texture (in both areas) and depth to soil C horizon (in Pleasant Valley). The property maps from the dmSoil approach capture the spatial gradation and details of soil properties better than those from the linking method. The new approach also shows consistent accuracy improvement at validation points. In addition to the improved performances, the inputs for the dmSoil approach are easy to prepare, and the approach itself is simple to deploy. It provides an effective way to derive better soil property information from soil category maps for hydrological modelling. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

克孜尔水库跨断层形变年变特征分析     

祖丽菲亚·尼亚孜  买买提·伊布拉音 《高原地震》2011,23(2):23-29

通过对克孜尔水库跨断层形变特征进行分析,结果显示:①垂直形变每年3～4月、10～11月分别为峰、谷值时间;水平形变每年6～7月、1月分别为峰、谷值时间.②垂直变形的峰-谷时间间隔在1997年之前多为5～8个月,1998年后多为1～3个月;谷-峰值时间间隔在1997年前多为4～7个月,1998年后多在8～11个月.水平形...  相似文献   

Downstream patterns of bed sediment-borne metals,minerals and organic matter in a stream system receiving acidic mine effluent: A preliminary study   总被引：1，自引：0，他引：1  

Yingqun Ma  Wenzhou Lu  Chuxia Lin 《Journal of Geochemical Exploration》2011

Different downstream variation patterns were observed for a range of bed sediment-borne metals (aqua regia-extractable fraction) in a subtropical stream system receiving acid mine drainage. Mine-originated Fe tended to be deposited in the acidic (mean pH < 4.9) upstream reach in forms of goethite and/or hematite. In contrast, other metals tended to be transported farther downstream and settled in a low-gradient reach with high pH (mean pH > 5.6). The peak of sediment-borne Al, Be, Ca, Cd, Co, Cu, La, Mn, Ni and Zn corresponded very well with the peak of the sediment-borne organic matter, suggesting a close association between the water-borne organic colloids and the inorganic metal oxides/hydroxides during their transport. The marked increase in the sediment-borne Al and Pb started more upstream than the other metals, suggesting that the water-borne Al and Pb were more susceptible to pH rise-induced precipitation, as compared to the other metals. It appeared that the organic colloids played no important role in Pb transport and settlement. The iron precipitates had a limited role to play in affecting the transport and fates of other metals since they were predominantly formed and deposited in the acidic reach, which made them incapable of scavenging cationic metals by co-precipitation or adsorption.  相似文献   

洞庭湖水沙变化分析及影响初探   总被引：4，自引：0，他引：4  

李正最  谢悦波  徐冬梅 《水文》2011,31(1):45-53,40

水沙变化是洞庭湖演变和江湖关系调整的关键因子。综合运用数理统计、小波分析、Mann-Kendall法和累加过滤器等方法,分析1956～2008年洞庭湖入湖和出湖径流和输沙量的变化特征。结果表明:①洞庭湖入湖水量以湘、资、沅、澧四水入流为主,洞庭湖入湖泥沙以荆江三口分沙为主。四水年均入湖水量约占洞庭湖出湖总水量的59.2%;三口入湖沙量约占入湖总沙量的80.9%。②由于荆江裁弯、葛洲坝工程运用、三峡水库拦蓄以及长江上游的水土保持措施的影响,从三口河道进入洞庭湖的水沙呈现明显的衰减趋势,入湖水量所占比重已由荆江裁弯前的42.6%下降到了三峡水库运用初期的21.7%;入湖沙量所占比重已由荆江裁弯前的87.7%下降到了三峡水库运用初期的59.6%。③近50年洞庭湖的泥沙沉积总量达52.9×108t,但泥沙沉积比已由荆江裁弯前的73.3%下降到了三峡水库运用初期的34.0%,洞庭湖泥沙淤积的趋势明显减弱,有利于保持洞庭湖的调洪湖容,延长洞庭湖的寿命;但三峡水库运用初期,三口分流的衰减将加剧洞庭湖区西部地区枯水供水的紧张态势,并使水环境容量下降;同时城陵矶下游长江河道的淤积导致洞庭湖洪水位抬升。  相似文献