2018年9月8日墨江地震及周边地区构造应力场特征分析   总被引：1，自引：0，他引：1       下载免费PDF全文

李泽潇  万永革  崔华伟  李振月  胡晓辉  黄骥超  靳志同 《地球物理学报》2020,63(4):1431-1443

2018年9月8日,云南省墨江县发生MS5.9地震并伴随一系列余震,探究该地震周围的应力场对于理解该地震的发生机制和后续地震的发展趋势具有着重要的参考意义.本研究收集了震源及其邻区中前人研究和Global CMT所给出的震源机制资料,对该地区进行了构造应力场反演,并同时利用反演得到的应力张量模拟墨江地区的震源机制解表现.结果表明:(1)在应力轴整体分布上,自西向东σ1轴(压轴)从NNE-SSW向逐渐转向NNW-SSE向,σ3轴(张轴)从WWN-EES向逐渐转向WWS-EEN向,张轴呈弧形分布,压轴呈放射状分布.(2)在应力轴倾伏角上,研究区域内的压应力轴和张应力轴倾伏角都比较小,即两轴均接近水平.(3)R值分布大体是在东南部相较于西北部大,结合当地地质背景分析得到,物质逃逸自西北向东南呈逐渐变缓的趋势.(4)利用反演得到的应力张量和应力状态计算墨江地震震源区的相对剪应力和相对正应力大小.由此推测,墨江地震恰好发生在相对剪切应力值和相对正应力正值最大的节面上.从而可以确定墨江地震的发震节面的基本参数:走向216.32°,倾角86.91°,滑动角0.27°,相对剪应力值0.9,相对正应力值0.3.本研究为此次墨江地震的发震背景和地震动力学研究提供了基础性资料.  相似文献   

Analysis of city centrality based on entropy weight TOPSIS and population mobility:A case study of cities in the Yangtze River Economic Belt     

罗静  陈四云  孙璇  朱媛媛  曾菊新  陈广平 《地理学报(英文版)》2020,30(4):515-534

Based on statistical data and population flow data for 2016,and using entropy weight TOPSIS and the obstacle degree model,the centrality of cities in the Yangtze River Economic Belt(YREB)together with the factors influencing centrality were measured.In addition,data for the population flow were used to analyze the relationships between cities and to verify centrality.The results showed that:(1)The pattern of centrality conforms closely to the pole-axis theory and the central geography theory.Two axes,corresponding to the Yangtze River and the Shanghai-Kunming railway line,interconnect cities of different classes.On the whole,the downstream cities have higher centrality,well-defined gradients and better development of city infrastructure compared with cities in the middle and upper reaches.(2)The economic scale and size of the population play a fundamental role in the centrality of cities,and other factors reflect differences due to different city classes.For most of the coastal cities or the capital cities in the central and western regions,factors that require long-term development such as industrial facilities,consumption,research and education provide the main competitive advantages.For cities that are lagging behind in development,transportation facilities,construction of infrastructure and fixed asset investment have become the main methods to achieve development and enhance competitiveness.(3)The mobility of city populations has a significant correlation with the centrality score,the correlation coefficients for the relationships between population mobility and centrality are all greater than 0.86(P<0.01).The population flow is mainly between high-class cities,or high-class and low-class cities,reflecting the high centrality and huge radiating effects of high-class cities.Furthermore,the cities in the YREB are closely linked to Guangdong and Beijing,reflecting the dominant economic status of Guangdong with its geographical proximity to the YREB and Beijing's enormous influence as the national political and cultural center,respectively.  相似文献   

气候变化下基于物种与植物耦联机制的小白额雁(Anser erythropus)潜在生境及适宜性研究--以长江流域中下游为例     

向伶  高翔  彭玉辉  梁婕 《资源与生态学报(英文版)》2020,11(2):140-149

气候变化和人类活动通过改变物种生境而影响物种多样性。小白额雁是长江流域中下游的一种具有较高生态价值的食草型濒危候鸟,受气候变化和人类活动威胁。本文以小白额雁为代表性物种,定量分析了气候变化对长江流域中下游候鸟潜在生境及适宜性空间分布格局的影响。采用Maxent模型模拟了当前情景和全球环流模型(GCMs)气候场景下小白额雁潜在生境及其适宜性分布。研究结果表明,小白额雁分布特征与其栖息地周边植物分布呈显著相关关系;运用Maxent模型模拟小白额雁六种主要食源植物的分布特征,并将其结果作为环境变量,将显著改善小白额雁潜在生境及其适宜性模型的模拟性能;在两种典型浓度情景(RCP 2.6和RCP8.5)下,2070年小白额雁潜在生境适宜性面积将下降。为应对气候变化对小白额雁的影响,应采取更加合理的管理措施和保护政策,包括调整保护区的大小、形状和用途。  相似文献   

Cryospheric Changes and Their Impacts on Water Resources in the Belt and Road Regions     

Shichang Kang  Wanqin Guo  Tonghua Wu  Xinyue Zhong  Rensheng Chen  Min Xu  Jinlei Chen  Ruimin Yang 《地球科学进展》2020,35(1):1-17

“Belt and Road” regions include Asia, Europe and eastern and northern Africa, with a wide spatial distribution. The cryosphere is undergoing rapid changes in the Belt and Road regions with global warming, and has an important impact on water resources, ecosystems and Arctic waterways in these regions. This article reviewed recent cryospheric changes and associated impacts on water resources in the Belt and Road regions during the last decades. The main cognitions are as follows: \mathrm{①} Most glaciers are shrinking and glacier mass balances are most negative, but there are regional differences in the changes of glaciers. \mathrm{②} Global temperature rise has resulted in permafrost degradation, including a rise in permafrost temperature and decreasing permafrost thickness as well as an increase in active layer thickness. \mathrm{③} There is a significant decrease in snow cover extent and an increase in snow depth. Snow cover duration has shortened, the onset of snow cover has delayed, and the end of snow cover has advanced. However, there are still obvious regional differences in the changes of snow cover. \mathrm{④} Arctic sea ice has declined precipitously in both extent and thickness in summer, and multi-year sea ice has decreased，indicating the precipitous retreat of sea ice. The freeze-up date of some lakes has been delayed, the break-up date has advanced, and the ice cover duration of river/lake ice has significantly shortened. \mathrm{⑤} Glacial runoff has increased significantly in China. Snowmelt and permafrost degradation have also increased the basin runoff, which indicates the important impact of cryospheric changes on runoff. This study will provide a baseline and important scientific support for addressing climate change and regional sustainable development.  相似文献   

长江下游刀鲚(Coilia nasus)仔稚鱼的时空分布     

刘熠  任鹏  杨习文  李新丰  徐东坡  方弟安 《湖泊科学》2020,32(2):506-517

刀鲚(Coilia nasus)是长江下游重要的经济鱼类之一,具有溯河洄游型和淡水定居型两种生态类型本研究于2016年5 8月在刀鲚繁殖高峰期内同时对长江下游湖口、安庆和靖江江段进行刀鲚早期资源调查,研究分析对比了长江下游江段刀鲚仔稚鱼的丰度情况、时空格局及其与主要环境因子的关系结果表明:在调查期间,靖江江段刀鲚仔稚鱼平均密度最高;刀鲚仔稚鱼在调查各江段于6月下旬至7月上旬之间均出现一段较短时间的高峰期,这与刀鲚的产卵类型有关;湖口刀鲚仔稚鱼的爆发时间早于安庆和靖江江段,这种现象可能是由于湖口江段存在的定居型刀鲚产卵造成的;推测长江江水倒灌的特殊环境现象刺激了刀鲚性腺的发育,使得湖口江段8月产卵群体较多;各江段断面空间上的刀鲚仔稚鱼密度差异可能是沿岸地形和水体动力学差异所产生的现象;各江段刀鲚仔稚鱼密度最高峰时的水流量均处于较低水平,水温分别为25.87、25.27和21.67℃,均达到了刀鲚产卵所需条件研究结果初步反映了长江下游刀鲚仔稚鱼的时空特征,为长江下游刀鲚资源的保护提供了参考依据.  相似文献   

珠江三角洲地区登革热流行风险空间模拟与预测     

郑斓  任红艳  施润和  鲁亮 《地球信息科学学报》2019,21(3):407-416

近年来日益严重的登革热疫情已在中国南部地区形成疫情高发区,并对中国的公共卫生安全形成了一定的威胁。登革热主要受到区域内复杂的自然环境条件以及社会经济因素的影响,而利用地理空间分析方法和模型探究登革热疫情的影响因素,并对其未来流行风险的空间分布进行模拟,是有效开展登革热预防控制工作的重要基础。本文收集了珠江三角洲地区2010-2014年的登革热病例资料和土地利用、人口密度两种社会经济要素数据,构建土地利用回归（LUR）模型以分析登革热疫情与不同空间范围内的土地利用和人口密度之间的关系,并结合SLEUTH模型获取的2030年土地利用数据以及基于人口密度预测模型获取的2030年人口密度数据,预测珠江三角洲地区2030年登革热疫情风险的空间分布。结果表明,社会经济要素对登革热疫情空间分布的影响在不同范围内存在差异,半径分别为10、7、10、2和1 km的缓冲区内的人口密度、草地、城镇用地、林地和耕地进入LUR模型并对疫情有显著的影响（相关系数分别为0.779、-0.473、0.818、-0.642和-0.403）,所构建的LUR模型效果较好（调整R²为0.796,F=390.409,P<0.01）,留一交叉检验结果显示模型的相对均方根误差为0.7046,预测值与实测值的拟合精度达到0.7101。2030年城市空间扩展的区域主要分布在深圳、东莞以及广佛的交界地区,而登革热风险预测模型表明2030年登革热疫情风险较大的区域与珠江三角洲城镇用地占比、人口分布较高的地区有高度的一致性,尤其是广佛地区。因此,LUR模型可以较好地预测登革热疫情的空间分布,从而为当地卫生部门防控登革热提供方法支持。  相似文献   

基于新型高频声学多普勒流速剖面仪的河口近底部边界层观测初探     

兰庭飞  吴昊  唐杰平  李占海  汪亚平 《海洋通报》2019,38(6):640-649

河口物质输运、能量交换与底边界层内的水动力过程密切相关,底边界层参数(如切应力、拖曳系数)的确定至关重要。挪威Nortek公司生产的新型声学多普勒流速剖面仪AD2CP相比传统ADCP具有高频、低噪的优点,可用于高频(16Hz)流速剖面观测,而被广泛应用于底边界层观测的ADV只能测量单点高频流速。本文采用AD2CP在长江口南槽最大浑浊带区域进行座底式观测,并与同步近底部三脚架上ADV的观测结果进行对比。结果表明,使用AD2CP测得的近底部平均流速与ADV的测量结果吻合良好;使用惯性耗散法计算了底切应力,基于ADV的单点高频流速数据计算结果为2.16×10~(-2)～5.69×10~(-1)N/m~2,基于AD2CP的结果为2.09×10~(-2)～4.26×10~(-1)N/m~2,二者范围大致相当。在此基础上,基于AD2CP数据计算出摩阻流速为4.55×10~(-3)～2.06×10~(-2)m/s、底拖曳系数范围为1.84×10~(-4)～2.49×10~(-3),与ADV的计算结果基本一致。此外,由于AD2CP可以获得高频的流速剖面数据,优于单点ADV,具备观测近底部边界层参数和边界层内湍流剖面的潜力。  相似文献   

黄河三角洲孤东近岸冲淤演变及其影响因素   总被引：1，自引：0，他引：1  

程慧  陈沈良  徐丛亮  姬泓宇  凡姚申 《海洋科学》2019,43(11):11-18

为更好地了解近40年来孤东近岸的演变过程,以研究区剖面水深地形、Landsat影像和利津站水沙数据为数据源,采用遥感技术及数理统计法对研究区域岸线及面积变化进行监测计算,并分析1976—1986年、1986—1996年、1996—2002年、2002—2014年4个不同阶段的冲淤演变及影响因素。结果表明:(1)孤东近岸经历"强淤积-冲淤平衡-侵蚀-强侵蚀"4个阶段。孤东近岸海域由淤积向侵蚀转变始于1996年,且在2002—2014年间侵蚀最为严重,大部分近岸海域蚀深达到6～8 m,侵蚀最大深度超过8 m;(2)等深线变化时空差异明显,蚀退最先出现在北侧,且近岸5 m水深区域内冲淤变化较水深10 m内敏感;(3)研究区近岸侵蚀,离岸淤积,剖面冲淤平衡位置由CS19剖面的11 m水深变化到CS21剖面的5m水深;(4)黄河入海水沙的减少、河口人工改汊、孤东大堤建设和海洋动力作用都对孤东近岸的冲淤演变产生影响,维持研究区冲淤平衡的年均来沙阈值为3.78亿t/a。通过此来进一步探究孤东近岸演变进程,为孤东近岸防护提供科学指导。  相似文献   

Decadal link between longitudinal morphological changes in branching channels of Yangtze estuary and movement of the offshore depo-center     

Boyuan Zhu  Yao Yue  Alistair G.L. Borthwick  Wenjun Yu  Enhang Liang  Jinwu Tang  Yuanfang Chai  Yitian Li 《地球表面变化过程与地形》2020,45(11):2689-2705

In estuaries, the morphology of inland and offshore areas usually evolves synergistically. This study examines the decadal link between longitudinal changes in morphology of branching channels and movement of the offshore depo-center (where sediment deposition rate is maximum) of the Yangtze River estuary, under intense human interference. Integrated data analysis is provided on morphology, runoff discharge, and ebb partition ratio from 1950 to 2017. Channel-volume reductions and change rates between isobaths in branching channels reflect the impact of estuarine engineering projects. Ebb partition ratio and duration of discharge ≥ 60 000 m³ s^-1 act as proxies for the water excavating force in branching channels and runoff intensity. It is found that deposition occurs in the lower/upper sub-reaches (or further downstream/upstream channels) of the inland north/south branching channels, and the offshore depo-center moves southward or southeastward, as runoff intensity grows; the reverse occurs as runoff intensity declines. This is because the horizontal circumfluence in the Yangtze estuary rotates clockwise as ebb partition ratios of the north/south branching channels increase/decrease for increasing runoff, and conversely rotates anticlockwise for decreasing runoff. Land reclamation activities, the Deepwater Channel Project, and the Qingcaosha Reservoir have impacted greatly on longitudinal changes of morphology in the North Branch and the South Passage and on ebb partition ratio variations in the North/South Channel and the North/South Passage. Dam-induced runoff flattening has enhanced deposition in the upper/lower sub-reaches of the north/south branching channels and caused northward movement of the offshore depo-center, except in areas affected by estuarine engineering projects. Dam-induced longitudinal evolution of branching channel morphology and offshore depo-center movement will likely persist in the future, given the ongoing construction of large cascade dams in the upper Yangtze and the completion of major projects in the Yangtze estuary. © 2020 John Wiley & Sons, Ltd.  相似文献   

Lidar-aided analysis of boreal forest backscatter at Ku band     

《International Journal of Applied Earth Observation and Geoinformation》2020

This paper analyzes the backscatter of the microwave signal in a boreal forest environment based on a Ku -band airborne Frequency-Modulated Continuous Waveform (FMCW) profiling radar—Tomoradar. We selected a half-managed boreal forest in the southern part of Finland for a field test. By decomposing the waveform collected by the Tomoradar, the vertical canopy structure was achieved. Based on the amplitude of the waveform, the Backscattered Energy Ratio of Canopy-to-Total (BERCT) was calculated. Meanwhile, the canopy fraction was derived from the corresponding point cloud recorded by a Velodyne VLP-16 LiDAR mounted on the same platform. Lidar-derived canopy fraction was obtained by counting the number of the first/ the strongest returns versus the total amount of returns. Qualitative and quantitative analysis of radar-derived BERCT on lidar-derived canopy fraction and canopy height are investigated. A fitted model is derived to describe the Ku-band microwave backscatter in the boreal forest to numerically analyze the proportion contributed by four factors: lidar-derived canopy fraction, radar-derived canopy height, the radar-derived distance between trees and radar sensor and other factors, from co-polarization Tomoradar measurements. The Root Mean Squared Error (RMSE) of the proposed model was 0.0958, and the coefficient of determination R2 was 0.912. The fitted model reveals that the correlation coefficient between radar-derived BERCT and lidar-derived canopy fraction is 0.84, which illustrates that lidar surface reflection explains the majority of the profiling /waveform radar response. Thus, vertical canopy structure derived from lidar can be used for the benefit of radar analysis.  相似文献