An interpretation and catalogue of paleoseismicity in Sweden   总被引：1，自引：0，他引：1  

Nils-Axel Mrner 《Tectonophysics》2005,408(1-4):265

Paleoseismic data provide a long-term record of seismic activity to predict hazards for periods longer than one to a few centuries. In Sweden, the analysis reveals there was a drastic change in dominant seismic mode from a high to super-high deglacial mode to a low to moderately low mode in present and Late Holocene time. Paleoseismic criteria and characteristics include numerous different sources of information; viz. primary faults, bedrock deformation, sedimentary deformation, rock and sediment slides, liquefaction, sorting by shaking, tsunamis, differing geomorphic expressions, disordering and ordering of magnetic particles. By applying multiple criteria, it was possible to identify 44 paleoseismic events, including 23 events of estimated M 6–7, 12 events of M 7–8 and 6 events of M > 8. Varve-dating often allows a precision as to a single year, in one case even to the season of a year. The key for paleoseismic reconstruction and testing is the application of multiple criteria.  相似文献   

Petrogenesis of Mesozoic Western Shandong： High-Mg Diorites in Evidence from Chronology and Petro-geochemistry     

《中国地质大学学报(英文版)》2005,16(4):297-308

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New magnetostratigraphic and pedostratigraphic investigations of loess deposits in north‐east China and their implications for regional environmental change during the Mid‐Pleistocene climatic transition          下载免费PDF全文

Lin Zeng  Huayu Lu  Shuangwen Yi  Yongxiang Li  Anqi Lv  Wenchao Zhang  Zhiwei Xu  Haifeng Wu  Han Feng  Mengchun Cui 《第四纪科学杂志》2016,31(1):20-32

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A critical evaluation of multi‐proxy dendroclimatology in northern Finland     

Danny McCarroll  Mervi Tuovinen  Rochelle Campbell  Mary Gagen  Håkan Grudd  Risto Jalkanen  Neil J. Loader  Iain Robertson 《第四纪科学杂志》2011,26(1):7-14

Twentieth‐century summer (July–August) temperatures in northern Finland are reconstructed using ring widths, maximum density and stable carbon isotope ratios (δ¹³C) of Scots pine tree rings, and using combinations of these proxies. Verification is based on the coefficient of determination (r²), reduction of error (RE) and coefficient of efficiency (CE) statistics. Of the individual proxies, δ¹³C performs best, followed by maximum density. Combining δ¹³C and maximum density strengthens the climate signal but adding ring widths leads to little improvement. Blue intensity, an inexpensive alternative to X‐ray densitometry, is shown to perform similarly. Multi‐proxy reconstruction of summer temperatures from a single site produces strong correlations with gridded climate data over most of northern Fennoscandia. Since relatively few trees are required (<15) the approach could be applied to long sub‐fossil chronologies where replication may be episodically low. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Continuous measurement of whole‐tree water balance for studying urban tree transpiration          下载免费PDF全文

Takashi Asawa  Tomoki Kiyono  Akira Hoyano 《水文研究》2017,31(17):3056-3068

Street and garden trees in urban areas are often exposed to advection of strong vapour pressure deficit (VPD) air that can raise the whole‐tree transpiration rate (E_T), known as the oasis effect. However, urban trees tend to have small soil volume compared with natural conditions, and so they are believed to strongly regulate stomata. E_T characteristics of such urban trees have not been well understood because of a lack of reliable measurement methods. Therefore, we propose a novel weighing lysimeter method and investigate the whole‐tree water balance of an isolated container‐grown Zelkova serrata to examine (a) which biotic and abiotic factors determine E_T and (b) which spatial and temporal information is needed to predict E_T under urban conditions. Whole‐tree water balance and environmental conditions were measured from 2010 to 2012. Although leaf area substantially increased in the study period, daily E_T did not vary much. E_T increased with VPD almost linearly in 2010 but showed saturation in 2011 and 2012. Root water uptake lagged E_T by 40 min in 2012. These results suggest that the small planter box interfered with root growth and that hydraulic supply capacities did not increase sufficiently to support leaf area increase. From analysis of water balance, we believe that neglecting soil drought effects on street trees without irrigation in Japan will overestimate E_T over 4–5 sunny days at the longest. This is unlike previous studies of forest.  相似文献   

Building a model-based personalised recommendation approach for tourist attractions from geotagged social media data     

Xiaoyu Sun  Xia Peng  Yiran Chen  Yu Liu 《International Journal of Digital Earth》2019,12(6):661-678

When travelling, people are accustomed to taking and uploading photos on social media websites, which has led to the accumulation of huge numbers of geotagged photos. Combined with multisource information (e.g. weather, transportation, or textual information), these geotagged photos could help us in constructing user preference profiles at a high level of detail. Therefore, using these geotagged photos, we built a personalised recommendation system to provide attraction recommendations that match a user's preferences. Specifically, we retrieved a geotagged photo collection from the public API for Flickr (Flickr.com) and fetched a large amount of other contextual information to rebuild a user's travel history. We then created a model-based recommendation method with a two-stage architecture that consists of candidate generation (the matching process) and candidate ranking. In the matching process, we used a support vector machine model that was modified for multiclass classification to generate the candidate list. In addition, we used a gradient boosting regression tree to score each candidate and rerank the list. Finally, we evaluated our recommendation results with respect to accuracy and ranking ability. Compared with widely used memory-based methods, our proposed method performs significantly better in the cold-start situation and when mining ‘long-tail’ data.  相似文献   

基于随机森林特征选择的城市绿化乔木树种分类     

温小乐  钟奥  胡秀娟 《地球信息科学学报》2018,20(12):1777-1786

城市绿化在改善空气、水和土壤质量,吸收和减少二氧化碳及各种污染物,缓解城市热岛和减少雨水径流等方面发挥着重要作用。及时准确地获取树种信息是城市规划与绿化管理的先决条件,对进一步改善城市生态环境也具有重要意义。基于遥感技术,使用高空间分辨率的WorldView-2卫星影像,采用光谱、纹理、指数以及几何等多种特征相结合的面向对象方法,并通过随机森林进行特征选择,对福州大学旗山校区北部的榕树、杧果、香樟、重阳木、羊蹄甲、垂叶榕以及木棉7种主要绿化乔木进行树种分类。实地验证结果表明：通过特征选择可以减少或规避数据冗余以及休斯效应的产生,该方法可以提高现有同类型树种分类的精度,当淘汰全部特征的20%,利用34个特征（包括15个光谱特征、6个纹理特征、8个指数特征和5个几何特征）进行分类时,总精度最高,可达74.95%,Kappa系数为0.67。其中,光谱平均值的特征重要性最高,而各波段的标准差的重要性较低。WorldView-2卫星影像的4个新增波段,特别是黄光和红边波段及其构建的指数特征重要性较高,也说明这些波段在植被遥感,特别是树种分类中极具应用前景。  相似文献   

土体约束对海底管道整体屈曲的影响机理研究     

李成凤  刘润  彭碧瑶  王秀妍 《海洋科学》2018,42(2):56-63

高温高压下海底管道的整体屈曲稳定性分析是管道设计的重要组成部分,而选取多长的管道进行分析对其整体屈曲稳定性结果影响显著。依据临界管长将管道分为"长管"与"短管",基于动力显式分析方法,揭示了长管与短管在发生整体屈曲过程中,屈曲幅值与波长、管壁轴向压力、轴向应变及轴向位移的变化规律;研究了土体约束力影响管道临界长度的规律性,分析了土体约束力系数对长管与短管整体屈曲变形的影响。研究发现,土体约束力对短管的整体屈曲行为影响显著,短管的整体屈曲幅值随土体约束力系数的增大呈现先增大后减小的趋势。该项研究对区分不同长度管道的整体屈曲类型进而采取有效防控措施具有重要参考价值。  相似文献   

Tensionless–frictionless interaction of flexible annular foundation with a transversely isotropic multi‐layered half‐space          下载免费PDF全文

Morteza Eskandari‐Ghadi  Ghasem Gorji‐Bandpey  Azizollah Ardeshir‐Behrestaghi  Seyed Masoud Nabizadeh 《国际地质力学数值与分析法杂志》2015,39(2):155-174

A transversely isotropic multi‐layered half‐space, with axis of material symmetry perpendicular to the free surface, supports a flexible either annular or solid circle foundation. The contact area of the foundation and the half‐space is considered to be both frictionless and tensionless. The foundation is assumed to be affected by a vertical static axisymmetric load. Detailed analysis of the interaction of these two systems with different thickness of layers is the target of this paper. With the use of ring load Green's functions for both the foundation and the continuum half‐space, an integral equation accompanied with some inequalities is introduced to model the complex BVP. With the incorporation of ring‐shape FEM, we are capable of capturing both regular and singular solution smoothly. The validity of the combination of the analytical and numerical method is proved with comparing the results of this paper with a number of benchmark cases of both linear and nonlinear interaction of circular and annular foundation with half‐space. Some new illustrations are presented to portray the aspect of the anisotropy and layering of the half‐space. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

Long‐term monitoring of a mercury contaminated estuary (Ria de Aveiro,Portugal): the effect of weather events and management in mercury transport          下载免费PDF全文

J. P. Coelho  P. Pato  B. Henriques  A. Picado  A. I. Lillebø  J. M. Dias  A. C. Duarte  M. E. Pereira  M. A. Pardal 《水文研究》2014,28(2):352-360

The main aim of this research was to assess the mercury transport from an estuarine basin with a background of anthropogenic contamination during a spring tidal cycle (year 2009) and compare it with two previous tidal cycles (years 1994 and 1999), as part of a long‐term monitoring program. Results showed that effective mercury transport occurs both in the dissolved and particulate fractions (0.18 and 0.20 kg per tidal cycle, respectively), and despite an overall decrease in environmental contamination, results more than double previous findings on particulate transport in the system. These findings result essentially from changes in the tidal prism (net export of 2 million m³ of water), given that both dissolved and particulate concentrations did not increase over time. Hydrodynamic simulations were performed to evaluate the effect of physical disturbance (dredging) and weather events (increased freshwater flow) in these processes, and results suggest the increased freshwater flow into the system as the main forcing function for the mercury transport increment. These results highlight the importance of long‐term monitoring programs, since despite an overall improvement in local contamination levels, the enhancement of transport processes through hydrological changes increases environmental pressure away from the contamination source. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献