Low Free-Field Accelerations of the 1999 Kocaeli Earthquake?     

Joachim?MiksatEmail author  Friedemann?Wenzel  Vladimir?Sokolov 《Pure and Applied Geophysics》2005,162(5):857-874

The August 17, 1999 Kocaeli earthquake ruptured the earths surface along 145 km and produced a magnitude of M_w=7.4. As expected for such an event Modified Mercalli intensities of typically IX and X in the vicinity of the fault were determined. Yet the observed accelerations at the five near-fault sites remained amazingly small with horizontal PGA values of 0.14 g to 0.4 g. We attempt to resolve the enigma by modeling surface ground motion with a finite-difference algorithm, utilizing two different rupture and slip histories derived from the strong-motion observations and translate the computed horizontal motion in intensity values. We can show that (a) in a given simple crustal velocity model different slip distributions result in significantly different ground motion distributions in the vicinity of the fault even though both slip distributions fit the observed accelerometer data quite well. (b) Both slip distributions project high ground motion into areas adjacent to the fault where no accelerometer was located. (c) Both slip distributions are not fully compatible with observed intensity observations around the fault, although this could be partly attributed to the lack of knowledge regarding to the crustal structure. In the light of our results it would thus be misleading if the few strong-motion observations around the Kocaeli earthquake fault were taken as typical or representative for the entire area and for potential future events.  相似文献   

Vegetation and climate change since 14,810 C yr B.P. in southeastern Uruguay and implications for the rise of early Formative societies     

José Iriarte 《Quaternary Research》2006,65(1):20-32

This article presents a combined pollen and phytolith record of a 1.70-m sediment core from the wetlands of India Muerta (33° 42′ S, 53° 57′ W) in the lowland Pampa (grasslands) of southeastern Uruguay. Six ¹⁴C dates and the pollen and phytolith content of the samples permitted the recognition of four distinct climatic periods between 14,850 ¹⁴C yr B.P. and the present. The Late Pleistocene period (between ca. 14,810 and ca. 10,000 ¹⁴C yr B.P.) was characterized by drier and cooler conditions indicated by the presence of a C3-dominated grassland. These conditions prevailed until the onset of the warmer and more humid climate of the Holocene around 9450 ¹⁴C yr B.P. The early Holocene (between around 10,000 and 6620 ¹⁴C yr B.P.) was characterized by the establishment of wetlands in the region as evidenced by the formation of black peat, the increase in wetland taxa, and the replacement of C3 Pooideae by C4 Panicoideae grasses. During the mid-Holocene, around 6620 ¹⁴C yr B.P., began a period of environmental change characterized by drier climatic conditions, which resulted in the expansion of halophytic communities in the flat, low-lying areas of the wetlands of India Muerta. About 4020 ¹⁴C yr B.P. a massive spike of Amaranthaceae/Chenopodiaceae coupled with a radical drop in wetland species indicates another major and more severe period of dryness. After ca. 4000 ¹⁴C yr B.P., a decrease of halophytic species indicates the onset of more humid and stable climatic conditions, which characterized the late Holocene.The findings reported in this article substantially improve our knowledge of the late Glacial and Holocene climate and vegetation in the region. The data provide a detailed record of the timing and severity of mid-Holocene environmental changes in southeastern South America. Significantly, the mid-Holocene drying trend coincided with major organizational changes in settlement, subsistence, and technology of the pre-Hispanic populations in the region, which gave rise to early Formative societies. This study also represents the first combined pollen and phytolith record for southeastern South America reinforcing the utility of phytoliths as significant indicators of long-term grassland dynamics.  相似文献   

A new look at an old problem: magnetotelluric modelling of 1-D structures   总被引：2，自引：0，他引：2  

Gaston Fischer  Pascal Weibel 《Geophysical Journal International》1991,106(1):161-167

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Approximate Solutions For The Obukhov Length And The Surface Fluxes In Terms Of Bulk Richardson Numbers     

H. A. R. De Bruin  R. J. Ronda  B. J. H. Van De Wiel 《Boundary-Layer Meteorology》2000,95(1):145-157

Simple analytic approximate solutions arepresented for the set of equations that follows fromthe Monin–Obukhov flux-profile relationships using thestability functions of Dyer (unstable case) andBeljaars–Holtslag (stable case). Several publicationsare devoted to the same subject, however the currentapproach contains some new features, namely: (a) itappears to be more accurate for unstable situationsand (b) it applies also to the general case where windspeed (u) and potential temperature() are given at different levels. In order toillustrate the accuracy of the approach a comparisonwith the actual solutions is presented for someselected combinations of and u levelstypical for various practical applications.  相似文献   

Small pelagics in upwelling systems: patterns of interaction and structural changes in "wasp-waist" ecosystems     

Cury  Philippe; Bakun  Andrew; Crawford  Robert J. M.; Jarre  Astrid; Quinones  Renato A.; Shannon  Lynne J.; Verheye  Hans M. 《ICES Journal of Marine Science》2000,57(3):603-618

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基于自然资源大数据的城市多功能景观识别与国土空间规划分区   总被引：1，自引：0，他引：1  

黄隆杨  王静  李泽慧  赵晓东  刘晶晶  方莹 《地球信息科学学报》2021,23(9):1617-1631

多功能景观能够同时提供多种景观功能,可以充分缓解生态环境压力。在自然资源大数据支撑下基于基层行政管理单元开展的多功能景观研究,可以更加快速准确地反映区域自然地理格局与社会经济发展格局的空间特征与区域差异,其将景观功能管理和行政管理有效结合,能为市县级国土空间规划中控制线的划定和国土空间规划分区提供从功能评估到空间识别等多方面的技术支撑。本文在广泛收集土地利用变更调查数据、自然资源调查评价数据、气象数据、多源遥感数据等自然资源大数据的基础上,结合社会经济数据和兴趣点数据,基于InVEST模型、CASA模型、通用土壤流失方程以及核密度分析等方法对烟台市6种景观功能进行了空间量化;再以村级管理单元为基本空间单元进行景观功能热点分析以识别多功能景观区;利用Spearman相关系数分析各种景观功能间的权衡与协调作用;最后基于二阶聚类法进行景观功能聚类以开展烟台市国土空间规划分区,并制定相应的保护与发展策略。研究表明：① 烟台市35.5%的村级管理单元为多功能景观区;② 自然景观功能间呈协同作用,而自然景观功能与居住和经济承载功能间存在显著的空间冲突和权衡作用;③ 根据景观功能聚类结果,烟台市被划分为生态保护区、农业农村发展区、城镇功能发展区和城镇核心区,面积占比分别为30%,55%,11%,4%。规划分区与现状管理边界在空间上具有较强的一致性和协调性,表明在自然资源大数据支撑下,基于景观功能聚类分析的国土空间规划分区具有相当的准确性和实用性。  相似文献   

基于语义的GP服务多层次发现算法     

魏海涛  杜云艳  何亚文  周成虎  张镭 《地球信息科学学报》2014,(1):39-44

随着云技术的飞速发展,"一切资源皆服务"成为可能,"数字地球"的实现也不例外。观测技术的快速发展使数据资源变得很丰富,但数据利用率低是普遍存在的现象,如何完成空间数据信息的再加工是亟待解决的问题,在云时代,具有数据处理功能的服务是解决此问题的方法之一,如何描述、发现和集成数据处理服务,从云端服务池中发现最优的服务是其关键所在。为了提高服务的查全率和查准率,引入了本体的概念,服务的语义描述很大程度上提高了空间数据处理服务的应用范围,缓解了非专业用户和专业人员之间的沟通障碍。本文分析了相关领域服务匹配算法的优缺点,结合GP服务自身的特点,提出了本体的GP服务的多层次发现算法:通过包含关系和线索关系完成服务间隐含关系的挖掘,主要是父子关系和前驱后继关系的表述;扩展传统本体表达模型,增加包含和线索关系,为服务的查找做准备;服务的多层次查找,第一次筛选主要针对服务预处理中包含和线索关系的表达查找,第二次筛选利用神经网络的突触原理,结合传统的服务匹配算法,完成服务的准确查找。经试验证明,此方法大大地提高了服务的查准率和查全率,具有重要的实践意义。  相似文献   

黄河口大型底栖动物群落结构特征及其与环境因子的耦合分析   总被引：6，自引：4，他引：2  

吴斌  宋金明  李学刚 《海洋学报》2014,36(4):62-72

为探究复杂环境下的河口大型底栖生物群落结构特征,研究了黄河口及其毗邻海域内14个站位的底栖生物群落结构及其与主要环境因子的耦合关系。研究结果表明调查海域底栖生物群落组成和结构的空间异质性较高。底栖生物优势度不明显,优势物种集中于河口附近站位。生物多样性随离河口距离增加而增加,物种丰富度和生物多样性指数等的高值区均出现在远离河口的渤海湾和渤海中部站位,低值区位于近河口站位。对底栖生物群落的非参数多维排序(nMDS)和等级聚类分析显示,底栖生物群落结构相似性较低。丰度/生物量曲线(ABC曲线)分析显示,黄河口底栖生物群落整体上处于稳定状态,但近河口和莱州湾中西部站位受到干扰影响,群落结构不稳定。研究还表明生物量大的底栖生物(软体动物)倾向于向重金属含量较高的站位聚集。综合沉积物化学、预测毒性和底栖生物群落结构变化的评价结果可知,远离黄河口的沉积物环境质量普遍较好,而河口附近的沉积物环境质量较差。  相似文献   

基于多源遥感数据的水体信息提取研究   总被引：1，自引：0，他引：1  

张依欣  张涛  刘芳  许忠雄  李长春 《测绘与空间地理信息》2014,(5):47-50

卫星遥感技术已被广泛应用到水体信息提取中,但目前基于遥感技术的水体信息提取多采用单一的遥感数据源,而没有充分利用多源数据的信息复合优势,因此,提取结果经常受天气气候或空间分辨率限制。本文研究了不同尺度、不同平台的多种遥感数据源的水体信息提取方法。首先,基于波谱间关系决策树分类算法对Landsat ETM+图像进行水体提取,利用其分辨率优势较准确地提取出水体范围;其次,在Radarsat SAR图像上利用阈值法粗提取水体信息后,结合DEM剔除阴影得到水体信息;最后,利用灾前Landsat ETM+图像水体信息提取结果和灾中Radarsat SAR图像水体信息提取结果,进行差值处理,得到洪水淹没范围。研究结果可以为洪水灾害监测与评估提供信息依据。  相似文献   

地理信息共享框架及模型研究     

余旭 《测绘科学》2011,36(2):30-32

地理信息共享是地理信息系统研究领域的重要研究方向之一.自地理信息共享的概念提出以来,对其研究更多的是集中在技术层面,但并不能期望所有地理信息共享的障碍都能通过技术上来解决.论文从非技术视角分析了近年来国内外的几个典型地理信息共享框架/模型,对它们的优缺点做了较为详细的评述,提出了地理信息共享未来的研究方向.  相似文献