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81.
Earthquake records from a 1984 temporary seismograph array set up in La Molina, Lima, Peru, are re-analysed. The array comprised eight three-component geophones; seven soil based and one rock based. Values of horizontal-to-vertical spectral ratio (HVSR) for two small earthquakes peaked at around 1.3 Hz. In one distant earthquake, four of the seven soil-based stations showed a peak at 1.25 Hz in soil-to-rock spectral ratio (SSR), the same dominant frequency observed during an aftershock of a damaging earthquake. Because this frequency is not compatible with the shear wave velocity profile attributed to La Molina, and because the spectral peak is confined to a small ground area, it is concluded that the peak is caused by a localised deposit of soft soil. Because the area associated with the spectral peak includes the area of great damage in 1974, it is concluded that coherent monochromatic behaviour is responsible for the damage. 相似文献
82.
Janet M. Fischer Tara Reed-Andersen Jennifer L. Klug Alice G. Chalmers 《Estuaries and Coasts》2000,23(4):565-571
Geomorphology may be an important predictor of vegetation pattern in systems where suceptibility to disturbance is unevenly
distributed across the landscape. Salt marsh communities exhibit spatial pattern in vegetation at a variety of spatial scales.
In coastal Georgia, the low marsh is a virtual monoculture ofSpartina alterniflora interspersed with patches of species that are more typical of the high marsh. These localized disturbances are most likely
created by wrack mats, mats of dead vegetation which can compact and smother underlying vegetation creating bare patches for
colonization by high marsh species. We investigated the spatial pattern of disturbed patches along a 2 km section of Dean
Creek, a tidal creek at the southwestern end of Sapelo Island, Georgia, U.S. We used a discriminant model to explore the relationship
between tidal creek morphology (e.g., the presence of drainage channels and creek bends) and the spatial distribution of disturbed
patches. The model predicted vegetation pattern along the creek with relatively high accuracy (>70%). Areas where water movement
is slowed or multidirectional (e.g., along creek bends and near drainage channels) were most susceptible to disturbance. Our
findings suggest an important functional linkage between geomorphology and vegetation pattern in salt marsh communities. 相似文献
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Janet S. Wright 《The Australian geographer》2000,31(3):333-347
Four types of tufa occur along creeks draining the Oscar Range in the Kimberley region of Western Australia; stream-bed tufa, tufa dams, stream-bed tufa waterfalls, and rimstone pools. Well-developed tufa dam and waterfall formations occur at significant breaks of slope within the channel long profile. This suggests that disruption of the hydraulic flow regime and increased turbulence at these points has an important role to play in determining the location of tufa deposits. However, the best-developed stream-bed tufa deposits are located immediately upstream of dam and waterfall formations, which indicates that the evaporation of water ponded behind these flow obstructions may lead to calcium carbonate precipitation during the dry season. The presence of plant and cyanobacterial communities on, and the incorporation of organic material into, the best-developed tufa formations indicates that biological activity may have an important role to play in determining both the rate of tufa deposition and the internal structure of the resulting accumulations. 相似文献
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崎岖地形动植物栖息地生态环境遥感制图与应用 总被引:1,自引:1,他引:0
黄文声 《地球信息科学学报》2008,10(4):527-532
传统制图方法周期长、成本较高,影响了大面积精细动植物栖息地生态环境制图的生产。鉴此,本文采用IKONOS(VHR)图像对香港郊野公园崎岖地形的动植物栖息地生态环境制图进行了研究。由于香港植被的多样性,而且观察的动植物相互作用出现于结构的层面,所以对动植物栖息地的分类应以结构为基础而非以植物为基础。本文利用图像处理技术,运用决策树之多层次地物导向分割分类(MOOSC)方法绘制九种动植物栖息地类型图。MOOSC方法和其他现有的几种分类方法相比,其分类精度高、成本低。 相似文献
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Hu Dunxin Wang Fan Sprintall Janet Wu Lixin Riser Stephen Cravatte Sophie Gordon Arnold Zhang Linlin Chen Dake Zhou Hui Ando Kentaro Wang Jianing Lee Jae-Hak Hu Shijian Wang Jing Zhang Dongxiao Feng Junqiao Liu Lingling Villanoy Cesar Kaluwin Chalapan Qu Tangdong Ma Yixin 《中国海洋湖沼学报》2020,38(4):906-929
The Western Tropical Pacific(WTP) Ocean holds the largest area of warm water(28℃) in the world ocean referred to as the Western Pacific Warm Pool(WPWP),which modulates the regional and global climate through strong atmospheric convection and its variability.The WTP is unique in terms of its complex 3-D ocean circulation system and intensive multiscale variability,making it crucial in the water and energy cycle of the global ocean.Great advances have been made in understanding the complexity of the WTP ocean circulation and associated climate impact by the international scientific community since the 1960 s through field experiments.In this study,we review the evolving insight to the 3-D structure and multi-scale variability of the ocean circulation in the WTP and their climatic impacts based on in-situ ocean observations in the past decades,with emphasis on the achievements since 2000.The challenges and open que stions remaining are reviewed as well as future plan for international study of the WTP ocean circulation and climate. 相似文献