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921.
Structural, geomorphological, geophysical and volcanological data have been processed for the implementation of a dedicated
GIS through which the structural evolution of the Pleistocene trachytic Cimini volcano (central Italy) has been reconstructed.
The evolution of the Cimini complex includes three main close-in time phases: (1) intrusion of a shallow laccolith, rising
along NW and NE trending faults and stagnating at the contact between the Mesozoic-Cenozoic and the Pliocene-Pleistocene sedimentary
units constituting the bedrock of the volcano; (2) emplacement of lava domes along radial and tangential fractures formed
by the swelling induced by the laccolith growth; (3) ignimbrite eruptions and final effusion of olivine-latitic lavas. Domes
are both of Pelean and low lava dome type and their morphology was controlled by the location on the inclined surface of the
swelled area. Some domes show to have uplifted upper Pliocene thermally metamorphosed clay sediments, suggesting a cryptodome-like
growth. Comparison of the top of the Mesozoic-Cenozoic units with the top of the upper Pliocene-Pleistocene sedimentary complex,
suggests that the laccolith emplaced in a graben of the Mesozoic-Cenozoic sedimentary complex filled by the Pliocene–Pleistocene
sediments uplifted by the shallow intrusion. Stress patterns acting on the Cimini area have been deduced analysing the drainage
network and the morphotectonic lineaments. Rose diagrams show a large dispersion of the lineaments reflecting the local presence
of radial and tangential fractures. The most frequent extensional NW and NE trending lineaments have regional significance
and controlled the magma uprise leading to the laccolith emplacement. 相似文献
922.
The paper presents the method of local magnitude determination used at Polish seismic stations to report events originating
in one of the four regions of induced seismicity in Poland or its immediate vicinity. The method is based on recalculation
of the seismic moment into magnitude, whereas the seismic moment is obtained from spectral analysis. The method has been introduced
at Polish seismic stations in the late 1990s but as of yet had not been described in full because magnitude discrepancies
have been found between the results of the individual stations. The authors have performed statistics of these differences,
provide their explanation and calculate station corrections for each station and each event source region. The limitations
of the method are also discussed. The method is found to be a good and reliable method of local magnitude determination provided
the limitations are observed and station correction applied. 相似文献
923.
采用正交回归方法, 利用中国地震局地球物理研究所(IGCEA)和美国地质调查局国家地震信息中心(USGS/NEIC)1983——2004年的观测资料,对这两个机构测定的面波震级进行了系统的比较,得到了中国地震台网与美国地震台网面波震级之间的关系式. 结果表明,由于使用的震级计算公式和观测仪器不同,IGCEA测定的面波震级总体上要比NEIC测定的结果偏高0.2级;对于3.5~4.5级的地震,IGCEA测定的震级比NEIC测定的震级偏高0.3级;对于5.0~6.5级的地震,IGCEA偏高0.2级;对于7.0级以上的地震,IGCEA偏高小于0.1级. 相似文献
924.
925.
Because atmosphere itself is a nonlinear system and there exist some problems using the linearized equations to study the initial error growth, in this paper we try to use the error nonlinear growth theory to discuss its evolution, based on which we first put forward a new concept: nonlinear local Lyapunov exponent. It is quite different from the classic Lyapunov exponent because it may characterize the finite time error local average growth and its value depends on the initial condition, initial error, variables, evolution time, temporal and spatial scales. Based on its definition and the at-mospheric features, we provide a reasonable algorithm to the exponent for the experimental data, obtain the atmospheric initial error growth in finite time and gain the maximal prediction time. Lastly, taking 500 hPa height field as example, we discuss the application of the nonlinear local Lyapunov exponent in the study of atmospheric predictability and get some reliable results: atmospheric predictability has a distinct spatial structure. Overall, predictability shows a zonal distribution. Prediction time achieves the maximum over tropics, the second near the regions of Antarctic, it is also longer next to the Arctic and in subtropics and the mid-latitude the predictability is lowest. Particularly speaking, the average prediction time near the equation is 12 days and the maximum is located in the tropical Indian, Indonesia and the neighborhood, tropical eastern Pacific Ocean, on these regions the prediction time is about two weeks. Antarctic has a higher predictability than the neighboring latitudes and the prediction time is about 9 days. This feature is more obvious on Southern Hemispheric summer. In Arctic, the predictability is also higher than the one over mid-high latitudes but it is not pronounced as in Antarctic. Mid-high latitude of both Hemispheres (30°S―60°S, 30°―60°N) have the lowest predictability and the mean prediction time is just 3―4 d. In addition, predictability varies with the seasons. Most regions in the Northern Hemisphere, the predictability in winter is higher than that in summer, especially in the mid-high latitude: North Atlantic, North Pacific and Greenland Island. However in the Southern Hemisphere, near the Antarctic regions (60°S―90°S), the corresponding summer has higher predictability than its winter, while in other areas especially in the latitudes of 30°S―60°S, the prediction does not change obviously with the seasons and the average time is 3―5 d. Both the theoretical and data computation results show that nonlinear local Lyapunov exponent and the nonlinear local error growth really may measure the predictability of the atmospheric variables in different temporal and spatial scales. 相似文献
926.
通过对广西矿产资源开发与地方经济发展的关系进行研究,总结了矿产资源开发对地方经济发展的促进作用,同时分析了两者之间存在的矛盾。指出,国有企业在资源开发、利用和地方经济发展中起着主导作用,同时提出了构建广西矿产资源开发与地方经济发展良性互动关系的对策和措施。 相似文献
927.
介绍了双网卡在本实验室局域网中所起到的安全、保密作用,论述了Linux系统的优越性及管理办法。用一个网卡接国际互联网,另一网卡接本室SUN工作站,形成本室独立局域网,确保了本室SUN工作站不受国际互联网的干扰。 相似文献
928.
青藏高原念青唐古拉峰地区气候特征初步分析 总被引:7,自引:1,他引:7
利用青藏高原念青唐古拉峰地区扎当冰川垭口(30°28.07′N,90°39.03′E,5 800 m a.s.l.)、南坡(30°22.87′N,90°40.36′E,5 100 m a.s.l.)和北坡(30°29.06′N,90°37.46′E,5 400 m a.s.l.)三台自动气象站一年的近地层观测资料,分析了该地区温度、湿度、风速风向和辐射等气象要素的季节变化特征,探讨了南、北坡局地气候差异形成的原因。结果表明:垭口、南坡、北坡年平均气温分别为-6.9℃、-1.1℃和-3.4℃;北坡(扎当冰川)消融期气温直减率大,年平均值为0.87℃/100 m;海拔越高,气温日较差、气温直减率波动越大;垭口相对湿度最大,饱和水汽压最小;该地区相对湿度与海拔呈正向关系,而饱和水汽压与之呈反向关系;该地区局地环流特征明显;总辐射5月出现最大值,南坡辐射比北坡小,与大气所含水汽、天空云量、下垫面性质差异等因素有关。 相似文献
929.
930.
Thomas G. Measham 《The Australian geographer》2007,38(2):145-159
Community-based natural resource management (CBNRM) continues to attract interest as a way of achieving social and environmental outcomes at the local and regional scale. Central to the success of CBNRM is the importance of capacity building and participatory approaches to research and management. This paper discusses an initiative in East Gippsland which involved a facilitated process to assist local residents build their capacity to manage their landscape. Through conducting a community survey, the project facilitated landholders to voice, develop and refine their understanding of remnant vegetation management, dieback and revegetation on private land. In doing so, landholders have improved not only their understanding of the issues but also their ability to act upon them. The empirical findings of the study highlight two issues of relevance to dieback on the East Gippsland Red Gum Plains. First, there is a perception that dieback has remained stable for at least 10 years. Second, scattered trees and small patches of trees are more vulnerable to dieback than clumped trees in larger patch sizes, as well as roadside vegetation. The research demonstrates the value of a community-based approach to NRM in terms of harnessing local knowledge, fostering human and social capital and engaging with interested landholders. 相似文献