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61.
Henry Villegas 《国际地球制图》2013,28(1):67-74
Abstract On November the 13th of 1985, the City of Armero (Colombia) was destroyed by debris flows generated by a reactivation of the Nevado del Ruiz Volcano. The flows ocurred in at least three principal pulses, as was observed by the disater's survivors. Landsat TM 5 data processing was carried out in subscenes taken before and after the lahar sedimentation. False color composites were generated and combined with the geological information available in order to visualize the magnitude of the catastrophe and the flow characteristics. Taking advantage of Landsat TM 5 images with high spectral resolution, a detailed photogeological mapping of the three principal pulses of the debris flows was carried out. Landsat TM 5 proved to be a powerful complementary source of information for hazard assesment of these catastrophic debris flows. The images were used in addition to ground‐based information, and were an easy way to help ordinary people and decision makers understand such hazardous volcanic situations. 相似文献
62.
Advanced Land Observing Satellite Phased Array L-band Synthetic Aperture Radar (ALOS PALSAR) data from different observation modes were analysed to determine (1) which observation mode most accurately retrieves tropical forest biomass information and (2) whether different modes, when considered together, yield improved results in comparison to identical data-sets analysed independently. We performed regression analysis to estimate above-ground forest biomass using PALSAR backscatter data for natural and planted forests in south-eastern Bangladesh. The coefficient of determination (r 2) was lower or equal to 0.499 (n = 70) when PALSAR data from different observation modes were separately considered, but increased sharply when one class (rubber) is dropped and average backscatter of fine beam single (FBS) and polrimetric (PLR) modes are used in the analysis. The results presented in this article are useful for both regional and global forest biomass inventories and fixing acquisition modes for planned L-band SAR missions. 相似文献
63.
陵水17-2气田位于中国南海琼东南盆地,是中国海油自营勘探发现的第一个深水高产气田,探明储量规模超千亿立方米.在水深200~1600 m区域,采用工程调查船与自主式水下潜器调查结合的方式,进行地球物理资料采集、海底表层取样及钻探取样,并对多波束测深、后向散射强度、侧扫声呐、浅地层剖面、室内测试分析等数据进行综合分析,研... 相似文献
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65.
This paper presents the results of a 3-year-long (November 2004–November 2007) study based on the use of acoustic Doppler current profilers (ADCPs) to estimate the solid transport through the three inlets of Venice lagoon. In each of the three inlets instruments were mounted both on survey boats and deployed on the channel bed. The three bottom-mounted ADCPs were positioned in the central part of the inlets, continuously monitoring vertical profiles in the water column. Periodic transects along the investigated sections were collected by the boat-mounted ADCP. Both installations measured current speed and acoustic backscatter intensity. The latter expresses the attenuation of acoustic energy due to material in the water column. 相似文献
66.
Deformation-related microstructures in magmatic zircon and implications for diffusion 总被引:1,自引:1,他引:0
Steven Michael Reddy Nicholas E. Timms Patrick Joseph Hamilton Helen R. Smyth 《Contributions to Mineralogy and Petrology》2009,157(2):231-244
An undeformed glomeroporphyritic andesite from the Sunda Arc of Java, Indonesia, contains zoned plagioclase and amphibole
glomerocrysts in a fine-grained groundmass and records a complex history of adcumulate formation and subsequent magmatic disaggregation.
A suite of xenocrystic zircon records Proterozoic and Archaean dates whilst a discrete population of zoned, euhedral, igneous
zircon yields a SHRIMP U-Pb crystallisation age of 9.3 ± 0.2 Ma. Quantitative microstructural analysis of zircon by electron
backscatter diffraction (EBSD) shows no deformation in the inherited xenocrysts, but intragrain orientation variations of
up to 30° in 80% of the young zircon population. These variations are typically accommodated by both progressive crystallographic
bending and discrete low angle boundaries that overprint compositional growth zoning. Dispersion of crystallographic orientations
are dominantly by rotation about an axis parallel to the zircon c-axis [001], which is coincident with the dominant orientation of misorientation axes of adjacent analysis points in EBSD
maps. Less common <100> misorientation axes account for minor components of crystallographic dispersion. These observations
are consistent with zircon deformation by dislocation creep and the formation of tilt and twist boundaries associated with
the operation of <001>{100} and <100>{010} slip systems. The restriction of deformation microstructures to large glomerocrysts
and the young magmatic zircon population, and the absence of deformation within the host igneous rock and inherited zircon
grains, indicate that zircon deformation took place within a low-melt fraction (<5% melt), mid-lower crustal cumulate prior
to fragmentation during magmatic disaggregation and entrainment of xenocrystic zircons during magmatic decompression. Tectonic
stresses within the compressional Sunda Arc at the time of magmatism are considered to be the probable driver for low-strain
deformation of the cumulate in the late stages of initial crystallisation. These results provide the first evidence of crystal
plastic dislocation creep in zircon associated with magmatic crystallisation and indicate that the development of crystal-plastic
microstructures in zircon is not restricted to high-strain rocks. Such microstructures have previously been shown to enhance
bulk diffusion of trace elements (U, Th and REE) in zircon. The development of deformation microstructures, and therefore
multiple diffusion pathways in zircon in the magmatic environment, has significant implications for the interpretation of
geochemical data from igneous zircon and the trace element budgets of melts due to the potential enhancement of bulk diffusion
and dissolution rates. 相似文献
67.
声遥测水中悬浮粒子(如泥沙)的反向散射强度,可反演获得粒子浓度。可是,遥测系统对采样体积采集的声反向散射,除了粒子的散射信号外,还包含附加的干扰和噪声。本文探讨采集悬浮粒子声反向散射信号时,如何降低干扰源和噪声源对其影响的若干对策。 相似文献
68.
We use quantitative microstructural analysis including misorientation analysis based on electron backscatter diffraction (EBSD) data to investigate deformation mechanisms of naturally deformed plagioclase in an amphibolite gabbro mylonite. The sample is from lower oceanic crust exposed near the Southwest Indian Ridge, and it has a high ratio of recrystallized matrix grains to porphyroclasts. Microstructures preserved in porphyroclasts suggest that early deformation was achieved principally by dislocation creep with subgrain rotation recrystallization; recrystallized grain (average diameter ∼8 μm) microstructures indicate that subsequent grain boundary sliding (GBS) was active in the continued deformation of the recrystallized matrix. The recrystallized matrix shows four-grain junctions, randomized misorientation axes, and a shift towards higher angles for neighbor-pair misorientations, all indicative of GBS. The matrix grains also exhibit a shape preferred orientation, a weak lattice preferred orientation consistent with slip on multiple slip systems, and intragrain microstructures indicative of dislocation movement. The combination of these microstructures suggest deformation by dislocation-accommodated GBS (DisGBS). Strain localization within the recrystallized matrix was promoted by a transition from grain size insensitive dislocation creep to grain size sensitive GBS, and sustained by the maintenance of a small grain size during superplasticity. 相似文献
69.
70.
江苏废黄河口光学后向散射浊度计的沉积物标定 总被引:1,自引:0,他引:1
以往的光学后向散射浊度计(Optical Backscatter,OBS)标定,多用其输出的浊度值进行研究,此研究目的是对OBS的原始输出的值进行了标定。利用在江苏北部废黄河口获得的表层沉积物样品和水样悬沙数据,分别对OBS的原始输出的值进行了室内标定和现场标定。结果表明:OBS值与悬沙含量呈强的线性关系,特别是在近岸悬浮体含量较高的水域。此外,室内用表层沉积物标定结果获得的悬沙含量值比实有含沙量高。像OBS的浊度值一样,OBS的原始输出的值能应用于悬沙的分析。这说明,即使没有浊度标定文件,使用OBS获得的数据也可以进行悬沙含量分析。 相似文献