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51.
S. Naseema Beegum K. Krishna Moorthy Vijayakumar S. Nair S. Suresh Babu S. K. Satheesh V. Vinoj R. Ramakrishna Reddy K. Rama Gopal K. V. S. Badarinath K. Niranjan Santosh Kumar Pandey M. Behera A. Jeyaram P. K. Bhuyan M. M. Gogoi Sacchidanand Singh P. Pant U. C. Dumka Yogesh Kant J. C. Kuniyal Darshan Singh 《Journal of Earth System Science》2008,117(1):303-313
Spectral aerosol optical depth (AOD) measurements, carried out regularly from a network of observatories spread over the Indian mainland and adjoining islands in the Bay of Bengal and Arabian Sea, are used to examine the spatio-temporal and spectral variations during the period of ICARB (March to May 2006). The AODs and the derived Ångström parameters showed considerable variations across India during the above period. While at the southern peninsular stations the AODs decreased towards May after a peak in April, in the north Indian regions they increased continuously from March to May. The Ångström coefficients suggested enhanced coarse mode loading in the north Indian regions, compared to southern India. Nevertheless, as months progressed from March to May, the dominance of coarse mode aerosols increased in the columnar aerosol size spectrum over the entire Indian mainland, maintaining the regional distinctiveness. Compared to the above, the island stations showed considerably low AODs, so too the northeastern station Dibrugarh, indicating the prevalence of cleaner environment. Long-range transport of aerosols from tshe adjoining regions leads to remarkable changes in the magnitude of the AODs and their wavelength dependencies during March to May. HYSPLIT back-trajectory analysis shows that enhanced long-range transport of aerosols, particularly from the west Asia and northwest coastal India, contributed significantly to the enhancement of AOD and in the flattening of the spectra over entire regions; if it is the peninsular regions and the island Minicoy are more impacted in April, the north Indian regions including the Indo Gangetic Plain get affected the most during May, with the AODs soaring as high as 1.0 at 500 nm. Over the islands, the Ångström exponent (α) remained significantly lower (~1) over the Arabian Sea compared to Bay of Bengal (BoB) (~1.4) as revealed by the data respectively from Minicoy and Port Blair. Occurrences of higher values of α, showing dominance of accumulation mode aerosols, over BoB are associated well with the advection, above the boundary layer, of fine particles from the east Asian region during March and April. The change in the airmass to marine in May results in a rapid decrease in α over the BoB. 相似文献
52.
Mass loading and chemical composition of atmospheric aerosols over the Arabian Sea during the pre-monsoon months of April and May have been studied as a part of the Integrated Campaign for Aerosols, gases and Radiation Budget (ICARB). These investigations show large spatial variabilities in total aerosol mass loading as well as that of individual chemical species. The mass loading is found to vary between 3.5 and 69.2 μg m?3, with higher loadings near the eastern and northern parts of Arabian Sea, which decreases steadily to reach its minimum value in the mid Arabian Sea. The decrease in mass loading from the coast of India towards west is estimated to have a linear gradient of 1.53 μg m?3/° longitude and an e?1 scale distance of ~2300 km. SO 4 2? , Cl? and Na+ are found to be the major ionic species present. Apart from these, other dominating watersoluble components of aerosols are NO 3 ? (17%) and Ca2+ (6%). Over the marine environment of Arabian Sea, the non-sea-salt component dominates accounting to ~76% of the total aerosol mass. The spatial variations of the various ions are examined in the light of prevailing meteorological conditions and airmass back trajectories. 相似文献
53.
Zhenming Wang 《Journal of Earth System Science》2008,117(2):749
Microzonation is an effort to evaluate and map potential hazards found in an area, urban area in particular, that could be induced by strong ground shaking during an earthquake. These hazards include: ground motion amplification, liquefaction, and slope failure. The microzonation maps, depicting ground-motion amplification, liquefaction, and landslide potentials, can be produced if the ground motion on bedrock (input) and the site conditions are known. These maps, in combination with ground-motion hazard maps (on bedrock), can be used to develop a variety of hazard mitigation strategies such as seismic risk assessment, emergency response and preparedness, and land-use planning. However, these maps have certain limitations that result from the nature of regional mapping, data limitations, generalization, and computer modeling. These microzonations show that when strong ground shaking occurs, damage is more likely to occur, or be more severe, in the higher hazard areas. The zones shown on the hazard maps should not serve as a substitute for site-specific evaluations. 相似文献
54.
Alan Yong Susan E. Hough Michael J. Abrams Christopher J. Wills 《Journal of Earth System Science》2008,117(2):797
Estimation of the degree of local seismic wave amplification (site effects) requires precise information about the local site conditions. In many regions of the world, local geologic information is either sparse or is not readily available. Because of this, seismic hazard maps for countries such as Mozambique, Pakistan and Turkey are developed without consideration of site factors and, therefore, do not provide a complete assessment of future hazards. Where local geologic information is available, details on the traditional maps often lack the precision (better than 1:10,000 scale) or the level of information required for modern seismic microzonation requirements. We use high-resolution (1:50,000) satellite imagery and newly developed image analysis methods to begin addressing this problem. Our imagery, consisting of optical data and digital elevation models (DEMs), is recorded from the ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) sensor system. We apply a semi-automated, object-oriented, multi-resolution feature segmentation method to identify and extract local terrain features. Then we classify the terrain types into mountain, piedmont and basin units using geomorphometry (topographic slope) as our parameter. Next, on the basis of the site classification schemes from the Wills and Silva (1998) study and the Wills et al (2000) and Wills and Clahan (2006) maps of California, we assign the local terrain units with V s 30 (the average seismic shear-wave velocity through the upper 30m of the subsurface) ranges for selected regions in Mozambique, Pakistan and Turkey. We find that the applicability of our site class assignments in each region is a good first-approximation for quantifying local site conditions and that additional work, such as the verification of the terrain’s compositional rigidity, is needed. 相似文献
55.
The coal seams of Sawang Colliery, East Bokaro Coalfields are bituminous to sub-bituminous in nature and categorized as high
gaseous seams (degree II to degree III level). These seams have the potential for coal bed methane (CBM) and their maturity
increases with increasing depth, as a result of enhanced pressure-temperature conditions in the underground. The vitrinite
maceral group composition of the investigated coal seams ranges from 62.50–83.15%, whereas the inertinite content varies from
14.93–36.81%. The liptinite content varies from 0.66% to 3.09%. The maximum micro-pores are confined within the vitrinite
group of macerals. The coal seams exhibit vitrinite reflectance values (Ro% calculated) from 0.94% (sample CG-97) to 1.21%
(sample CG-119).
Proximate analyses of the investigated coal samples reveal that the moisture content (M%) ranges from 1.28% to 2.98%, whereas, volatile matter (VM%) content is placed in the range of 27.01% to 33.86%. The ash
content (A%) ranges from 10.92% to 30.01%. Fixed carbon (FC%) content varies from 41.53% to 55.93%. Fuel ratio variation shows a restricted
range from 1.53 to 1.97. All the coal samples were found to be strongly caking and forming coke buttons.
The present study is based on the adsorption isotherm experiments carried out under controlled P-T conditions for determination of actual gas adsorption capacity of the coal seams. This analysis shows that the maximum methane
gas adsorbed in the coal sample CG-81 is 17 m3/t (Std. daf), at maximum pressure of 5.92 MPa and experimental temperature of 30°C. The calculated Langmuir regression parameters
PL and VL range from 2.49 to 3.75 MPa and 22.94 to 26.88 m3/t (Std. daf), respectively. 相似文献
56.
Singh et al (2005) examined the potential of the ANN and neuro-fuzzy systems application for the prediction of dynamic constant of rockmass.
However, the model proposed by them has some drawbacks according to fuzzy logic principles. This discussion will focus on
the main fuzzy logic principles which authors and potential readers should take into consideration. 相似文献
57.
Masyhur Irsyam Donny T. Dangkua Hendriyawan Drajat Hoedajanto Bigman M. Hutapea Engkon K. Kertapati Teddy Boen Mark D. Petersen 《Journal of Earth System Science》2008,117(2):865-878
This paper presents the development of spectral hazard maps for Sumatra and Java islands, Indonesia and microzonation study for Jakarta city. The purpose of this study is to propose a revision of the seismic hazard map in Indonesian Seismic Code SNI 03-1726-2002. Some improvements in seismic hazard analysis were implemented in the analysis by considering the recent seismic activities around Java and Sumatra. The seismic hazard analysis was carried out using 3-dimension (3-D) seismic source models (fault source model) using the latest research works regarding the tectonic setting of Sumatra and Java. Two hazard levels were analysed for representing 10% and 2% probability of exceedance (PE) in 50 years ground motions for Sumatra and Java. Peak ground acceleration contour maps for those two hazard levels and two additional macrozonation maps for 10% PE in 50 years were produced during this research. These two additional maps represent short period (0.2 s) and long-period (1.0 s) spectra values at the bedrock. Microzonation study is performed in order to obtain ground motion parameters such as acceleration, amplification factor and response spectra at the surface of Jakarta. The analyses were carried out using nonlinear approach. The results were used to develop contour of acceleration at the surface of Jakarta. Finally, the design response spectra for structural design purposes are proposed in this study. 相似文献
58.
59.
内蒙古敖包吐萤石矿床的Sr、Nd、Pb同位素地球化学特征 总被引:2,自引:1,他引:1
敖包吐萤石矿床是内蒙古北部苏莫查干地区单一萤石矿集区中的一个代表性矿床,产于早二叠世大石寨组火山-沉积岩与早白垩世敖包吐花岗岩的接触带上。文章通过分析该矿床岩、矿石的微量元素和稀土元素,揭示出萤石的成矿作用可分为2个阶段,即交代作用和充填作用。交代作用过程中大石寨组的结晶灰岩可能为萤石的形成提供了部分Ca来源,萤石矿石的稀土元素配分模式与海水基本类似,具有Ce负异常;成矿作用后期主要表现为充填作用,形成颗粒粗大的萤石,表现为重稀土元素富集的特征,并随着萤石的沉淀析出,稀土元素总量逐渐下降,反映出成矿流体经历了较长期的演化过程。各地层单元、花岗岩体和萤石矿石的Sr、Nd、Pb同位素研究表明,萤石的放射性同位素组成具有壳、幔源混合的特点,成矿物质来源具有多源性。早白垩世敖包吐花岗岩可能是萤石中F的主要来源,而大石寨组的结晶灰岩则可能提供了Ca。另外,Pb、Nd同位素的极大不均一性,有可能是成矿流体在运移过程中对艾力格庙群放射性组分的选择性吸收的结果。萤石成矿作用与钾玄岩的时空关系暗示了萤石的成矿过程可能是中国东部岩石圈减薄和下地壳的置换地质事件的结果。在构造转型的过程中,燕山中期富碱的酸性花岗岩浆的活动分异出富含F的成矿流体,与幔源流体混合,沿区域重新活化的深大断裂和大石寨组的层间破碎带上升,交代其间的灰岩透镜体,从而形成敖包吐中型萤石矿床。 相似文献
60.
Using ALSM to map sinkholes in the urbanized covered karst of Pinellas County,Florida—1, methodological considerations 总被引:1,自引:0,他引:1
Larry D. Seale Lee J. Florea H. L. Vacher Robert Brinkmann 《Environmental Geology》2008,54(5):995-1005
Comparison of a database of interpreted sinkholes made using airborne laser swath mapping (ALSM) with databases of sinkholes
made from interpretation of aerial photographs reveals substantial disagreement. The discrepancies involve the location, number,
areas, and circularity of interpreted sinkholes. Methodological factors that contribute to the discrepancies include blockage
of ALSM laser returns in thick vegetation, multi-path reflections, and misrepresentation of the true extent of sinkholes.
Comparison of two ALSM-derived databases made (1) independently from versus (2) in combination with earlier air photo analysis
in undeveloped regions had the following result: one-fourth of the sinkholes interpreted by using the composite method were
missed by the independent analysis, and one-third of the sinkholes that were interpreted from the independent analysis were
not interpreted as sinkholes using the composite method. Subjective interpretation leads to a high level of uncertainty such
that the results of the remote sensing studies are suspect, if not invalid. 相似文献