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In the quantitative data interpretation for HLEM induction prospecting, a vertical half-plane model in an insulating medium is widely employed. For this assumption to be valid, the steeply dipping massive sulphide dykes must have large strike lengths and depth extents, but small thickness. We report investigations, using the laboratory scale-modelling method, on the response variation of large vertical conductors as the thickness is varied. We conclude that a steeply dipping large dyke can be approximated by a half-plane model only if its thickness is less than half the skin depth. An inductively thick conductor produces larger amplitudes and relatively higher quadrature compared to a thin conductor, even if both have the same induction number. 相似文献
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Response of climate to regional emissions of ozone precursors: sensitivities and warming potentials 总被引：2，自引：0，他引：2
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An alluvial bajada has been recognized along a part of the active Narmada-Son Fault(NSF) and confined by the Karjan River on the eastern side and by the Madhumati River on western side.The bajada sequence exposed along the incised cliffs of various north flowing parallel streams has been studied in their proximal,medial and distal part. The sediments are characterized on the basis of grain size,fabric,sedimentary structures,bed geometry and sorting, and lithologs prepared from the mapped cliff sections.Detailed study of sedimentary characteristics,lithofacies analysis and facies associations indicate that sediments are mainly of three types-sediments that were deposited by debris flows and sediment gravity flows,and as extensive bar deposits.Three major aggredational sequences are recognized.Each sequence is composed of coarsening-upward sequence of proximal facies overlain by fining-upward sequence of distal facies.Coarsening upward sequence record periods of tectonic activity related to uplift along the NSF and fan progradation,whereas fining-upward sequence results from tectonic quiescence periods.The presence of rhizocretions,calcium carbonate nodules and calcite sheets within the basal debris flow and sediment gravity flow indicate semi-arid climate,whereas the formation of pedoginized paleosol indicate relatively wetter climate prevailing in the study area.Tectonic activity along the NSF has played dominant role by controlling the geometry and volume of bajada sediments.Climate is found to be responsible for compositional and temporal distribution of bajada sediments.OSL dating suggests that the bajada sediments were deposited during the later part of late Pleistocene.The incision of the sediments is attributed to uplift due to inversion of the lower Narmada basin during the early Holocene. 相似文献
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Abstract The planning of water resources depends on the type and size of projects, the ecological factors involved, etc. Emphasis is placed on presenting an overview of water resources through meteorological, hydrological, ecological and economic data. Economic data include all costs and benefits, specifically those hitherto under estimated, environmental social costs and benefits. This study was carried out on the Bedthi and Aghnashini rivers in the Uttara Kannada district of the Western Ghats region, Karnataka State, India. It is estimated that 720 and 510 million kWh of electricity can be generated in Bedthi and Aghnashini River basins, respectively, if all the streams are harnessed. Focusing on land submergence impact, a model is proposed to minimize submergence and maximize net energy in a region with seasonal power generation, reservoir storage capacity (to meet the region's demand during all seasons) and installed generation capacity as the decision variables. Net energy analyses incorporating biomass energy lost in submergence show that maximization in net energy at a site is possible if the hydroelectric generation capacity is adjusted according to the seasonal variations in the river's water discharge. A Decision Support System (DSS) used for optimal design of hydroelectric projects in Uttara Kannada district is discussed. 相似文献
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V CHOWKSEY D M MAURYA PARUL JOSHI N KHONDE ARCHANA DAS L S CHAMYAL 《Journal of Earth System Science》2011,120(6):979-999
The Kachchh Mainland Fault (KMF) is a major E–W trending seismically active fault of the Kachchh palaeorift basin whose neotectonic
evolution is not known. The present study deals with the eastern part of the KMF zone where the fault is morphologically expressed
as steep north facing scarps and is divisible into five morphotectonic segments. The Quaternary sediments occurring in a narrow
zone between the E–W trending KMF scarps and the flat Banni plain to the north are documented. The sediments show considerable
heterogeneity vertically as well as laterally along the KMF zone. (The Quaternary sediments for a northward sloping and are
exposed along the north flowing streams which also show rapid decrease in the depth of incision in the same direction.) The
deposits, in general, comprise coarse as well as finer gravelly deposits, sands and aeolian and fluvial miliolites. The Quaternary
sediments of the KMF zone show three major aggradation phases. The oldest phase includes the colluvio-fluvial sediments occurring
below the miliolites. These deposits are strikingly coarse grained and show poor sorting and large angular clasts of Mesozoic
rocks. The sedimentary characteristics indicate deposition, dominantly by debris flows and sediment gravity flows, as small
coalescing alluvial fans in front of the scarps. These deposits suggest pre-miliolite neotectonic activity along the KMF.
The second aggradation phase comprises aeolian miliolites and fluvially reworked miliolites that have been previously dated
from middle to late Pleistocene. The youngest phase is the post-miliolite phase that includes all deposits younger than miliolite.
These are represented by comparatively finer sandy gravels, gravelly sands and sand. The sediment characteristics suggest
deposition in shallow braided stream channels under reduced level of neotectonic activity along the KMF during post-miliolite
time evidenced by vertical dips of miliolites and tilting of gravels near the scarps. The tectonically controlled incision
and dissection of the Quaternary deposits is the result of neotectonic activity that continues at present day. The overall
nature, sedimentary characteristics and geomorphic setting of the sediments suggest that the KMF remained neotectonically
active throughout the Quaternary period. 相似文献
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Abstract Supraglacial Imja Lake (lake level, 5010 m a.m.s.l.), Khumbu, Nepal Himalaya, has increased its size on the tongue of Imja Glacier since the 1950s. In order to clarify the mechanism of the lake expansion, the physical conditions, water budget and heat budget of the lake were examined by measuring water temperature, water turbidity, lake level, meteorology and water discharge. These measurements were carried out in the monsoon season of July 1997, when the glacier melt occurred in the ablation area with air temperature of more than 0°C. Density stratification in the lake is built up by an effect of water pressure on lake water, but, neglecting the effect, lake water density is defined by suspended sediment concentration rather than temperature. Glacier-melt water from the subaqueous part of the glacier terminus mixed with lake surface water of 4–8°C, and diffused the water of about 3°C into the deeper zone of the lake. This advective, thermal diffusion occurs by sediment-laden underflow and relatively clear density interflow. The sediment-laden underflow is induced by intermittent glacier-melt sediment discharge at the terminus, while the density interflow is probably produced by continuous glacier-melt water discharge. Calculation of water budget of the lake indicates that meltwater inflow at the glacier terminus and surface water outflow at the outlet determine the hydrological conditions of the lake. The net heat transfer by melting of the terminal ice and dead ice, connected to the lake expansion, was evaluated by calculating the heat budget of the lake. 相似文献
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A Hidden Markov Model (HMM) has been developed for prediction of quantitative snowfall in Pir-Panjal and Great Himalayan mountain ranges of Indian Himalaya. The model predicts snowfall for two days in advance using daily recorded nine meteorological variables of past 20 winters from 1992–2012. There are six observations and six states of the model. The most probable observation and state sequence has been computed using Forward and Viterbi algorithms, respectively. Baum–Welch algorithm has been used for optimizing the model parameters. The model has been validated for two winters (2012–2013 and 2013–2014) by computing root mean square error (RMSE), accuracy measures such as percent correct (PC), critical success index (CSI) and Heidke skill score (HSS). The RMSE of the model has also been calculated using leave-one-out cross-validation method. Snowfall predicted by the model during hazardous snowfall events in different parts of the Himalaya matches well with the observed one. The HSS of the model for all the stations implies that the optimized model has better forecasting skill than random forecast for both the days. The RMSE of the optimized model has also been found smaller than the persistence forecast and standard deviation for both the days. 相似文献
10.
Laboratory scale model experiments have been performed to obtain the electromagnetic response of a finitely conducting half plane embedded in resistive/conductive surrounding and excited by an oscillating magnetic dipole. Inphase and quadrature profiles are presented for two horizontal coplanar transmitter-receiver systems (inline and broadside) for normal and skew traverses and for different dips of the conductor. It is observed that the broadside system is more diagnostic in delineating the strike and dip of the conductor and is more sensitive to the conducting host rock. The broadside profile over a vertical or dipping half plane is characterized, when traversing perpendicular to strike, by two positive peaks flanking a zero response when the coils are over the top edge of the conductor. For skew traverses a negative peak replaces the zero response. An increasing asymmetry in the anomalies is caused by changing the dip of the conductor from the vertical in both the systems, but it is more pronounced for the broadside system. The quadrature response in the broadside system changes in a characteristic way when the target is surrounded by a conducting host rock. The comparative results of the two systems may, therefore, be useful in the induction prospecting for ore deposits approximated by a half plane, especially in delineating the strike, dip, and effect of conductive host rock. 相似文献