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221.
Rakesh Kumar 《Pure and Applied Geophysics》1980,119(2):339-348
The solution of a boundary value problem modelling a two-dimensional basin structure has been obtained by using the Schwartz-Christoffel conformal transformation technique and numerical methods of solving non-linear differential equations. Utilizing this solution, the telluric field and its first horizontal derivative have been theoretically computed for field directions perpendicular to the strike of the structure. On the basis of systematic analysis of a large number of such anomaly curves, two nomograms have been prepared to be used in the quantitative interpretation of telluric data. An interpretation procedure to evaluate the geometric parameters of the basin from the observed telluric data is outlined. This procedure is demonstrated on an actual field example. 相似文献
222.
Data on the fabric properties of gravels have been collected at 10 locations over a distance of 27 km from the Chakki River — a braided channel of the Beas River system. The imbrication of AB-planes reveals a close correspondence with the channel direction; the deviations seldom exceed 30°. Increase in sinuosity and the existence of subsidiary channels contribute, at some locations, to larger deviations. Imbrication directions tend to be modified because of the influence of local channels which develop temporarily on the bar surfaces.A current-normal mode exists for the A-axis orientation data. Bimodal distributions are recognised and attributed to shifting flow conditions. Variance values are low for both the imbrication and A-axis data. The range in mean values of the dip of AB-planes is between 22.6° and 37.6° with s = 8° to 14°. The mean values of plunge of the A-axis vary from 2.9° to 13.2° with s = 3.4° to 12.69°. There is a marked decrease in plunge of the A-axis in the downstream direction in the Chakki River.A particle size versus orientation approach indicates that, irrespective of size, there is a strong upcurrent imbrication. Longitudinal alignment of particles in the smaller size intervals is not supported by the data obtained in this study. A particle shape versus orientation approach reveals that the A-axis orientation is not dependent on particle shape. The A-axis fabric patterns of both tabular and bladed clasts show a peripheral circular arrangement of the maxima, the bisectrix of which points in a current-normal direction. Orientation patterns do not reflect any control in terms of the lithic composition of clasts. 相似文献
223.
The spaceborne laser ranging (or lasering) system provides a method of precise positioning of a large number of points on
the earth's surface in a short period of time. That is, a measure of the relative location of geodetic markers from a space
platform can maintain horizontal and vertical control to 2 to 5 cm. At this level of control, small earth surface crustal
motions should be detectable. Development of a model for the strain field can be constructed. Furthermore, the spaceborne
lasering system can survey an area in a very short period of time (one to two weeks) and resurvey the area as required.
System design parameters are now being established by NASA for a possible test flight aboard the Shuttle in 1982. These include
design specifications of economical corner cubes for ground retroreflectors coupled with the evolution of engineering model
to flight model development. If the experiment of the Shuttle proves to be successful, it is hoped to put the laser in a free
flight satellite. This paper presents the results of a simulated analysis for this latter case.
The system is conceived as an orbiting ranging device with a ground base grid of reflectors or transponders (spacing 10 to
30 km), which are projected to be of low cost (maintenance-free and unattended) and which will permit the saturation of a
local area to obtain data useful to monitor crustal movements. The test network includes 75 stations with roughly half of
them on either side of the San Andreas fault zone. Critical study comparatively evaluates various observational schemes and
statistically analyzed crustal motion recovery.
The study considers laser radar as the main ranging system pending final selection from many possible candidates. The satellite
orbit is inclined at 110° and slightly eccentric (e=0.04) with orbital altitudes varying from 370 km to 930 km.
The results indicate that the geometric mode (simultaneous ranging) with a minimum of five grid and three distant (fundamental)
stations and mixed ranging to satellite and airplane seems to be most promising. The fundamental stations are distinguished
from the grid station in their location and this location should be “distant” enough from the area of crustal movement so
that they can be considered stationary over the time span of the motion involved.
Presented at the 1977 I.A.G. International Symposia on Satellite Geodesy, Budapest, Hungary, June 28–July 1, and on Recent
Crustal Movements, Palo Alto, California, USA, July 25–30. 相似文献
224.
Subir Kumar Ghosh 《Tectonophysics》1974,21(3):249-272
Two series of experiments were carried out with soft model-materials in order to assess the relative importance of initial homogeneous strain, external rotation and late-stage strain in reorienting early lineations during superposed buckle-folding. In the first series cylindrical buckling folds were produced in embedded planar sheets containing a “lineation”. In the second series noncylindrical folds were produced by compression of a set of cylindrical folds. The experiments indicate that the ratio of buckle shortening to layer-parallel strain is much smaller when the principal extension is parallel to the fold-axis than in the case when the principal extension is perpendicular to the fold-axis. In very competent rocks, the reorientation of old lineations is mainly by external rotation and by the associated concentric longitudinal strain. In moderately competent rocks, the orientation of early lineations always changes by initial homogeneous strain before buckling becomes significant. Because of the unlike amounts of initial strain in layers of different competences, orientations of unrolled lineations may not be parallel in disharmonically folded layers of unlike competences. Under certain conditions the early lineation may become virtually parallel to the later fold-axis. The experiments indicate that the effects of late-stage strain in buckle-folding are largely restricted to the incompetent layers of a multilayer. Hence, if orientation data of early lineations in both competent and incompetent rocks are lumped together, the pattern of orientation may become quite complex. Even for a single competent layer, the pattern of early lineations can locally become complex because of the complex nature of concentric longitudinal strain (and strain resulting from stretching of middle surface of the layer), development of conical folds, development of shear strain along hinge zones of deformed early folds and also because of the development of different orders of folds in both the first and the second deformations. 相似文献
225.
Water samples were collected from cold and warm karst springs for stable isotopes (δ18O and δD) and 3H from SE of Kashmir valley (western Himalayas) to distinguish the sources of recharge and infer their recharge areas. The spring water samples were most depleted in heavier isotopes in May (average δ18O: ?8.87‰ and δD: ?50.3‰) and enriched in September (average δ18O: ?7.58‰ and δD: ?48.1‰). The depleted 18O and 2H of spring waters bear the signatures of winter precipitation while as the enriched 18O and 2H of spring waters bear the signature of summer rainfall. D‐excess and 3H corroborate with the stable isotope results that the spring flow in spring season (May) and autumn (September) is dominantly controlled by the melting of winter snowmelt and summer rainfall, respectively. The results showed that unlike δD, the δ18O value in the karst spring waters decreases in January suggesting δ18O shift. The spring water samples also fall above the Local Meteoric Water Line and Global Meteoric Water Line indicating the δ18O shift due to interaction of groundwater with the host carbonate rocks during its traverse. The mean elevation of the recharge areas of the springs using δ18O and δD tracers was also estimated. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
226.
Cylindrically symmetric inhomogeneous string cosmological model in presence of electromagnetic field is investigated. We have
assumed that F
23 is the only non-vanishing component of F
ij
. To get the deterministic solution, it has been assumed that the expansion (θ) in the model is proportional to the eigen value σ
1
1 of the shear tensor σ
i
j
. The physical and geometric aspects of the model are also discussed.
相似文献
227.
It is well established that sea surface temperature (SST) plays a significant role in the hydrologic cycle in which precipitation is the most important part. In this study, the influence of SST on Indian subdivisional monthly rainfall is investigated. Both spatial and temporal influences are investigated. The most influencing regions of sea surface are identified for different subdivisions and for different overlapping seasons in the year. The relative importance of SST, land surface temperature (LST) and ocean–land temperature contrast (OLTC) and their variation from subdivision to subdivision and from season to season are also studied. It is observed that LST does not show much similarity with rainfall series, but, in general, OLTC shows relatively higher influence in the pre‐monsoon and early monsoon periods, whereas SST plays a more important role in late‐ and post‐monsoon periods. The influence of OLTC is seen to be mostly confined to the Indian Ocean region, whereas the effect of SST indicates the climatic teleconnection between Indian regional rainfall and climate indices in Pacific and Atlantic Oceans. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
228.
Praveen Gupta Amit Kumar Dubey Nandita Goswami Raghvendra Pratap Singh Prakash Chauhan 《Marine Geodesy》2015,38(3):614-625
In the absence of many gauging stations in the major and mighty river systems, there is a need for satellite-based observations to estimate temporal variations in the river water storage and associated water management. In this study, SARAL/AltiKa application for setting up hydraulic model (HEC-RAS) and river flow simulations over Tapi River India has been discussed. Waveform data of 40 Hz from Ka band altimeter has been used for water levels retrieval in the Tapi river. SARAL/AltiKa retrieved water levels were converted to discharge in the upstream location (track-926) using the rating curve available for the nearby gauging site and using linear spatial interpolation technique. Steady state simulations were done for various flow conditions in the upstream. Validation of river flow model was done in the downstream location (track-367) by comparing simulated and altimeter retrieved water levels (RMSE 0.67 m). Validated model was used to develop rating curve between water levels and simulated discharge for the downstream location which enables to monitor discharge variations from satellite platform in the absence of in situ observations. It has been demonstrated that SARAL/AltiKa data has potential for river flow monitoring and modeling which will feed for flood disaster forecasting, management and planning. 相似文献
229.
Kamaljit Singh Rajkumar Megha Maheshwari Jayaprasad Pallipad Dhani Ram Rajak Raj Kumar 《Marine Geodesy》2015,38(3):497-509
Radar altimetry provides an important geophysical parameter, backscatter coefficient (σ0), which is useful in studying target surface characteristics. Ku-band (Oceansat-2 scatterometer- OSCAT) and Ka-band (SARAL-AltiKa altimeter) data are concurrently used to characterize polar surface features over the Antarctic region. Maximum-likelihood classification has been employed to classify combined data set (AltiKa and OSCAT) for discrimination among sea ice, open water, and ice sheet (interior and exterior). The sea ice region obtained using the current approach has been compared with sea ice boundary derived from passive microwave data. 相似文献
230.