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21.
22.
Prantik Mandal R. K. Chadha N. Kumar I. P. Raju C. Satyamurty 《Pure and Applied Geophysics》2007,164(10):1963-1983
During the last six years, National Geophysical Research Institute, Hyderabad has established a semi-permanent seismological
network of 5–8 broadband seismographs and 10–20 accelerographs in the Kachchh seismic zone, Gujarat with a prime objective
to monitor the continued aftershock activity of the 2001 Mw 7.7 Bhuj mainshock. The reliable and accurate broadband data for the 8 October Mw 7.6 2005 Kashmir earthquake and its aftershocks from this network as well as Hyderabad Geoscope station enabled us to estimate
the group velocity dispersion characteristics and one-dimensional regional shear velocity structure of the Peninsular India.
Firstly, we measure Rayleigh-and Love-wave group velocity dispersion curves in the period range of 8 to 35 sec and invert
these curves to estimate the crustal and upper mantle structure below the western part of Peninsular India. Our best model
suggests a two-layered crust: The upper crust is 13.8 km thick with a shear velocity (Vs) of 3.2 km/s; the corresponding values
for the lower crust are 24.9 km and 3.7 km/sec. The shear velocity for the upper mantle is found to be 4.65 km/sec. Based
on this structure, we perform a moment tensor (MT) inversion of the bandpass (0.05–0.02 Hz) filtered seismograms of the Kashmir
earthquake. The best fit is obtained for a source located at a depth of 30 km, with a seismic moment, Mo, of 1.6 × 1027 dyne-cm, and a focal mechanism with strike 19.5°, dip 42°, and rake 167°. The long-period magnitude (MA ~ Mw) of this earthquake is estimated to be 7.31. An analysis of well-developed sPn and sSn regional crustal phases from the bandpassed
(0.02–0.25 Hz) seismograms of this earthquake at four stations in Kachchh suggests a focal depth of 30.8 km. 相似文献
23.
B C Sarkar B S Deota P L N Raju D K Jugran 《Journal of the Indian Society of Remote Sensing》2001,29(3):151-164
GIS. a potential tool for facilitating the generation and use of thematic information, has been applied to groundwater potentiality of the Shamri micro-watershed in Shimla Taluk. The role of various parameters, namely, drainage. lineament. lithology . slope and landuse have been emphasised for delineation of groundwater potential iones. IRS-I C IAN and LISS Ill FCC merged satellite images on 1:25000 scale and Topographic map no. 53L/4 SI together with field traverses have been used as the data source. A multi-criteria evaluation following probability weighted approach has been applied for overlay analysis that allows a linear combination of weights of each thematic map with the individual capability value. 1 he resultant map indicates a high groundwater potentiality in the flood plains, river terraces and river channels in the vicinity of the Shamri nala. Other sites of high potentiality include places showing break in slopes and criss-crossing of lineaments. 相似文献
24.
A meridional scanning OI 630.0-nm dayglow photometer was operated from Ahmedabad (17.2°N dip lat.) scanning a region towards the south in the upper atmosphere extending over \sim5° in latitude from 10.2°N to 15.2°N dip latitude. From the spatial and temporal variabilities of the dayglow intensity in the scanning region we show for the first time, evidence for the passage of the crest of the equatorial ionization anomaly (EIA) in the daytime by means of a ground-based optical technique. The relationship between the daytime eastward electric field over the dip equator in the same longitude zone as inferred from the equatorial electrojet strength and the evolutionary pattern of EIA is clearly demonstrated. The latter as inferred from the dayglow measurements is shown to be consistent with our present understanding of the electrodynamical processes in the equatorial region. The present results reveal the potential of this ground-based optical technique for the investigation of ionospheric/thermospheric phenomena with unprecedented spatial and temporal resolution. 相似文献
25.
Parabolic density function in sedimentary basin modelling 总被引:1,自引:0,他引:1
For modelling sedimentary basins of large thickness from their gravity anomalies, the concept of parabolic density function which explains the variation of true density contrast of the sediments with depth in such basins is introduced inBott's (1960) procedure. The analytical expression the gravity anomaly of a two-dimensional vertical prism with parabolic density contrast needed to estimate the gravity effect of the basin in modelling procedure is derived in a closed form. Two profiles of gravity anomalies, one across San Jacinto Graben, California and the other across Tucson basin, Arizona where the density of sediments is found to vary with depth are interpreted. 相似文献
26.
N. Janardhana Raju 《Environmental Geology》2007,52(6):1067-1074
In the management of water resources, quality of water is just as important as its quantity. In order to know the quality
and/or suitability of groundwater for domestic and irrigation in upper Gunjanaeru River basin, 51 water samples in post-monsoon
and 46 in pre-monsoon seasons were collected and analyzed for various parameters. Geological units are alluvium, shale and
quartzite. Based on the analytical results, chemical indices like percent sodium, sodium adsorption ratio, residual sodium
carbonate, permeability index (PI) and chloroalkaline indices were calculated. The pre-monsoon waters have low sodium hazard
as compared to post-monsoon season. Residual sodium carbonate values revealed that one sample is not suitable in both the
seasons for irrigation purposes due the occurrence of alkaline white patches and low permeability of the soil. PI values of
both seasons revealed that the ground waters are generally suitable for irrigation. The positive values of Chloroalkaline
indices in post-monsoon (80%) and in pre-monsoon (59%) water samples indicate absence of base-exchange reaction (chloroalkaline
disequilibrium), and remaining samples of negative values of the ratios indicate base-exchange reaction (chloroalkaline equilibrium).
Chadha rectangular diagram for geochemical classification and hydrochemical processes of groundwater for both seasons indicates
that most of waters are Ca–Mg–HCO3 type. Assessment of water samples from various methods indicated that majority of the water samples in both seasons are suitable
for different purposes except at Yanadipalle (sample no. 8) that requires precautionary measures. The overall quality of groundwater
in post-monsoon season in all chemical constituents is on the higher side due to dissolution of surface pollutants during
the infiltration and percolation of rainwater and at few places due to agricultural and domestic activities. 相似文献
27.
B. R. Phanikumar Jagapathi Raju m Ramanjaneya Raju e 《Geomechanics and Geoengineering》2020,15(1):64-77
ABSTRACTExpansive soil subgrades, which are subjected to dual swell-shrink problem consequent upon absorption and evaporation of water, need to be improved by chemical stabilization or compacted cushion or geosynthetic reinforcement in order that pavements constructed over them are even, stable and safe. This paper presents extensive experimental data on plasticity, free swell index (FSI) and compaction characteristics of a highly swelling expansive clay stabilized with varying silica fume contents. In another series of tests on a laterite soil to be used as a cushion over the expansive clay subgrade, plasticity properties, compaction characteristics and strength characteristics were determined at varied silica fume contents. Further, CBR of the expansive clay subgrade was determined in the laboratory stabilizing it with varied silica fume contents and providing a cushion of 50 mm thickness of silica fume-stabilized lateritic soil. Liquid limit (LL), plasticity index (PI) and free swell index (FSI) of the expansive clay decreased with increasing silica fume contents. The compaction and strength characteristics of both the soils improved with silica fume stabilization. The CBR of the expansive clay provided with silica fume-stabilized cushion improved significantly. 相似文献
28.
The lifetimes and spatial scales of emission network cells in the solar chromosphere were studied from a nearly continuous sequence of Caii K filtergrams, obtained from Antarctica. The temporal autocorrelation function (ACF) was calculated for spatially-aligned windows from the time sequence of filtergrams. The lifetime of network cells was found to be dependent on the activity of the region. The estimated lifetimes are 24–34 hours for quiet-region cells and 58–61 hours for active-region cells. The temporal ACF shows prominent undulations in some of the quiet-region windows. The spatial ACF reveals the periodicity of the emission network in quiet regions. 相似文献
29.
The first optical signatures of plasmapause associated processes were gleaned from the daytime auroral emissions monitored
from Maitri, the Indian station in Antarctica, using the newly built, ground-based, Multiwavelength Daytime Photometer (MWDPM).
The plasmapause boundary inferred from these measurements conforms well with the known empirical relationship with the geomagnetic
indexKp. The measurements made at 391.4, 486.1, 557.7 and 630.0 nm emissions revealed significant day-to-day variations in their
spatial and temporal extents. These preliminary results are presented and discussed. 相似文献
30.
R. S. Dwivedi A. N. Singh K. K. Raju 《Journal of the Indian Society of Remote Sensing》1981,9(2):33-40
Measuring spectral reflectance of soils in situ which simulates measurements made from aircraft and by satellite scanner system has become an integral part of soil mapping using remote sensing techniques. A preliminary study has been conducted to measure the spectral reflectance of some typical red and black soils of India using a field radiometer (EXOTECH-100-A) and to study the changes in specrtral reflectance patterns due to tillage and crop and non-crop cover, The spectral reflectance were measured in four different pands of electromagnetic spectrum—two in visible (0.5-0.6μ and 0.6-0.7μ) and two in infrared (0.7-0.8μ and 0.8-1.0μ) region. Spectral reflectance curves were drawn from these values which helped in understanding the spectral separability and mixing of various red and black soil types. Black soils having grass cover showed maximum reflectance value followed by ploughed one and bare counterparts whereas, the order of decrease in spectral reflectance of red soils was bare soils> ploughed soil> soils with grass cover. 相似文献