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M. V. M. S. Rao K. J. Prasanna Lakshmi L. P. Sarma K. B. Chary 《Journal of Earth System Science》2006,115(6):673-683
Compressional and shear wave velocities and attenuation measurements have been carried out in some of the borehole samples
of acidic, basic and intermediate granulites of Mahabalipuram, Tamil Nadu, India. The results have been obtained at ambient
conditions using ‘time-of-flight’ pulse transmission technique at 1.0 MHz frequency. The results show linear relationships
between velocity and density, and velocity and attenuation properties of the rocks. The acidic granulites show lower velocities
and higher attenuation than the intermediate and basic granulites. The average values of the Poisson’s ratio of acidic, intermediate
and basic granulites have been found to be 0.210, 0.241 and 0.279 respectively. The variations in velocities and attenuation
in these low porosity crystalline rocks are found to be strongly influenced by their mineral composition. The laboratory velocity
data (extrapolated to high pressure) of the present study and the published field velocity data from deep seismic sounding
studies indicate that these granulite facies rocks may belong to mid-crustal depths only. 相似文献
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Stress field and seismicity in the Indian shield: Effects of the collision between India and Eurasia
Intraplate stresses and intraplate seismicity in the Indian subcontinent are strongly affected by the continued convergence between India and Eurasia. The mean orientation of the maximum horizontal compression in the Indian subcontinent is subparallel to the direction of the ridge push at the plate boundary as well as to the direction of compression expected to arise from the net resistive forces at the Himalayan collision zone, indicating that the intraplate stresses in the subcontinent, including the shield area, are caused by plate tectonic processes. Spatial distribution of historic and instrumentally recorded earthquakes indicate that the seismic activity is mostly confined to linear belts while the remaining large area of the shield is stable. The available conventional heat flow data and other indicators of heat flow suggest hotter geotherms in the linear belts, leading to amplification of stresses in the upper brittle crust. Many of the faults in these linear belts, which happen to be 200–80 m.y. old, are being reactivated either in a strike-slip or thrust-faulting mode. The reactivation mechanisms have been analyzed by taking into consideration the amplification of stresses, pore pressures, geological history of the faults and their orientation with respect to the contemporaneous stress field. The seismicity of the Indian shield is explained in terms of these reactivation mechanisms. 相似文献
4.
T. N. Gowd S. V. Srirama Rao K. B. Chary F. Rummel 《Journal of Earth System Science》1986,95(3):311-319
The firstin situ stress measurements in India were carried out in 176 m deep borehole by employing deep-hole wireline hydraulic fracturing equipment. The results reveal that the direction of maximum compression is oriented at N 35° E, and the existence of high-near-surface horizontal stresses compared with the overburden pressure. This can be attributed to the continuing convergence of Indian and Eurasian plates. Earthquakes experienced near Hyderabad could be due to refracturing of some NNE or NE trending mineralized fractures which persistently occur in the area, as these fractures are critically oriented with respect to the present-day stress field. 相似文献
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N. Sundararajan Y. Srinivas M. Narasimha Chary G. Nandakumar A. Hanmantha Chary 《Journal of Earth System Science》2004,113(3):259-267
The contacts associated with an outlier in biotite gneiss and sandstones near Tiruvuru, Krishna district, Andhra Pradesh which
are generally favourable for groundwater occurrence were investigated employing refraction seismic method. Results were examined
by correlating the signals with local geology, bore well data and other available information in order to improve the reliability
of interpretation 相似文献
6.
E.E. Becklin M. Silverstone R. Chary J. Hare B. Zuckerman C. Spangler A. Sargent 《Astrophysics and Space Science》1997,255(1-2):113-118
The DEBRIS project is a search for infrared excess around Sun-like main sequence stars, and other types of stellar targets,
using the Infrared Space Observatory. Some results, calibration issues, and changes to our original program are presented.
Future platforms for advancing this project after the conclusion of the ISO mission are indicated.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
7.
Edward L. Chapin Alexandra Pope † Douglas Scott Itziar Aretxaga Jason E. Austermann Ranga-Ram Chary Kristen Coppin Mark Halpern David H. Hughes James D. Lowenthal Glenn E. Morrison Thushara A. Perera Kimberly S. Scott Grant W. Wilson Min S. Yun 《Monthly notices of the Royal Astronomical Society》2009,398(4):1793-1808
We present results from a multiwavelength study of 29 sources (false detection probabilities <5 per cent) from a survey of the Great Observatories Origins Deep Survey-North (GOODS-N) field at 1.1 mm using the Astronomical Thermal Emission Camera (AzTEC). Comparing with existing 850 μm Submillimetre Common-User Bolometer Array (SCUBA) studies in the field, we examine differences in the source populations selected at the two wavelengths. The AzTEC observations uniformly cover the entire survey field to a 1σ depth of ∼1 mJy. Searching deep 1.4 GHz Very Large Array (VLA) and Spitzer 3–24 μm catalogues, we identify robust counterparts for 21 1.1 mm sources, and tentative associations for the remaining objects. The redshift distribution of AzTEC sources is inferred from available spectroscopic and photometric redshifts. We find a median redshift of z = 2.7 , somewhat higher than z = 2.0 for 850 μm selected sources in the same field, and our lowest redshift identification lies at a spectroscopic redshift z = 1.1460 . We measure the 850 μm to 1.1 mm colour of our sources and do not find evidence for '850 μm dropouts', which can be explained by the low signal-to-noise ratio of the observations. We also combine these observed colours with spectroscopic redshifts to derive the range of dust temperatures T , and dust emissivity indices β for the sample, concluding that existing estimates T ∼ 30 K and β∼ 1.75 are consistent with these new data. 相似文献
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S. V. Srirama Rao K. B. Chary T. N. Gowd F. Rummel 《Journal of Earth System Science》1999,108(2):93-98
In situ stress measurements by hydraulic fracturing were carried out in the 617 m deep borehole specially drilled in the epicentral
zone of the 1993 Latur earthquake for the purpose of research. The stress measurements carried out at 592 m depth in this
borehole are the deepest of all such measurements made so far in the Indian shield. The maximum and minimum principal horizontal
stresses (S
H max andS
h min) have been derived from the hydrofracture data using the classical method. TheS
H max andS
h min are found to be 16.5 and 9.6 MPa at 373 m depth, and 25.0 and 14.1 MPa at 592 m depth, indicating that the vertical gradients
ofS
hmax andS
hmin in the epicentral zone are 39 MPa/km and 21 MPa/km respectively. The principal horizontal stresses in the epicentral zone
are comparable with those at Hyderabad and 30% higher than in most other comparable intra-continental regions. Analysis of
the results indicate that the stresses in the focal region of the 1993 Latur earthquake have not undergone any significant
change following its occurrence and this is in agreement with a similar inference drawn from the seismic data analysis. It
appears that the Latur earthquake was caused due to rupturing of the overpressured fault segment at the base of the seismogenic
zone. 相似文献
9.
Assessment of soil erosion using remote sensing and GIS in Nagpur district, Maharashtra for prioritisation and delineation of conservation units 总被引:1,自引:0,他引:1
C V Srinivas A K Maji G p Obi Reddy G R Chary 《Journal of the Indian Society of Remote Sensing》2002,30(4):197-212
In the present study, soil loss in Nagpur district of Maharashtra is predicted employing USLE method and adopting integrated analysis in GIS to prioritise the tahsils for soil conservation and for delineation of suitable conservation units. Remote sensing techniques are applied to delineate the land cover of the district and to arrive at annual cover factors. Results indicate that potential soil loss of very slight to slight (>5–10 tons/ha/year) exist in the valleys in north western, northern and in the plains of central and eastern parts of the district. Moderate to moderately severe erosion rates (10 to 20 tones/ha/year) is noticed in the southeastern and some central parts. Severe, very severe and extremely severe erosion types (20 to 80 tons/ha/year) are noticed in the northern, western, southwestern and southern parts of the district. The average soil loss is estimated to be 23.1 and 15.5 tons/ha/yr under potential and actual conditions respectively. Slight, moderate, moderately severe and extremely severe potential erosion covering about 41 per cent area of the district is reduced to negligible and very slight rates of actual erosion under the influence of present land cover leading to a reduction of 7421.2 tones of potential soil loss. Priority rating of the tahsils is evaluated from the area weighted mean quantum of soil loss. Multi-criteria overlay analysis with the parameters of soil erosion, slope, soil depth, land cover and surface texture with rating for the constituent classes has resulted in delineation of nine conservation units. Appropriate agronomic and mechanical practices are suggested in the identified units for minimizing the erosion hazard. 相似文献
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