A new precambrian paleomagnetic pole for northern Europe     

G.S. Murthy  E.R. Deutsch 《Physics of the Earth and Planetary Interiors》1975,11(2):91-96

A paleomagnetic study was made of the granitic rock farsundite, exposed in southern Norway. An objective was to test the contemporaneity of this body with the neighbouring Egersund anorthosite of presumed age about 900 m.y. Two of the nine sites sampled were rejected, as the magnetization was dominantly unstable. At the seven other sites, this unstable component was either absent or it could be equally well removed by AF or thermal demagnetization: after AF treatment, all samples from these sites were left with a very stable remanence, directed steeply upwards. This magnetization was probably acquired at the time of either emplacement or recrystallization of the farsundite. A magnetic test for anisotropy indicated that the stable remanence is misaligned with the ancient Earth's field direction by about 3°, apparently due to layering of the rock fabric. After correction for this anisotropy, the mean direction from the seven sites is D = 341°, I = 82.2°, k = 142, α = 5.0°, corresponding to a paleomagnetic north pole at 43.3°S, 166.0°W, dp = 9.3°, dm = 9.7°, which lies on Spall's European polar wandering curve. The farsundite pole is not significantly different from a pole position based on the Egersund anorthosite, which supports the supposition that the two rock formations are cogenetic.  相似文献   

A simple formula for the second derivative method of interpretation     

B. S. R. Rao  I. V. Radhakrishna Murthy  S. Jeevananda Reddy 《Pure and Applied Geophysics》1970,80(1):5-26

Summary Second derivative coefficients for various grid systems are derived followingPeters' andElkins' approaches. Two simple formulae, one for three dimensional bodies and the other for two dimensional bodies are also suggested. These utilise the average of the anomalies around a single circle and the anomaly at the central point.All the coefficient sets and the proposed simple formulae are applied to gravity fields of spheres and cylinders. Coefficients ofElkins' type derived with a weightage of 1/r ⁴ to all the circles gave excellent results in both the cases of spheres and cylinders, whereasPeters' coefficients without any weightage to the circles gave reliable results in case of cylinders only. The simple formulae suggested gave more accurate results than any of the above coefficient sets.  相似文献   

Terrain analysis of Panna District,Bundelkhand, Madhya Pradesh,using LANDSAT imagery   总被引：1，自引：0，他引：1  

Vikram Singh  R. S. Murthy  R. M. Pofali  R. K. Saxena 《Journal of the Indian Society of Remote Sensing》1983,11(1):43-48

Visual interpretation of LANDSAT imagery in bands 6 and 7 covering Panna district, Bundelkhand, Madhya Pradesh was carried out for terrain analysis and present land use. The physiographic units viz. hills and hill ranges, escarpments, ridges, table-land, pediment, piedmont plain and sub-units of second order were identified and delineated using inter pretation elements. Area of each unit and sub-unit is calculated and presented in the table showing extent, tone, texture, shape and land use. Land use in relation to physiographic units is also described in the paper and shown in the form of small scale map. Visual interpretation technique helps in broad terrain analysis on scale 1:1 million. This information could be used for making a rapid resource inventory.  相似文献   

On the complex magnetic behaviour of titanomagnetites     

C. Radhakrishnamurty  S. D. Likhite  E. R. Deutsch  G. S. Murthy 《Physics of the Earth and Planetary Interiors》1982,30(4):281-290

The bulk magnetic properties, including Curie temperature, susceptibility and hysteresis at various temperatures, and the Mössbauer spectra of coarse synthetic members of the titanomagnetite series are compared as a function of titanium content, using some previously reported and some new results. It has been noted previously that the titanium-rich members fail to show the expected “true multidomain” behaviour observed in pure magnetite. One possible explanation is that the behaviour observed may be due to a tendency to inhibit domain wall formation in some titanomagnetites. In this paper we discuss some other possible mechanisms to account for the magnetic properties of such titanomagnetites observable even when domain-wall-related structures do form in them. These mechanisms suggest that magnetocrystalline anisotropy and its temperature dependence in titanomagnetites may be related to local magnetic inhomogeneities, and do not depend only on crystal structure as in the case of classical ferromagnetic materials.  相似文献   

Satellite-based assessment of physiographic disposition to health problems in kasargod district,Kerala, India     

P. P. Nageshwara Rao  S. Elango  H. R. Rajmohan  V. Krishna Murthy 《Journal of the Indian Society of Remote Sensing》2004,32(1):75-79

Photo interpretation and digital classification of IRS LISS -III sensor data have been carried out for a few villages affected by abnormal health problems in the Kasargod district of Kerala State. Physical location of the affected villages in relation to the agricultural lands use, watershed characteristics and the extent of cashewnut plantations are studied. It was found that the villages affected by the health problems are located in the microwatersheds that have steep slopes, nearly circular in shape, high runoff potential. The first order streams within these micro-watersheds are originating from the cashewnut plantations that are sprayed with a toxicant called Endosulfan. The study recommends to stop aerial spraying of any toxicant on the cash crops of these watersheds.  相似文献   

Modeling potential forest fire danger using modis data     

K. V. S. Badarinath  K. Madhavilatha  T. R. Kiran Chand  M. S. R. Murthy 《Journal of the Indian Society of Remote Sensing》2004,32(4):343-350

Generation of fire danger maps play a vital role in forest fire management like forest fire research, locating lookout towers, risk assessment and for various other simulation studies. The present study addresses remote sensing and GIS applications in generating fire danger maps for tropical deciduous forests. Fire danger variables such as fuel type, topography, temperature, and relative humidity have been used in modeling fire danger. Information on local climate patterns and past fire records has been used to derive fire frequency map of the study area. Intermediate indices were derived using multiple regressions, where fire frequency data is taken as dependent variable. Results indicate that forests near human settlements are more vulnerable to forest fires.  相似文献   

Estimation of surface heat flux and inversion height with a Doppler acoustic sounder     

L. K. Sadani  B. S. Murthy 《Journal of Earth System Science》1996,105(3):289-307

In this paper, acoustic sounder (sodar) derived vertical velocity variance (σ _w ² ) and inversion height (Z _i) are used to compute the surface heat flux during the convective activity in the morning hours. The surface heat flux computed by these methods is found to be of the same order of magnitude as that obtained from tower measurements. Inversion heights derived from sodar reflectivity profiles averaged for an hour are compared with those obtained from the σ _w ² /Z profile. Variation of σ _w ² in the mixed layer is discussed. The data were collected during the Monsoon Trough Boundary Layer Experiment 1990 at Kharagpur. The analysis is made for four days which represent the pre-monsoon, onset, active and relatively weak phases of the summer monsoon 1990. The interaction of the ABL with the monsoon activity is studied in terms of the variation of inversion height, vertical velocity variance and surface heat flux as monsoon progresses from June to August.  相似文献   

Magnetic studies on the remanence carriers in igneous rocks of different ages     

C Radhakrishnamurty  S D Likhite  G S Murthy 《Journal of Earth System Science》1988,97(1):81-85

A critical study on the type of the magnetic grains, both in composition and domain state, in rocks of different ages has been carried out. One simple, fast and non-destructive test, which can provide useful information on the nature of the magnetic grains in freshly collected samples, seems to be the ratio of susceptibilities at 77 and 300 K. This ratio, termed relative susceptibility, ranges from 0·1, for samples containing 70% ulvospinel bearing titanomagnetite (TM70) to 1·50 for cation deficient magnetite bearing ones. The results indicate that the value of 0·1 for TM70 is not greatly affected even if some amount of TM80, which is nonmagnetic at 300 K, is present in a rock sample. However, the coercive force at 77 K will increase considerably for such a sample. The effects of mixed compositions and domain states of magnetic grains on the overall behaviour of basalts are discussed.  相似文献   

Productivity optimisation in weak sedimentary formations for improved coal production and roof stability—an approach     

V. M. S. R. Murthy  Santosh Kumar Ray 《Geotechnical and Geological Engineering》2002,20(3):273-290

Far-field peak particle velocity (PPV) measurements were made in the roof while blasting in coal development drivages at Tandsi Mine, Western Coalfields Limited, India. The roof was fragile at this mine and was posing constant support problems for mining, resulting in low productivity. The PPV measurements have been used to decipher the damage zone in the roof. The extent of damage obtained has been compared to establish the threshold limits for the damage zone. Conversely, the maximum charge per delay that can be exploded is calculated and a suitable blast design has been recommended for maintaining the roof stability and pull. A roof vibration predictor equation has been developed that shows a consistent trend indicating that it may have future use in a similar geo-mining setup. The blast pattern recommended has reduced the damage extent, though marginally, but helped in improving pull. Critical PPV for incipient rock damage in underground coal mine development drivages under fragile roof were computed. The PPV level for incipient crack growth was found to vary from 500 to 800 mm/s while for overbreak it varied from 800 to 1200 mm/s. It was also observed that the location of cut holes, charge concentration and firing sequence were found to be responsible for the difference in their damage potential.  相似文献   

Scattering coefficient for S wave incident in a random medium characterized by exponential correlation function     

Jayant N. Tripathi 《Geophysical Journal International》2002,150(2):415-421

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