014841   Ratan Singh;Singh K D;Parandiyal A K (NO, Central Soil and Water Conservation Research and Training Institute,, Kota-324 002) : Characterisation and erodibility of soil under different land uses for their management and sustained production. Indian J Soil Conserv 2006, 34(3), 226-8.

Soil characteristics and erodibility indices of three soil depths viz. 0-5, 5-15 and 15-30 cm under five different land uses namely land under Leucaena, Prosopis, rainfed agriculture, grasses and open gullied lands were determined for their management and sustained production in south-east Rajasthan. Soils under Leucaena and Prosopis land uses had higher organic carbon and clay content followed by land under grasses and rainfed agriculture and lowest in open gullied land. Considering the erosion ratio and dispersion ratio, the erodibility of soils was in the order of open gullied <62> rainfed agriculture <62> Prosopis <62> Leucaena <62> grass lands. The highly significant correlation was observed between erosion ratio and dispersion ratio (r = + 0.87), percolation ratio (r = + 0.95), clay ratio (r = + 0.86), suspension percentage (r = + 0.69) and colloid : moisture equivalent ratio (r = + 0.69) indicating their important role in eroding soils. Land under Prosopis and Leucaena can be managed by their plantation of other fast growing multi-vegetational forest plants and protection against biotic interferences. Open gullied lands may be managed with cost effective mechanical and vegetative measures and gully plugging. Grasslands may be managed by replacing degenerated grasses in rortation and control grazing and rainfed agriculture by adopting agronomical measures to reduce erodibility for sustainable production.

2 tables, 10 ref

014840   Purkait N N;Saha A K;De S;Chakrabarty D K (S K Mitra Centre for Research in Space Environment, Institute of Radiophysics & Electronics,University of Calcutta, 92, Acharya Prafulla Chandra Road, Calcutta-700 009) : Behaviour of methane emission from a paddy field of high carbon content. Indian J Radio Space Phys 2007, 36(1), 52-8.

Behaviour of methane emission from the paddy field of Lakshmikantapur has been studied for two full crop years, 1998-99 and 2003-04. The soil of this place has carbon content greater than 0.7%. Two types of crops, namely, Kharif and Rabi are grown during a full crop year. Measurements were made from the beginning to the end of the plant life. Simultaneously water level and soil temperature were also measured. It is found that occasionally methane emission takes place by ebullition-yielding high value of concentration. It has diurnal variation with maximum around 1400 hrs LT. There are two peaks of emission in the whole plant life; for Kharif, the second peak is lower than the first peak and for Rabi, it is the other way round. Soil temperature affects methane emission more than water level.

7 illus, 2 tables, 17 ref

014839   Oyekola O S (Physics Dep, University of Ibadan, Ibadan, Nigeria, Email: osoyelila@yahoo.com) : Seasonal and magnetic activity variations of nighttime ionspheric F-region vertical plasma drifts at Ibadan. Indian J Radio Space Phys 2007, 36(1), 14-19.

Nighttime F-region vertical electrodynamic drifts at Ibadan (lat. 7.4°N long. 3.9°E; -6° dip) are obtained from the hourly-recorded ionosonde h'F data during 1957-58 International Geophysical Year (IGY) under geomagnetic quiet and disturbed conditions. The present results indicate strong seasonal variations in the drifts, even during quiet geomagnetic conditions. The downward nighttime average electrodynamic drift is found to be nearly 10 m/s. The drifts are consistently downward between -2100 and 0500 hrs LT sector. The evening reversal time from upward daytime to downward nighttime does not vary much except during the June solstice months when it is found to be least, while it occurs early in December solstice and equinox. An equinoctial maximum in pre-reversal enhancements of the vertical drift is also noted. The present results are found to be completely consistent with some results obtained for some low latitude ionospheric stations, Jicamarca (lat. 11.9°S, long. 76.8°W; 1°N dip), and Trivandrum (lat. 8.36°N, long. 76.6°E; 0.5°N dip) that use different measurement techniques. Possible sources of the quiet-time variability in the electrodynamics can arise from changes in the global wind system and their resultant dynamo conditions, and changes in conductivity due to solar flux variability.

5 illus, 26 ref

014838   Ojasvi P R;V N Sharda;Mandal D (NO, Central Soil and Water Conservation Research and Training Institute, 218 Kaulagarh Road, Dehradun-248 195) : Evaluation of interrill erodibility parameter for soil erosion estimation in a sub-humid climate. Part II. Model validation using under cultivated lands. Indian J Soil Conserv 2006, 34(3), 183-7.

Interrill erosion model developed by using simulated rainfall data in Part I of this study was validated under natural rainfall conditions on 8% sloping field runoff plot of 90 x 18m size. The plot was maintained under cultivated fallow conditions and no cropping or soil conservation management practice was imposed. Therefore, the baseline interrill erodibility parameter evaluated for the soil of study area was used without any adjustment factor for prediction of soil loss. Runoff and soil loss data collected under natural rainfall conditions during 2003 to 2005 were used for validation of output of interrill model. The relative error in the prediction of total soil loss for the year 2003 was 4.04% when the value of b as 1.49. Event-wise predictions of soil loss by interrill equation were in close agreement with the observed values for all the three years. The predictions were found to be better for high intensity storms. Total soil loss predictions by interrill equation with calibrated parameter were much better and realistic as compared to USLE.

3 illus, 1 tables, 15 ref

014837   Ojasvi P R;Sharda V N;Om Prakash (NO, Central Soil and Water Conservation Research and Training Institute, 218 Kaulagarh Road, Dehradun-248 195) : Evaluation of interrill erodibility parameter for soil erosion estimation in a sub-humid climate. Part I. development of model using simulated rainfall data. Indian J Soil Conserv 2006, 34(3), 178-82.

In India, the parameters of interrill-erosion model have not been determined from experimental studies for different soils and rainfall conditions. Therefore, study was conducted under simulated rainfall conditions on standard runoff plots (14 m²), having 8% slope to evaluate the interrill erodibility parameters as affected by rainfall intensity and slope gradient under silty clay loam soil in a sub-humid climate. A reciprocating boom type rainfall simulator was used. Five rainfall intensities varying from 101.8 to 315.5 mm h^-1 and 15 minutes duration were used in the study. Sufficient time gap was allowed between two experimental runs to ensure uniform initial surface soil conditions for all the runs. During the duration of 15 minutes, no rill development was observed, hence the data was analyzed for interrill erosion only. The interrill erodibility paratmeter (K₁) was computed from the observed interrill detachment rates (D_i) by relating D_i to rainfall intensity with a proportionality exponent. It was concluded that the exponent value of 1.49 for the rainfall intensity parameter in interrill equation better explains the observed soil erosion predictions as compared to normally used value of 2. The estimates of soil erosion by interrill equation developed through simulated rainfall data were in better agreement with the observed soil loss as compared to those prediced by USLE.

4 illus, 4 tables, 19 ref

014836   Nair R S (Geological Survey of India, Unit: Kerala, Thampanoor (E), Thiruvananthapuram-695 014) : Geochemisty and tetonic environment of deposition of the metasediments of Chitradurga Schist belt near Gadag, Karnataka. Indian Miner 2005, 59(3,4), 77-98.

The northern extension of Chitradurga schist belt, near Gadag under the Dharwar Supergroup comprises metavolcanics of oceanic tholeiite and calc-alkaline affinities, metasediments and intrusives. Metasediments include conglomerate, grit-argillite-metagrey wacke suite, chlorite phyllite interbedded with limestone and banded iron formation (BIF), quartz-sericite phyllite, quartz-mica schist and garnetiferous muscovite schist. Geochemistry of the metasediments indicates: (i) a mixed mafic-ultramafic and felsic nature of the source area-the high content of FeO, CaO, Ni, Cr, V and Co and high Cr/Ni ratio in the chlorite phyllite, metagreywacke and gritty schist confirm its derivation from an ultramafic-mafic source, whereas the high content of Ba, Sr and Zr in quartz-sericite phyllite suggests its derivation from a more felsic source; (ii) the major- and trace-element characteristics and diagenetic assemblages of banded iron formation- oxide or silicate facies(BIF-OS) indicate that they are different from the BIF-OS of Algoma-type; (iii) the high content of Ni, Cr, V and Co and low K depicts the primary features of the Gadag sediments and the relative maturity ( Al₂,O₃/Na₂O : 5-20 ) is mostly controlled by the composition of source rocks rather than sedimentary processes; (iv) the average SiO₂, A1₂,O3, FeO+Fe₂,O₃, CaO, Na₂O/K₂O, MgO/CaO, Cr, V and Ni of metasediments of Gadag are closer or similar to the Archaean sediments; and (v) the deposition of the sediments.of Gadag was in tectonic environments of mainly oceanic and continental island arcs.

10 illus, 5 tables, 34 ref

014835   Meshram S;Sonakia A;Biswas S (Palaeontology Division, Geological Survey of India, Nagpur-440 006) : Did elk (arctic deer) occur in peninsular India during the pleistocene. Indian Miner 2005, 59(3,4), 139-42.

^ssc5 illus, 9 ref

014834   Meshram D T;Apprao V V;Bagle B G;Dhandhar D G (Central Horticulture, Experiment Station (ICAR), Godhra-Baroda Highway, Vejalpur-389 340) : Computational models of rainfall erosion index (EI₃₀for Panchmahal district of Central Gujarat. Indian J Soil Conserv 2006, 34(3), 192-4.

Rainfall erosion index (EI₃₀) is one of the most important parameters to estimate soil loss by the Universal Soil Loss Equation (USLE) The daily, monthly and annual erosion index values (EI₃₀) were computed to assess the rainfall erosivity and develop computational models for Panchmahal of central Gujarat. The average annual EI₃₀ at Panchmahal was computed as 601.1. Nearly, 98 % of annual erosion index is concentrated during June to September. July was found to be the most erosive month. The actual values were significantly related with computed values of kinetic energy of rain and rainfall erosion index (EI₃₀). These models have been found to be useful in quick determination of kinetic energy and erosion index of storms.

2 illus, 2 tables, 9 ref

014833   Mandal V;De U K;Basu B K (School of Environmental Studies, Jadavpur Univ, Kolkata-700 032) : Verification of NCMRWF temperature output with observed data over West Bengal region during 2000-2002 monsoon period. Indian J Radio Space Phys 2006, 35(6), 407-17.

The temperature forecasts of the National Centre for Medium Range Weather Forecasting (NCMRWF) global model are validated over West Bengal (WB) region against the observations from 39 or more agricultural field stations of the Government of West Bengal and 11 observatories of India Meteorological Department (IMD), Government of India. The validation was done at 0700 hrs 1ST and 1400 hrs 1ST for 2000-2002 and at 0830 hrs 1ST in addition for 2000 only. The agreement between forecast and observed surface temperatures is within the reasonable limit for forecast up to 5 days, though it deteriorates gradually with the length of forecast time. Weekly performance of the model for the whole region is remarkably good throughout the season in each of the years under study. It is noted that from the north to south, both root mean square error and correlation coefficient decrease.

10 illus, 3 tables, 15 ref

014832   Konwar M;Sarma D K;Das J;Sharma S (NO, Kohima Science College, Jotsoma, Kohima, Nagaland-797 002, Email: sanjay_sharma11@hotmail.com) : Shape of the rain drop size distributions and classification of rain type at Gadanki. Indian J Radio Space Phys 2006, 35(5), 360-7.

Three different rain drop size distribution (RDSD) models namely exponential, lognormal and gamma distribution are fitted to RDSD as spectra observed from Joss-Waldvodgel Disdrometer (JWD) at Gadanki (13.8°N, 79.18°E). Gamma distribution shows overall good agreement with observed RDSD for all ranges of rainfall rate. Rainfall rate calculated from gamma drop size distribution is found to have minimum root mean square error and biasing compared to exponential or lognormal distribution. The intrinsic shape of RDSD is found out from normalized RDSD which follows an "S" shape for both low rain ≤ 10 mm h^-1 and high rain <62> 10 mm h^-1. The convective and stratiform rains are separated for an event. The equations of separation for convective and stratiform rains have been derived assuming power law for log₁₀ (R) - D_m, log₁₀ (N₀) - log₁₀ (R) and log₁₀ (N₀) - D_m. The coefficients and exponent for these equations are α_DR =0.145, α_RN = 10³, α_DN =0.85x10^3.15, and β_DR =4.70, β_RN =-0.15, β_DN =-0.94 , respectively.

6 illus, 1 table, 19 ref

014831   Kane R P (Instituto Nacional de Pesquisas Espaciais (INPE), C.P. 515, 12245-970-Sao Jose dos Campos, SP, Brazil, Email: kane@dge.inpe.br) : Long-term variations of solar, interplanetary, geomagnetic indices and comic ray intensities-A brief tutorial. Indian J Radio Space Phys 2006, 35(5), 312-23.

The long-term variations of the 12-month running means of several solar, interplanetary and geomagnetic parameters during the last several sunspot cycles revealed that during cycles 11-23 (1868-2004), the geomagnetic act index showed several peaks within 3-5 years around the sunspot maxima, with some peaks during the declining phases of the sunspot cycles, whereas the sunspot numbers R_z showed smooth but broad maxima for 2-3 years in each cycle. The calcium plage area also showed multiple peaks but none in the declining phases. The 11-yr running means showed very good parallelism between R_z aa index and global sea-surface temperature (SST). During 1940-2004, R_z and F10 (2800 MHz radio emission) showed similar 11-yr fluctuations of varying amplitudes, but coronal index, CI, showed monotonically increasing amplitudes by almost a factor of two. The open magnetic flux emanating from the sun during 1968-2004 showed long-term fluctuations, very different at low and high solar latitudes. The variations of the fluxes at low latitude (0-45°) were almost parallel to the sunspot cycle (there was a slight N-S asymmetry), while fluxes at high latitudes (45°-90°) were almost anti-parallel to the sunspot cycle. Cosmic ray neutron monitor intensities at Climax were well anti-correlated with sunspot cycle and interplanetary magnetic field (B), but poorly correlated with interplanetary number density (N), solar wind speed (V), and geomagnetic index aa. The geomagnetic index aa was best correlated with the product VB.

3 illus, 1 table, 34 ref

014830   Joshi R R;Narender Singh;Deshpande S M;Damle S H;Pant G B (NO, Indian Institute of Tropical Meterology, Dr. Homi Bhabha Road, Pashan, Pune-411 008) : UHF wind profiler observations of monsoon low level jet over Pune. Indian J Radio Space Phys 2006, 35(5), 349-59.

Data from a UHF (404 MHz) wind profiler during the active monsoon periods in 2003, 2004 and 2005 have been analyzed. Details of July 2003 as representative have been presented, which clearly show existence of jet stream over the wind profiler site at Pune (18.3 °N, 73.5 °E) throughout the day and night. The paper presents observed occurrence statistics of low level jet (LLJ) during monsoon month of July 2003. Wind speeds in excess of 20 ms^-1 are frequently observed during active monsoon phase and peak found around a height of 2-3 km. Wind speed then decreases on either side of the peak without more than 40° change in the prevailing wind directions. The evolution of monsoon LLJ, particularly its diurnal variation and its difference with respect to nocturnal LLJ phenomenon have been brought out. The observed vertical velocities are predominantly upward, up to 4 km in the presence of LLJ with mean downward momentum flux. This upward directed clear air vertical velocities probably help in developing convective systems. The energy dissipation rates (C) are also estimated and shown to be maximum near the LLJ height.

14 illus, 20 ref

014829   Gupta M;Mishra V K;Tiwari D P;Mishra A P (Physics Dep, A P S Univ, Rewa, Madhya Pradesh, Email: vkmishra74@yahoo.com) : Occurrence of type-I radio bursts and their association with solar cycle. Indian J Radio Space Phys 2006, 35(5), 324-6.

A minimum between solar cycle 22 and 23 has been defined earlier on the basis of type-I radio burst only. In the present paper a re-visit to the occurrence of type-I radio bursts in relation to general level of solar activity (sunspot number) is made covering the minima of cycle 21 to complete cycles 22-23. The study shows that, it is not appropriate to speculate solar cycle minima on the basis of type-I radio burst only.

2 illus, 15 ref

014828   Devikar P T;Pandey V K;Pandey R P (Soil and Water Engineering Dep, Faculty of Agricultural Engineering, Indira Gandhi Agricultural Univ, Raipur-492 006) : Analysis of pattern of past meterorological drought of Tel basin using standardized precipitation index. Indian J Soil Conserv 2006, 34(3), 195-8.

Study was aimed at drought severity analysis for different time scales using Standardized Precipitation Index (SPI) estimated for 1, 3, 6 and 12 months for monthly rainfall record of five raingauge stations viz. Bhawanipatna, Dumerbhal, Sunder, Sipala and Tikhali in Tel basin, of Mahanadi river system located in western part of Orissa. The study revealed that the selection of time scale for SPI estimation plays a significant role in analyzing the past meteorological drought events in the region. Phase pattern of z-score values with monsoon rainfall shows that the drought condition in the basin occurs mostly due to rainfall anomalies during the months of June to November. The SPI follows a trend similar to seasonal rainfall (June- November) of the basin.

4 illus, 2 tables, 12 ref

014827   Devender Singh;Bhatia R C (India Meterorogical Department, Lodhi Road, New Delhi-110 003) : Study of temperature and moisture profiles retrived from microwave and hyperspectral infrared sounder data over Indian regions. Indian J Radio Space Phys 2006, 35(4), 286-92.

The neural network technique has been used to retrieve atmospheric temperature and moisture profiles using Advanced Microwave Sounding Unit (AMSU) measurements onboard National Oceanic Atmospheric Administration (NOAA K, L and M) satellites over Indian region in real time. An attempt has been made to inter-compare these profiles, which are being generated from two different sets of spectral wavelengths-one from infrared and the other from microwave. These inter-comparisons have been made for the month of January and August 2004. It has been found that in general, the temperature and moisture profiles retrieved using microwave data at India Meteorological Department (IMD), New Delhi, are comparable with the temperature and moisture profiles from advanced infrared sounder (AIRS) data.

5 illus, 17 ref

014826   Deshpande S M;Kulkarni J R;Joshi R R;Singh N; Damle S H;Pant G B (NO, Indian Institute of Tropical Meteorology, Pune-411 008) : Atmospheric subsidence and the surface temperature variability in the pre-monsoon month over a semi-arid north peninsular Indian station. Indian J Radio Space Phys 2007, 36(1), 33-43.

Variability in maximum temperature in the month of March 2004 over Pune, a station representative of semi-arid region of north peninsular India, has been studied. The vertical wind velocity data measured by UHF wind profiler, installed at Pune (18.31°N, 73.58°E) has been utilized. Hourly averaged vertical wind velocity profiles were obtained four times a day, on a three hourly basis from 0800 to 1700 hrs IST (Indian Standard Time) in March 2004. The vertical velocity is found to have a typical mean and standard deviation of 10 and 15-20 cm/s, respectively. The mean structure of the vertical distribution showed predominately upward motion extending up to 2-3 km and predominately downward motion in the 3-6 km layers. After removing the effects of radiative and advective heating, the anomalies in the maximum temperature over Pune are found to be statistically related with the depth of the atmospheric column over which the subsidence occurs.

10 illus, 1 table, 18 ref

014825   De S S;De B K;Guha A;Mandal P K (Centre for Advanced Study in Radio Physics & Electronics, Calcutta Univ, Kolkata-700 009, Email: de_syam_sundar@yahoo.co.in) : Detection of 2004 leonid meteor shower by observing its effects on VLF transmission. Indian J Radio Space Phys 2006, 35(6), 396-400.

Results of the detection of 2004 Leonid meteor shower over Kolkata (22°34' N, 88°30' E). India is presented in this paper, by using a VLF amplifier tuned at one of the transmission frequencies of Indian Navy Traffic stations at Vijayananarayanam (8°25'59.88"N, 77°48' E) at 16.3 kHz. The shower was predicted to exhibit a peak activity on 19 Nov. 2004. In spite of low ZHR predicted, the peak activity had been observed earlier than the predicted times, which confirms the nongravitational 'A2 effect' on meteoioid trails. The observation also suggests that electromagnetic detection of meteor shower is better than the visual observation, as any time of day and night its effect on VLF transmission can be recorded.

6 illus, 2 tables, 14 ref

014824   Das I M L;Pramod Kumar, (M N Saha centre of Space Studies, University of Allahabad, Allahabad-211 002, Email: drimldas@yahoo.com.) : Retrival of the vertical temperature profile at atmosphere from MST radar backscattered singal. Indian J Radio Space Phys 2006, 35(4), 280-5.

The vertical temperature profile of the tropical lower atmosphere has been reconstructed from the backscattered signal received by Indian MST radar located at Gadanki (13.47°N, 79.2°E). The reconstructed temperature profile compares well with the altitude variation of temperature obtained from the simultaneously launched radiosonde flight.

3 illus, 11 ref

014823   Calla O P N;Bohra D;Agarwalla S K;Ghosh S; Bohra C;Vyas R (International Centre for Radio Science, , A-23, Shastri Nagar, Jodhpur-342 003) : Comparison of emissivity and scattering coefficient of two samples of Aravali rocks and dry soils of Rajasthan at frequencies of X-band. Indian J Radio Space Phys 2007, 36(1), 65-71.

By the action of climate and living organism, soil is formed from weathered rock. It inherits the mineral matter and organic matter from its parent rock and living organisms, respectively. The study of the emission behaviour and scattering behaviour of both soil and rock of a particular place is thus important, as the electrical properties of them may be different. In the paper, the comparison of emissivity and scattering coefficient values of loamy sand and pure sand type dry soils of Rajasthan and Aravali rock samples has been made. The values are estimated at microwave frequencies.

9 illus, 7 tables, 11 ref

014822   Bahduri S K;Banarjee D;Ghosh J B;Saha C;Roy N K;Das D K (Chemical Division, Eastern Region, Central Chemical Laboratory, Geological Survey of India, 15 Kyd Street Kolkata-700 016) : Analysis of stream sediment and soil samples by xrf spectrometry. Indian Miner 2005, 59(3,4), 115-22.

A pressed pellet XRF method was developed for determination of 27 elements, 10 major as well as minor and 17 trace elements (Cu, Pb, Zn, Ni, Co, Ba, Sr, V, Cr, Sc, Ga, Y, Nb, Zr, U, Th and Rb), in stream sediment and soil samples. In this method 4.5g of finely powdered and homogenised sample is pressed as a uniform disk of 37-mm diameter on a boric acid base in an aluminium cup. The pellet is irradiated and its fluorescence is measured on a Philips W'D PW 2424 MagiX XRF Spectrophotometer using Rh target X-ray tube operated at 2.4 KW. Twenty-four stream sediment and soil reference materials were used for calibration of the instrument. Three stream sediment and soil reference materials (GSD-6, GSD-12 and GSS-3) were analysed following the method developed and the results obtained are in good agreement with the recommended values. The detection limit achieved for many of the trace elements is in the order of 3 ppm. The method is fast and accurate and a large number of samples can be analysed in a short time.

1 illus, 6 tables, 11 ref

014821   Ashok Kumar;Singh S V;Singh K D;Prasad S N (NO, Central Soil and Water Research Conservation Research and Training Ins, ) : Long-term evaluation of watershed development project in south-eastern Rajasthan. Indian J Soil Conserv 2006, 34(3), 244-8.

Attempt has been made to assess returns to investment in the model Chhajawa national watershed development project executed during 1985-89 in south-eastern Rajasthan. The evaluation was based on data gathered through households survey of all the beneficiaries during 1997-98, and data of previous 12 years collected from various records and reports for testing the economic feasibility. Various indicators such as crop productivity index, cultivated land utilization index and crop diversification index were employed to assess the impact of different activities. The study revealed that land utilisation in the watershed increased by 57%, and gross irrigated area increased from 32.5 ha to 376.7 ha over a period of 12 years. A complete shift in cropping pattern in favour of more remunerative and quality crops such as soybean in kharif season and mustard, coriander and wheat in rabi season was observed. A remarkable improvement in the yield of all the crops were recorded. The significant improvement in land utilization and crop productivity was observed but diversification was reduced. The average productivity increased by 87% and gross returns from agriculture and dairy sectors increased by 8 times since project inception. Benefit-cost ratios for the increased crop and milk production was worked out to be 2.34 and 1.30, respectively. The overall B : C ratio was found to be 2.03 with a discount rate of 12%. The results suggest the economic viability of watershed management project in rainfed areas.

5 tables, 10 ref

014820   Ashok Kumar;Gupta V B;Jain S L;Ghude S D; Kulkarni P S (School of Future Studies and Planning, Devi Ahilya University, Indore-425 017, Email: ashok_kumarg@yahoo.com) : Surface ozone variability between two different antarctic sites. Indian J Radio Space Phys 2007, 36(1), 59-64.

Deals with the temporal and spatial variability of 365 days hourly mean surface ozone data for Syowa and McMurdo stations in Antarctica. The analyses not only show the seasonal and diurnal variation of surface O₃ in Antarctica, but also present statistics of surface O₃ variability on temporal scale. Diurnal variations of 3.9% and 0.8% have been observed in surface O₃ at Syowa and McMurdo, respectively. Surface O₃ during summer season at Syowa and McMurdo stations is observed to be 56% and 64%, respectively. The correlation between the surface O₃ concentrations at Syowa and McMurdo stations implies that the 18% of the variation is due to local weather conditions.

5 illus, 22 ref

013665   Stephen J (NO, National Geophysical Research Institute, Hyderabad-500 007) : Elastic strength and anisotropy of the continental lithosphere of India. Proc Indian Natn Sci Acad 2006, 72(3), 135-43.

Elastic strength of the Indian lithosphere is reviewed giving emphasis to the estimation of effective elastic thickness (Te) and its azimuthal variation showing the major weakness directions in the lithosphere. The estimations were carried out using advanced 2D multitaper (MTM) and mirrored periodogram (MPM) spectral based Bouguer gravity and topography coherence analysis and a comparison is made. These estimates differ considerably yielding an exaggerated Te from the MPM. However, both these estimations evidenced relatively low elastic strength for the entire Indian lithosphere compared to many other parts of the world. The study also depicts a noticeable variation across the central Indian tectonic zone, which acts as a major divide in the Indian shield. A higher Te range (20-25 km) is obtained for the northern region than the southern region (12-16 km). These values are almost in agreement with the prevailing earthquake focal depths, where there is more shallow earthquakes in the south than the north. This suggests that the elastic thickness is nearly confined within the seismogenic thickness. The present anisotropic results are in good agreement with the stress orientations in the north depicting the plate movement directions, whereas scattered in the south.

6 illus, 58 ref

013664   Shyamala B;Bhadram C V V (NO, , Green Park Wing A, Flat 204, Raheja Estate, Kulupwadi, Borivli East, Mumbai-400 066, Email: iyershyamala@rediffmail.com) : Impact of mesoscale-synoptic scale interactions on the Mumbai historical rain event during 26-27 July 2005. Curr Sci 2006, 91(12), 1649-54.

Exceptionally heavy rainfall event during 26-27 July 2005 over Mumbai and Thane districts has been analysed. Identify the meteorological conditions that possibly caused the phenomenally heavy rainfall. Using satellite and radar inputs combined with synoptic and thermodynamic analysis, it was found that formation of mesoscale convective systems over Mumbai, comprising super thunderstorm cells and their interaction with the synoptic scale low-pressure area from the Bay of Bengal led to the concentrated very high intensity rainfall.

6 illus, 2 tables, 10 ref

013663   Satpathy K K;Natesan U;Kalaivani S;Mohanthy A K;Rajan M;Baldev Raj (Enviromental and Industrial Safety Section, Safety group,, Indira Gandhi Centre for Atomic Research, Kalapakkam-603 102) : Total dissolved copper concentration in coastal water of Kalapakkam. Curr Sci 2006, 91(8), 1008-10.

1 illus, 1 table, 11 ref

013662   Ramasamy SM;Kumanan C J;Selvakumar C J; Saravanavel (Centre for Remote Sensing, School of Geosciences, Bharathidasan University, Tiruchirappalli-620 023, Email: cersbard@yahoo.co.in) : Anthropogenic input in Asian mega tusnami (2004) disaster along Tamilnadu coast India. Curr Sci 2006, 91(8), 1013-4.

1 illus, 5 ref

013661   Ramasamy S M;Saravanavel J;Yadava M G;Ramesh R (Centre for Remote Sensing, School of Geosciences, Bharathidasan University, Tiruchirappalli-620 023, Email: cersbord@yahoo.co.in) : Radiocarbon dating of some palaeochannels in Tamil Nadu and their significance. Curr Sci 2006, 91(12), 1609-13.

2 illus, 38 ref

013660   Pant P;Hedge P;Dumka U C;Saha A;Srivastava M K;Ram Sagar (NO, Aryabhatta Research Institute of Observation Sciences, Manorra Peak, Nainital-263 129, Email: ppant@aries.ernet.in) : Aerosol characteristics at a high altitude location during ISRO-GBP l and campaign-II. Curr Sci 2006, 91(8), 1053-61.

Detailed analysis of the extensively measured aerosol parameters at the Aryabhatta Research Institute of Observational Sciences (ARIES), Manora Peak Nainital, during ISRO-GBP Land Campaign-II This land campaign was focused on the winter monthly of December 2004, using eight fixed stations distinctly located over the Gangetic belt in the North Indian corridor, where thick fog conditions generally prevail during winter. Among these stations, Manora Peak was selected due to its high-altitude location, at an altitude of -2 km, having a pristine location in the Shivalik Ranges of Central Himalayas and allowing a free tro-pospheric siet. The diurnal variation of BC mass concentration shows a typical behaviour compared with other low-altitude stations, where simultaneous measurements were made by other investigators during the campaign. This behaviour in the diurnal trend of aerosols is due to the topography and the boundary-layer dynamics over the high-altitude station of ARIES of Nainital.

9 illus, 25 ref

013659   Nayak G K;Agarwal P K;Rama Rao C;Pandey O P (NO, National Geophysical Research Institute, Hyderabad-500 007, Email: goutam_mi@hotmail.com) : Thickness estimation of Deccan flood basalt of the Koyna area, Maharashtra (India) from inversion of aeromagnetic and gravity data and implications for recurring seismic activity. Curr Sci 2006, 91(7), 961-5.

Thickness estimation of volcanic suite and delineation of underlying Achaean basement topography using geophysical methods have always been a challenging-problem confronting the geoscientific community. In most cases, their estimations are unsatisfactory due to lack of quality dataset or inverse geological situation, where high susceptibility/velocity rocks at the surface are underlain by low susceptibility/velocity rocks. In order to circumvent the above situation, an inversion scheme has been attempted to model aeromagnetic and gravity datasets acquired over the seismically active Koyna region situated over the Deccan Traps of western Maharashtra. Inversion of aeromagnetic data results into a Deccan basalt thickness of about 1500 m below the Koyna region. Further, inversion of gravity data indicates that the entire column of lava below this region is made up of non-massive vesicular type of basalts having a low density of 2.58 g/cm³ and a porosity of about 17%. Presence of vesicles, faults and fractures within the porous basaltic column appears to facilitate the diffusion of fluid in the surrounding medium and in the basement, thus causing the reactivation of faults which may be responsible for recurring seismic activity in this region.

8 illus, 1 table, 32 ref

013658   Nalina E;Puttaiah E T (Chemistry Dep, A.I.T., Chikmagalur) : Characteristics of ground water quality of Kadur taluk - a preliminary observation. Ecol Envir Conserv 2006, 12(4), 617-20.

Deals with physico-chemical analysis of ground water of Kadur taluk area. The analysis of bore well water is carried out to examine its suitability for drinking purposes. For the analysis the ground water samples were collected both from the bore wellard hand pumps of the area. The data generated was compared with reference to BIS and WHO standards 1991. It is found that some of the physicochemical, parameters are within the maximum permissible limits of drinking water standards. However, fluoride was found to be less than 1mg/L in about 25% of the bore well sample studied. While about 80% of the samples showed more of hardness. Further the other parameters such as conductivity, TDS, nitrates and iron were found to be high in about in 10-12% sample. The study also reveals that the ground water of area is very hard and is dominated by carbonate and bicarbonate anion with calcium and magnesium cations.

6 illus, 11 ref

013657   Karanth R V;Thakker P S;Gadhavi M S (Geology Dep, Baroda M.S. Univ, Vadodara-390 002, Email: r_v_karanth@yahoo.co.in) : Preliminary report on the possible impact crater of Kachchh. Curr Sci 2006, 91(7), 877-9.

3 illus, 9 ref

013656   Jafri S H;Subba Rao M V;Ramesh S L (NO, National Geographical Research Institute, Hyderabad- 500 007, Email: syed1401@rediffmail.com) : Occurence of ash beds in radiolarian cherts from South Andaman Island, Bay of Bengal, India: Evidence for late cretaceous explosive volcanism. Curr Sci 2006, 91(12), 1614-15.

3 illus, 21 ref

013655   Hussain S M;Krishnamurthy R;Sureh Gandhi M; Ilayaraja K;Ganesan P;Mohan S P (Geology Dep, University of Madras, Guindy Campus, Chennai-600 025, Email: hussain.sm7@gmail.com) : Micropalaeontological investigations on tsunamigenic sediments of Andaman Islands. Curr Sci 2006, 91(12), 1655-8.

Inorder to understand the type of microfauna (Fora-minifera and Ostracoda), which might have been transported by tsunamigenic sediments that deposited on the beaches, estuaries/creeks and mangrove location of Andaman Islands, a detailed fieldwork has been carried out from these islands. Record and document the calcareous microfaunal assemblage and its distribution pattern in the tsunamigenic sediment samples collected from Andaman group of Islands. Total of 46 surface and nine core samples have been collected from various coastal geomorphological features such as beaches, estuaries/creeks and mangrove areas of Andaman Islands. These samples are analysed for Foraminifera and Ostracoda, by applying standard micropalaeontological techniques. It is inferred that the 26 December 2004 tsunamigenic sediments deposited on the coastal landforms in Andaman group of islands have been derived from shallow littoral to neritic depths and not from deeper bathyal territories.

7 illus, 2 tables, 11 ref

013654   Dan singh;Ganju A (Research and Development Centre, Snow and Avalanche Study Establishmen, , Chandigarh-160 036, Email: dan_@rediffmail.com) : Improvement in nearest neighbour weather forecast model performance while considering the previous day's forecast for drawing forecast for the following day. Curr Sci 2006, 91(12), 1686-91.

Nearest neighbour model for prediction of weather in terms of snow day/no snow day for consecutive three days in advance (lead time up to 72 h) was tested in two different modes of prediction for two different stations; Dhundi in Himachal Pradesh and Stage-II in Jammu and Kashmir (J&K), in the Pir Panjal range of NW Himalaya, with two different types of data. The model performance was tested with incomplete and complete data respectively, in two different modes. Prediction of weather is made based on the probability of snowfall calculated from nearest days/nearest situations. Prediction was made considering the previous day's probability of snowfall also, along with the probability of snowfall calculated from nearest days/situations, i.e. while forecasting for day-2 (lead time 48 h), probability of snowfall for day-1 (lead time 24 h) is also taken in to account. Model performance is found to be better for mode II compared to mode I for all three days except for day-1 forecast with incomplete data.

2 illus, 4 tables, 15 ref

013653   Chandrasekar K;Sesha Sai M V R;Jeyaseelan A T;Dwiwedi R S;Roy P S (National Remote Sensing Agency, , Hyderabad-500 037, Email: Chandrasekar_k@nrsa.gov.in) : Vegetation response to rainfall as monitored by NOAA-AVHRR. Curr Sci 2006, 91(12), 1626-33.

Rainfall is an important meteorological parameter, which influences the type of vegetation in a region. The relationship between rainfall and vegetation is well established but it varies from region to region. Normalized Difference Vegetation Index (NDVI) is a< simple index to monitor vegetation which can be derived from satellite data. Use of NDVI is well established in assessing the vigour and productivity of the vegetation. An attempt has been made to find the relation between rainfall and NDVI in a few districts of Andhra Pradesh, India. The mean of maximum NDVI from 1989 to 1998 is correlated with seasonal normal rainfall. The NDVI lag to the monthly rainfall and reason for the lag based on land use of the districts was investigated. Districts were classified based on their NDVI profile and coefficient of variation of NDVI and finally the first three-month cumulative southwest monsoon rainfall effect on the seasonal cumulative NDVI of the district was correlated. The result shows that there is a high degree of correlation (r = 0.81) between the mean of maximum NDVI with the normal rainfall. The NDVI lags rainfall by two months in most of the districts and the initial three months rainfall correlates well with the seasonal cumulative NDVI.

5 tables

013652   Agrawal S K;Chawla J (Central Building Research Institute, Roorkee-247 667, , Email: agrawal_shaileshkr@yahoo.com) : Seismic hazard assessment for Delhi region. Curr Sci 2006, 91(12), 1617-24.

Seismic hazard assessment is the process of evaluating the design parameters of earthquake ground motion at any site. The design parameters most widely used are intensity and peak ground acceleration (PGA). Some-times peak velocities, peak displacements and response spectrum are also used. Seismic hazard assessment can be carried out either in the deterministic framework or probabilistic framework. It is more appropriate to estimate seismic hazard at a given place in probabilistic terms. This can be done in two ways: (i) estimating the probability with which a prescribed level of strong ground motion, say, 0.1 g (in terms of PGA), is exceeded over a period of, say, 50 years; (ii) estimating the PGA which is exceeded with a prescribed probability, say, 10%, in a period of, say, 50 years. The main objective of the communication is to estimate earthquake hazard in Delhi region in two ways, i.e. (i) estimating the probability with which a prescribed level of strong ground motion (in terms of PGA), is exceeded over a certain period (in years), which is taken as 50 years; and (ii) estimating the PGA which is exceeded with a prescribed probability over a prescribed period, which is taken as 10% probability of exceedance within 50 years. The results are presented in the form of contour maps spreading over Delhi region depicting exceedance probabilities and PGAs. These hazard maps are of paramount importance for seismic zonation for building codes, designing earthquake-resistant new structures, estimating vulnerability of existing structures and their retrofitting, and finally for future habitat planning.

3 illus, 11 ref

011481   Virdi N S;Philip G (NO, Wadia Institute of Himalayan Geology, Dehra Dun, Email: gphilip@wihg.res.in) : Neotectonic activity and its control on drainage changes in the Northwestern frontal Himalaya between the rivers Satluj and Yamuna. Himalayan Geol 2006, 27(2), 129-44.

In an active orogenic belt like the Himalaya, the terminal phases of orogenesis are responsible for carving out the present day topography and physiographic features. In the Western Himalaya, effects of neotectonic activity are manifested along major and active faults and lineaments, which have exercised a profound control on alignment of channels of many rivers and their tributaries. Past activity along major active faults have not only produced seismicity but also caused slope failures resulting into landslides and debris flows. The drainage channels are often temporarily blocked by slope failures resulting into formation of lakes in the upstream regions. Remnant lacustrine deposits and high level terraces are witnesses to past instabilities and channel alignments. Movements along active faults also cause uplift or subsidence of the terrain and result into shifts in drainage channels and capture by other streams or river piracy due to accelerated head ward erosion. Aerial photos, satellite images and topographic maps supported by field checks have revealed numerous examples of drainage changes in the north western Himalaya, in Himachal and Uttaranchal river basins, owing to neotectonic activity. Dexcribes some known and newly recognized examples of drainage changes due to neotectonic activity in the Outer Himalaya between the Satluj and Yamuna rivers.

11 illus, 30 ref

011480   Upadhyaya A;Singh A K;Sikka A K (ICAR Research Complex for Eastern Region, , Walmi Complex, Phulwari Sharif, Patna-801 505) : Consecutive days maximum rainfall prediction using one-day maximum rainfall. Int J Trop Agric 2006, 24(3-4), 501-6.

In order to determine drainage coefficient and to evolve drainage criteria it is necessary to analyze daily and consecutive days maximum rainfall of various return periods that creates the problem of water congestion in the area. Daily rainfall of 40 years at Patna was studied and 1-day as well as 2 to 6 consecutive days maximum rainfall was computed corresponding to various return periods using Gringorten's plotting position method. A simple mathematical relationship was obtained to correlate I-day maximum rainfall, number of consecutive days and consecutive days maximum rainfall. Results show that the mathematical relationship is capable enough to predict reliable values of 2 to 6 consecutive days maximum rainfall of various return periods using 1-day maximum rainfall. Results also reveal that the maximum percentage error in the predicted values at Patna is 2.02 percent only.

7 tables, 4 ref

011479   Srivastava P K;Manhas R S;Ansal A (Geology Dep, Jammu Univ, Jammu-180 006) : Geochemistry of magnesite from Tundah, Chamba district, Himachal Pradesh: evidence for genesis. Himalayan Geol 2006, 27(2), 189-99.

The Veitsch type magnesite mineralization from Tundah (Chamba district) is hosted within the dolomitic bands of the Batal Formation. It is present in the form of lensoid body trending NW-SE. Replacement of dolomite by magnesite along the margin and fractures at mega and micro scales are very frequently observed. Magnesite occurs as grey to white coloured sparry crystals embedded within the fine gained carbonaceous matrix. The magnesite and host dolomite show comparable bulk content of MnO, P₂O₅ and SiO₂, while Al₂O₃ is higher in dolomite. MgO content of magnesite varies from 30.47 to 38.80%. CaO (3.93-12.42%) in magnesite is on the higher side suggesting the presence of dolomite as micro-inclusions. Trace element content of the magnesite suggests a higher concentration of Sr, Rb, Cs, Ni and Co with respect to the host dolomite. The total REE content of the magnesite is low having a limited range (4.18-6.69 ppm). (Ce/Yb)CN ratio for magnesite is less than dolomite. Chondrite normalized RRE pattern for magnesite and host dolomite show different trends suggesting different origins. The positive Ce and negative Eu anomalies suggest the presence of impurities in the magnesite which is also indicated by its higher Al₂O₃ content.

7 illus, 3 tables, 32 ref

011478   Singh T;Devi M (Wadia Institute of Himalayan Geology, North East Unit, Itanagar-791 113, Email: tskaith@rediffmail.com ) : Landslide occurrences and risk assessment in Itanagar capital complex, Arunachal Himalaya. Himalayan Geol 2006, 27(2), 145-62.

Itanagar Capital Complex, which came into existence only in 1981, has reached a critical state of human settlement and other developmental activities. A number of lineaments and active faults have made the area more vulnerable to the landslides, which are occurring not only along the roads but also in the urban agglomeration area. Nearly 46 major landslides have been recorded and detailed inventory of these landslides has been prepared. The landslides, which include both old and presently active slides, are located within the unconsolidated Quaternary deposits and poorly cemented Siwalik sediments. Landslides, and other geologic and geomorphic features suggest that the area is tectonically unstable and geodynamically active. Risk due to landslide occurrences has been assessed in terms of damage potential to loss of life, land and property. It indicates that most of the Itanagar urban agglomeration falls under the Low to Moderate Risk category. A few isolated areas of this agglomeration, however, fall under High to Very High Risk category, which have particularly been resulted due to disturbance of natural stabilized slopes; at some places due to disturbing the natural course of streams; and at some places because of gully erosion. The sector between Banderdewa and Itanagar on the National Highway - 52A mostly falls under low to moderate risk slopes, whereas the sector between Chimpu and Solangi (locally spelled as Holangi) falls under High to Very High Risk category.

10 illus, 1 table, 13 ref

011477   Singh A K (Wadia Institute of Himalayan Geology, Northeast Unit, Itanagar-791 113, Email: kk_luwang@rediffmail.com) : Petrography, geochemistry and petrogenesis of Abor volcanics, Eastern Himalayan syntaxial bend. Himalayan Geol 2006, 27(2), 163-81.

The core of the Siang Window of Eastern Himalayan Syntaxial Bend exhibits the presence of thick pile of mafie volcanic rocks known as Abor volcanics and sedimentary sequences. The mafic volcanic rocks are dominated by basalt with subordinate basaltic andesite and agglomeratic basalt. Their sub-aqueous and violent eruption natures of volcanism are indicated by the presence of pillow structures and pyroclastics, respectively. They are predominantly subalkaline-tholeiitic affinity with minor alkaline affinity. Petrographically, tholeiitic basalt exhibits subophitic, glomeroporphyritic, intergranular, intersertal and trachytic textures and consist of plagioclase (An₅₇-An₄₃), pyroxene (augite-pigeonite), Fe-Ti oxides (magnetite, ilmenite) and volcanic glasses whereas alkaline basalt is characterized by the presence of alkali feldspar phenocrysts and absence of plagioclase phenocryst; groundmass is composed of clinopyroxene, plagioclase, alkali amphibole, apatite, titanite, feldspar, epidote, Fe-Ti oxides exhibiting intergranular to intersertal and variolitic textures with occasionally sub-ophiolitic texture. The tholeiitic basalt is enriched in large ion lithophile elements (LILE), light rare earth elements (LREE), depleted in high field strength elements (HFSE) and REE fractionated nature [(La/Yb)_N = 3.01-7.47)] along with insignificant Eu anomaly illustrate their close similarity with low-Ti basalt (Ti/Y <60>500). Alkali basalt shows significantly high value of TiO₂, P₂O₅, K₂O, Rb, Sr, Ba, Zr, Th; depleted in SiO₂, Na₂O, Al₂O₃ and Fe₂O₃ which is identified as high-Ti basalt (Ti/Y <62>500). It has extremely enriched REE [ΣREE (515-779.29)] with strongly fractionated REE abundances [(La/Yb)N = 26.34-44.10]. Enrichment of incompatible elements and LREE in alkaline basalt suggested that the source was affected by a melt phase enrichment and compatible with H₂O or CO₂ rich fluid phase metasomatism in the mantle. Similarity in immobile trace element compositions together with their ratio (rock)/ratio (PM) and normalized multi-element abundances reveal their cogenetic nature. Geochemical and petrogenetic studies suggest that they might have generated from enriched mantle source by multi-stage metasomatic processes with varying degrees of partial melting and they were emplaced in the 'within plate' tectonic setting.

12 illus, 2 tables, 65 ref

011476   Mundepi A K; (NO, Wadia Institute of Himalayan Geology, 33, GMS Road, Dehradun-248 001, Email: akmundepi@wihg.res.in) : Effective soft sediment thickness in Dehradun city (India) using ground ambient vibrations. Himalayan Geol 2006, 27(2), 183-8.

The densely populated city of Dehradun is located in a tectonic valley near a highly seismically active region in Himalaya. An estimate of the soft sediment thickness provides the basic information to the geotechnical engineers for the calculation of local site amplification, which in turn contributes to the seismic hazard assessment of the region. The ground ambient vibrations were used to estimate the predominant frequencies of the soil and then the soft sediment thickness at the respective sites.

5 illus, 21 ref

011475   Ibotombi S (Earth Sciences Dep, Manipur Univ, Imphal-795 003, Email: ibotombi2002@yahoo.co.uk) : Relative plate motions in and around Manipur and its implications on the tectonics of Indo-Myanmar ranges. Himalayan Geol 2006, 27(2), 111-22.

Computation of relative plate motions in and around Manipur using rotation vectors given by various workers yields interesting results. Motion of India plate relative to Eurasia plate (_EV₁) has a velocity of about 5.45 cm yr^-1 towards NNE. Similarly relative motion of Myanmar (Burma) plate with respect to the China (Eurasia) plate (_EV_M) is found to have an approximate value of 3.50 cm yr^-1 towards N. These plate motions are nearly parallel to the regional tectonic trend (NNE-SSW or N-S) of the Indo-Myanmar Ranges (IMR) and so, may not be directly responsible for the evolution of the IMR. As a result, rotation vectors of India and Myanmar plates pair is worked out and their relative motion computed. Rotation vectors of the plate pair is found to be as - pole of rotation: 36.83°N, 78.77°E, and relative angular velocity (ω) = 7.967x10^-7deg yr^-1. And relative motion of India plate with respect to Myanmar plate (MV:) is about 2.75 cm yr^-1 towards NE. Possibly motion of India plate relative to Myanmar plate is responsible for the evolution of the IMR of the Northeast India since the tectonic structures of the range can develop at about 45° to the motion vector under a dextral shear couple mechanism.

7 illus, 4 tables, 54 ref

011474   Gupta R P;Sarkar I (Department of Earth Sciences, Indian Institute of Technology Roorkee, Roorkee-247 667, Email: rpgesfes@iitr.ernet.in) : Earthquake evidence for active extension of some major lineaments in Garhwal Himalaya. Himalayan Geol 2006, 27(2), 123-8.

The Garhwal Himalaya lie within a prominent seismic gap. About an intense zone of local contemporary small-magnitude (m_b≤ 5.0) earthquake activity in the area that appears to be closely related to a set of major transverse lineaments observed on satellite sensor images, both in terms of three-dimensional spatial distribution and source mechanism has been reported. The clustering of these small events in the vicinity of the termini of these lineaments suggests that the geological discontinuities corresponding to these lineaments are presently in the process of lateral extension and active development. In terms of reliable seismic hazard assessment of the region, the identification of these lineaments, exhibiting distinct seismic activity, appears highly significant.

5 illus, 26 ref

011473   Chamlagain D;Hayashi D (Physics and Earth Sciences Dep, Ryukyus Univ, Okinawa, 903-0213, Japan, Email: dchamlagain@hotmail.com) : Numerical modelling of graben faults with special reference to Thakkhola Half Graben, Central Nepal Himalaya. Himalayan Geol 2006, 27(2), 95-110.

Thakkhola half graben is a product of Late Cenozoic extensional tectonics in the Himalaya-Tibetan region. A series of 2D finite element models are generated to simulate its first order characteristics using stress field and induced fault pattern as structural proxies. Extensional graben faults form in the upper weak layer and propagate downward with increasing extension. Clusters of failure elements at the two ends of the graben directly correspond to the graben bounding faults and the asymmetric feature is characterized by uneven development of faults therein. The syntectonic deposits are characterized by normal fauls in the tensional stress field, which is a common feature of the small-scale graben at post rift deformation stage. The proposed models suggest that depth of a graben growth fault is primarily controlled by the initial fault and density of the syntectonic deposits. Assumption of a weak zone (Thakkhola fault system) does not make significant difference in stress distribution and faulting. It is thus suggested that a weak zone only can not contribute to the development of a half graben. The spreading boundary condition could not simulate the existing fault configuration in the Thakkhola half graben. Our modelling results for the graben suggest gravitational collapse of the elevated plateau rather than mantle upwelling during spreading.

16 illus, 1 table, 38 ref

012609   Vinod Kumar K;Martha T R;Roy P S (NO, National Remote Sensing Agency, Balanagar, Hyderabad-500 037, Email: vinodkumar_k@nrsa.gov.in) : Detection of volcanic eruption in Barren island using IRS P6 A WiFS. Curr Sci 2006, 91(6), 752-3.

3 illus, 4 ref

012608   Tiwari V M;Singh B;Vyaghreswara Rao M B S; Mishra D C (NO, , Hyderabad-500 007, Email: vmtiwari@ngri.res.in) : Absolute gravity measurements in India and Antarctica. Curr Sci 2006, 91(5), 686-9.

Series of absolute gravity measurements have been made at National Geophysical Research Institute, Hyderabad and at Maitri, Indian Antarctic station to establish precise reference gravity stations and also to monitor long-term gravity changes for different geophysical studies. These precise measurements are made with an FG-5 absolute gravity meter, which measures the gravitational acceleration with an accuracy of 20 nm-s^-2 (2 μGal). Non-tidal time series of measured absolute gravity values at these locations indicate systematic daily and seasonal variation of variable amplitudes. Daily changes are probably caused due to inaccurate global tidal model used in processing of data and suggest a need for better tidal model for the Indian subcontinent. Seasonal changes appear to be mainly caused due to hydrological effects, which can be modelled to derive the aquifer parameters.

4 illus, 13 ref

012607   Sur S;Schieber J;Banerjee S (Geol and Geophysics Dep, The University of Oklahoma, 100 East Boyd St., SEC Suite 810, Norman OK 73019, USA, Email: SSUR@ou.edu) : Petrographic observations suggestive of microbial mats from Rampur shale and Bijaigarh shele, Vindhyan basin, India. J Earth Syst Sci 2006, 115(1), 61-6.

Petrographic observations of two Vindhyan black shales (Rampur Shale of the Semri Group and Bijaigarh Shale of the Kaimur Group) revealed the following features: general wavy lamination, controrted and folded thin shreds of organic matter, wavy pyritic laminae, `teeth and socket' structure. These features are indirect evidence of microbial mat colonization during the Proterozoic. The microbial mats probably fixed carhon at the sediment surface, stabilized sediment and recycled organic matter and were the primary producers, unlike during the Phanerozoic time.

8 illus, 21 ref

012606   Sree S Kumar;Philip R;Achuthankutty C T (Marine Biology Dep, Microbiology and Biochemistry, School of Marine S, Cochin Univ of Science and Technology, Cochin-682 016) : Antiviral property of marine actinomycetes against white spot syndrome virus in penaeid shrimps. Curr Sci 2006, 91(6), 807-11.

Aquaculture farms, particularly in Southeast Asia are facing severe crisis due to increasing incidences of White Spot Syndrome Virus (WSSV). Actinomycetes have provided many important bioactive compounds of high prophylactic and therapeutic value and are continually being screened for new compounds. In this communication, the results of a study made to determine the efectiveness of marine actinomycetes against the white spot disease in penaeid shrimps are presented. Twenty-five isolates of actinomycdetes were tested for their ability to reduce infection due to WSSV among cultured shrimps. When these actinomycetes were made available as feed addities to the post-larvae of the black tiger shrimp Penaeus monodon for two weeks and challenged with WSSV, the post challenge survival showed variations from 11 to 83%. However, six isolates have shown to be te most potential candidates for further study.

1 illus, 2 tables, 22 ref

012605   Singh S K;Iglesias A;Dattatrayam R S;Bansal B K;Rai S S;Campus X P;Suresh G;Baidya P R;Gautam J L (Instituto de Geofisica, UNAM, CU, 04510 Mexico, D.F., Mexico, Email: krishna@ollin.igeofcu.unam.mx) : Muzaffarabad earthquake of 8 October 2005 (Mw 7.6): a preliminary report on source characteristics and recorded ground motions. Curr Sci 2006, 91(5), 689-95.

Source study of the Muzaf-farabad earthquake of 8 October 2005 (Mw 7.6) and the far-field ground motions that it generated. Analysis is based on regional broadband seismograms recorded at stations operated by the India Meteorological Department (IMD) which are situated to the south of the epicentre and at non-IMD stations which are located to the north. Source spectrum of the earthquake is reasonably consistent with ω²-source model with a seismic moment, M₀, of 2.94 x 10²⁰ N-m and a corner frequency, fc, of 0.051 Hz (Brune stress drop of 9.5 MPa). The radiated seismic energy, E_R, estimated from flue empirical Green's function (EGF) technique is 2.70 X 10¹⁶ J. This yields a normalized radiated energy, E_R/M₀, of 9.1 x 10^-5, and an apparent stress, τ_a, of 2.7 MPa. The rupture area of 100 x 15 km² (estimated from slip distribution mapped from the inversion of teleseismic body waves) gives a static stress drop of about 11.3 MPa. From these source parameters we estimate a radiation efficiency of 0.49, implying a 'brittle' rupture typical of inter-plate events. Stochastic method requires a stress drop of -10 MPa to explain the observed peak ground motions (A_max and V_max) recorded at regional distances, and predicts A_max and V_max exceeding 1 g and 100 cm/s, Respectively at hard sites in the epicentral region. The source parameters and far-field ground motions of the Muzaffarabad and Bhuj earthquakes are quite similar even though the tectonic environment and the depth of their occurrence are distinct.

5 illus, 2 tables, 19 ref