003385   Singh A P;Mishra O P;Dinesh Kumar;Santosh Kumar;Yadav R B S (NO, Institute of Seismological Research, Raisan, Ganbdhinagar-382 009, Email: apsingh07@gmail.com) : Spatial variation of the aftershock activity across the Kachchh Rift Basin and its seismotectonic implications. J Earth Syst Sci 2012, 121(2), 439-51.

Analyzed 3365 relocated aftershocks with magnitude of completeness (Mc) ≥1.7 that occurred in the Kachchh Rift Basin (KRB) between August 2006 and December 2010. The analysis of the new aftershock catalogue has led to improved understanding of the subsurface structure and of the aftershock behaviour. Characterized aftershock behaviour in terms of a-value, b-value, spatial fractal dimension (D_s), and slip ratio (ratio of the slip that occurred on the primary fault and that of the total slip). The estimated b-value is 1.05, which indicates that the earthquake occurred due to active tectonics in the region. The three dimensional b-value mapping shows that a high b-value region is sandwiched around the 2001 Bhuj mainshock hypocenter at depths of 20-25 km between two low b-value zones above and below this depth range. The Ds-value was estimated from the double-logarithmic plot of the correlation integral and distance between hypocenters, and is found to be 2.64 ± 0.01, which indicates random spatial distribution beneath the source zone in a two-dimensional plane associated with fluid-filled fractures. A slip ratio of about 0.23 reveals that more slip occurred on secondary fault systems in and around the 2001 Bhuj earhquake (Mw 7.6) source zone in KRB.

9 illus, 59 ref

003384   Shukla A;Guleria J S;Mehrotra R C (NO, Birbal Sahni Institute of Palaeobotany, 53 University Road, Lucknow-226 007, Email: anu_bsip@yahoo.co.in) : Fruit wing of Shorea Roxb. from the Early Miocene sediments of Kachchh, Gujarat and its bearing on palaeoclimatic interpretation. J Earth Syst Sci 2012, 121(1), 195-201.

New fossil fruit wing of Shorea Roxb. belonging to the family Dipterocarpaceae is described from the Early Miocene sediments of Kachchh, Gujarat. It resembles best the extant species Shorea macroptera Dyer, which is a prominent member of the tropical evergreen forests of the Malayan Peninsula. The present finding, along with the other megafossil records described from the same area, indicates a typical tropical vegetation with a warm and humid climate at the time of deposition in contrast to the present day xeric vegetation in the area. As the family Dipterocarpaceae no longer exists in western India, it is essential to discuss the time of its extinction and possible causes, which may include drastic changes in the climate of the region. The present finding also supports the theory of a Malaysian origin for the family in contrast to the hypothesis of a Gondwanan origin.

3 illus, 2 tables, 36 ref

003383   Sharma N L;Kuniyal J C;Singh M;Dhyani P P; Guleria R P;Thakur H K;Rawat P S (Physics Dep, Government Post Graduate College, Kullu-175 101, Email: nlsharmakullu@hotmail.com) : Atmospheric aerosol characteristics retrieved using ground based solar extinction studies at Mohal in the Kullu valley of northwestern Himalayan region, India. J Earth Syst Sci 2012, 121(1), 221-35.

Aerosol parameters are measured using a ground-based Multi-wavelength Radiometer (MWR) at Mohal (31.90±N, 77.11±E, 1154 m amsl) in the Kullu valley during clear sky days of a seasonal year. The study shows that the values of spectral aerosol optical depths (AODs) at 500 nm and the angstrom turbidity coefficient `β' (a measure of columnar loading in atmosphere) are high (0.41 ± 0.03, 0.27 ± 0.01) in summer, moderate (0.30 ± 0.03, 0.15 ± 0.03) in monsoon, low (0.19 ± 0.02, 0.08 ± 0.01) in winter and lowest (0.18 ± 0.01, 0.07 ± 0.01) in autumn, respectively. The angstrom wavelength exponent `α' (indicator of the fraction of accumulation-mode particles to coarse-mode particles) has an opposite trend having lowest value (0.64 ± 0.06) in summer, low (0.99 ± 0.10) in monsoon, moderate (1.20 ± 0.15) in winter and highest value (1.52 ± 0.03) in autumn. The annual mean value of AOD at 500 nm, `α' and `β' are 0.24 ± 0.01, 1.06 ± 0.09 and 0.14 ± 0.01, respectively. The fractional asymmetry factor is more negative in summer due to enhanced tourists' arrival and also in autumn months due to the monthlong International Kullu Dussehra fair. The AOD values given by MWR and satellite-based moderate resolution imaging spectro-radiometer have good correlation of 0.76, 0.92 and 0.97 on diurnal, monthly and seasonal basis, respectively. The AODs at 500 nm as well as `β' are found to be highly correlated, while `α' is found to be strongly anti-correlated with temperature and wind speed suggesting high AODs and turbidity but low concentration of fine particles during hot and windy days. With wind direction, the AOD and `β' are found to be strongly anti-correlated, while `α' is strongly correlated.

7 illus, 3 tables, 71 ref

003382   Sener M;Korkanc M;Furkan Sener M;Korkanc S Y; Zafer Ozgur F (Geological Engineering Dep, Nigde University, 51245, Nigde, Turkey, Email: mehmetfurkansener@hotmail.com) : Toxic gas emissions from the Kayseri peat deposit, Central Anatolia, Turkey. J Earth Syst Sci 2012, 121(5), 1305-15.

Toxic gases evolving from the soil in urbanized peatland regions constitute a serious hazard since buildings may be subject to the direct ingress of volatiles into the structures. Peat formed in swamp and rarely exposed to subaerial conditions has been associated with the development of the folded foreland of the Quaternary Kayseri pull-apart basin. The peat deposit is extensively urbanized but so far no studies have evaluated the extent of the ground gas hazard. In this paper, the geology, petrography and chemical variation of the Kayseri peat deposit have been studied in order to predict the public health risk from the land gases' behaviour, especially in soil gases. The main volatile species detected are methane (CH₄), hydrogen sulphide (H₂S) and carbon dioxide (CO₂), all of which are highly toxic. The primary means of gas entry is directly from the ground through the floors, walls, and especially subsurface telephone cable pipes. Indoor vents emit 1000-70,000 ppm CH4, 330-49,000 ppm CO₂ and 3.8-6.5 ppm H₂S in soil and subsurface pipes; concentrations high enough to present an acute respiratory hazard to persons close to the vents.

10 illus, 5 tables, 26 ref

003381   Saxena A;Sachan H K;Mukherjee P K;Mukhopadhya D K (NO, Wadia Institute of Himalayan Geology, Dehra Dun-248 001, Email: hksachan@wihg.res.in) : Fluid-rock interaction across the South Tibetan Detachment, Garhwal Himalaya (India): mineralogical and geochemical evidences. J Earth Syst Sci 2012, 121(1), 29-44.

Malari Leucogranite in the Garhwal Himalaya is cut across by a continental-scale normal fault system called the South Tibetan Detachment (STD). A mineralogical, geochemical and fluid inclusion study of samples from the fault zone of the Malari Granite was performed to reveal the imprints of fluid-rock interaction. Fluid inclusion assemblages observed in the alteration zone indicate the presence of NaCl-dominated aqueous fluids with varied salinity of 6 -16 wt.% of NaCl equivalent. Mineralogical changes include the alteration of feldspar to muscovite and muscovite to chlorite. This alteration took place at temperatures of 275°-335°C and pressures between 1.9 and 4.2 kbars as revealed by the application of chlorite thermometry, fluid isochores, and presence of K-feldspar+muscovite+chlorite+quartz mineral assemblage. Geochemical mass-balance estimates predict 32% volume loss during alteration. An estimated fluid/rock ratio of 82 is based on loss of silica during alteration, and reveals presence of a moderately low amount of fluid at the time of faulting. Results of fluid inclusion and alteration mineralogy indicate that the Malari Leucogranites were exhumed due to normal faulting along the STD and erosion from mid-crustal levels. Most of the leucogranites in the Himalayas occur along the STD and possibly a regional-scale fluid flow all along the STD might have caused similar alteration of leucogranites along this tectonic break. Regional fluid flow was probably concentrated along the STD and channelized through mesoscopic fractures, microcracks and grain boundaries.

8 illus, 3 tables, 78 ref

003380   Sanil Kumar V;Johnson G;Dora G U;Chempalayil S P;Singh J;Pednekar P (Ocean Engineering, National Institute of Oceanography, CSIR, Dona Paula, Goa-403 004, Email: sanil@nio.org) : Variations in nearshore waves along Karnataka, west coast of India. J Earth Syst Sci 2012, 121(2), 393-403.

Wind wave spectra were recorded simultaneously at three shallow (water depth 7-9 m) locations (Malpe, Honnavar and Karwar) along the 200 km stretch of the state of Karnataka in 2009 during 27 April-24 May (representing conditions prior to onset of the Indian summer monsoon), 12 June-8 July (monsoon), and 1-31 October (post-monsoon). Each spectrum was based on data recorded for half an hour using a waverider buoy. Describes characteristics of the spectra and the wave parameters derived from the spectra. Both reveal the dramatic changes that occur in the wave field due to the summer monsoon. The changes were virtually identical at all the three locations suggesting that the wave characteristics described here are representative of the conditions that exist along the coast of Karnataka State, west coast of India.

10 illus, 1 table, 18 ref

003379   Saikia B K (Quality Control Laboratory, Indian Oil Corporation Ltd., Haldia Refine, , Kolkota-721 606, Email: bksaikia@gmail.com) : Spectroscopic Studies of Minerals in Some Indian Coals. Asian J Chem 2011, 23(4), 1887-8.

Far-infrared spectra of the range, 400-200 cm^-l were recorded for eight different high sulphur coal samples from Assam (India) for the first time. The observed unusual spectral bands are accounts for the minerals viz., kaolinite, calcite, magnesite, illite, siderite, pyrite present in the coals.

1 illus, 11 ref

003378   Roy S S;Saha S B;Fatima H;Roy Bhowmik S K; Kundu P K (NO, India Meteorological Dep, Lodi Road, New Delhi-110 003, Email: somasenroy@yahoo.com) : Evaluation of short-period rainfall estimates from Kalpana-1 satellite using MET software. J Earth Syst Sci 2012, 121(5), 1113-23.

INSAT Multispectral Rainfall Algorithm (IMSRA) technique for rainfall estimation, has recently been developed to meet the shortcomings of the Global Precipitation Index (GPI) technique of rainfall estimation from the data of geostationary satellites; especially for accurate short period rainfall estimates. The study evaluates the 3-hourly precipitation estimates by this technique as well as the rainfall estimates by the GPI technique using data of the Kalpana-1 satellite, over the Indian region for the south-west monsoon season of 2010 to understand their relative strengths and weaknesses in estimating short period rainfall. The gridded 3 hourly accumulated TRMM satellite (3B42 V6 product or TMPA product) and surface raingauge data for stations over the Indian region for the same period is used as the standard measure of rainfall estimates. The Method for Object-based Diagnostic Evaluation (MODE) utility of the METv3.0 software, has been used for the evaluation purpose. The results show that the new IMSRA technique is closer to the TMPA rainfall estimate, in terms of areal spread, geometric shape and location of rainfall areas, as compared to the GPI technique. The overlap of matching rainfall areas with respect to TMPA rainfall patches is also higher for the IMSRA estimates as compared to the GPI values. However, both satellite rainfall estimates are observed to be generally higher compared to the TMPA measurements. However, the values for the highest 10% of the rainfall rates in any rainfall patch, is generally higher for rainfall measured by the IMSRA technique, as compared to the estimates by the GPI technique. This may partly be due to the capping maximum limit of 3 mm/hr for rainfall measured by the GPI technique limits the total 3-hour accumulation to 9 mm even during heavy rainfall episodes. This is not so with IMSRA technique, which has no such limiting value. However, this general overestimation of the rainfall amount, measured by both techniques, and the greater error in case of IMSRA estimates, is also validated independently with respect to surface raingauge observations. Hence the observed overestimation by the IMSRA technique for the highest 10th percentile rainfall rates in rainfall episodes, is real. This overestimation by the latter technique may become a significant source of error, if the IMSRA estimate is used for monitoring very heavy rainfall episodes. In all other respects, since the IMSRA method shows significant improvement over the GPI, the rainfall estimates by the IMSRA method may be used for operational short period rainfall estimation.

4 illus, 32 ref

003377   Roy Bhowmik S K;Durai V R (NO, India Meterological Dep, ) : Development of multimodel ensemble based district level medium range rainfall forecast system for Indian region. J Earth Syst Sci 2012, 121(2), 273-85.

India Meteorological Department has implemented district level medium range rainfall forecast system applying multimodel ensemble technique, making use of model outputs of state-of-the-art global models from the five leading global NWP centres. The pre-assigned grid point weights on the basis of anomaly correlation coefficients (CC) between the observed values and forecast values are determined for each constituent model at the resolution of 0.25°x0.25° utilizing two season datasets (1 June-30 September, 2007 and 2008) and the multimodel ensemble forecasts (day-1 to day-5 forecasts) are generated at the same resolution on a real-time basis. The ensemble forecast fields are then used to prepare forecasts for each district, taking the average value of all grid points falling in a particular district. Describes the development strategy of the technique and performance skill of the system during summer monsoon 2009. The study demonstrates the potential of the system for improving rainfall forecasts at five days time scale over Indian region. Districtwise performance of the ensemble rainfall forecast reveals that the technique, in general, is capable of providing reasonably good forecast skill over most states of the country, particularly over the states where the monsoon systems are more dominant.

12 illus, 11 ref

003376   Rastogi R G;Chandra H;Condori L;Abdu M A; Reinisch B;Tsunoda R T;Prasad D S V V D;Pant T K;Maruyama T (NO, Physical Research Lab, Ahmedabad-380 009, Email: hchandra@prl.res.in) : Abnormally large magnetospheric electric field on 9 November 2004 and its effect on equatorial ionosphere around the world. J Earth Syst Sci 2012, 121(5), 1145-61.

There was a solar event around 1850 UT on 9th November 2004, associated with an abnormally large solar wind flow pressure and large southward interplanetary magnetic field, causing an abnormally large prompt penetration electric field between 1850 and 2100 UT. Abnormally large vertical F-region drifts by Jicamarca backscatter radar were reported associated with the event. The F-region over Jicamarca, Peru (14-16 LT) and Sao Luis, Brazil (16-18 LT) was lifted upward, broken into two portions and the upper one was blown out of the range of the ionosonde. At Fortaleza, an off-equatorial station in Brazil, the F-region was also lifted up but later the f₀F₂ increased due to the flow of ionization from upper layer blown up over the equatorial region. The F-region at Ascension Island (19-21 LT), an off-equatorial station, was lifted up without any deformations till 1915 LT but descended at 1930 LT due to reversal of electric field polarity. At Indian stations, Trivandrum and Waltair (00-02 LT), the F-region was pushed down and later disappeared as a consequence of enhanced westward ionospheric electric field in the night sector. The ionosonde did not receive any echo for a couple of hours till the next sunrise. The F-region at Kototaban (03-05 LT), Indonesia also disappeared after a rapid descend. At Kwajelien (06-08 LT) there was no equatorial type of sporadic-E at 07 to 09 LT due to the westward electric field.

13 illus, 1 table, 19 ref

003375   Rao P V N;Swaroop P C;Karimulla S (Geology Dep, Acharya Nagarjuna University, Nagarjunanagar-522 510, Email: pusapati_unr@yahoomail.com) : Mineral chemistry of Pangidi basalt flows from Andhra Pradesh. J Earth Syst Sci 2012, 121(2), 525-36.

Elucidates the compositional studies on clinopyroxene, plagioclase, titaniferous magnetite and ilmenite of basalts of Pangidi area to understand the geothermometry and oxybarometry conditions. Petrographic evidence and anorthite content (up to 85%) of plagioclase and temperature estimates of clinopyroxene indicate that the clinopyroxene is crystallized later than or together with plagioclase. The higher An content indicates that the parent magma is tholeiitic composition. The equilibration temperatures of clinopyroxene (1110-1190°C) and titaniferous magnetite and ilmenite coexisting mineral phases (1063-1103°C) are almost similar in lower basalt flow and it is higher for clinopyroxene (900-1110°C) when compared to titaniferous magnetite and ilmenite coexisting mineral phases (748-898°C) in middle and upper basalt flows. From this it can be inferred that the clinopyroxene is crystallized earlier than Fe-Ti oxide phases reequilibration, which indicates that the clinopyroxene temperature is the approximate eruption temperature of the present lava flows. The wide range of temperatures (900-1190°C) attained by clinopyroxene may point out that the equilibration of clinopyroxene crystals initiated from depth till closer to the surface before the melt erupted. Pangidi basalts follow the QFM buffer curve which indicates the more evolved tholeiitic composition. This suggests the parent tholeiitic magma suffered limited fractionation at high temperature under increasing oxygen fugacity in lower basalt flow and more fractionation at medium to lower temperatures under decreasing oxygen fugacity conditions during cooling of middle and upper basalt flows. The variation of oxygen fugacity indicates the oxidizing conditions for lower basalt flow (9.48-10.3) and extremely reducing conditions for middle (12.1-15.5) and upper basalt (12.4-15.54) flows prevailed at the time of cooling. Temperature vs. (FeO+Fe₂O₃) /(FeO+Fe₂O₃+MgO) data plots for present basalts suggested the lower basaltic flow is formed at higher temperatures while the middle and upper basalt flows at medium to lower temperatures. The lower basalt flow is represented by higher temperatures which shows high modal values of opaques and glass whereas the medium to lower temperatures of middle and upper flow are caused by vesicular nature which contain larger content of gases and humid to semi-arid conditions during cooling.

13 illus, 5 tables, 28 ref

003374   Ramakrishnan R;Rajawat A S (Geosciences Div, Marine, Geo and Planetary Sciences Group, Earth, Ocea, Space Applications Centre, ISRO, Ahmedabad-380 015, Email: unnirathesh@gmail.com) : Simulation of suspended sediment transport initialized with satellite derived suspended sediment concentrations. J Earth Syst Sci 2012, 121(5), 1201-13.

Suspended sediment transport in the Gulf of Kachchh is simulated utilizing the suspended sediment concentration (SSC) derived from Oceansat OCM imagery, as the initial condition in MIKE-21 Mud Transport model. Optimization of the model mud parameters, like settling velocity and critical shear stress for erosion are realized with respect to the sediment size distribution and the bottom bed materials observed in the Gulf. Simulated SSCs are compared with alternate OCM derived SSC. The results are observed to be impetus where the model is able to generate the spatial dynamics of the sediment concentrations. Sediment dynamics like deposition, erosion and dispersion are explained with the simulated tidal currents and OCM derived sediment concentrations. Tidal range is observed as the important physical factor controlling the deposition and resuspension of sediments within the Gulf. From the simulation studies; maximum residual current velocities, tidal fronts and high turbulent zones are found to characterise the islands and shoals within the Gulf, which results in high sediment concentrations in those regions. Remarkable variability in the bathymetry of the Gulf, different bed materials and varying tidal conditions induces several circulation patterns and turbulence creating the unique suspended sediment concentration pattern in the Gulf.

11 illus, 34 ref

003373   Rajeev Ranjan Kumar;Ramana D V;Singh R N (Geology and Geophysics Dep, Indian Institute of Technology, Kharagpur-721 902, Email: dvr@ngri.res.in) : Modelling near subsurface temperature with mixed type boundary condition for transient air temperature and vertical groundwater flow. J Earth Syst Sci 2012, 121(5), 1177-84.

Near-subsurface temperatures have signatures of climate change. Thermal models of subsurface have been constructed by prescribing time dependent Dirichlet type boundary condition wherein the temperature at the soil surface is prescribed and depth distribution of temperature is obtained. In this formulation it is not possible to include the relationship between air temperatures and the temperature of soil surface. However, if one uses a Robin type boundary condition, a transfer coefficient relates the air and soil surface temperatures which helps to determine both the temperature at the surface and at depth given near surface air temperatures. This coefficient is a function of meteorological conditions and is readily available. Developed such a thermal model of near subsurface region which includes both heat conduction and advection due to groundwater flows and have presented numerical results for changes in the temperature-depth profiles for different values of transfer coefficient and groundwater flux. There are significant changes in temperature and depth profiles due to changes in the transfer coefficient and groundwater flux. The analytical model will find applications in the interpretation of the borehole geothermal data to extract both climate and groundwater flow signals.

6 illus, 1 table, 33 ref

003372   Rahman M M;Islam M N;Ahmed A U;Georgi F (NO, SAARC Meteorological Research Centre, Dhaka, Bangladesh, Email: mrahman426@yahoo.com) : Rainfall and temperature scenarios for Bangladesh for the middle of 21st century using RegCM. J Earth Syst Sci 2012, 121(2), 287-95.

Regional Climate Model of version 3 (RegCM3) was driven with Emissions Scenarios A2 of ECHAM4 at 0.54°x0.54° horizontal grid resolution in two parameterizations: Grell scheme with Arakawa-Schubert (GAS) and Fritch-Chappell (GFC) assumptions. The simulated rainfall and mean surface air temperature were calibrated and validated against ground-based observed data in Bangladesh during the period 1961-1990. The Climate Research Unit (CRU) data is also used for understanding the model performance. Better performance of RegCM3 obtained through validation process, made it confident in utilizing it in rainfall and temperature projection for Bangladesh in the middle of 21st century. Rainfall and mean surface air temperature projection for Bangladesh is experimentally obtained for 2050 and 2060. Discloses that simulated rainfall and temperature are not directly useful in application-oriented tasks. However, after calibration and validation, reasonable performance can be obtained in estimating seasonal and annual rainfall, and mean surface air temperature in Bangladesh. The projected change of rainfall for Bangladesh is about +35% for monsoon season (JJAS), -67% for pre-monsoon (MAM), -12% for post-monsoon (ON) and 107% for winter (DJF) for 2050. On an average, rainfall may be less by more than 50% for all seasons for the year 2060. Similarly, change of mean surface air temperature in different months is projected about 0.5°-2.1°C and 0.9°-3.5°C for the year 2050 and 2060, respectively.

11 illus, 2 tables, 18 ref

003371   Qian H;Zhang X D;Li P Y (School of Environmental Science and Engineering, Chang'an University, No. 126, Yanta Road, Xi'an 710054, Shaanxi, P.R. China, Email: qianhui@chd.edu.cn) : Calculation of CaCO₃ solubility (Precipitability) in natural waters. Asian J Chem 2012, 24(2), 668-72.

It is an important issue to calculate the CaCO₃ solubility (precipitability) in natural waters in karst geochemistry. This paper pointed out some serious problems in the existing methods dealing with this issue and put forward a new method to calculate the CaCO₃ solubility (precipitability) in natural waters. This new method is based on the calculation of CaCO₃ saturation index and takes the changes of pH values, activity coefficients and concentration changes of species into account and these factors are studied in open and closed systems, respectively. The results showed that if the above-mentioned changes were ignored, there would be significant errors in the calculated results.

5 tables, 15 ref

003370   Patwardhan S;Kulkarni A;Krishna Kumar K (NO, Indian Institute of Tropical Meteorology, Pune, Maharashtra, Email: patwar@tropmet.res.in) : Impact of global warming on cyclonic disturbances over South Asian region. J Earth Syst Sci 2012, 121(1), 203-10.

State-of-the-art regional climate modelling system, known as PRECIS (Providing REgional Climates for Impacts Studies) developed by the Hadley Centre for Climate Prediction and Research, UK is applied over the Indian domain to investigate the impact of global warming on the cyclonic disturbances such as depressions and storms. The PRECIS simulations at 50 x 50 km horizontal resolution are made for two time slices, present (1961-1990) and the future (2071-2100), for two socioeconomic scenarios A2 and B2. The model simulations under the scenarios of increasing greenhouse gas concentrations and sulphate aerosols are analysed to study the likely changes in the frequency, intensity and the tracks of cyclonic disturbances forming over north Indian Ocean (Bay of Bengal and Arabian Sea) and the Indian landmass during monsoon season. The model overestimates the frequency of cyclonic disturbances over the Indian subcontinent in baseline simulations (1961-1990). The change is evaluated towards the end of present century (2071-2100) with respect to the baseline climate. The study indicates that the storm tracks simulated by the model are southwards as compared to the observed tracks during the monsoon season, especially for the two main monsoon months, viz., July and August. The analysis suggests that the frequency of cyclonic disturbances forming over north Indian Ocean is likely to reduce by 9% towards the end of the present century in response to the global warming. However, the intensity of cyclonic disturbances is likely to increase by about 11% compared to the present.

6 illus, 1 table, 21 ref

003369   Misar A;Mujumdar A M (Botany Group, Plant Sciences Div, Agharkar Research Institute, Pune-411 004, Email: ashwini_misar@rediffmail.com) : Antidiarrhoeal activity of methanolic extract of Acacia farnesiana Bark. Asian J Chem 2011, 23(4), 1767-70.

Based on ethno-botanical use the bark of Acacia farnesiana Willd. (family-Mimosaceae) was studied for the antidiarrhoeal activity. Bark of Acacia farnesiana was successively extracted with petroleum ether, methanol and distilled water. The extracts were dried under reduced temperature and pressure. The methanolic extract of Acacia farnesiana bark (AFM) showed significant antidiarrhoeal activity in exploratory studies. The methanolic extract of Acacia farnesiana bark at 100, 200 and 400 mg/kg, p.o. produced a significant and dose dependent inhibition of in castor oil induced diarrhoea. Therefore methanolic extract of Acacia farnesiana bark was studies in detail for magnesium sulphate induced diarrhoea, intraluminal fluid accumulation and normal as well as barium chloride induced charcoal transit. Antimicrobial activity of methanolic extract of Acacia farnesiana bark against diarrhoea causing micro-organisms has also been studied in vitro. The methanolic extract of Acacia farnesiana bark showed significant inhibition of castor oil and magnesium sulphate induced diarrhoea. It also inhibits fluid accumulation against castor oil challenge in enteropooling assay. The methanolic extract of Acacia farnesiana bark reduced normal as well as barium chloride induced peristalsis of small intestine in mice. The methanolic extract of Acacia farnesiana bark also showed antimicrobial activity against common pathogens responsible for diarrhoea in vitro.

3 illus, 3 tables, 24 ref

003368   Mehta M;Majeed Z;Dobhal D P;Srivastava P (NO, Wadia Institute of Himalayan Geology, 33 GMS Road, Dehra Dun, Email: Pradeep@wihg.res.in) : Geomorphological evidences of post-LGM glacial advancements in the Himalaya: a study from Chorabari Glacier, Garhwal Himalaya, India. J Earth Syst Sci 2012, 121(1), 149-63.

Field geomorphology and remote sensing data, supported by Optical Stimulated Luminescence (OSL) dating from the Mandakini river valley of the Garhwal Himalaya enabled identification of four major glacial events; Rambara Glacial Stage (RGS) (13 ± 2 ka), Ghindurpani Glacial Stage (GhGS) (9 ± 1 ka), Garuriya Glacial Stage (GGS) (7 ± 1 ka) and Kedarnath Glacial Stage (KGS) (5 ± 1 ka). RGS was the most extensive glaciation extending for <126>6 km down the valley from the present day snout and lowered to an altitude of 2800 m asl at Rambara covering around <126>31 km² area of the Mandakini river valley. Compared to this, the other three glaciations (viz., GhGS, GGS and KGS) were of lower magnitudes terminating around <126>3000, <126>3300 and <126>3500 m asl, respectively. It was also observed that the mean equilibrium line altitude (ELA) during RGS was lowered to 4747 m asl compared to the present level of 5120 m asl. This implies an ELA depression of <126>373 m during the RGS which would correspond to a lowering of <126>2±C summer temperature during the RGS. The results are comparable to that of the adjacent western and central Himalaya implying a common forcing factor that we attribute to the insolation-driven monsoon precipitation in the western and central Himalaya.

10 illus, 5 tables, 55 ref

003367   Mankad B M;Sharma R;Basu S;Pal P K (NO, Atmospheric and Oceanic Sciences Group, Space Applications Centre, Ahmedabad-380 015, Email: rumi_jhim@yahoo.com) : Altimeter data assimilation in the tropical Indian Ocean using water property conserving scheme. J Earth Syst Sci 2012, 121(1), 251-62.

Altimeter data have been assimilated in an ocean general circulation model using the water property conserving scheme. Two runs of the model have been conducted for the year 2004. In one of the runs, altimeter data have been assimilated sequentially, while in another run, assimilation has been suppressed. Assimilation has been restricted to the tropical Indian Ocean. An assessment of the strength of the scheme has been carried out by comparing the sea surface temperature (SST), simulated in the two runs, with in situ derived as well as remotely sensed observations of the same quantity. It has been found that the assimilation exhibits a significant positive impact on the simulation of SST. The subsurface effect of the assimilation could be judged by comparing the model simulated depth of the 20°C isotherm (hereafter referred to as D20), as a proxy of the thermocline depth, with the same quantity estimated from ARGO observations. In this case also, the impact is noteworthy. Effect on the dynamics has been judged by comparison of simulated surface current with observed current at a moored buoy location, and finally the impact on model sea level forecast in a free run after assimilation has been quantified in a representative example.

10 illus, 34 ref

003366   Mahapatra P S;Jena J;Moharana S;Srichandan H; Das T;Roy Chaudhury G;Das S N (NO, CSIR-Institute of Minerals and Materials Technology, Bhubaneshwar-751 013, Email: trupti.sreyas@gmail.com ) : Surface ozone variation at Bhubaneswar and intra-corelationship study with various parameters. J Earth Syst Sci 2012, 121(5), 1163-75.

Summarizes the results of year long (December 2009 to January 2011) continuous measurements of daytime (0700-1745) ozone (O₃) in the ambient air and related meteorological parameters at Bhubaneswar (21°15'N-85°15'E), Odisha. The seasonal variation shows distinct daytime ozone maxima during winters with a peak in January (<126>85 ppbv), a slight increase (<126>38 ppbv) in June and lowest in August (<126>20 ppbv). The backward trajectory analysis during winter months suggests long distance transport of airmass from mainly Indo-Gangetic Plains (IGP) and western part of Indian peninsula, a major industrial hub. In other seasons, wind reaches the observation site from less polluted landmasses and the Bay of Bengal, thereby considerably reducing the pollution load. On the contrary, ozone build-up was found to be maximum and minimum in pre-monsoon and monsoon, respectively. An anti-weekend ozone effect (<126>5 ppbv) was observed in winter. Paired t-test and F-test along with principal component analysis (PCA) were done to determine significance between various components (ozone, precursors and meteorological parameters). The t- and F-test showed significant monthly variation of ozone mixing ratio. The PCA showed that three components explained 79.1% of variances.

3 illus, 5 tables, 44 ref

003365   Litta A J;Mohanty U C;Idicula S M (Centre for Atmospheric Sciences, Indian Institute of Technology, Delhi, Hauz Khas, New Delhi-110 016, Email: littaaj@gmail.com) : Diagnosis of severe thunderstorms with high-resolution WRF model. J Earth Syst Sci 2012, 121(2), 297-316.

Thunderstorm, resulting from vigorous convective activity, is one of the most spectacular weather phenomena in the atmosphere. A common feature of the weather during the pre-monsoon season over the Indo-Gangetic Plain and northeast India is the outburst of severe local convective storms, commonly known as `Nor'westers'(as they move from northwest to southeast). The severe thunderstorms associated with thunder, squall lines, lightning and hail cause extensive losses in agricultural, damage to structure and also loss of life. Sensitivity experiments have been conducted with the Non-hydrostatic Mesoscale Model (NMM) to test the impact of three microphysical schemes in capturing the severe thunderstorm event occurred over Kolkata on 15 May 2009. The results show that the WRF-NMM model with Ferrier microphysical scheme appears to reproduce the cloud and precipitation processes more realistically than other schemes. Also, we have made an attempt to diagnose four severe thunderstorms that occurred during pre-monsoon seasons of 2006, 2007 and 2008 through the simulated radar reflectivity fields from NMM model with Ferrier microphysics scheme and validated the model results with Kolkata Doppler Weather Radar (DWR) observations. Composite radar reflectivity simulated by WRF-NMM model clearly shows the severe thunderstorm movement as observed by DWR imageries, but failed to capture the intensity as in observations. The results of these analyses demonstrated the capability of high resolution WRF-NMM model in the simulation of severe thunderstorm events and determined that the 3 km model improve upon current abilities when it comes to simulating severe thunderstorms over east Indian region.

14 illus, 5 tables, 34 ref

003364   Kundu A;Matin A;Mukul M (Geology Dep, Asutosh College, 92, S.P. Mukherjee Road, Kolkata-700 026, Email: kundu.abhik@gmail.com) : Depositional environment and provenance of Middle Siwalik sediments in Tista valley, Darjiling District, Eastern Himalaya, India. J Earth Syst Sci 2012, 121(1), 73-89.

Frontal part of the active, wedge-shaped Indo-Eurasian collision boundary is defined by the Himalayan fold-and-thrust belt whose foreland basin accumulated sediments that eventually became part of the thrust belt and is presently exposed as the sedimentary rocks of the Siwalik Group. The rocks of the Siwalik Group have been extensively studied in the western and Nepal Himalaya and have been divided into the Lower, Middle and Upper Subgroups. In the Darjiling-Sikkim Himalaya, the Upper Siwalik sequence is not exposed and the Middle Siwalik Subgroup exposed in the Tista river valley of Darjiling Himalaya preserves a <126>325 m thick sequence of sandstone, conglomerate and shale. The Middle Siwalik section has been repeated by a number of north dipping thrusts. The sedimentary facies and facies associations within the lithostratigraphic column of the Middle Siwalik rocks show temporal repetition of sedimentary facies associations suggesting oscillation between proximal-, mid- and distal fan setups within a palaeo-alluvial fan depositional environment similar to the depositional setup of the Siwalik sediments in other parts of the Himalaya. These oscillations are probably due to a combination of foreland-ward movement of Himalayan thrusts, climatic variations and mountain-ward shift of fanapex due to erosion. The Middle Siwalik sediments were derived from Higher- and Lesser Himalayan rocks. Mineral characteristics and modal analysis suggest that sedimentation occurred in humid climatic conditions similar to the moist humid climate of the present day Eastern Himalaya.

6 illus, 4 tables, 73 ref

003363   Kraiem Z;Chkir N;Zouari K;Parisot J C;Agoun A;Hermitte D (Radio-Anmalysis and Environment Lab, National School of Engineers of Sfax, BP 1173, 3038 Sfax, Tunisia, Email: kraiemzohra@yahoo.fr) : Tomographic, hydrochemical and isotopic investigations of the salinization processes in the oasis shallow aquifers, Nefzaoua region, southwestern Tunisia. J Earth Syst Sci 2012, 121(5), 1185-1200.

Electrical imaging tomography survey was carried out to identify the lateral and vertical salinity distribution in the oasis shallow aquifers of the Nefzaoua region located in southwestern Tunisia. In addition, hydrochemical and isotopic data were examined to determine the main factors and mechanisms controlling the groundwater chemistry and salinity. Locally, with respect to salinization processes, electrical imaging tomography results show that the storage basins of irrigation excess-water contribute to the increase of the salinity for the major part of the oasis nearby these basins. Major elements distribution and saturation indices indicate that dissolution of evaporites (halite, anhydrite and gypsum) is the main process controlling the groundwater mineralization. Isotopic data highlighted the effect of evaporation in the salinization of these waters. The correlation between the oxygen 18 and the chlorides data confirms the importance of evaporation effect and dissolution as main processes controlling the groundwater mineralization.

17 illus, 4 tables, 44 ref

003362   Kolathayar S;Sitharam T G;Vipin K S (Civil Engineering Dep, Indian Institute of Science, Bangalore-560 012, Email: sreevals@civil.iisc.ernet.in) : Deterministic seismic hazard macrozonation of India. J Earth Syst Sci 2012, 121(5), 1351-64.

Earthquakes are known to have occurred in Indian subcontinent from ancient times. Presents the results of seismic hazard analysis of India (6°-38°N and 68°-98°E) based on the deterministic approach using latest seismicity data (up to 2010). The hazard analysis was done using two different source models (linear sources and point sources) and 12 well recognized attenuation relations considering varied tectonic provinces in the region. The earthquake data obtained from different sources were homogenized and declustered and a total of 27,146 earthquakes of moment magnitude 4 and above were listed in the study area. The sesismotectonic map of the study area was prepared by considering the faults, lineaments and the shear zones which are associated with earthquakes of magnitude 4 and above. A new program was developed in MATLAB for smoothing of the point sources. For assessing the seismic hazard, the study area was divided into small grids of size 0.1° x 0.1° (approximately 10 x 10 km), and the hazard parameters were calculated at the center of each of these grid cells by considering all the seismic sources within a radius of 300 to 400 km. Rock level peak horizontal acceleration (PHA) and spectral accelerations for periods 0.1 and 1 s have been calculated for all the grid points with a deterministic approach using a code written in MATLAB. Epistemic uncertainty in hazard definition has been tackled within a logic-tree framework considering two types of sources and three attenuation models for each grid point. The hazard evaluation without logic tree approach also has been done for comparison of the results. The contour maps showing the spatial variation of hazard values are presented.

8 illus, 3 tables, 81 ref

003361   Kachhara R P;Jodhawat R L;Bigyapati Devi K (Geology Dep, M.L. Sukhadia University, Udaipur-313 001, Email: kachharar@yahoo.com) : Lower Oligocene bivalves of Ramanian Stage from Kachchh, Gujarat, India. J Earth Syst Sci 2012, 121(2), 405-38.

Marine Oligocene sequences in India outcrop only in western part of Kachchh. Earlier researchers have recognized the Oligocene strata under the Nari Series (Nagappa 1959; Chatterji and Mathur 1966). The Nari Series has a type area in Pakistan. It has two subdivisions - the Lower Nari (Lower Oligocene) and the Upper Nari (Upper Oligocene). It seems that there is no valid proof about the age of the Lower Nari due to lack of proper fauna (Eames 1975), and according to Pascoe (1962), the Upper Nari slightly transgress into Aquitanian (Lower Miocene), therefore, one has to be very cautious. Biswas and Raju (1971) reclassified the Oligocene strata of Kachchh and lithostratigraphically clubbed them as the Maniyara Fort Formation with type section along the Bermoti stream. This Formation has four members. The lower three members correspond to the Ramanian Stage (Lower Oligocene, Biswas 1971, 1973) while the uppermost to the Waiorian Stage (Upper Oligocene, Biswas 1965, 1971, 1973). The Ramanian Stage is characterized by large forams especially Nummulites fichteli, Nummulites fichteli intermedius, Lepidocyclina (Eulepidina) dialata and Operculina sp. Several ostracods are also known to occur. Megafauna include bivalves, gastropods, echinoids, corals, mammals and reptiles. Concerning bivalves earlier researchers have recorded a few taxa namely Trisidos semitorta (Lamarck), Cubitostrea angulata (J de C Sowerby), Pecten (Amussiopecten) labadyei d'Archiac and Haime, Periglypta puerperal (Linne') var. aglaurae Brongniart, Ostrea fraasi Mayer Eymer and listed Pecten laevicostatus J de C Sowerby, Callista pseudoumbonella Vredenburg and Clementia papyracea (Gray) from Kachchh as against overall 42 forms from the Nari Series as a whole (Vredenburg 1928). This tempted us to make an attempt to collect bivalve fauna systematically which are occurring prolifically in the Ramanian Stage. In the work, for this purpose, sections are worked out around Lakhpat (23°50'N; 68°47"E), Maniyara Fort (23°28'05"N; 68°37'E) Rakhdi Dam (23°27'26"N; 68°40'10"E) and Waior (23°25'05"N;: 68°41'37"E) with a view to highlight the entombed bivalve taxa. Authors have encountered 53 species of which 23 are restricted to the Ramanian Stage.

39 illus, 49 ref

003360   Ghazi S;Mountney N P;Butt A A;Sharif S (NO, School of Earth and Environment, University of Leeds, Leeds LS2 9JT, UK, Email: ghazigeo@yahoo.com) : Stratigraphic and palaeoenvironmental framework of the Early Permian sequence in the Salt Range, Pakistan. J Earth Syst Sci 2012, 121(5), 1239-55.

Early Permian Gondwana regime succession of the Nilawahan Group is exposed only in the Salt Range of Pakistan. After a prolonged episode of non-deposition that spanned much of the Palaeozoic, the 350 m thick predominantly clastic sequence of the Nilawahan Group records a late glacial and post-glacial episode in which a range of glacio-fluvial, marine and fluvial environments evolved and accumulated. The Early Permian succession of the Salt Range has been classified into four formations, which together indicates a changing climatic regime during the Early Permian in the Salt Range region. The lower-most, Tobra Formation unconformably overlies a Cambrian sequence and is composed of tillite, diamictite and fresh water facies, which contain a floral assemblage (Gangamopteris and Glossopteris) that confirms an Asselian age. The Tobra Formation is overlain by marginal marine deposits of the Dandot Formation (Sakmarian), which contain an abundant brachiopods assemblage (Eurydesma and Conularia). Accumulation of the Dandot Formation was terminated by a regional sea-level fall and a change to the deposition of the fluvial deposits of the Warchha Sandstone (Artinskian). The Warchha Sandstone was deposited by high sinuosity meandering, avulsion prone river with well developed floodplains. This episode of fluvial sedimentation was terminated by a widespread marine transgression, as represented by the abrupt upward transition to the overlying shallow marine Sardhai Formation (Kungurian). The Early Permian Gondwana sequence represented by the Nilawahan Group is capped by predominantly shallow shelf carbonate deposits of the Tethyan realm. The sedimentologic and stratigraphic relationship of these four lithostratigraphic units in the Salt Range reveals a complex stratigraphic history for the Early Permian, which is mainly controlled by eustatic sea-level change due to climatic variation associated with climatic amelioration at the end of the major Gondwana glacial episode, and the gradual regional northward drift to a lower latitude of the Indian plate.

8 illus, 57 ref

003359   Ganjoo R K;Vinod Kumar (Geology Dep, University of Jammu, Jammu-180 006, Email: ganjoork@rediffmail.com) : Late Quaternary fine silt deposits of Jammu, NW Himalaya: genesis and climatic significance. J Earth Syst Sci 2012, 121(1), 165-82.

Fine silt deposits of Jammu (J & K State, India) stretch all along the Siwalik foothills from Jammu to the Potwar Plateau in Pakistan. The post-Siwalik deposits, first discussed by de Terra and Paterson (1939), are attributed to wind action. The deposits termed as `Potwar loessic silt' comprising sandy silt are essentially of late Quaternary age (75-18 ka) and are re-looked herein from the point of view of genesis and climatic significance. The sorting, skewness and kurtosis parameters of fine silts of Jammu suggest fluvial environment of the deposits wherein the water budget fluctuated. The weak pedogenesis of fine silts at certain intervals corroborate to periods of less or no sedimentation. The bivariant plot studies further suggest fluvial environment of deposition for the fine silt at Jammu, with regular fluctuations in the budget of river water that was perhaps in consonance with oscillations in the climate of the region.

20 illus, 4 tables, 73 ref

003358   Ganguly S;Ray J;Koeberl C;Ntaflos T;Banerjee M (Geology Dep, University of Calcutta, 35 Ballygunge Circular Road, Kolkata-700 019, Email: sganguly.geocal@gmail.com) : Mineral chemistry of lava flows from Linga area of the Eastern Deccan Volcanic Province, India. J Earth Syst Sci 2012, 121(1), 91-108.

Several basaltic lava flows have been identified in the study area in and around Linga, in the Eastern Deccan Volcanic Province (EDVP) on the basis of distinctly developed structural zones defined by primary volcanic structures such as columnar joints and vesicles. These basaltic lava flows are spatially distributed in four different sectors, viz., Bargona-Gadarwara (BG) sector, Shikarpur-Linga (SL) sector, Arjunvari-Survir Hill (AS) sector and Kukrachiman-Morand Hill (KM) sector. A three tier classification scheme has been adopted for the characterization and classification of individual lava flows. Each lava flow consists of a Lower Colonnade Zone (LCZ) overlain by the Entablature Zone (EZ) and Upper Colonnade Zone (UCZ). The LCZ and UCZ grade into a distinct/indistinct Lower Vesicular Zone (LVZ) and Upper Vesicular Zone (UVZ), respectively. The LCZ and UCZ of the flows are characterized by columnar joints while the EZ is marked by multi-directional hackly jointing. The geometry of different joint patterns corresponds to different styles of cooling during solidification of lava flows. Detailed petrographic studies of the investigated lava flows reveal inequigranular phenocrystal basalts characterized by development of phenocrystal phases including plagioclase, clinopyroxene and olivine, whereas groundmass composition is marked by tiny plagioclase, clinopyroxene, opaque mineral and glass. Electron microprobe analyses indicate that the olivine has a wide range <126>Fo₂₂ to Fo₆₆ revealing a wide spectrum of compositional variation. Pyroxene compositions are distinctly designated as Quad pyroxenes. Phenocrystal pyroxenes are mostly diopsidic, while the groundmass pyroxenes mainly correspond to augite with a minor pigeonite component. Pyroxene phenocrysts are characterized by a prominent Tienrichment. Phenocrystal plagioclase grains are calcic (An_52.7-An_72.9), whereas groundmass plagioclase are relatively sodic (An_39.2-An_61.6). Groundmass opaque minerals are characteristically found to be Ti-magnetite/ilmenite/pyrophanite. Pyroxene thermometry reveals a temperature span of 850° to 1280°C for the studied lavas while olivine-clinopyroxene thermometry yields a temperature range from 1040°-1160°C. The variation of temperature for the lava flows is ascribed to their normal cooling history after eruption.

5 illus, 6 tables, 8 ref

003357   Dutta S;Ramanathan A L;Linda A (Glacier Research Group, School of Environmental Sciences, Jawaharlal Nehru University, New Delhi, Email: sakshishruti@gmail.com) : Glacier fluctuation using satellite data in Beas basin, 1972-2006, Himachal Pradesh, India. J Earth Syst Sci 2012, 121(5), 1105-12.

Glaciers are widely recognized as sensitive indicators for regional climate change. Very few studies have been conducted to investigate the long term deglaciation status in the Himalaya. In the present study, glaciers in the Beas basin, Himachal Pradesh, India were mapped by interpretation of various glaciomorphological features using the Landsat and IRS images. The mapping of 224 glaciers during the period 1972-2006 reveals that the glacier cover reduced from 419 to 371 km², witnessing approximately 11.6% deglaciation in the Beas basin. A higher rate of retreat of the glaciers was observed during 1989-2006 as compared to the retreat during 1972-1989. Also, the loss has been more prominent in the glaciers with an areal extent of 2-5 km². The number of glaciers increased from 224 to 236 due to fragmentation in this period. The average elevation of the ablation zone basin showed an upward shift from 3898 m (1972) to 4171 m (2006) which may be a consequence of a shift in Equilibrium Line Altitude (ELA) reflecting imbalance.

4 illus, 3 tables, 30 ref

003356   Dixit S;Bera S K (NO, Birbal Sahni Institute of Palaeobotany, 53 University Road, Lucknow-226 007, Email: swatidixit26@gmail.com) : Holocene climatic fluctuations from Lower Brahmaputra flood plain of Assam, Northeast India. J Earth Syst Sci 2012, 121(1), 135-47.

Pollen analysis of a 3.2-m deep sedimentary profile cored from the Dabaka Swamp, Nagaon District, Lower Brahmaputra flood plain, Assam has revealed persistent fluvial activity during 14,120-12,700 cal years BP which may be attributed to the paucity of pollen and spores with encounterance of fluvial marker taxa like Ludwigia octavalvis and Botryococcus. Later, fluvial activity was succeeded by the tropical tree savanna under cool and dry climate between 12,700 and 11,600 cal years BP corresponding to that of global Younger Dryas. Between 11,600 and 8310 cal years BP, relatively less cool and dry climate prevailed with inception of tropical mixed deciduous taxa like Shorea robusta and Lagerstroemia parviflora. This phase is further followed by a fluvial activity between 8310 and 7100 cal years BP as evidenced by trace values of pollen and spores. Fluvial activity was further succeeded by enrichment of tropical mixed deciduous forest under warm and humid climatic regime between 7100 and 1550 cal years BP which is well-matched with the peak period of the Holocene climatic optimum. However, during 1550-768 cal years BP, final settlement of tropical mixed deciduous forest occurred under increased warm and humid climate followed by deterioration in tropical mixed deciduous forest under warm and relatively dry climatic regime since 768 cal years BP onwards due to acceleration in human settlement as evidenced by Cerealia. Increase in Melastoma, Ziziphus and Areca catechu imply forest clearance at this phase. The occurrence of degraded pollen-spore along with adequate fungal elements especially, Xylaria, Nigrospora and Microthyriaceous fruiting body is suggestive of aerobic microbial digenesis of rich organic debris during sedimentation.

4 illus, 1 table, 22 ref

003355   Dimri A P (NO, School of Environmental Sciences, Jawaharlal Nehru University, New Delhi, Email: apdimri@hotmail.com) : Wintertime land surface characteristics in climatic simulations over the western Himalayas. J Earth Syst Sci 2012, 121(2), 329-44.

Wintertime regional climate studies over the western Himalayas with ICTP-RegCM3 simulations through 22 years has shown systematic biases in precipitation and temperature fields. The model simulated precipitation shows systematically wet bias. In surface temperature simulations, positive and negative biases of 2°-4°C occurred. Experiment without (CONT) and with subBATS (SUB) shows that later scheme performs better, especially for precipitation. Apart from the role of topography and model internal variability, land surface characteristics also have profound impact on these climatic variables. Therefore, in the study, impacts of land surface characteristics are investigated through cool/wet and warm/dry winter climate by CONT and SUB simulations to assess systematic biases. Since SUB experiment uses detailed land-use classification, systematic positive biases in temperature over higher elevation peaks are markedly reduced. The change has shown reduced excessive precipitation as well. Most of the surface characteristics show that major interplay between topography and western disturbances (WDs) takes place along the foothills rather than over the higher peaks of the western Himalayas.

12 illus, 1 table, 74 ref

003354   Dey G K;Das P K (Physics Dep, Pandu College, Guwahati-781 012, Email: deygautam63@yahoo.com) : Estimation of radon concentration in dwellings in and around Guwahati. J Earth Syst Sci 2012, 121(1), 237-40.

It has been established that radon and its airborne decay products can present serious radiation hazards. A long term exposure to high concentration of radon causes lung cancer. Besides, it is also known that out of the total radiation dose received from natural and man-made sources, 60% of the dose is due to radon and its progeny. Taking this into account, an attempt has been made to estimate radon concentration in dwellings in and around Guwahati using aluminium dosimeter cups with CR-39 plastic detectors. Results of preliminary investigation presented in this paper show that the mean concentration is 21.31 Bq m^-3.

1 illus, 2 tables, 13 ref

003353   Deepulal P M;Gireesh Kumar T R;Sujatha C H (Chemical Oceanography Dep, School of Marine Sciences, CUSAT, Kochi-682 016, Email: dlpmchem@gmail.com) : Behaviour of REEs in a tropical estuary and adjacent continental shelf of southwest coast of India: evidence from anomalies. J Earth Syst Sci 2012, 121(5), 1215-27.

Distribution and accumulation of the rare earth elements (REE) in the sediments of the Cochin Estuary and adjacent continental shelf were investigated. The rare earth elements like La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and the heavy metals like Mg, V, Cr, Mn, Fe, Cu, Zn, U, Th were analysed by using standard analytical methods. The Post-Archean Australian Shale composition was used to normalise the rare earth elements. It was found that the sediments were more enriched with the lighter rare earth elements than the heavier ones. The positive correlation between the concentrations of REE, Fe and Mn could explain the precipitation of oxyhydroxides in the study area. The factor analysis and correlation analysis suggest common sources of origin for the REEs. From the Ce-anomalies calculated, it was found that an oxic environment predominates in all stations except the station No. 2. The Eu-anomaly gave an idea that the origin of REEs may be from the feldspar. The parameters like total organic carbon, U/Th ratio, authigenic U, Cu/Zn, V/Cr ratios revealed the oxic environment and thus the depositional behaviour of REEs in the region.

7 illus, 4 tables, 53 ref

003352   Das R;Wason H R;Sharma M L (Earthquake Engineering Dep, Indian Institute of Technology Roorkee, Roorkee, Email: Wason2009@gmail.com) : Temporal and spatial variations in the magnitude of completeness for homogenized moment magnitude catalogue for Northeast India. J Earth Syst Sci 2012, 121(1), 19-28.

Northeast India region is one of the most seismically active areas in the world. Events data for the period 1897-2010, used in this study has been largely compiled from global ISC, NEIC and GCMT databases. Historical seismicity catalogue of Gupta et al (1986) and some events data from the bulletins of India Meteorological Department are also used. Orthogonal regression relations for conversion of body and surface wave magnitudes to M_{w, HRVD} based on events data for the period 1978-2006 have been derived. An Orthogonal Standard Regression (OSR) relationship has also been obtained for scaling of intensity estimates to M_{w, NEIC} using 126 global intensity events with intensity VI or greater during the period 1975-2010. Magnitude of completeness and Gutenberg-Richter (GR) recurrence parameter values have been determined for the declustered homogenized catalogue pertaining to four different time periods namely, 1897-1963, 1964-1990, 1964-2000 and 1964-2010. The M_c and `b' values are observed to decrease and increase, respectively, with addition of newer data with time. The study region has been subdivided into nine seismogenic zones keeping in view the spatial variations in earthquake occurrence and prevalent tectonics. Mc, `b' and `a' values have been estimated with respect to each zone, and the variations in the values of these parameters have been analysed.

6 illus, 3 tables, 30 ref

003351   Das K;Bose S;Karmakar S;Chakraborty S (Earth Sciences Dep, Bengal Engineering and Science University, Shibpur, Howrah, Email: kaushik.met@gmail.com) : Petrotectonic framework of granulites from northern part of Chilka Lake area, Eastern Ghats Belt, India: compressional vis-…-vis transpressional tectonics. J Earth Syst Sci 2012, 121(1), 1-17.

Granulite-facies rocks occurring North-East of the Chilka Lake anothosite (Balugan Massif) show a complex metamorphic and deformation history. The M₁-D₁ stage is identified only through microscopic study by the presence of S₁ internal foliation shown by the M₁ assemblage sillimanite-quartz-plagioclase-biotite within garnet porphyroblasts of the aluminous granulites and this fabric is obliterated in outcrop to map-scale by subsequent deformations. S₂ fabric was developed at peak metamorphic condition (M₂-D₂ª) and is shown by gneissic banding present in all lithological units. S₃ fabric was developed due to D₃ deformation and it is tectonically transposed parallel to S₂ regionally except at the hinge zone of the F₃ folds. The transposed S₂/S₃ fabric is the regional characteristic structure of the area. The D₄ event produced open upright F₄ folds, but was weak enough to develop any penetrative foliation in the rocks except few spaced cleavages that developed in the quartzite/garnet-sillimanite gneiss. Petrological data suggest that the M₄-D₄ stage actually witnessed reactivation of the lower crust by late distinct tectonothermal event. Presence of transposed S₂/S₃ fabric within the anorthosite arguably suggests that the pluton was emplaced before or during the M₃-D₃ event. Field-based large-scale structural analyses and microfabric analyses of the granulites reveal that this terrain has been evolved through superposed folding events with two broadly perpendicular compression directions without any conclusive evidence for transpressional tectonics as argued by earlier workers. Tectonothermal history of these granulites spanning in Neoproterozoic time period is dominated by compressional tectonics with associated metamorphism at deep crust.

11 illus, 42 ref

003350   Dadolahi Sohrab A;Garavand Karimi M;Riahi H; Pashazanoosi H (Marine Environment Dep, Faculty of Marine Natural Resources, Khorramshahr University of Marine Science and Technology, 669, Khorramshahr, Iran, Email: P-dadolahi@yahoo.com) : Seasonal variations in biomass and species composition of seaweeds along the Northern coasts of Persian Gulf (Bushehr Province). J Earth Syst Sci 2012, 121(1), 241-50.

Study was carried out to evaluate the seasonal variations of seaweed biomass and species composition at six different sites along the coastal areas in Bushehr Province. Sampling depths varied among sites, from 0.3 to 2.0 m below mean sea level. A total of 37 (i.e., 10 Chlorophyta, 12 Phaeophyta and 15 Rhodophyta) seaweed species were collected. Studies were conducted for quantifying the seaweeds during four seasons from October 2008 until July 2009. During present research, Ulva intestinalis and Cladophora nitellopsis of green, Polycladia myrica, Sirophysalia trinodis and Sargassum angustifolium of brown and Gracilaria canaliculata and Hypnea cervicornis of red seaweeds showed highest biomass in coastal areas of Bushehr Province. The Cheney's ratio of 2.1 indicated a temperate algal flora to this area. All sites exhibited more than 50% similarity of algal species, indicating a relatively homogenous algal distribution. Total biomass showed the highest value of 3280.7 ± 537.8 g dry wt m^-2 during summer and lowest value of 856.9 ± 92.0 g dry wt m^-2 during winter. During this study, the highest and lowest seaweed biomass were recorded on the site 2 (2473.7 ±311.0 g dry wt m^-2) and site 5 (856.7 ± 96.8 g dry wt m^-2), respectively.

1 illus, 9 tables, 21 ref

003349   Chang C K;Azamathulla H M;Zakaria N A;Ghani A A (River Engineering and Urban Drainage Research Centre, Universiti Sains Malaysia, 14300 Nibong Tebal, Pulau Pinang, Malaysia, Email: mdazmath@gmail.com) : Appraisal of soft computing techniques in prediction of total bed material load in tropical rivers. J Earth Syst Sci 2012, 121(1), 125-33.

Evaluates the performance of three soft computing techniques, namely Gene-Expression Programming (GEP) (Zakaria et al 2010), Feed Forward Neural Networks (FFNN) (Ab Ghani et al 2011), and Adaptive Neuro-Fuzzy Inference System (ANFIS) in the prediction of total bed material load for three Malaysian rivers namely Kurau, Langat and Muda. The results of present study are very promising: FFNN (R² = 0.958, RMSE = 0.0698), ANFIS (R² = 0.648, RMSE = 6.654), and GEP (R² = 0.97, RMSE = 0.057), which support the use of these intelligent techniques in the prediction of sediment loads in tropical rivers.

5 illus, 3 tables, 35 ref

003348   Ardie W A;Sow K S;Tangang F T;Hussin A G; Mahmud M;Juneng L (Climate and Ocean Analysis Lab, Research Centre for Tropical Climate C, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor, Malaysia, Email: juneng@ukm.my) : Performance of different cumulus parameterization schemes in simulating the 2006/2007 southern peninsular Malaysia heavy rainfall episodes. J Earth Syst Sci 2012, 121(2), 317-27.

Performance of four different cumulus parameterization schemes (CPS) in the Weather Research and Forecasting (WRF) model for simulating three heavy rainfall episodes over the southern peninsular Malaysia during the winter monsoon of 2006/2007 were examined. The modelled rainfall was compared with the 3-hourly satellite observation and objectively scored using a verification technique called the acuity-fidelity. The technique is based on minimization of a cost function that is calculated from four parameters taking into account errors in distance, time, intensity, and missed events. All simulations were made for 72 hours for the three episodes starting at 1200 UTC 17 December 2006, 1200 UTC 24 December 2006 and 1200 UTC 11 January 2007, respectively. The four different CPSs used are the new Kain-Fritsch scheme (KF2), the Betts-Miller-Janjic scheme (BMJ), the Grell-Devenyi ensemble scheme (GD) and the older Kain-Fritsch scheme (KF1). While the BMJ scheme shows some success in the second and third episodes, it shows high location errors in the first episode, leading to high acuity errors. The GD, KF2 and KF1 schemes performed poorly, although both the BMJ and GD schemes simulated the observed drastic increase of rainfall at 2100 UTC 18 December 2006 during the first episode. Overall, the KF1 and KF2 schemes produced positive biases in terms of coverage, while the GD scheme showed persistent location bias, producing a scattered line of precipitation over the eastern coastline of peninsular Malaysia. Although the BMJ scheme has better results, its poor performance for the first episode suggests that suitability of CPS may be case dependent.

8 illus, 3 tables, 35 ref

003347   Anupam Kumar;Roy Bhowmik S K;Das A K (NO, India Meteorological Dep, New Delhi-110 003, Email: skrb@imdmail.gov.in) : Implementation of Polar WRF for short range prediction of weather over Maitri region in Antarctica. J Earth Syst Sci 2012, 121(5), 1125-43.

India Meteorological Department has implemented Polar WRF model for the Maitri (lat. 70°45'S, long. 11°44'E) region at the horizontal resolution of 15 km using initial and boundary conditions of the Global Forecast System (GFS T-382) operational at the India Meteorological Department (IMD). Main objective of the study is to examine the performance skill of the model in the short-range time scale over the Maitri region. An inter-comparison of the time series of daily mean sea level pressure and surface winds of Maitri for the 24 hours and 48 hours forecast against the corresponding observed fields has been made using 90 days data for the period from 1 December 2010 to 28 February 2011. The result reveals that the performance of the Polar WRF is reasonable, good and superior to that of IMD GFS forecasts. GFS shows an underestimation of mean sea level pressure of the order of 16-17 hPa with root mean square errors (RMSE) of order 21 hPa, whereas Polar WRF shows an overestimation of the order of 3-4 hPa with RMSE of 4 hPa. For the surface wind, GFS shows an overestimation of 1.9 knots at 24 hours forecast and an underestimation of 3.7 knots at 48 hours forecast with RMSE ranging between 8 and 11 knots. Whereas Polar WRF shows underestimation of 1.4 knots and 1.2 knots at 24 hours and 48 hours forecast with RMSE of 5 knots. The results of a case study illustrated, reveal that the model is capable of capturing synoptic weather features of Antarctic region. The performance of the model is found to be comparable with that of Antarctic Meso-scale Prediction System (AMPS) products.

11 illus, 3 tables, 12 ref

003346   Ali K;Inamdar S R;Beij G;Ghude S;Peshin S (NO, Indian Institute of Tropical Meteorology, Pune, Dr. Homi Bhabha Road, Pashan, NCL Post Office, Pune-411 008, Email: kaushar@tropmet.res.in ) : Surface ozone scenario at Pune and Delhi during the decade of 1990s. J Earth Syst Sci 2012, 121(2), 373-83.

Data on surface ozone concentration compiled for a 10-year period from 1990 to 1999 for Pune and Delhi are analyzed in terms of its frequency distribution, annual trend, diurnal variation and its relation with various meteorological and chemical parameters. It is found that the surface ozone concentration range showing highest frequency of occurrence at Pune is 0-5 ppb during winter and post-monsoon seasons and 15-20 ppb and 5-10 ppb during summer and monsoon seasons, respectively. It is 0-5 ppb at Delhi during all the seasons. The surface ozone concentration has shown a decreasing trend at Pune during the observational period with an average rate of decrease of 1.54 ppb/year. On the other hand, there is no trend whatsoever in the variation of surface ozone concentration at Delhi. Minimum value of surface ozone occurs before sunrise and maximum in the afternoon hours. Regression analyses of surface ozone with maximum temperature (r = 0.46 for Pune and 0.51 for Delhi, significant at more than 0.1%) and NO₂ at respective locations indicate that surface ozone at these locations is mainly produced by photochemistry. Transport mechanism is also understood to have contributed significantly to the total concentration of ozone. Inverse relationship obtained between surface ozone concentration and relative humidity indicates that major photochemical paths for removal of ozone become effective when humidity increases at these locations.

9 illus, 2 tables, 32 ref

003345   Acharya T;Mallik S B (Geology Dep, Durgapur Government College, University of Burdwan, Durgapur-713 214, Email: tacharya3@yahoo.com) : Analysis of lineament swarms in a Precambrian metamorphic rocks in India. J Earth Syst Sci 2012, 121(2), 453-62.

Addressing the geologic significance of lineaments and their correlation with joints/fractures is still unclear. The study attempts to analyse the lineament swarms developed in a Precambrian metamorphic terrain in India using both unfiltered and filtered techniques. The unfiltered analysis technique shows that the major lineament and fracture trends are oriented along EW and NS directions respectively, thus failing to provide any correlation between them. The application of domain-based filtering techniques identifies a highly predominant fracture-correlated lineaments in mica schist constituting the EW trending shear zone in the area. This correlation is not evident in the areas north and south of the shear zone, where the lineaments are consistently oriented along the foliation planes of the rocks and are designated as `foliation correlated'. The analysis indicates that the fracture frequency and the strain history may have played significant roles for the formation of fracture-correlated lineaments in the metamorphic terrain.

11 illus, 3 tables, 43 ref

003344   Abdalla F A;Scheytt T (Geology Dep, Faculty of Science, South Valley University, Qena, Egypt, Email: traugott.scheytt@tu-berlin.de) : Hydrochemistry of surface water and groundwater from a fractured carbonate aquifer in the Helwan area, Egypt. J Earth Syst Sci 2012, 121(1), 109-24.

Groundwater is an important water resource in the Helwan area, not only for drinking and agricultural purposes, but also because several famous mineral springs have their origin in the fractured carbonate aquifer of the region. The area is heavily populated with a high density of industrial activities which may pose a risk for groundwater and surface water resources. The groundwater and surface water quality was investigated as a basis for more future investigations. The results revealed highly variable water hydrochemistry. High values of chloride, sulphate, hardness and significant mineralization were detected under the industrial and high-density urban areas. High nitrate contents in the groundwater recorded in the southern part of the study area are probably due to irrigation and sewage infiltrations from the sewage treatment station. The presence of shale and marl intercalation within the fissured and cavernous limestone aquifer promotes the exchange reactions and dissolution processes. The groundwater type is sodium, sulphate, chloride reflecting more mineralized than surface water. The results also showed that water in the study area (except the Nile water) is unsuitable for drinking purposes, but it can be used for irrigation and industrial purposes with some restrictions.

9 illus, 3 tables, 57 ref

002321   Zohrabi N;Bavani A R M;Sedghi H;Telvari A R; Bajestan M S (Irrigation Dep, Science and Research Branch Islamic Azad Univ, Tehran, Iran, Email: nargeszohrabi@gmail.com) : Identification of temporal fluctuations in the annual flood series of Karoun and Dez rivers in Iran. Ecol Envir Conserv 2011, 17(2), 169-75.

Annual flood series in seven main stations in the Large Karoun river (consist of Karoun and Dez rivers) in Iran, measured during 1958 - 2009, were examined to identify the temporal character of changes in flood series. Two approaches were used to evaluate temporal changes in flood series during the period 1958 -2009. The first approach is based on an analysis of standardized departures, and the second approach based on a Multiple trend tests were computed by varying the beginning and ending date of the time series. These method are used for identification of an abrupt change in flood series rather than a gradual trend. Results indicate a noticeable step increase in flood series around 1983 rather than as a gradual trend. This step change is that the climate system has shifted to a new regime that Will likely remain relatively constant until a new shift or step change occurs.

5 illus, 1 table, 15 ref

002320   Singh B;Khurana S C;Manish Kumar;Yadav N; Yadav R (Zoology Dep, D.A.V. P.G. College, Kanpur, Uttar Pradesh) : Evaluation of ground water quality of residential areas on the basis of chemical parameters. Asian J expl Chem 2012, 7(1), 15-8.

Laboratory study was analyzed to observe the ground water quality of residential areas (Higher Income Group, Minimum Income Group, Lower Income Group, Juggi Jhopari, and Industrial Area) of Kanpur metro by examining the chemical parameter like calcium (Ca⁺²), magnesium (Mg⁺²), sulphate (SO₄^-2), chloride (Cl^-2), fluoride (F^-) and nitrate (NO₃^-2) as per the method assessment of ground water quality described in Standard methods for the examination of water and wastewater Indian Council of Medical Research (ICMR) and WHO. The result revealed that much variation was observed during October to April, most parameters decreased during summer and increase during the rainy season and then began to decrease again in winter followed by summer. HIG groundwater appeared to be the best ground water available in Kanpur metro.

5 tables, 9 ref

002319   Shukla V;Jaiswal V K (Geography Dep, Allahabad Univ, Allahabad, Uttar Pradesh, Email: vimalmmpg@gmail.com) : Pattern of irrigation in Ambedkar Nagar district (Uttar Pradesh). Indian J Landsc Syst ecol Stud 2012, 35(2), 244-50.

Agriculture is the prime occupation of the rural inhabitants of the study area and the productivity is primarily determined by irrigation facility available in the area. The irrigation and agricultural output creates a nexus of the rural economy. Irrigation itself is determined by the water resource and its optimum use in the study area. District Ambedkar Nagar is quite lucky in terms of high ground water table so in the irrigation facility. The present paper tries to elaborate some of these prominent features in the area.

1 illus, 3 tables, 8 ref

002318   Sheshu Kumar G;Padma Kumari B;Bhadram C V V (NO, Centre for Earth Atmosphere & Weather Modification Technologies, 3 floor ECE Building, Jawaharlal Nehru Technological Univ, Kukatpally, Hyderabad-85) : Study of aerosol distribution over Indian region based on satellite retrieved data. J Indian Geophys Union 2012, 16(4), 189-97.

Atmospheric aerosols play a major role in climate change. However, aerosol measurements, particularly their vertical distribution, are sparse over Indian region. Data from Vertical distribution of aerosols obtained from space-borne Lidars such as CALIPSO Cloud-Aerosol and Infrared Pathfinder Satellite Observation) has been used to study the properties of pollution aerosols, dust aerosols and biomass burning aerosols on randomly selected days over Indian region in the pre-monsoon and monsoon seasons of 2009. The first case study describes the presence of dust aerosols as retrieved by CALIPSO over central India on 18 March 2009. It is observed that thick layer of aerosols is present up to a height of 5km across India extending from south to north. It is also interesting to observe that the aerosols are being lifted along the slopes of Himalayas. In the second study on a monsoon day, the strong westerly winds with patches of upward and downward vertical winds give a good insight to understand the weather conditions on 22 June 2009. A significant variation in the vertical distribution of aerosols is seen from day to night. During day maximum total attenuated backscatter is at 2-3 km and during night the maximum is at 4 km. Dust and polluted dust aerosols are dominating during both day and night. The year 2009 being a bad monsoon year, the presence of high aerosol levels up to a height of <126> 4 km is clearly seen. MODIS derived Aerosol Optical Depth (AOD) also confirms high aerosol loading ranging from 0.4 to 1 μm.

10 illus, 7 ref

002317   Shabanlou S (NO, Kermanshah Branch Islamic Azad Univ, Kermanshah, Iran, Email: saeid.shabanlou@gmail.com) : Reservoirs scenario for river branches of Golestan watershed. Ecol Envir Conserv 2011, 17(2), 201-7.

Flood is often said to be a phenomenon that leaves harmful effects by submerging lands and coastal areas. Flood control is in fact said to all preparations and methods that lead to the reduction of the harmful effects of a flood. The point we want to reach in this paper, is to find out the rate of the submergence of the flood plains in the edges of the rivers with different return period discharges in Golestan province. Since the data periods in stations are different and because of the fact that some stations were established in the area from 1337 to the recent years, after surveying and doing the competence data test based on Matusen Fon relation, the data period was selected from 1350 up to now. Among the mentioned stations, some were newly-built and some had a lot of lost data, so, their data was not enough in the best fit test and therefore was removed. After completing and prolonging this data by means of SMADA software, HEC-SSP software was used in order to estimate the maximum instantaneous discharge of these stations with different return periods. Then, the file of geometrical characteristics of the sections of the flood channels of the basin under study was provided in HEC-GeoRAS and then was exported from GIS to HEC-RAS. Then the flood Encroachment for the rivers of the area was done by the flood hydrographs with different return periods which was obtained by HEC-SSP software, and the area under threat was specified. Then making reservoir scenario was studied. After recognizing total area and cost of damage for Golestan watershed, in every stage a reservoir was spotted in the end of rivers branch. After running HEC-RAS with reservoir the amount of flood hazard areas and damage was obtained and effect of every reservoir was recognized.

4 illus, 6 tables, 12 ref

002316   Santra D;Das S K;Samanta S K (NO, Chandernagore Govt. College, West Bengal) : Terrain condition of the Siri Khola basin, Darjeeling district, West Bengal. Indian J Landsc Syst ecol Stud 2012, 35(2), 351-9.

The Siri khola basin is one of the important geomorphic units of the Darjiling Himalaya. Being located on the eastern slope of the Southern Singalila range the area exhibits a unique type of landscape produced over a very sensitive lithological composition. Due to fragile nature of the tract a set of tectono-geomorphic hazards play their conspicuous role : some of which occur intermittently but many come out frequently in response to their favourable seasonal conditions. Local forests as well as human activities in the terrain modify their results in some cases too. The present paper is thus going to reveal an inter-related scenario of all these settings in an abridged but vivid description.

7 illus, 12 ref

002315   Rao M J;Greeshma Gireesh A G;Avatharam P;Anil N C;Karuna Karudu T (Delta Studies Institute, Andhra Univ, Visakhapatnam) : Coastal geomorphology along Visakhapatnam to Bhimunipatnam, East coast of India. J Indian Geophys Union 2012, 16(4), 179-87.

An attempt has been made to study and record the diverse coastal geomorphic features along Visakhapatnam - Bhimunipatnam coast. The study area is marked by geomorphic features resulted from various coastal and land ward processes. The geomorphic units under different heads namely, features formed by present day wave action, features formed due to sea level oscillations and features formed by rock and sea water interaction have been presented. The influence of sea level oscillations and land and sea interaction forms a diverse coastal geomorphology along the coast. The details of features such as beach, dune system, inter tidal deposits, red sediments, wave cut platform, marine terrace, sea stack, sea cave, serpent hood structures, promontories, wind gap and natural bridge have been recorded and the formation as well as significance of their occurrence are presented. The coastal geomorphology of the study area clearly established not only the sea level oscillations but also variations in climatic conditions in this part of the coast.

14 illus, 16 ref

002314   Rao C S;Chaudhari M S (NO, Central Water and Power Research Station, Khadakwasla, Pune-411 024) : Delineating unevem bedrock topography by continuous seismic refraction study. J Indian Geophys Union 2012, 16(4), 169-74.

For designing and deciding the level of foundation for heavy civil structures, information on depth to rock and its quality are pertinent. Information on rock quality and its topography can be obtained from boreholes at discrete locations. However, information gathered covers a small volume around the hole. Interpolation of geological information between boreholes in areas of uneven weathering could be erroneous and misleading. Continuous seismic refraction study along with the information from a few boreholes can overcome these limitations and provide the required information reliably. The efficacy of the method is illustrated through a study conducted at Indira Gandhi Center for Atomic Research (IGCAR), Tamil Nadu. Continuous refraction study was carried out along 24 line km in the form of 20 m grid in two mutually perpendicular directions to decipher subsurface stratigraphy including rock topography, to infer its quality and to check anisotropy in rock velocities, if any. Special efforts were made to ensure good coupling of explosives with dry sand in shot holes and also of geophones with loose sand on surface, for generating and efficient recording of seismic waves in windy conditions near the sea coast. Seismic depth sections revealed two to three layers viz., loose sand, compact sand/ weathered rock and good quality charnockite rock. The rock topography was very uneven indicating differential weathering pattern. The depth to rock varied from 5.9m to 25.8m and the rock velocity ranged between 4000 m/sec and 5800 m/sec, which for charnockite rock indicated good quality. However, a few zones in bedrock having lower wave velocity (< 3500 m/sec), corresponding to inferior quality rock, were inferred and their lateral extent delineated. The seismic velocities obtained in the two mutually perpendicular directions were comparable and did not show any anisotropy in rock. The study showed that at the sites with uneven weathering, only boreholes at discrete locations are not enough to define rock topography and quality precisely. Instead, continuous seismic refraction study in conjunction with limited borehole data provided optimum coverage economically.

6 illus, 5 ref