July, 2010

July, 2010   ||  Volume 14 No.3


Mass transport model studies in the industrial aquifers of Visakhapatnam, Andhra Pradesh 

Y.Somu Naidu and C.Kavitha

Department of Geophysics, Andhra University, Visakhapatnam - 530 003
1Department of Electronics, GITAM University, Visakhapatnam - 530 045
E-mail: naiduys1231@rediffmail.com

The city of Visakhapatnam has many randomly located industrial sites, sharing common groundwater aquifers. The average TDS levels of groundwaters of industrial aquifers were around 500 mg/l in 1980. In 2005 it has reached an average level of 2500 mg/l. Three major industries, namely, Hindustan Zinc Limited (HZL), Coromandal Fertilizers Limited (CFL) and Hindustan Petroleum Corporation Limited (HPCL), located on a common aquifer and separated by a distance of 2 to 3 Km, have contributed hazardous levels of contaminants to groundwater. Mass Transport Model studies are conducted using Visual MODFLOW (MT3D) to predict the areas that come under the impact of these three industrial effluents with respect to the increasing TDS time and space. The areas, predicted to under the industrial contamination impact by 2025 by model studies are demarcated. The hazardous levels of salinity predicted are also shown.


Characterization and evaluation of continental basalts from two sites in Maharashtra using ultrasonic measurements in the laboratory
K.J.Prasanna Lakshmi, K.B.Chary, K.Vijay Kumar, M.V.M.S.Rao, S.Ravinder, J.Venukumar and K.Venkatesh
National Geophysical Research Institute (CSIR), Uppal Road, Hyderabad - 500 606.
E-mail: kjplakshmi@yahoo.com

The Deccan volcanic province comprises ~3.4 km thick ~65 Ma tholeiitic basalt flows with subordinate amount of alkaline and picritic basalts. The flows show a wide range of texture and microstructures. These rocks are widely used as a main construction material in various engineering structures in India, where these rock formations are exposed. Therefore, understanding of their physico-mechanical properties is useful to determine their suitability as the construction material. We studied basalt samples from the Khadakpurna link canal project site and the Koyna borehole. Density, ultrasonic P-wave velocity (VP) and Uniaxial Compressive Strength (UCS) of these samples were measured and Schmidt’s hardness and United Alteration Index (UAI) were derived. The results show that the Khadakpurna samples show a wide range of VP from 3578 m/s to 5163 m/s, while the Koyna samples show a narrow range, from 5617 m/s to 5789 m/s, indicating the effect of weathering on the ultrasonic P-wave velocity. Accordingly, the other properties such as density, uniaxial compressive strength, Schmidt’s hardness, United Alteration Index (UAI) are also found to vary significantly. When the results of these two sites are compared, the Koyna rocks can be used for building heavy engineering structures.

Seismic Refraction Survey for Rolep Hydroelectric Power Project, Sikkim

C.Krishnaiah, A.Saha, R.S.Ramteke, R.S.Wadhwa and N.Ghosh
Central Water and Power Research Station, Khadakwasla, Pune - 411 024
E-mail: krishnaiahc@yahoo.com

Rolep hydropower project is proposed to be constructed in the hilly terrain of east Sikkim at the downstream of confluence of the rivers Rangpo and Nathung Chu near Rolep village. The terrain represents mainly granitiferous quartz-biotite gneiss belonging to Darjeeling Group of Precambrian age. The area falls under the zone IV of seismic zoning map and experiences frequent shallow focus micro-earthquakes. The area had undergone tectonic disturbance resulting in differential weathering give rise to varied type of geotechnical conditions. Seismic refraction survey was carried out to find out the bedrock profile and to infer its quality, the status of the overburden as well as the structural features such as, micro faults/shear zones and other tectonically disturbed zones, which may affect the stability of the hydraulic structures. Twenty-five continuous seismic refraction traverses of varying lengths were run to cover the area where the important civil structures are to be located.
The results of the refraction survey revealed a three layer geo-seismic section consisting of loose overburden wave velocity between 200 and 500 m/sec followed by normal to compact and compact overburden (500 - 1700 m/sec). This overburden overlies the weathered to good quality bedrock (2000 - 4400 m/sec).
The depth to the bedrock was evaluated to be the deepest i.e. 40 m below ground level in the surge shaft area and the same occurred at shallow depths at dam axis i.e., from 6-17 m below ground level. Along the Head Race Tunnel (HRT) alignment, which is passing through surge shaft area the bedrock velocity was in the range of 2600 – 3400 m/sec suggesting the weathered grade rock. In the powerhouse area foundation grade gneissic rock was found with the velocity range of 2000 – 4400 m/sec. No major shear zones/weak zones were found in the area covered by seismic refraction method. Seismic results are in accordance with the borehole data. 

Ionospheric drifts over Udaipur during counter electrojet events
R.K.Rai, M.Mittal1 and H.Chandra2
M.S.University Udaipur - 313 001
1Govt. Holkar Science College, Indore - 452 017
2Physical Research Laboratory, Ahmdabad - 380 009

Ionospheric drift measurements made at Tiruchirapalli, situated close to the magnetic equator and Udaipur a tropical latitude station during the years 1973-74 are examined on few counter-electrojet days covering both winter and summer seasons. The examples presented here show that on counter electrojet days the drift velocity tends to shift eastward not only at equatorial stations but also at Udaipur. This suggests that there is change in the global scale wind pattern during counter electrojet events.



Diurnal seismicity and temperature
Vinayak Kolvankar, Shashank Deshpande1, Abhijeet Manjre1, Samruddha More1 and Nisha Thakur1

C/O Computer Division, Bhabha Atomic Research Centre. Mumbai – 400 085
1BVMIT CBD Belapur, Mumbai
E-mail: vkolvankar@yahoo.com

Global earthquake catalog data are systematically examined to see the seismicity variation with local time over 24 hours basis. It is observed that the occurrences of earthquakes are more during the night than during the day. The earthuake counts go down during the day and it is minimum in the afternoon at 15 – 16 hours and then steadily goes up till midnight. This typical signature of the diurnal seismicity seems to be consistent for the global earthquake data for different periods, seasons, longitudes and depths. The sagging of the earthquake counts during the day, reduces for latitudes away from the equators. It is seen that this diurnal seismicity plot obtained for large number of earthquakes is modulated by the inverse of diurnal temperature plot applicable for any place close to the equator. 



Solar and geomagnetic activity control on equatorial VHF Scintillations in the Indian region
S.Banola, R.N.Maurya and H.Chandra1

Indian Institute of Geomagnetism, Navi Mumbai- 410 218
1Physical Research Laboratory, Ahmedabad- 380 009
E.mail :sbanola@iigs.iigm.res.in

A network of stations was operated monitoring amplitude scintillations of 244/251 MHz signal from FLEETSAT (73º E) in India for over a solar cycle. Latitudinal width of the equatorial belt of scintillation is higher during D-months and E-months compared to J-months. There is a positive correlation between the width of the belt and solar activity. Width of the belt decreases with magnetic activity. Equatorial scintillations are inhibited during magnetic disturbances with seasonal and solar cycle dependence. An analysis covering more than 200 geomagnetic storm events show scintillations at low latitudes can be either inhibited or triggered during storms depending on the phase of the storm and local time of occurrence.