October, 2005

October, 2005   ||  Volume 9 No.4

Crustal density model along Gopali- Port Canning profile, West Bengal basin using seismic and gravity data

A.S.S.S.R.S.Prasad, N.Venkateswarlu and P.R.Reddy
National Geophysical Research Institute, Hyderabad - 500 007


An integrated approach of processing and interpretation of the seismic, gravity, geological and structural details along Gopali- Port Canning Deep Seismic Sounding (DSS) profile, West Bengal basin has helped in deriving a crustal density model. This model clearly explains the trend, shape and magnitude of the Bouguer gravity anomalies across southern parts of the West Bengal basin.
The study pointed out that the thick sedimentary column (thickening towards east) and lateral structural variations in the middle and lower crustal layers coupled with structural trends in the basement have jointly contributed to gravity effect. The prominent lateral variations in the Bouguer gravity anomalies could mainly be attributed to regionally extending causative factors. The derived model is useful in understanding the complex structural trends of geodynamic importance.

Saline Water Contamination of the Aquifer Zones of Eastern Kolkata
D.K.Saha and K.Choudhury
Central Geophysics Division, Geological Survey of India, 27, J.L. Nehru Road, Kolkata - 700 016



A number of saline/brackish water zones are present in the subsurface around the Kolkata metropolis. Mixing of fresh and brackish ground water has created environmental problems in certain areas. Vertical Electrical Soundings (VES) employing Schlumberger configuration have been deployed in the eastern and south eastern Kolkata metropolis for delineating the subsurface saline water zones. Interpretation of VES data has indicated disposition of saline / brackish and fresh water zones at different depth level which would be useful in the ground water management with minimum risk of saline contamination. Resistivity surveys have also delineated clay formations, which act as barriers for saline water percolation or transmission. Aquifer zone at some depths south of Bhangar canal is vulnerable for saline water contamination as large part of this area is occupied by brackish/saline water in the subsurface. It has been found that the area north of the canal does not contain any appreciable saline water in the subsurface. It is further inferred that the sea water was trapped inland in the Holocene times during marine transgression causing salinity of ground water at several places.

Deep Crustal Structure across Krishna-Godavari Basin from Gravity Data
L.V.Ramana, K.V.Swamy1 and C.Visweswara Rao2
Indian Institute of Geomagnetism, New Panvel, New Mumbai
1National Centre for Antarctic Ocean Research, Goa
2Corresponding author : Department of Geophysics, Andhra University, Visakhapatnam - 530 003)



Gravity data over the Krishna Godavari (KG) basin is reinterpreted primarily for attributing the causative source for the conspicuous gravity high over the southeastern side of the Tanuku horst, namely, Kakinada Terrace (KT). Three-layered crust is assumed based on DSS studies in this region. Using the available gravity data the crust is modeled along two profiles as a three-layered unit. Densities of layers required in this modeling are determined on the basis of seismic P wave velocity ranges and well log data. The models are constrained with available depth values of the basement at some places along the profiles. The resulted model supports a basement of high-density of 2.90 gm/cc below the KT instead of Archean igneous and metamorphic basement with a density of 2.76 gm/cc. In other parts of the basin this denser layer is traced below the usual Archean basement complex. Different densities and seismic wave velocities characterize these two layers with a boundary between the two terminating in KT region. A denser basement in the KT region is perhaps due to the subsidence of sedimentary sequences in southeastern parts of East Godavari sub basin that may have contributed a steep step fault zone in Paleocene basalts, known as Matyapuri -Palakollu Fault Zone (MPFZ) and subsequent tectonic readjustment. The interpretation also rules out a Moho rise below this region supporting the conclusion arrived at by DSS studies in this region.

GPS Satellite and Receiver Instrumental Biases Estimation using Linear Adaptive Filter Algorithm

K. Ramalingam, G. Sasibhushana Rao, P. V. D. Somasekhar Rao1 and A.D.Sarma2

Airports Authority of India, Hyderabad – 500 016
1Department of ECE, J.N.T.University, Hyderabad
R & T Unit for Navigational Electronics, Osmania University, Hyderabad - 500 007
E-mail: ad_sarma@yahoo.com

The ozone data obtained from Total Ozone Mapping Spectrometer (TOMS) and Solar Back scatter Ultra Violet spectrometer (SBUV) on Nimbus 7 satellite have been used to study the variability of the total column amount of ozone and ozone concentration in different atmospheric layers respectively at Rajkot (22.30N, 70.8 0E) over a period from 1980 –2004. An examination of the monthly mean values obtained from TOMS indicates a marked seasonal variation with a maximum around June and a minimum around December.
The SBUV profile of springtime ozone indicates that the stratospheric ozone concentration at Rajkot has decreased consistently from 1982 to1999. The concentration is found to have increased suddenly in 2000 and further in 2001. Thereafter it decreased in 2002 and again increased in 2003. An insignificant overall downward trend is observed in the total column amount of ozone (0.85%) from 1997 to 2004. Latitudinal variation of ozone from Srinagar to Kanyakumari has also been studied for the year 2003, which indicates an increase in ozone concentration with latitude. The results are discussed in the light of photochemical and dynamical effects.

Planetary Configuration: Implications for Earthquake Prediction and Occurrence in Southern Peninsular India

N.Venkatanathan, N.Rajeshwara Rao, K.K.Sharma and P.PeriakaliDepartment of Applied Geology, University of Madras, School of Earth & Atmospheric Sciences,
Guindy Campus, A.C.College Buildings, Chennai – 600 025

Though there have been several attempts at earthquake prediction from different perspectives, this attempt aims at establishing planetary configurations as a definitive means of earthquake prediction. When two or more planets, Sun and Moon are aligned more or less in line (0o or 180o) with the Earth, then the Earth would be caught in the middle of a huge gravity struggle between the Sun and the planets. The gravitational stresses would change the speed of the Earth in its orbit and when the speed of rotation of the earth changes the tectonic plate motion also gets affected. The total angular momentum of planets involved in earthquake triggering mechanism can be calculated and the total force acting at the epicenter in a direction opposite to that of the earth’s rotation can also be determined. At the epicenter, the speed of rotation of the earth can be calculated with the help of available software. So the planetary forces in the opposite direction to the rotation of earth act as a triggering mechanism for the accumulated stress at faults and plate boundaries to be released abruptly. This does not, however, mean that earthquakes will occur at all edges of the plate boundaries. Two of the parameters contributing to the triggering of an earthquake at a place are a) distance of epicenter from the planet position and b) direction of force acting at the possible epicenter. From the analysis of “significant earthquakes” over the past 100 years from all over the world and from Southern Peninsular India, the relationship between (i) latitude, longitude, and magnitude of the tremor and (ii) distance from the planet and direction of forces acting at any point can be inferred. Such inferences already made for different localities in other parts of world have unfolded an accuracy of more than 75% with regard to earthquake prediction.

A Rayleigh lidar study of the atmospheric temperature structure over Mt. Abu, India
H.Chandra, Som Sharma, Y.B.Acharya and A.Jayaraman
Physical Research Laboratory, Navrangpura, Ahmedabad - 380 009
E.mail : hchandra44@gmail.com

A Nd-YAG laser based Rayleigh Lidar was set up at Guru Shikhar, Mount Abu (24.5o N, 72.7o E, altitude 1.7 km) by the Physical Research Laboratory to study the temperature structure in the altitude region of 30-75 km at tropical latitudes. Temperature profiles are derived from relative density measurements, following the method described by Hauchecorne & Channin (1980). Photon counts are averaged over one hour (2 hour during the later phase) in time and 480 m in altitude. Measurements were made for about 5 nights of each month around new moon except the monsoon season (June-August). Temperature profiles obtained on 109 nights during the period November 1997 to November 2001 are used to derive average temperature profile for each month (September to May) and are compared with the CIRA-86 model. Observed temperature profiles are in good agreement with CIRA-86 below 50 km but are higher by up to 10 K above 50 km. The agreement is better during winter months. The temperature profiles are also compared with the equatorial model for the Indian region (Sasi & Sengupta 1979) based on rocket and balloon measurements. Day to day variability is less than ± 5 K for altitudes below 50 km and up to ± 10 K around 70 km. The variability is the least around 40-50 km. The mean values of the stratopause level and temperature are found to be 48 km and 271 K respectively over the measurement site. Seasonal variation of the temperature below 60 km shows equinoctial and summer maxima whereas above 70 km winter maximum with equinoctial minima are seen.

Studies on some aspects of the intensification of Hydrologic Cycle over India

A.A.L.N. Sarma and S.Srinivas

Dept. of Meteorology & Oceanography, Andhra University,
Visakhapatnam – 530 003
E.mail: aalnsarma_met@rediffmail.com

It is widely reported that the intensified hydrologic cycle in the climate spectrum of the world is as a consequence of global warming which is not uniform over the world. In the present investigation, an attempt has been made to study and understand some of the aspects of hydrologic extremities in terms of prevalence of varied degrees of drought, humidness and climate shifts on All India basis through the revised water balance model during the monsoon period from 1901 to 1990. Trend aspects in seasonal All India aridity, humidness and climate shifts of the s-w monsoon period are studied compared to the march of Southern Oscillation (SO) Index and Sea Surface Temperature (SST) of NINO3 region. One of the important aspects of the present investigation is the appraisal of the modulation of the basic water budget elements of All India during extreme dry and wet shifts of the s-w monsoon compared to normal and in the context of ElNino – Southern Oscillation (ENSO) signal.
The paper also analyzes the mean monsoon seasonal flows of Krishna river basin at Vijayawada point along with its trend in relation to ElNino – Southern Oscillation (ENSO) and LaNina – Southern Oscillation (LNSO) signals.
A comparative study of the frequency of cyclonic disturbances and storms in the Indian region during distinct epochs compared to normal and in the context of global warming is made. The investigation also address not only in approximating a third order polynomial fit for the number of storms and cyclones in the Indian region, but also the trend aspects for the study period from 1901 to 1990 in relation to short term climate signal.

2-D Analytic signal application in electrical profiling problems

Rambhatla G. Sastry and Mukesh Gupta1

Department of Earth Sciences, IIT, Roorkee – 247 667
1Well Log Services, ONGC Mehsana Asset, Mehsana, Gujarat
E.mail: rgss1fes@iitr.ernet.in, rgssastry@yahoo.com, mukeshgupta04@yahoo.com,


Our 2-D stabilized analytic signal algorithm (RESAS) is used in interpreting synthetic electrical profiling data due to 2-D resistive / conductive bodies of both closed and open geometries. For bodies of closed geometry, pole-pole profiles with buried current pole above body center are considered while for open geometries, pole-pole (Half - Wenner) / pole-dipole apparent resistivity profiles are opted for. The analytic signal parameters like, Amplitude of the Analytic Signal (AAS), Real (RIAS) and imaginary parts (IIAS) of complex analytic signal inverse are used in the analysis.
Synthetic buried pole-pole data is generated by finite-difference based resistivity modeling algorithm and this data served as input to RESAS. The numerical models included conductive bodies of closed geometry (Prism in 2-layered earth medium and two inclined dyke model) and open geometry (a faulted bed and Horst – Graben model).
Achieved results show that AAS generally meets the interpretation requirements; but analyses of RIAS and IIAS are needed either to confirm the lateral coordinates inferred by AAS or supplement such information in case AAS fails.
For body corners with same lateral coordinates (bodies with vertical dips), analytical signal method fails in segregating them and ambiguity arises. Further, numerical results confirm that profiles of sufficient length are needed to image the lower corners of anomaly causative sources. The obtained results validate the proposed interpretation procedure.