April, 2011

April, 2011   ||  Volume 15 No.2


Geomagnetic secular variation anomalies investigated through tectonomagnetic monitoring in the seismoactive zone of the Narmada-Son Lineament, Central India

P.B.Gawali, S.Y.Waghmare, L.Carlo and A.G.Patil

Indian Institute of Geomagnetism, New Panvel (W),

Navi Mumbai - 410 218
E-mail: pravin@iigs.iigm.res.inm

Data from repeated geomagnetic observations at seventy stations on the five profiles have revealed secular variation anomalies of the total geomagnetic field in the seismically active area of Jabalpur and adjoining regions, in the Narmada-Son Lineament (NSL), Central India. For this tectonomagnetic monitoring, a reference base station was established within study area at seismic observatory Jabalpur. Using proton precession magnetometers with sensitivity 0.1 nT, simultaneous measurements of the total geomagnetic field were made annually at the base station and all field stations. Seven cycles of repeated observations have been performed between 2003 and 2009. For data analysis, a difference method has been applied and the residuals calculated as secular variations of the total geomagnetic field with values ranging from ±0.1 nT/yr to ±9.5 nT/yr over different stations. The anomalies in secular variation of the total geomagnetic field may be related to anomalous accumulation of tectonic stresses and tensions on the deep fault zones and crustal blocks of the NSL as a piezomagnetic effect. However, the geomagnetic depth sounding data have revealed high electrical conductivity anomaly due to saline fluids in the deep crust of Jabalpur area. The fluids related to electrokinetic effect can not be ruled out for causing the anomalies in the secular variation of total geomagnetic field. Thus, tectonomagnetic phenomenon such as piezomagnetic and/or electrokinetic effect or, both these mechanisms may have caused the secular variation anomalies in the seismoactive zone of NSL.


Seismic Hazard based on Simulated Accelerograms due to Moderate/ Strong Earthquakes in National Capital (Delhi) Region
Manisha, Dinesh Kumar and S.S.Teotia
Department of Geophysics , Kurukshetra University Kurukshetra – 136 119

The National Capital Region (NCR) of India lies in the geological realm of the Peninsular India and is about 200 km from the India plate boundary (Himalaya).The NCR may be affected by a great earthquake in Central Seismic Gap (CSG) of Himalaya and/or by moderate/strong earthquake in NCR .The occurrence of moderate/strong earthquake in a densely populated city with several old and weak structures such as Delhi can be devastating and highlights the hazard potential due to local earthquakes here .The envelopes of accelerograms have been generated at bed rock level from hypothetical moderate/strong earthquakes (M 5.5 – 6.0 ) in the National Capital Region to estimate the seismic hazard and risk from such events .The simulations have been done at number of points distributed on a grid. A semi- empirical technique has been used for this purpose .The peak ground acceleration values have been extracted from the simulated accelerograms and contoured to show the spatial distribution. The results of present analysis may be used for the preparation of scenario hazard maps of the region.

Delineation and evaluation of groundwater potential zones using electrical resistivity survey and aquifer performance test in Uppodai of Chittar – Uppodai water shed, Tambaraparani River Basin, Tirunelveli-Thoothukudi Districts, Tamilnadu

T.Jeyavel Raja Kumar, A.Balasubramanian1, R.S.Kumar, C.Dushiyanthan, K.Karthikeyan2, B.Thiruneelakandan, D.Davidraju3 and K.Manoharan
Department of Earth Sciences, Annamalai University, Annamalai Nagar – 608 002.
1Department of Geology, University of Mysore, Mysore
2Department of Civil Engineering, Annamalai University, Annamalai Nagar – 608 002.
3PSN Institute of Technology & Science, Melathediyoore, Tirunelveli.
E-mail: tjeyavel@rediffmail.com

Geophysical Resistivity survey and aquifer performance test were conducted to delineate groundwater potential zones of Uppodai, Chittar – Uppodai water shed, Tambaraparani River Basin, Tirunelveli and Thoothukudi Districts. It is located between the North latitude of 8º 52’ to 9 º 10’ and the east Longitude of 77 º 35’ to 77 º 55’. The area is constrained with crystalline rocks of Achaean age consisting of gneisses, charnockites, granites, basic and acidic intrusives. In order to understand the subsurface lithology, 12 Vertical Electrical Soundings (VES) were carried out. The field resistivity data have been interpreted using RESIST 87 software. The resistivity value and subsurface layer thickness for the first layer varied from 18 Wm to 122 Wm and 8.3m to 41.4m.The depth to basement is observed at a shallow depth of 10.m in the northwestern part and more than 50m in southern part of the study area.
For understanding the aquifer characteristics 5 aquifer performance tests were conducted in the study area. The transmissivity and storage coefficient values computed from Jacob’s straight line method varied from 43.6525 msq /d to 167.4367 msq/d and 0.00001 to 0.00163 respectively. The optimum yield and Recovery rate have been obtained as 3.0 m3/d to 100 m3/d and 34.0 hours to 379.3 hours respectively. The interpreted result of VES synchronizes with aquifer characteristics. The present study has proved the use of resistivity method and aquifer test as excellent tools to delineate groundwater potential zones and subsurface lithology.

Geomagnetic disturbances and Cyclonic Activity over the North Indian Ocean during 22nd Solar Cycle
R.Samuel Selvaraj and R.Uma1
Department of Physics, Presidency College, Chennai - 600 005
1Department of Physics, D.G.Vaishnav College, Chennai - 600 106

Tropical Cyclone activities over the North Indian Ocean (comprising Bay of Bengal and Arabian Sea) constitute one of the major natural disasters of our country. To understand the Tropical Cyclonic activities, estimations of their frequencies are necessary. In this study, the number of Geomagnetic Storms (Sudden and Gradual type) during 22nd solar cycle and Cyclonic Activity includes Depression, Cyclonic Storm and Severe Cyclonic Storm over the North Indian Ocean has been analysed using Spearman Rank Correlation technique. A positive correlation is found in both cases. When compared to Sudden or Gradual type of Geomagnetic Storms, the Gradual type of Geomagnetic Storms increases the Cyclonic Activity over the North Indian Ocean during 22nd solar cycle.



Run-off and flood estimation in Krishna River Delta using Remote Sensing & GIS
B.S.Prakasa Rao, P.Pernaidu, E.Amminedu, T.V.Rao, M.Satyakumar1,
K.Sathi Devi2, P.Jagadeeswara Rao, N.Srinivas and N.Bhaskara Rao

Department of Geo-engineering, College of Engineering, Andhra University, Visakhapatnam -530 003.
1IMD, Hyderabad -500 016.
2IMD, Pune - 411 008
E.mail : bosukonda@gmail.com

Run-off and flood estimation is attempted for cyclone induced rainfall in this study using real time data. A cyclone has potentially destructive characteristics such as strong winds, heavy rains and waves induced from storm surges as exemplified by the severe storm that crossed the Bay of Bengal coast in the Krishna delta region, 40 km south of Machilipatnam on 9th May 1990 is the subject of present investigation. Flood mapping and hazard zonation are indispensable for a real time study of floods and is only possible through remote sensing and GIS. An attempt is made to estimate run-off and flood with real time information derived from remote sensing as conventional approach does not give accurate estimates nor is fast. Soil Conservation Society (SCS) model is adopted to estimate storm run-off. Weighted Curve Number (CN) of the Krishna river basin (India) is determined as 72.4 based upon combinations of land use, soil type and hydrologic features. Flood estimation in the Krishna river basin using SCS Run-off model is estimated at 989.74 MCM during rainfall of 11 days from 5th may to 15th May 1990. The method of weighted curve number is easier, less time consuming and accurate with real time data, hence is applicable for the assessment of flood due to cyclone elsewhere.


Study on Nagarjunasagar to Somasila link canal alignment and its impact on environment using IRS-P6, AWiFS data
N.Bhaskara Rao, N.Srinivas, B.S.Prakasa Rao, G.Jai Sankar,V.Venkateswara Rao,
E.Amminedu, N.Venkateswarlu1, N.Rajesh, P.Kesava Rao2 and M.Satya Kumar3

Dept. of Geo-Engineering, College of Engineering, Andhra University, Visakhapatnam-530 003
1National Geophysical Research Institute, Hyderabad - 500 007
2National Institute of Rural Development, Hyderabad - 500 030
3Indian Meteorological Department, Hyderabad - 500 016
E.mail : bosukonda@gmail.com


The rainfall in the country is extremely erratic and unevenly distributed. A huge amount of water is wasted into the sea as run-off whenever there is heavy precipitation due to monsoon/cyclones. Run- off/ surplus water can be harvested through the proposed linking of river basins envisaged by National Water Development Agency (NWDA). The NWDA suggested three link canals from Krishna River to Pennar River to harvest the surplus water as well as the transferred surplus from Godavari. The present study is confined to Nagarjunasagar to Somasila link canal, which is one of them, is 341 km length. The study includes 10 km buffer area on either side of the alignment and the proposed command area 3252 sq km in Prakasam district. The total study area is 9,367.5 sq km. IRS-P6 AWiFS data of March 2009 is utilized for the real time study. The study revealed that 162 villages, which are fallen in the alignment, are to be rehabilitated while executing the canal. About 1202 villages will be benefitted by way of drinking water /groundwater recharge and additional irrigation source. The environmental impact on forest, agriculture land, roads and drainage are discussed in the study. Remote sensing study revealed that a large extent of area is under the class of wasteland (229,483 ha) in the study area. Hence, this canal water is extremely useful for the mankind and at the same time mitigating floods in the donor basin (Krishna basin).