January, 2008

January, 2008   ||  Volume 12 No.1

Geomagnetic Investigation in the Seismoactive area of Narmada-Son Lineament, Central Indian

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

Indian Institute of Geomagnetism, New Panvel (W), Navi Mumbai - 410 218

Activation of Narmada south fault caused the devastating Jabalpur earthquake (6.0 M) on May 22, 1997. To understand the secular variation of the total geomagnetic field in the vicinity of Narmada south fault, particularly comprising the seismoactive zone of Jabalpur and its adjoining areas in the Narmada-Son Lineament, Central India, tectonomagnetic studies were undertaken by carrying repeat surveys since 2003. The repeat survey area covers a total of 70 observation stations falling in areas of Jabalpur, Mandla, Seoni, Lakhnadon and Narsimhapur in Deccan Trap provinces. Using the Proton Precession Magnetometer of sensitivity 0.1nT, simultaneous measurements of total geomagnetic field were made at all stations and at base station and the process was repeated at yearly intervals. In this study, Seismic Observatory, Jabalpur was used as reference base station. For data interpretation purpose, five magnetic profiles were drawn i.e. the Katangi-Mandla (AA'), Mandla-Lakhnadon (BB'), Lakhnadon-Narsimhapur (CC'), Narsimhapur-Jabalpur (DD') and Jabalpur-Seoni (EE'). Repeated yearly surveys of 2003, 2004, 2005, 2006 and 2007 bring out secular changes in total geomagnetic fields that seem to be concentrating locally. Results of these observations have shown the anomalous geomagnetic field secular variations in a range of ± 0.06 to ± 9.54 nT at separate stations over the distinct profiles. The anomalies in secular variation of the total geomagnetic field may be related to anomalous accumulation of tectonic stresses and tensions on the fault zones and crustal blocks due to recent geodynamic processes and tectonic setting of the Narmada-Son Lineament.


Attenuation of P and S waves in the Kachchh Region
Sumer Chopra, Dinesh Kumar1 and K.M.Rao
Institute of Seismological Research, Gandhinagar 382 018, Gujarat
1Department of Geophysics, Kurukshetra University Kurukshetra 136 119, Haryana
E.mail: sumerchopra@yahoo.co.in, dineshk5@rediffmail.com

The quality factor Q has been estimated using spectral amplitudes of P and S waves from earthquakes recorded by the seismic network of Institute of Seismological Research (ISR) in Kachchh region. The earthquakes recorded at two stations – Lakadia (LAK) and Suvai (SUV) have been used. The spectral amplitude ratios have been calculated between 2 - 25 Hz and single station spectral ratio method has been applied for this purpose. The results show that the quality factors for both P and S waves (Qp and Qs) increase as a function of frequency according to law Q = Q0fn. The frequency dependent relations estimated for the Qp and Qs at the two stations are : Qp = (111±1.5)f1±0.01 , Qs = (107±4)f0.76±0.03 for Lakadia and Qp = (72±1.4)f1.22±0.01 , Qs = (193±3)f0.86±0.01 for Suvai. The average frequency dependent relations for Q have been estimated as Qp = (89±1)f 1.12±0.004 and Qs = (121±1)f 0.92±0.004 in the region. The ratio Qs/QP is close to one at Lakadia and greater than one at Suvai. The reported coda-Q (Qc) for this region has been found to be more than that of average Qs value estimated here. This supports the Zeng’s model of attenuation in the region. The results of this study have been found to be consistent with the findings of other studies in this region using different methods. The frequency dependent relations for Q estimated here have been compared with those of other parts of the world. These relations are useful for the estimation of source parameters of earthquakes and simulation of earthquake strong ground motions.

Estimation of sediment volume through Geophysical and GIS analyses - A case study of the red sand deposit along Visakhapatnam Coast

K. Nageswara Rao, Ch.Udaya Bhaskara Rao1 and T.Venkateswara Rao
Department of Geo-Engineering, Andhra University, Visakhapatnam - 530 003
1Department of Geography, Mizoram University, Aizawal - 796 001
E.mail: nrkakani@yahoo.com

Estimation of the volume of the coastal red sediment deposit near Bhimunipatnam north of Visakhapatnam, which is reported to contain heavy minerals of potential economic importance, was attempted in this study. The contours that represent the surface configuration of the area were extracted from the topographic map and the bedrock contours were interpolated from the depth to bedrock estimated from the geo-electrical resistivity survey at 100 points in the 10.55 km2 area of study. Both these maps were used to generate digital elevation models in GIS software to obtain the thickness as well as the volume of the sediment in the area. The study revealed that the volume of the red sediment deposit is ~145 million cubic meters.

Carbon Monoxide Pollution Levels at Environmentally Different Sites
G.Mohan Kumar, S.Sampath, V.S.Jeena and R.Anjali
Atmospheric Sciences Division, Centre for Earth Science Studies
PB 7250, Akkulam, Thiruvananthapuram - 695 001
E-mail. gmk4833@yahoo.com

Environmental characteristics such as topography, altitude, anthropogenic activity such as traffic, industrial gaseous effluents, proximity to all sources of pollution etc., have considerable influence on the abundance, residence time and retention of tropical trace gases over a locale. When the trace gas is toxic with its source at the surface of the Earth and has residence time of the order of several days, like in the case of carbon monoxide (CO), this trace gas becomes a criteria pollutant. Under the ISRO Geosphere Biosphere Programme (ISRO-GBP), a scientific study was initiated with a view to studying CO baseline at a tropical coastal station (Thiruvananthapuram) and to compare short-term CO measurements carried out in different environments such as a metropolis, a mining site and a pristine midland environment. CO is an air pollutant and is being monitored at a tropical coastal station Thiruvananthapuram since 2003 using an infrared analyzer. Also, for short durations CO was measured at three other environmentally different sites viz., Palode (near Thiruvananthapuram, a midland hill station with dense vegetation at an altitude of 140m ASL on Western Ghats), New Delhi (metropolitan city) and at Jaduguda (a mining site in Jharkhand state) near Kolkatta. From these measurements, the behaviour of CO at different environments was studied. Ambient CO at these sites, their diurnal patterns and the effect of vehicular emission inferred from weekday-weekend behaviour was delineated. This study revealed that Palode has the lowest ambient CO, followed by Thiruvananthapuram, Jaduguda and then New Delhi. Modulation of ambient CO by the vehicular emissions was observed at New Delhi, Thiruvananthapuram and Palode, but was absent at Jaduguda. The results of the characteristic CO levels encountered at different environmental locations, the response to traffic, the main anthropogenic activity that affects CO levels, are presented in detail and discussed in the manuscript.



Geomorphological, Fractal Dimension and b – value mapping in Northeast India
Pradip Kumar Pal

Visva Bharati University, Santiniketan – 731 235, West Bengal, India

Satellite based geomorphological mapping is an essential tool for natural hazard estimation in Northeast India. The geomorphological mapping of the study region (26 – 27 0 N, 91 – 95 0 E) was carried out with the help of IRS – 1D LISS – III imagery of March 5, 2003 on 1:250, 000 scales by visible interpretation technique. The individual satellite imagery has been studied and compared with the Survey of India (SOI) topographical sheets on 1:50, 000 scale to demarcate geomorphic features. The geomorphological maps of the study region refers to, (i) flood plain, (ii) younger alluvial plain, (iii) older alluvial plain, (iv) upper piedmont, (v) lower piedmont, (vi) valley fill area, (vii) structural hills of Tertiary group, (viii) structural hills of Shillong group, (ix) denudational hills of Tertiary group, (x) denudational hills of Shillong group, (xi) denudational hills of Gneissic group and (xii) pediment surface. The statistical characteristics of seismicity and drainage parameters, fractal dimension and b – values are mapped in the study region. The maps revealed that the fractal dimension of drainage parameters are comparable with the seismogenic structures and are very appropriate for earthquake risk evaluation.




Delineation of cavities in a canal bed by Geophysical Survey in Navargaon Project Area, Maharashtra

R.S.Wadhwa, N.Ghosh, M.S.Chaudhari, V.Chandrashekhar and Rajib K Sinharay

Central Water and Power Research station, Khadakwasla, Pune 411024
E.mail: wadhwa_rs@cwprs.gov.in

28 km main canal and a dam are part of Navargaon medium irrigation project. Three cavities exposed in the canal-bed were noticed after release of water for the first time through canal. Ground penetrating radar, electrical resistivity imaging and electrical gradient techniques were deployed to get the exact dimensions of the exposed cavities as well as to delineate subsurface cavities, if any. Number of anomalies depicting trough (low) and crest (high) like pattern were noticed on GPR records. A plausible interpretation for this cluster of anomalies was a partially water and/ or clay-filled lows and partially air-filled (high) cavity system. The presence of some of these cavities was confirmed by electrical resistivity imaging and electrical gradient techniques.