May, 2017

May, 2017   ||  Volume 21 No.3


Variations of Total Magnetic Field before two small magnitude Earthquakes in Kachchh, Gujarat, India

Shivam Joshi*, C.P. Simha, K.M. Rao and M.S.B.S. Prasad
Institute of Seismological Research, Department of Science &Technology, Gandhinagar, Gujarat, India
*Corresponding Author:

In this study, variations of Total Magnetic field recorded in overhauser magnetometer at Multi Parametric Geophysical Observatories (MPGO) of Badargadh and Desalpar are analysed to correspond with small magnitude earthquakes occurred in 2014 in Kachchh, Gujarat employing different techniques such as power spectral density, fractal dimensions and principal component analysis. To reduce the effects of manmade and atmospheric perturbations magnetic data of mid night (i.e., 18-21 UTC) times were considered. Two small magnitude earthquakes occurred on 9th March 2014 (Mw 4.1, R=58 km) and 29th April 2014 (Mw 3.8, R=43 km) within the preparatory zone were studied in this analysis. In order to discriminate the effect of geomagnetic storm activity, the planetary index Kp and Dst were also analyzed in the corresponding period. These parameters are found to be normal during 9th March event and high during 29th April event. Total Magnetic field however, recorded considerable enhancement (10 nT for 9th March event and 30 nT for 29th April event) three days prior to these events. These enhancements persisted during the event and latter decreased exponentially. The difference between the total magnetic field data of the two MPGO Observatories (Badargadh and Desalpar), which is free of the secular trend of the geomagnetic field showed exponential increase prior to these events. We here by conclude that the observed magnetic anomaly prior to 9th March earthquake might be related to seismogenic origin while we cannot attribute the variations before 29th April with local earthquake activity as there was a record of global geomagnetic effects during this period.
Key words: Total magnetic field, Principal Component analysis, Fractal dimension, PSD, earthquake.

Meandering-braiding aspects of the middle-lower part of the Ganga River, India

Raghunath Pal
Centre for the Study of Regional Development, School of Social Science,
Jawaharlal Nehru University, New Delhi-110067, India

The present study is focused on the analysis of some geometric characteristics regarding meandering and braiding of the middle-lower part of the Ganga River at different axes. The middle-lower part of the Ganga River is the study reach and it ranges from Bhagalpur to Jangipur. The methods that applied in this study are: braid-channel ratio, sinuosity index and different parameters of maximum asymmetry. The relationship between the relative bend-entry curvature or channel width ratio and relative bend curvature is very strong and positive. The relationship between bend-entry curvature and meander wavelength is positive along with the positive relationship between relative bend curvature and meander wavelength. In the study reach sinuosity ranges from 1.08 to 1.90 and braid-channel ratio ranges from 1.21 to 4.26. The sinuosity index and range of sinuosity are not very high compared to the braid-channel ratio and its range. Statistically the relation between sinuosity and the braid-channel ratio is negative but the value is not significant in the reach. Hence, the channel lies in between the sinuous-braided structure or the meander-braided structure in the study reach.
Key words: Ganga River, channel geometry, braid-channel ratio, sinuosity index, maximum asymmetry.

Lutetium-Hafnium isotope evidence for the cogenesis of Neoarchean Veligallu and Gadwal greenstone belts, eastern Dharwar craton, India

Tarun C. Khanna
CSIR – National Geophysical Research Institute, Hyderabad-500 007, India

This research contribution elucidates the genetic link between the Veligallu and Gadwal greenstone belts that are located to the south and north respectively, of the Proterozoic Cuddapah basin in Eastern Dharwar Craton, India. The metavolcanic sequences in both these Neoarchean belts are characterised by an identical initial isotopic composition. Recent study indicates field and petrological similarities, identical nature of magmatism and most significantly, the corresponding metavolcanic rocks from these two belts relate to the same initial 176Hf/177Hf isotope composition. Therefore, it is inferred that these two greenstone terranes form part of a linear N-S trending Neoarchaean arc system, which is extensively obscured by the sedimentary cover of the Proterozoic Cuddapah basin, subsequent to post-accretionary geodynamic processes in the eastern Dharwar craton, India.
Key words: Lutetium-Hafnium, Veligallu, Gadwal, Greenstone belt, Dharwar craton, India.

Textural Analysis of Coastal Sands from Ramakrishna Beach - Bhimunipatnam tract (Visakhapatnam) East Coast of India

B. Suvarna1, C. H. Posendra Mohan2 and V. Sunitha*1
1Department of Geology, Yogi Vemana University, 516003, Kadapa A.P, India
2Department of Geology, Andhra University, Visakhapatnam-530003, A.P, India
*Corresponding Author: 

This paper presents textural analyses; study of Particle-size distribution parameters, Mean size (Mz), Standard Deviation (σ), Skewness (Sk) and Kurtosis (KG) pertaining to beach sands of Ramakrishna beach– Bhimunipatnam tract, East coast of Visakhapatnam, Andhra Pradesh. As part of this study, detailed textural characteristics of 23 representative samples from nine traverses of coastal sediments in different environments (Backshore, Foreshore, Dune, Berm) which lies between 17º46’-17º54’ latitudes and 83º21’- 83º27’ longitudes have been carried out. By treating with sieves of different size, the samples for textural analyses have been divided into nine (18,25,35,45,60,80,120,170,230) fractions. Statistical studies indicate that the coastal sediment average values are mean size (0.55 to 2.34), Standard Deviation (0.42 to 0.99), Skewness (- 0.53 to .27) and Kurtosis (- 0.41 to 1.64). Scatter Plots are used to know the interrelation ship and geological significance of the size parameters. Frequency distribution curves and scatter plots drawn between different grain size parameters clearly establish that the nature of the sediments is dominantly unimodal of which, the dominant constituent is medium sand in various microenvironments i.e. backshore, foreshore, dune and Berm.
Key words: Textural analysis, Backshore, Foreshore, Dune, Berm, East Coast.

A morphological study of low latitude ionosphere and its implication in identifying earthquake precursors

Devbrat Pundhir*1, 3, Birbal Singh1, O. P. Singh2 and Saral Kumar Gupta3
1Department of Electronics & Communication Engineering, Raja Balwant Singh Engineering Technical Campus,
Bichpuri, Agra, India-283105
2Department of Physics, Raja Balwant Singh Engineering Technical Campus, Bichpuri, Agra, India-283105
3Department of Physics, Banasthali Vidyapith, Banasthali, Rajasthan, India-304022
*Corresponding Author:

The low latitude ionosphere is highly variable because of the existence of equatorial ionization anomaly (EIA) and irregularities like spread-F and sporadic E. The GPS-TEC data have been analyzed from 01 January to 31 December 2007 (Period-I) and then from 01 January to 31 December, 2011 (Period-II) during low and high solar activity periods respectively. The results are validated with the recent ionospheric model IRI-2012 and we found a very good agreement in trend. However, IRI model indicated larger values of diurnal variations for both the periods. We have found a strong correlation (≈ 0.98) between IRI and TEC data during each of the three seasons (winter, summer, and equinox) for both periods except for winter season (≈ 0.85) of period-I. The TEC values are larger during equinox and smaller during winter season which may be attributed to solar activity. The peak GPS-TEC values are found in the range of 15-25 TECU and 25-30 TECU during the first and second periods respectively. To examine the effect of magnetic storms on TEC data, monthly correlation coefficients have been calculated between ∑Kp and TEC for period-II but it was very poor. A few specific cases of magnetic storms have shown their delayed effect on the TEC data at low latitude Agra station, 1-4 days after the occurrence of event. Therefore, TEC anomalies attributed to earthquakes have to be examined in the light of anomalies caused by the above factors.
Key words: GPS-TEC, morphological study, low latitude, IRI-2012 model, Earthquakes.

Analysis of trends in extreme precipitation events over Western Himalaya Region: intensity and duration wise study 

M. S. Shekhar*1, Usha Devi1, Surendar Paul2, G. P. Singh3 and Amreek Singh1
1Snow and Avalanche Study Establishment, Research and Development Centre, Sector 37, Chandigarh - 160036, India
2 India Meteorological Department, Chandigarh - 160036, India
3Department of Geophysics, Institute of Science, Banaras Hindu University, Varanasi-221005, India
*Corresponding Author:

The impact of climate change on precipitation has received a great deal of attention by scholars worldwide. Efforts have been made in this study to find out trends in terms of intensity and duration of precipitation for different altitudes and ranges in Western Himalaya region representing Jammu & Kashmir and Himachal Pradesh. In terms of intensity, precipitation has been classified as Low, Medium and Heavy. Durations of precipitation are classified as prolonged dry days (PDD), short dry days (SDD), prolonged wet days (PWD) and short wet days (SWD). Analysis indicates significant positive trends for low and heavy precipitation events and negative for medium precipitation events in Pir-Panjal range. For Shamshawari and Great Himalaya ranges, there is no significant trend for low, medium and heavy precipitation events. In terms of altitude, significant positive trends in low precipitation events have been observed for lower and middle altitudes and no significant trend has been found for medium and heavy precipitation events for other altitudes. In terms of duration, PDD/SDD shows significant increasing/decreasing trends for all ranges and altitudes. PWD and SWD show decreasing and increasing trends alternatively but not significant for all ranges and altitudes. For this study, the widely accepted Mann-Kendall test was run at 0.1, 0.05, 0.01 and 0.001 significance levels on time series data for the time period, 1991 to 2016.
Key words: Precipitation events, Dry and Wet days, Mann-Kendall test, Tele-connections, Western Himalaya.

A study of Cyclonic Storms of the South Indian Ocean And Indian Summer Monsoon Rainfall

P. Chandrasekhara Rao*1, Vishal. S. Thorat2, Vrishali V. Kulkarni1 and P.H. Raghavendra Rao1
1India Meteorological Department, Pune, India
2Junior Research Fellow, India Meteorological Department, Pune, India
*Corresponding Author:

Coastal regions of the globe that have potential threat from the storms are studied well, but mid-oceanic storms which rarely approach the coast are not paid adequate attention. One such region is the South Indian Ocean (SIO) basin, where more than 15 storms form every year. Over 80% of these do not impact countries either in the West basin or those in the East basin but die out in the ocean itself. However they are likely to show considerable effect on the Indian summer monsoon rainfall. Hence, in this study an attempt is made to find the correlation of these storms with the Indian Summer Monsoon Rainfall (ISMR). Also, the effect of El-Nino Southern Oscillation (ENSO) on the genesis of storms is studied. During El-nino episodes, storms of the SIO get shifted to the Western part with the ultimate result of less rainfall over India. Storm activity gets significantly reduced in the Eastern part of SIO during El-nino. It is found that the correlation coefficient is -0.37 for the West SIO storms and all India rainfall during El-Nino years. Correlation coefficient of -0.15 is obtained for the West SIO storms and 0.26 for East SIO storms with the June all India summer monsoon rainfall.
Key words: South Indian Ocean, Indian Summer Monsoon Rainfall, El Nino, La Nina, Storms

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Autonomously Deployed Deep-Ocean Seismic System (ADDOSS) –the emerging technology for Ocean Seismic Network

Raja Acharya
India Meteorological Department, Regional Meteorological Centre, Kolkata (Ministry of Earth Sciences)1