Current Issue

November, 2017   ||  Volume 21 No.6

Editorial


1 
Geophysical attributes to evaluate subsurface structural features using ground magnetic data in parts of Karimnagar district, Telangana

M. Laxminarayana1, Ram Raj Mathur*2 and S.P. Anand1
1Indian Institute of Geomagnetism, New Panvel (W), Navi Mumbai 410218
2Center for Exploration Geophysics, Osmania University, Hyderabad 500007
*Corresponding Author: ramrajmathur@gmail.com

ABSTRACT
To decipher both the shallow and deeper features related to Godavari and Kaddam Rivers and the lineaments present in the eastern margin of Deccan Volcanic Province (DVP) in the Indian Precambrian shield, a total field ground magnetic survey was carried out around Jagtial town, Karimnagar district, Telangana. The total field anomaly map based on 653 magnetic observations acquired at 300 m station interval reveals a combination of NE-SW, NNE-SSW and NW-SE trends, which coincide with the trends in the earlier observed aeromagnetic anomaly map of the region. The Reduction-to-pole (RTP) map also reveals lineaments that trend in the NW–SE and NE–SW with varying wavelength and amplitude. From the analysis of magnetic data we have mapped the north-west extension of the Kinnerasani Godavari Fault (KGF). From our observations the Kaddam Lineament Zone (KLZ) has been deciphered to be bounded by the Kaddam Lineament to the north and Kinnerasani Godavari Fault (KGF) to the south forming a small linear basin. Both the Kaddam Lineament and the KGF appear to be deep seated lineaments/faults. Also, the north-west extension of charnockites within the KLZ, which form the basement for the deposition of Proterozoic sediments, have been delineated. Results of the present study detailed in this paper may help to understand better some of the structural features in this region, which had not been ascertained in earlier studies.
Key words: Eastern Dharwar Craton, Geophysical attributes, Total Magnetic Field, Ground magnetic data, Kaddam Lineament, Kinnerasani Godavari Fault, Karimnagar Granulite Belt, Deccan Volcanic Province (DVP).



Delineation of groundwater potential zones using geo-electrical surveys in SSW part of Yeleru river basin, East Godavari District, Andhra Pradesh

M. Subrahmanyam* and P. Venkateswara Rao
Department of Geophysics, Andhra University, Visakhapatnam
*Corresponding Author: smangalampalli@rediffmail.com

ABSTRACT
Data of 40 Vertical Electrical Resistivity soundings covering an area of about 144 square kms located in SSW part of Yeleru river basin, East Godavari district provided by Andhra Pradesh state Ground Water department was analyzed to delineate potential sources of ground water, its extent and depth of water table. The study revealed mainly a three layer subsurface with top layer consisting of clay/lateritic gravel, followed by the sandstones. The general geology of the study area is Rajahmundry sandstone. Saturated sandstone with a resistivity range of 10-50 Ωm extending to a maximum depth of approximately 135 m forms the major aquifer, while layers with less than 10 Ωm may be possibly due to high clay content and hence poor aquifers. The fence diagrams and geoelectric sections reveal potential aquifers in the northern part of the region dominated by a thickness of 21-50m with a small patch showing a thickness above 50m and clay dominated zones in the southern part of the region, which are unevenly distributed. Thus, the study provides vital clues on the distribution and thickness of the aquifer, which helps to decide the type of well to be built (dug well, bore well) in future groundwater exploration/ exploitation programs.
Key words: Yeleru river basin, Vertical Electrical Soundings, Groundwater potential zones, Fence diagram, geo electric sections.



An Appraisal of the Plate Tectonic Forces: Role of Gravitational Potential Energy (GPE) in the Deformation of Indo-Eurasian Collision Zone

C.D. Reddy*1 and Mahesh N. Shrivastava2,3
1Indian Institute of Geomagnetism, Navi Mumbai, 410218, India
2Universidad Católica del Norte, Antofagasta, Chile
3National Research Center for Integrated Natural Disaster Management, Santiago, Chile
*Corresponding Author: cdreddy@iigs.iigm.res.in

ABSTRACT
Concording with the plate tectonic theory, lithosphere consists of several tectonic plates moving in different directions and stimulating various tectonic processes and consequencing mountains, earthquakes, volcanoes, mid-oceanic ridges and oceanic trenches. It is excogitated that three main plate tectonics driving forces viz. ridge push, slab pull and trench suction together with resistance force viz. collisional resistance, basal drag etc. maneuvering deformation in Indo-Eurasian collision region. But these forces acting in tandem are not sufficient in explaining the discrepancies in regional surficial lithospheric deformation pattern explicitly. Hence, we invoke Gravitation Potential Energy (GPE) derived deviotoric stress in explaining the deformation pattern of Indo-Eurasian collision region. We also provide explanation for the occurrence of Mw 7.3 aftershock following the 2015 Mw 7.9 Nepal earthquake construing the GPE as an important proxy to the deviatoric stress field.
Key words: Tectonic forces,Topography,GPE, Indo-Eurasian, Himalaya, deformation.



Tsunami forces acting on ocean structures: A synthetic study

Mounica Jakkula*1,2, Harini Guruhappa2, Manaswini Ganjam2 and Kirti Srivastava1,2
1Academy of Scientific and Innovative Research (AcSIR), 2CSIR- National Geophysical 2Research Institute (CSIR-NGRI), Hyderabad, 500007, India.
*Corresponding Author: mounica.jakkula.iitk@gmail.com  

ABSTRACT
Andaman-Sumatra subduction zone had produced several large and great earthquakes in the past, some of which have generated destructive tsunamis. Tsunami forecast model is used to provide an estimate of wave arrival time, wave height, and inundation area immediately after a tsunami event. Forces caused due to a tsunami on different structures also play an important role. Considerable amount of research has been done on shape, size and strength of near-coastal structures. But, the impact on the ocean structures (like Oil Rigs) has not been addressed. In this paper, the lateral forces due to tsunami acting on a vertical hypothetical wall constructed in an ocean or sea are calculated. The location of the wall is taken in between India and Sri-Lanka due to the large scale destruction of structures on land and in the ocean caused by 2004 tsunami. To address the problem in an organized way, firstly, a hypothetical wall divided into 6 sections has been selected. Secondly, the wave heights are calculated for each section using TUNAMI N2 model. Thirdly, calculation of forces using the wave heights are made separately for each section for a better understanding of forces acting. And lastly, change in forces with time is calculated to bring out varied nature of forces with time. The acquired information is then plotted to explicitly show the changes. Results reveal that the hydrostatic forces acting on the wall structure in the ocean or the sea shall not pose a great threat to the structure. Also, due to the presence of such barriers the tsunami wave energy would get dissipated and less damage would happen to the adjoining coastal region. We have also followed the same approach to calculate the changes in tsunami forces with time on the Oil Rigs in the Ravva Offshore field.
Key words: Tsunami, Hydrostatic force, Wave heights, Vertical hypothetical wall, TUNAMI N2 model, Andaman-Sumatra subduction zone.



Study of Effects of Basin Shape, Shape-Ratio and Angle of Incidence of SH-Wave on Ground Motion Characteristics and Aggravation Factors
 

Kamal*1 and Komal Rani2
1Department of Geophysics, Kurukshetra University Kurukshetra, Haryana
2B.A.R. Janta College, Kaul, Kaithal, Haryana
*Corresponding Author: kamalbattan@gmail.com

ABSTRACT
This paper presents the effects of basin-shape, shape-ratio, impedance contrast (IC), sediment-damping and angle of incidence of SH-waves on the ground motion characteristics and associated spatial variations of average spectral amplification (ASA) and average aggravation factor (AAF) in the basins. Seismic responses of basin models were simulated using a SH wave fourth-order spatial accurate time-domain finite-difference algorithm based on staggered-grid approximation of viscoelastic velocity-stress wave equations. The obtained ASA and AAF were largest in the semi-circular basin and least in the trapezoidal basin for the considered model parameters. On an average, an increase of ASA and AAF were obtained with an increase of IC, sediment quality factor and the basin shape-ratio (in the shape-ratio range 0.03 - 0.16). An increase of ASA and AAF with the increase of angle of incidence of SH-wave was inferred.
Key words: Basin effects, basin-generated Love waves, aggravation factor and finite difference simulation.



Interpretation of Seismic data for thrust/fault identification using variance and inverse of variance attribute analysis

Mausam Gogoi*1 and G.K. Ghosh2
1Dibrugarh University, Assam
2Oil India Limited, Assam
*Corresponding Author: mausamgogoi@gmail.com

ABSTRACT
Seismic attribute is classically defined as a component extracted from seismic data that can be analyzed in order to enhance the hidden information used to identify a better geological or geophysical prospect in certain depositional environment. Seismic attributes are the components of the seismic data which are obtained by measurement, computation, and by logical or experience based reasoning. It is well established by seismic experts that seismic attributes help visual enhancement or quality of the features of interpretation interest. They became a valid analytical tool for lithology prediction and reservoir characterization. A good seismic attribute is either directly sensitive to the desired geological features or reservoir properties of interest. In this study, variance and inverse of variance attribute analysis has been carried out first for the synthetic data and thereafter applied to the real field seismic data for automatic fault /thrust identification. Synthetic seismic traces are generalized and data has been digitized to calculate the variance on the said seismogram. With the help of MS excel sheet, theoretical formulation has been carried out to study, variance and inverse of variance of different traces using three point window in the excel sheet. After studying the variance and inverse of variance attribute, it is noted that these attributes can provide better identification for fault/thrust and edge detection. The variance and inverse of variance attribute analysis applied to the real field seismic data for automatic interpretation for thrust/fault identification, has helped in clearly distinguishing the fault locations.
Key words: Seismic data, attribute analysis, three point window, variance and inverse of variance, attribute analysis.


7
Analysis of Tectonically controlled Valley Floor morphology of the Central Segment of Sabarmati River Basin: An Integral approach using satellite images and GIS Techniques

Nisarg H. Bhatt*and R.D. Shah
M.G. Science Institute, Navarangpura, Ahmedabad, 380007, Gujarat
*Corresponding Author: nisarg@nisargbhatt.com

ABSTRACT
Present paper deals with the integrated study of satellite and field investigation in the central segment of Sabarmati River basin that covers ~ 20,000 km2 area along Cambay fault system. The valley floor morphology within the central segment of the Sabarmati River basin is controlled by several NNW-SSE, NW-SE, and NE-SW trending faults of Cambay basin. The sequential reactivation of these faults gives rise to morphological changes in the river system, leading to incision and widening of valley floor, favorable sites for deposition of Quaternary sediments. The consequence of sequential reactivation and deposition of sediments is reflected in the form of tectonic geomorphology in the area. Several geomorphic markers, such as paleochannels, wind gap, uplifted strath terraces, incised ravine surfaces, compressed meandering, and offset of drainage pattern associated with tectonic activity have been identified in the region.
Key words: Sabarmati River, Morphotectonics, Neotectonics, GIS, Geomorphology


8
Paleoproterozoic magmatism in the Cuddapah basin, India

V. V. Sesha Sai1*, Vikash Tripathy2, Santanu Bhattacharjee2 and Tarun C. Khanna3
1Petrology Division, Geological Survey of India, Southern Region, Hyderabad-India-68
2Geological Survey of India Training Institute, Hyderabad-India-68
3CSIR-National Geophysical Research Institute, Hyderabad-India-07
*Corresponding Author: seshu1967@gmail.com

ABSTRACT
The Proterozoic Cuddapah basin of Southern India, with an aerial extent of 44,500 km2, is one of the largest sedimentary basins in the world that witnessed significant events of magmatism during its evolution. Initiated around 2.1 – 2.0 Ga, the basin preserves a protracted history of sedimentation, magmatism and tectonism from Paleo to Neoproterozoic. Through this paper we explicate the Paleoproterozoic ultramafic-mafic-felsic magmatic events that are contemporaneous with the sedimentation of Cuddapah Supergroup. The ~ 1.9 Ga ultramafic-mafic sills, along with basic and felsic volcanics and the interbedded tuffaceous rocks are stratigraphically confined to the Cuddapah Supergroup; that hosts substantial sedimentary sequence in the Cuddapah basin of Eastern Dharwar Craton. We provide a chronological illustration of Paleoproterozoic ultramafic-mafic-felsic magmatic events with details of available geochronological ages; their location and position in the stratigraphic succession constituting the Cuddapah Supergroup (see Table 1). Confinement of the Paleoproterozoic ultramafic-mafic sills within the clastic to shallow marine non-clastic sequences of Papaghni and Chitravathi sub basins, their configuration parallel to the basins arcuate western margin, associated Paleoproterozoic felsic volcanic, disposition of this geological domain along the eastern margin of the stabilised Dharwar craton, indicate a continental arc extensional setting for the evolution Paleoproterozoic segment of Cuddapah basin, India.
Key words: Proterozoic magmatism, extensional tectonics, Cuddapah basin, eastern Dharwar craton, India.


9
Dust storms and their influence on optical and chemical properties of aerosols along north-western Indo-Gangetic Plains

Disha Sharma and Umesh Kulshrestha*
School of Environmental Sciences, Jawaharlal Nehru University, New Delhi, India
*Corresponding Author: umeshkulshrestha@gmail.com

ABSTRACT
Dust storms are an important climatic phenomenon in the Indian subcontinent affecting air quality in the pre monsoon season. In this study, the variation in the optical and the chemical properties of mineral dust aerosols along the north-western Indo Gangetic Plains (IGP) is recorded during major dust storm events during April to June, 2015. Dustfall fluxes were measured at five sites lying on the downwind trajectory of the long-transported dust plume. The sites were - Bikaner (BK), Jaipur (JP), Hisar (HS), Delhi (DL) and Agra (AG). Five major dust storm events were identified based on the aerosol optical depth (AOD) values derived from the MODIS and OMI instruments and corroborated by the ground monitored dust fall flux measurements. An analysis of the optical properties reveals the dominance of coarse mode particles during all the events with MODIS Angstrom Exponent (AE) values lying in the range of 0.40 – 0.03 for dust events observed at the sites located in the close proximity of Thar desert. Chemical characterization of the samples showed that Ca2+ was the most dominating cation with flux in the range of 106.7 mg/m2/day (at BK) to 7.4 mg/m2/day (at DL), indicating the dominance of crustal sources in the dust aerosols. Among anions, highest flux was recorded for SO42- and NO3-. NO3- flux was observed to increase downwind towards the sites (DL and HS) with high anthropogenic emissions. The flux Na+ and Cl-was also high during major dust events. However, it was seen to decrease downwind indicating the influence of sea salt fraction in the dust plume transported from the Arabian sea.
Key words: Dust Storms, Air quality, Optical and chemical qualities of aerosols, Aerosol optical depth, MODIS and OMI instruments, North western Indo-Gangetic Plains.


10
Types of Irrigation and Historical development - a comprehensive compilation

P.R.Reddy
Director Grade Scientist (Retd), CSIR-NGRI, Hyderabad- 500007, Telangana State
parvatarreddy@gmail.com


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