Current Issue

September, 2018   ||  Volume 22 No.5

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2D Seismic reflection data filtering using Time Slice Singular Spectrum Analysis for noise suppression: A case study from Singareni coalfield, India

R.K. Tiwari, R. Rajesh*, K. Dhanam and T. Seshunarayana
CSIR- National Geophysical Research Institute, Uppal Road, Hyderabad-500007, India.
*Corresponding Author: rekapalli@gmail.com

ABSTRACT
Complex noises that arise due to the nonlinear interaction of unwanted seismic signals (coherent and random noises), alter the primary reflections and create severe problems than the simple random noise in recognizing geological structures from seismic stack sections. We present here Time Slice Singular Spectrum Analysis (TSSSA) for the suppression of such noises from seismic records in time domain. The TSSSA involves organizing the spatial data (corrected for NMO) which corresponds to constant time into trajectory matrix for the reduction of noises that do not show large spatial coherency. The singular value decomposition based rank reduction of the trajectory matrix formulated from constant time slice helps to identify the noise in TSSSA with low Eigen values. We test the method on synthetic data contaminated with complex noises to demonstrate its ‘robustness’ for the identification of faults and then apply to high-resolution seismic reflection observations from Singareni coalfield, India. We find a good correlation between de-noised and pure synthetic data, which indicates the suppression of complex noise without any loss of seismic features. The application of TSSSA to pre and post stack seismic field data suggests significant improvement in signal to noise ratio. The reflections resembling the coal beds in the pre and post stack TSSSA processed depth sections clearly match with the reflectors in the synthetic trace generated from well log data. Finally, improvement in SNR and clear matching of fault structures and coal beds identified in the TSSSA processed data with regional fault structures and available geological information suggest the TSSSA as a robust method for seismic data conditioning.
Keywords: Complex noise suppression, Rank reduction, Singular Spectrum Analysis (SSA), Seismic reflection data, Singareni coalfield..



Potential of shale gas in Cambay basin, Gujarat, India

Anurodh Mohan Dayal
Former Emeritus Scientist, CSIR-National Geophysical Research Institute, Uppal Road, Hyderabad 500007 (India) Email: anurodhisotope@gmail.com

ABSTRACT
Carbonaceous shale is an organic rich sedimentary rock that forms the main source for all conventional and nonconventional hydrocarbons. Though, formation of oil and gas takes place in shale but due to very low porosity, it cannot be reservoir rock for hydrocarbons in case of conventional hydrocarbons. Shale is an excellent source rock for nonconventional natural gas and in the last one and half decade, the development of hydrofracturing and horizontal drilling has made it possible to exploit the carbonaceous shale as nonconventional gas source. The exploration and exploitation of shale gas changed the global economics of hydrocarbons and the oil prices came down from 110$ per barrel to 30$ per barrel. With the exploitation of shale gas, USA stopped importing oil and gas. It has now more than 2 million barrel of shale oil as surplus and thus exports it to various countries, including India.

In India, the Cambay basin, which is a oil producing basin, contains thick deposits of carbonaceous shale. These Tertiary shales are fine grained and organic-rich and thus considered a good source for shale gas. For shale gas exploration, the thickness of shale in subsurface and the type of organic matter it contains, are important parameters for the generation of nonconventional shale gas. Rock Eval pyrolysis of the shale, is one of the most important basic organic geochemistry to understand such parameters. As an initial study, interbedded shale samples from Middle Eocene lignite sequence of Cambay formation (Nagori et al., 2013) of Tadkeshwar in Surat and Rajpardi in Bharuch, were sampled and analysed using Rock Eval Pyrolysis system. Total organic carbon in these shales varies from 0.2% to 47%, which are indicative of good source of shale gas deposits. The Tmax varies between 342°C to 450°C, and the hydrogen index (HI) ranges between 32 to 754 mg HC/ g TOC. The variation of HI vs. Tmax suggests an immature to mature stage for the hydrocarbons. The organic matter in shales suggest Type II or Type III kerogen, which are responsible for the generation of these hydrocarbons.

Key Words: Shale, Shale gas, Total Organic Carbon, Rock-Eval pyrolysis, Cambay Basin.



Significance of regional gravity survey in parts of Sidhi and Shahdol districts, M.P.

R. Kumar* and D.V. Punekar
Geophysics Division, Geological Survey of India, Central Region, Nagpur, India
*Corresponding Author: rajan.08.ism@gmail.com

ABSTRACT
This article highlights the significance of regional gravity survey in parts of Sidhi and Shahdol districts of Madhya Pradesh. Gravity values vary from a minimum of -84mGal to maximum of -16mGal, with an overall variation of 68mGal. The general trend of Bouguer gravity anomaly contour pattern is E-W and NE-SW direction. The high gravity along with swelling and pinching is recorded near Chauphal, Nibuha, Harbaro, and Dol over Mahakoshal Group. The inferred structural features (Inferred fault/ Lineament/ Contact) are reflected in Bouguer gravity anomaly map, which is corroborated with geological map of the study area. The prominent shallow nature anomalies, recorded in the vertical derivative and residual gravity maps, correlate with the Bouguer gravity anomaly map. The Euler depth solutions provided depths less than 0.5km, 0.5 to 1.5km, 1.5 to 2.5km and beyond 2.5km. The majority of solutions are falling at the contact between two litho-units faults/ contacts, with varying depths from 0.5 to 2.5km. All these depth solutions nearly corroborate with the inferred structural features.
Keywords: Regional gravity studies, Mahakoshal Group, Chotanagapur, Sidhi, Shahdol .



Possible seismic hazards in Chandigarh city of North-western India due to its proximity to Himalayan frontal thrust

Nitish Puri1* and Ashwani Jain1
1Department of Civil Engineering, NIT Kurukshetra, Kurukshetra, Haryana – 136119, India
*Corresponding author: nitishpuri.ce.89@gmail.com  

ABSTRACT
Chandigarh, the first ever planned city in India, currently having an urban agglomeration of 1.2 million, is situated in the proximity of the Himalayan Frontal Thrust (HFT) zone. It falls under the seismic zone IV as per IS 1893 Part-1 (2016). It is ranked as second most seismically vulnerable city in India, based on expected peak ground acceleration (PGA) as per National Disaster Management Authority (NDMA). In the present study, the results of seismic hazard analysis for Chandigarh city, carried out adopting probabilistic approach are reported. The PGA values are estimated for rock sites, and a seismic hazard map for the city is prepared. Based on the observed PGA values, one-dimensional nonlinear wave amplification analysis and liquefaction potential assessment are also made. For this purpose, geotechnical data are collected for 41 boreholes from various government and private organizations, to have an assessment of soil properties and ground water conditions. For the sites under consideration, it is observed that ground motions get amplified at 5 sites due to local site effects and 18 sites in the city are prone to liquefaction. Therefore, a site-specific design approach should be adopted in the city for the design of important structures at vulnerable sites.
Keywords: Probabilistic seismic hazard, wave amplification, liquefaction potential, Himalayan thrust system.



Quartz syenites from the Prakasam alkaline province, Southern India; A comparative study with special emphasis on their rare earth element contents
 

N. Sridhar1, R. Mallikarjuna Reddy*1, and G. Nagendrababu 2
1Department of Geology, Kakatiya University, Warangal-506009.
2 Former Scientific officer, Atomic Mineral Directorate for Exploration and Research, Begumpet, Hyderabad.
*Corresponding Author: mallikragi@gmail.com

ABSTRACT
This paper elucidates the petrographic, geochemical and petrogenetic aspects of the quartz syenites from the Purimetla and other quartz syenite bearing plutons of the Prakasam Alkaline Province (PAP), which are towards the east of the Cuddapah basin within the Cuddapah Intrusive Province (CIP), Southern India. A comparative study of the REE contents of these quartz syenite bodies is presented with emphasis on their LREE abundance. Petrographically these quartz syenites are composed of K-feldspar perthite, quartz and plagioclase, while hornblende and biotite are the mafic minerals. These metaluminous rocks are enriched in total alkalies especially K2O, moderate in FeOt and impoverished in MnO, MgO, and CaO. The normative hypersthene indicates that these rocks can be designated under sub alkaline category. The chondrite normalized REE patterns indicate the LREE enrichment over HREE with a significant negative Eu anomaly. Allanite, apatite, zircon and monazite are the accessory phases that host significant LREE in these syenites. Based on the geological settings of the syenite plutons, which has quartz syenites as an integral part and considering their proximity to gabbros has led to a new petrogenetic model. The thermal trigger caused by the induction of gabbroic magma into the continental crust initiated the partial melting of LREE enriched amphibolite crust, yielding a melt with the composition corresponding to melasyenite. This melasyenite upon fractional crystallization produced the quartz syenites within the various syenite plutons emplaced into the PAP.
Key words: Cuddapah intrusive province, Quartz syenites, LREE enrichment, negative Eu anomaly.



Eigen Double Derivative Technique to further improve the seismic image generated by conventional data processing

R. Thandan Babu Naik1*, Uma Vadapalli1, Kalachand Sain1 and K. Satya Prasad2
1CSIR – National Geophysical Research Institute, Uppal Road, Hyderabad 500 007, India
2Department of ECE, Jawaharlal Technological University, Kakinada – 533001,India
*Corresponding Author: thandan@ngri.res.in

ABSTRACT
In conventionally processed seismic image, there is always a possibility of the presence of noise and scope for further improvement. Dealing and suppressing the residual noise, after application of several kinds of filters in conventional data processing, is challenging. Improving seismic image by reducing such noise, strengthens further analysis and interpretations. The Eigen Double Derivative Technique (EDDT) enhances the image by restoring the seismic amplitudes of conventionally processed seismic section, with average of neighbourhood data amplitudes in the low contrast direction. The low contrast orientation is indicated by Eigenvectors of double derivative image. Estimation of derivative images intoduces checkeredboard artefact, which is avoided by up-sampling of seismic amplitudes. In the present study, the efficiency of EDDT for improving seismic image is evaluated, by measuring contrast to noise ratio (CNR). Application of EDDT on seismic section of 3D seismic data from Balol oil field, Cambay basin, India has resulted into improvement of its CNR by 16%. Thus, the EDDT can be used to further improve the conventionally generated seismic image, by reducing inherent residual noise and improving contrast.
Keywords: Seismic image enhancement, Eigen values and vectors, Double derivative image, Up-sampling, Contrast to noise ratio.


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Spatial and temporal variability of atmospheric surface albedo over the central north region of India for the period of 2004-2016

Adarsh Kumar1, N. Jeni Victor2, T. Dharmaraj2*, G.R. Chinthalu2 and Devendraa Siingh2
1Department of Physics, Amity Institute of Applied Sciences, Amity University, Noida, India
*2Indian Institute of Tropical Meteorology, Pune, India
*Corresponding Author: dharam@tropmet.res.in

ABSTRACT
Thirteen years (2004-2016) of solar radiation data of the surface albedo over eight stations in the central north region of India was estimated and annual, seasonal, and geographical variations were also investigated. The selected sites of the central north region of India encounter a wide range of atmospheric conditions. The average annual surface albedo varies from ~ 0.144 to 0.34, and show high synoptic variability between different places and even at individual sites. The differences between the maximum and minimum surface albedo range from 0.02 to 0.44. The lowest mean was occurred in Nainital (~0.152) whereas, highest was recorded in Jaipur (~0.236). In examining the variations of the estimated albedo values with the altitude, sites were divided into three groups: low (<500 m), middle (500-1000 m), and high altitude (mountain sites) (> 1000 m); the mean albedo values for each category are ~ 0.198, ~ 0.167, and ~ 0.177 respectively. In studying the effects of latitude on albedo values, the sites were also further divided into three groups: low (<25 degree), middle (25-30 degree), and high latitudes (>30 degree), for which the mean monthly albedo values are 0.168, 0.222, and 0.183, respectively.
Key words: Surface and solar albedo, aerosol, solar radiation, solar energy, vegetation.


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The negative relation between the monsoon depressions and the rainfall over Rayalaseema (Andhra Pradesh), India

P. Chandrasekhara Rao* and Archana Shinde1 
A 44-307, Singapore Township, Pocharam, Hyderabad-500088
1India Meteorological Department, Pune
*Corresponding Author: pcsraoimd@gmail.com

ABSTRACT
The spatio-temporal variation of rainfall over India is largely dependent on the formation of cyclonic circulations, low pressure areas and depressions or cyclones in the Bay of Bengal and their movement along the monsoon trough. On the regional scale, the rainfall of Rayalaseema is considerably influenced by the low pressure systems that form in the Bay of Bengal. Rayalaseema receives rainfall in both the southwest and northeast monsoons. During both the seasons, the influence of the low pressure systems in the Bay of Bengal during the monsoon season, usually move in west north-westerly direction and cross the coasts of North Andhra, Orissa or West Bengal. They continue their movement inland and cause copious rainfall along their path. During this period, Telangana and coastal Andhra Pradesh also receive excess rain, but the rainfall received over Rayalaseema subdivision is found to be deficient with even ‘no rain’ at times. The wind pattern and the associated rainfall during the period of depressions crossing the coast and subsequent period have been analysed pertaining to a period of thirty years and the results are presented with some selected illustrations.
Keywords: Monsoon depression, Cyclonic storms, Rainfall, Rayalaseema (Andhra Pradesh), Bay of Bengal, Convergence.


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Role of various geomorphic parameters in landslide susceptibility of the Balason river basin of Darjeeling Himalaya, India

Subrata Mondal1* and Sujit Mandal2
1Department of Geography, University of Gour Banga, West Bengal, India-732103
2Department of Geography, Diamond Harbour Women’s University, Sarisha, West Bengal, India- 743368
*Corresponding Author: subratapanchagram@gmail.com

ABSTRACT
Occurrences of landslides are affected by geomorphic, tectonic and hydrologic parameters. Balason basin of Darjeeling Himalaya, exhibits these parameters which are analyzed in the context of landslides occurrences. In the present work, we carried out an overlay analysis of various data layers such as elevation, slope, geology, geomorphology, soil, rainfall, drainage density and drainage frequency with the landslide distribution data layer to assess the probability of class of the landslide causative factors. Frequency ratio (FR) value estimate, for both landslide affected pixels and total pixels of a class, help in establishing the relationship between the probability of landslide and each class of the landslide causative factor. The result showed that, those areas which are characterized by elevation of 2130 – 2603 m, slope of 47.00 – 71.00°, rainfall of 2559 – 2617 mm, drainage density 10.60 – 15.10 km/sq. km, 70.35 – 104.30 no. of stream/sq.km drainage frequency are registered with high frequency ratio and high landslide susceptibility. In addition, the probability of landslide occurrences is also found high in Darjeeling gneiss, lower hill and fine loamy to coarse loamy soil textural area.
Key words: Frequency ratio (FR), Susceptibility, RS and GIS, Balason river basin.


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A study on textural parameters of beach sands along some parts of the Nellore coast, east coast of India: Implications to Depositional Environment

K. Nagalakshmi1*, Madri Pramod Kumar1, T. Lakshmi Prasad1, N. Jayaraju2, M. Lakshmanna2 and G. Sreenivasulu3
1Department of Earth Sciences, Yogi Vemana University, Kadapa, (A.P), India
2Department of Geology, Yogi Vemana University, Kadapa, (A.P), India
3Department of Coastal Process, National Center for Earth sciences Studies, (Kerala), India.
*Corresponding author: ammulu.chani@gmail.com

ABSTRACT
An attempt has been made to evaluate the textural parameters and grain size distribution of coastal sands from Govindampalli to Durgarajupatnam, Nellore coast, east coast of India. The changes in textural parameters were studied by comparison of two seasons, i.e north east monsoon season (NE) in December 2015 and south west monsoon season (SW) in June 2016. A detailed account of textural parameters and grain size distribution of beach sands were carried out at each station in four microenvironments, by measuring various parameters like graphic mean size, graphic standard deviation, skewness, and kurtosis. To measure textural parameters, bivariate plots have been made to know the degree of freedom among various parameters. The analysis of textural parameters for two seasons indicates the prepotency of medium to fine grain and moderately well-sorted sediments with nearly symmetrical distribution. The textural parameters measurement and bivariate plots infer that prevailing intermittent energy conditions coalesced with rampant south west monsoon winds responsible for the platy to leptokurtic nature of sediments. In order to have a proxy on the mode of transportation and depositional environments CM (Percentile and Median) diagrams were plotted on the double logarithmic sheet, which suggests that sediments were transported by rolling, bottom suspension and rolling and graded suspension. Most of the sediments were deposited in tractive currents and beach environment regions. Factor analysis shows the dominance of mean size and kurtosis in NE monsoon season and skewness and kurtosis in SW monsoon season, where these parameters plays a dominant role in dispersal and distribution of sediments. Linear discrimination function (LDF) analysis shows high energy environments at the time of deposition of sediments.
Keywords: Textural studies; Beach sediments; Factor analysis; Linear discrimination function (LDF) analysis; Nellore coast.


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