Volume 27(1) (2023),2-6
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1
Volume, mass of sediments and igneous crustal thickness below the Arabian Basin, northwest Indian Ocean
Shravan Kumar1*, A.K. Chaubey2, Uma Shankar1, Akhil Mishra3 and Jensen Jacob4
1Department of Geophysics, Institute of Science, Banaras Hindu University, Varanasi-221005, India. 2Department of Applied Geophysics, Indian Institute of Technology (Indian School of Mines), Dhanbad-826004, India.
3CSIR- National Geophysical Research Institute, Hyderabad-500007, India
4CSIR-National Institute of Oceanography, Dona Paula, Goa-403004, India.
ABSTRACT
Evolutionary history of the Arabian Basin has been complex. It has evolved due to complex processes of seafloor spreading and ridge propagation along the paleo Carlsberg Ridge in the early Tertiary under the influence of Reunion hotspot. Although the crystalline crust of the basin is considered similar to a normal oceanic crust, basement depth anomalies are reported in the basin. Above complexity necessitates estimation of sediment and igneous crustal load below the seafloor of the basin in order to provide constraints for the evolution of the basin. In order to do so, ship-borne as well as satellite altimetry derived bathymetry and free-air gravity anomaly data, have been analyzed in the light of available seismic information. The purpose is to investigate spatial distribution of sediment thickness, igneous crustal thickness and depth to the Moho derived from 2D forward gravity modeling as well as 3D gravity inversion. The study shows that northwestern region of the Arabian Basin is carpeted with thick Indus fan sediments (~3.5 km), whereas northeastern flank of the Carlsberg Ridge is covered with a thin veneer of sediments (~500 m). Sediment gravity values are calculated from the parabolic density function obtained from P-wave seismic velocities. The Moho depth in the basin ranges from 9 km near the flanks of the Carlsberg Ridge to 13 km in northern part of the basin filled with thick sediments, whereas igneous crustal thickness varies between 3 km and 8 km. These results can be used as constraints to refine the tectonic evolution of the basin. These results may also be useful for investigating thermal subsidence in the oceanic lithosphere as well as paleo-bathymetry of the basin.
2
Geophysical investigation for lead and zinc and associated minerals around Phophonga Hill, Goalpara District, Assam
Ashish Kumar*1, 3, Om Prakash2 and Uma Shankar3
1Geological Survey of India, Northern Region, Lucknow-226024 2 Ex, Geological Survey of India, Northern Region, Lucknow-226024 3Department of Geophysics, Institute of Science, Banaras Hindu University, Varanasi-221005
ABSTRACT
The detailed geophysical survey comprising self-potential (SP), induced polarization (IP) time domain (TD) and magnetic vertical field (VF) has been carried out in and around Phophonga hill, Goalpara district (Assam) in an area of 1.9 sq. km in order to delineate the subsurface extension of the anomalous body. The area is mainly occupied by Assam-Meghalaya Gneissic Complex rocks. These rocks of Archaean to Proterozoic age are deeply weathered. They are comprised of banded biotite hornblende gneiss and quartzo-feldspathic gneiss with pegmatite and schist. The geophysical data were processed and interpreted for the identification of lithological contacts, as well as a favourable zone for mineralization. Magnetic and apparent resistivity maps reveal a wide range of variation in magnetic and resistivity values over the exposed formation. The smooth variation in magnetic and resistivity values is recorded in the central part, occupied by soil/cultivated land. The contacts of exposed formation on either side of the study area and soil/cultivated land in the central part, have been demarcated by magnetic and resistivity methods. Some important anomalies have been delineated by the geophysical investigations (W200/N240, 0/N190, E200/N190, E400/N120, and W2600/N200) from Phophonga hill area to Satbaini area for possible lead, zinc, and iron sulphide mineralization. These anomalous zones have been recommended for the verification of the causative sources.
3
Effects of artificial boundaries on SH-waves propagation in a Weiskopf type anisotropic liquid-filled porous medium
Vijay Kumar Kalyani*, Kajal Naik, Prashant Malavadkar and Shubhalaxmi Joshi
School of mathematics and statistics, Dr. Vishwanath Karad MIT-World Peace University,Pune, Maharashtra-411038, India.
ABSTRACT
Reported in the present paper are the results of the study of SH-waves propagation in a Weiskopf-type anisotropic porous medium. The finite difference method has been applied with artificial absorbing and reflecting boundaries to model the wave propagation and to study the reflections at the boundaries. Stability criteria have also been developed to make the finite difference scheme convergent and stable. Numerical values of the reflection coefficients are calculated at the left and right boundaries for different values of angle of incidence, anisotropic parameter and porosity parameter. A source term is considered to generate a wave field in the medium. Two-dimensional SH-waves profiles are generated and are depicted graphically to study the absorbing capabilities of the non-reflecting boundaries at different propagation times.
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Application of Fuzzy graph theory in brittle plane network analysis - A potential method for carbon sequestration models
O.T. Manjusha1 and Soumyajit Mukherjee2*
1Department of Mathematics, Govt. Arts and Science College, Kondotty, Malappuram- 673 041, Kerala, India
2Department of Earth Sciences, Indian Institute of Technology, Bombay (Powai), Mumbai-400 076, Maharashtra, India
ABSTRACT
Improved carbon sequestration (CCS) models with rocks as sinks require incorporation of uncertainty into the models. In such cases of uncertain geoscientific problems, fuzzy graph theory can be useful. Brittle shear plane network with indistinct shear planes is common in natural sheared rocks, and can be targeted for CCS. Due to non-unique possibility of continuity of P-planes, it is not possible to represent such networks as crisp graphs. We present few natural examples of the former type of P-planes in shear zones, and how fuzzy graph theory can represent the fracture network and fluid flow. The process involves assigning some sample numerical probability to represent the connectedness between the underdeveloped P-planes and the Y-planes. The presentation is a geometric exercise and does not extend to the genesis of the shear zones.
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Study of a dumpyard fire in Perungudi and its effect on tropospheric ozone in an urban region of Chennai, India
S. Tamil Selvi *1 and S. Najma Nikkath2
1 Department of Physics, KCG College of Technology, Chennai-600 097, Tamil Nadu, India
2 Department of Physics, Bhaktavasalam Memorial College for Women Chennai-600 080, Tamil Nadu, India
ABSTRACT
The rise of ozone in the atmosphere and its effects on human health and the environment are one of the main concerns in urban areas. This paper examines the environmental threats with focus on concentration of ozone in association with the burning of household waste in open piles in Perungudi. The effects of ozone were investigated from daily values of Perungudi and nearby residential area of Velachery during and after the dumpyard fire for the period April 27, 2022 to July 27, 2022. This study is an effective step toward a better understanding of ozone changes in Perungudi under the changing influence of smoke during the dumpyard fire. Box plot analysis is used to find the nature of the ozone data by identifying mean and median in both the places. Histogram is used to explore the nature of the frequency distribution. Autocorrelation is employed to check the presence of trend or randomness. Results indicate presence of trend, which are not random. The Pearson correlation coefficient was applied to correlate the ozone (O3) concentration in Velachery. The results show that the ozone concentration in Perungudi is higher when compared with the nearby residential area of Velachery.
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Structural inferences from Bouguer gravity data analysis in and around Armoor area, southern part of the Godavari basin, Eastern Dharwar craton (India)
Telu Raju*, Udaya Laxmi G, Linga Swamy Jogu and Kolipaka Venu
Centre of Exploration Geophysics, Osmania University, Hyderabad-500 007, India.
ABSTRACT
The Gravity survey area is located south of the Godavari basin in Eastern Dharwar Craton. Bouguer gravity anomaly is prepared which is based on 965 observations acquired at 200-meter station interval in and around the Armoor region (18°30'N-19°00'N and 78°00'E–78°30'E) in Nizamabad district, Telangana state of India, covering an area of about 604 sq km. The Bouguer gravity anomaly reveals the variance from -33 mGal to -54 mGal. The qualitative analysis of the Bouguer gravity anomaly map, low-pass, high-pass filtered and tilt derivative maps, reveal a combination of E-W, N-S and NW-SE trends that coincide with the lineaments and deep-seated faults present in the region. Six highs (H1-H6), three lows (L1-L3), and four deep-seated faults (F1-F4) are identified in this area. The high anomalies are attributed to the basement rocks, basic dykes and mineralized zones (banded magnetite quartzite) while low anomalies correspond to the variations in the peninsular gneissic complex.
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Investigations of GPS-based total electron content (TEC) data at different low latitude IGS stations and its relevance to earthquake precursor studies
Manish Awasthi1, 2, Raj Pal Singh2 and Devbrat Pundhir3*
1Department of Electronics and Communication Engineering, GLA University, Mathura-281406
2Department of Physics, GLA University, Mathura. India-281406
3Seismo-electromagnetics and Space Research Laboratory, Department of Physics, Raja Balwant Singh Engineering Technical Campus, Bichpuri, Agra, India-283105
ABSTRACT
In the present paper, IGS-TEC data of five low latitude stations which include Lucknow (26.9oN, 80.96oE), Bangalore (13.020N, 77.570E), Hyderabad (17.420N,78.550E), Port Blair (11.64oN, 92.71oE), and Lhasa (29.66oN, 91.10oE) are analyzed during high and low solar activity periods i.e. period-I and period-II, respectively to check its usefulness for earthquake precursory studies. The durational variations show that peak VTEC lies between 08:00 and 10:00 hrs (UT) at all the stations and ranges 25-50 TECU during period-I, it lies at the same time interval but within the range of 14-20 TECU during the period-II. The VTEC values are higher in the equinoctial months during both periods under consideration. In all seasons, seasonal peak VTEC values are noticed to vary between 14 and 42 TECU during period-I and 7 to 18 TECU during period-II. The influence of solar activity is studied on GPS-TEC in terms of sunspot numbers and solar flux index F10.7 cm and it is found that these solar indices are more fluctuating in the period-I than that period-II and attain peak values of ~ 175 and ~185 in period-I, and ~55 and ~85 during period-II. This enhanced solar activity causes more fluctuation in TEC data in period–I, compared to period -II. In addition, the effect of magnetic storms is also studied on GPS-TEC data and it is noticed that TEC is significantly affected in severe magnetic storms. This study provides a better understanding of the behavior of low latitude ionosphere during high and low solar activity periods.