Current Issue

November, 2016   ||  Volume 20 No.6

Editorial



The Stress State of The Region around İnönü-Eskişehir active fault system (Turkey); kinematic analysis accompanied with GPS Data

A.Sağlam Selçuk*1, Y.E.Gökten2 and B.Aktuğ3

1 Van Yüzüncü Yıl University, Department of Geology, Van, Turkey
2 Ankara University, Department of Geology, Ankara, Turkey 
3Ankara University, Department of Geophysics, Ankara, Turkey
*Corresponding Author: azadsaglam@gmail.com

 ABSTRACT
The İnönü-Eskişehir Fault System (IEFS) exhibits WNW−ESE striking right-lateral strike-slip character with a normal component that extends from Uludağ (Bursa) in the west to Sivrihisar (Eskişehir) in the east and separates the west Anatolian extensional region from the central Anatolia to the northeast. This fault system consists of E−W and NW−SE trending fault sets and segments which have potential to produce destructive earthquakes. In this study, we aim to identify the stress regime of the region around İnönü-Eskişehir active fault system by correlating the fault-slip data and GPS data. The strain rates are computed using the velocity vectors from 5 Turkish National Fundamental GPS Network (TUTGA) data, acquired from the General Command of Mapping (Turkey). Fault-slip data have been analysed using the stress inversion method of Angelier. The obtained contraction rate for the studied area is about 65±15 nanostrain/yr, which corresponds to a contraction rate of 0.7±0.15 mm/yr over 10 km. The strain rate results of last ten years calculated from the TUTGA-99 data suggest approximately NW-SE trending compressional tectonic regime in the region. This strain rate and orientations are confirmed by the Plio-Quaternary slip surface data collected along the İnönü-Eskişehir Fault System.
Key words: İnönü-Eskişehir Fault System, contraction rate, Kinematic analysis, TUTGA data and Central Anatolia.



Imaging of seismic discontinuities of the upper mantle in the western Himalaya through Receiver Function analysis

Nagaraju Kanna*, K.S. Prakasam, Sandeep Gupta, K. Sivaram, Sudesh Kumar, Somasish Bose and B.N.V. Prasad

CSIR-National Geophysical Research Institute, Uppal Road, Hyderabad-500007, India
*Corresponding Author: nagarajugeo@gmail.com

ABSTRACT
We present image of seismic velocity discontinuities of the upper mantle in the depth range of 200 to 800 km beneath the western Himalaya from Gangetic Plain (27.5ºN latitude) to Ladakh-Karakoram region (35ºN latitude), an active collision zone of Indo-Eurasian plates. We use 2088 Receiver Functions calculated from the data obtained from 44 digital broadband seismological stations. The results show a sharp 410 km discontinuity in the range of ~393 – 406 km from Gangetic Plain till Indus Zangpo Suture (IZS), and disturbed (double peaked) further north of the IZS. The 660 km discontinuity shows flat and sharp discontinuity in the Gangetic Plain through Himalaya and elevated ~12 to 17 km beneath Tibetan Himalaya to the north of IZS. We observe a distinct northward dipping velocity interface to the north of IZS in the depth range of ~460 to 490 km which indicates down going Indian subducting slab reported in earlier studies. This velocity interface may be responsible for earlier 660 km phase beneath this region. Thickened mantle transition zone (~255-262 km) is observed beneath Gangetic Plain and NW Himalaya than Tibetan Himalaya due to presence of cold material within (~100º C less than normal). 
Key words: Receiver Function, Common Depth Point Stacking, 410 and 660 global discontinuities, Mantle Transition Zone and Western Himalaya.



Microscopic Evidences for the Impact Origin of Ramgarh Structure, Rajasthan, India

Satyanarayan Rana* and Vinod Agrawal
Department of Geology, Faculty of Earth Sciences, Mohanlal Sukhadia University, Udaipur 313001, India
*Corresponding Author: snrana1984@gmail.com

ABSTRACT
An impact crater on the Earth is a depression that is formed by the high velocity impact of an extraterrestrial object like meteorite. Impacts produced on Earth are highly exposed to obliteration by various geological agents. This demands the use of certain diagnostic criteria for the identification and confirmation of impact structures on Earth, the most important of these are crater morphology, geophysical anomalies, evidences for shock metamorphism and the presence of meteoritic material. Microscopic features like Planar deformation features (PDFs) and Planar fractures (PFs) in quartz grains are uniquely diagnostic of an impact event and are the robust evidences of the shock metamorphism due to an impact. A crater-like structure at Ramgarh, Rajasthan, India has been a contentious subject amongst the geoscientists for its origin. Evidences presented for the impact origin of Ramgarh structure so far are insufficient, equivocal and controversial. In this communication, we have reported the microscopic shock alteration evidences from the Ramgarh structure in the form of Planar Fractures and Planar Deformation Features in quartz grains.
Key words: Impact craters, Ramgarh structure, Shock Metamorphism and Planar Deformation Features..



Petrology and geochemistry of the troctolite and ultramafic from the Paleoproterozoic Kandra Ophiolite Complex, Eastern Dharwar Craton, SE India

V.V. Sesha Sai
Geological Survey of India, Southern Region, Bandlaguda, Hyderabad-India-500068
E-mail : seshu1967@gmail.com 

ABSTRACT
Field and petrological studies indicate the presence of two spatially associated high Mg lithounits; troctolite and ultramafic within the southern gabbros of the Paleoproterozoic Kandra Ophiolite Complex (KOC), Eastern Dharwar Craton, SE India. Petrographic studies indicated that troctolite is essentially composed of olivine and plagioclase with sub-ordinate augite, while magnetite and ilmenite are noticed as accessory oxides. Mineral chemistry studies by EPMA reveal that olivine in troctolite is forsterite (Fo63.14) plagioclase is labrodorite (An­69.96) and the Fe-Ti oxide ilmenite in troctolite analysed TiO2-53.08 %, FeOT‑44.22%). Major oxides of troctolite indicated SiO2 - 43.10%, TiO2 - 0.29%, Al2O3 -15.81%, FeO - 10.44%, Fe2O3 - 5.56%, CaO-7.92% and MgO - 13.08%. Petrographically, ultramafic is essentially composed of magnesio hornblende with subordinate chlorite, while ilmenite is the accessory oxide phase. Mineral chemistry studies by EPMA of the ultramafic indicate that the magnesio hornblende analysed SiO2 – 43.71%, Al2O3 -14.61%, FeO – 15.35% and MgO - 9.94%, while chlorite analysed SiO2 – 27.02%, Al2O3 -22.6%, FeO – 19.75% and MgO - 19.7%. Ilmenite in the ultramafic analysed FeO – 45.14%, TiO2 – 53.44%. Major oxides of ultramafic indicated SiO2 - 28.6%, TiO2 - 0.65 %, Al2O3 - 17.22 %, FeO – 6.84 %, Fe2O3 - 6.88%, CaO – 0.41% and MgO- 26.84%. HFSE depletion is noticed in both these high Mg lithounits; (Zr- 42.17 ppm, Nb-2.65ppm and Y-5.35ppm) in troctolite and (Zr- 40.13ppm, Nb-2.47ppm and Y-3.16 ppm) in ultramafic. Rare Earth Element (REE) geochemical studies indicate that these spatially co-existing troctolite and ultramafic show an overall depleted but contrasting REE patterns. Troctolite exhibits a low magnitude positive Eu anomaly while the ultramafic exhibit a negative Eu anomaly indicating co-magmatic origin of the mafic-ultramafic lithounits in the southern gabbros of KOC. 
Key words: Troctolite, ultramafic, Kandra ophiolite, Eastern Dharwar Craton and India.



The effect of 10.7 cm solar flux on the monsoon rainfall over India 

S. K. Midya1, S. Goswami*2 and K. Sengupta1
1 Department of Atmospheric Science, University of Calcutta, 51/2 Hazra Road, Kolkata- 700019
2 Department of Chemistry, Dinabandhu Mahavidyalaya, Bongaon, North 24 Parganas- 743235
*Corresponding author: goswami_subhasis@yahoo.com

ABSTRACT
The present study attempts to find a probable correlation between the solar cycle and Monsoon Rainfall in India, using the S-Component of the 10.7cm Solar Radio Flux, measured at Ottawa by Remote Sensing Techniques, which varies in response to the Solar Activity, as the representative of the activity of the Sun. Results show a possibility of the Solar activity playing a role in determining the amount of rainfall over a particular region. The general trend is increase in rainfall amount with increase in the solar activity. A possible explanation is suggested for all the observations.
Key words: Solar activity, Solar Flux, Monsoon Rainfall, Monsoon Depressions (MD), Monsoon Low (ML), Mid Tropospheric Cyclone (MTC), Sea Surface Temperature (SST) and Southern Oscillation Index (SOI).



Chaotic analysis of daily and weekly rainfall timeseries over Chennai 

S. Tamil Selvi*1 and R. Samuel Selvaraj2
1Research centre, Department of Physics, Bharathiar University, Coimbatore, Tamil Nadu, India
2Department of Physics, Presidency College, Chennai, Tamil Nadu, India
*Corresonding Author : tssekar9773@gmail.com

ABSTRACT
In this work the reconstruction of phase space and G-P algorithm (correlation dimension) are used to study the chaotic characteristics of daily and weekly rainfall at Chennai, Tamil Nadu. The results show that the daily and weekly rainfall series have a low dimensional chaos. This is also verified using Lyapunov exponent method, which is used to confirm the presence of chaos.The maximum Lyapunov exponent is used to calculate the predictability time. The essential number of parameters in the embedding dimension for the two series were calculated to be 2. The sufficient number of parameters were calculated to be 4 and 6 respectively. The presence of large number of zeros in the high resolution time series may result in underestimation of the dimension, still correlation dimension is the elementary test for the chaos identification. The embedding dimension calculated from the correlation dimension givesthe underlining number of parameters to be used in the forecast model.
Key words: correlation dimension, daily and weekly rainfall, low dimensional chaos, Lyapunov exponent method and embedding dimension.


7
Characteristics of pre-monsoon convective activity over two contrasting environments from microwave radiometer data – A case study

P.P. Leena*, S. Sakharam, V. Anilkumar, S.K. Das and G. Pandithurai
Indian Institute of Tropical Meteorology, Pune, India 411008
*Corresponding Author: leena@tropmet.res.in

ABSTRACT
In the present study, microwave radiometer observations were used to understand the thermodynamic state of the atmosphere before, during and after the thunderstorm events occurred over two contrasting environments i.e. Pune and Mahabaleshwar. Initially thermodynamic state of atmosphere was analyzed using single cases from each site. Analysis of temporal variability of atmospheric parameters and associated thermodynamic indices of individual events showed significant positive differences between Pune and Mahabaleshwar in surface fields like temperature before thunderstorm, while surface relative humidity (RH) records indicated negative differences. Differences in various thermodynamic indices showed that strength of instability is higher over Pune compared to that over Mahabaleshwar. 
Later composite analysis along with difference of the mean was verified so as to confirm the results quantitatively. Among the represented thermodynamic indices lifted index, humidity index and show-alter index showed a negative difference, whereas total index, k-index and convective temperature showed positive difference before and during the storm. However, no significant changes were observed after the thunderstorm activity. Analysis suggested that there is a regional difference in thermodynamic features during the evolution of thunderstorm and also a possibility of thunderstorm potential over Pune compared to Mahabaleshwar. This work also shows the robustness of ground based microwave radiometry for the study of convective events.
Key words: Thunderstorm, Thermodynamic state, Western Ghats and Microwave Radiometer.


8
Long range forecast of rainfall during southwest monsoon in the states of Maharashtra and Goa 

Onkari Prasad*1, O.P. Singh2 and K. Prasad3 
143, Ritu Apartments, A-4 Paschim Vihar, New Delhi-110063
2B44, First Floor, Parshvnath Paradise, Mohan Nagar, Distt: Ghaziabad-201007 (U.P.)
3D-104, Seema Apartments, Sector 11, Dwarka, New Delhi-110085
*Corresponding Author: prasadonkari123@yahoo.in

ABSTRACT
The close relationship known between the activity of South Indian Ocean Convergence Zone and southwest monsoon rainfall for India as a whole also exists for all the four meteorological subdivisions of the states of Maharashtra and Goa (viz., Konkan & Goa, Madhya Maharashtra, Marathwada and Vidarbha). The present study has shown that long range forecast of rainfall for southwest monsoon season as a whole (June-September), bi-monthly periods of August+ September and for the month of September could be prepared for all the four subdivisions. Forecast for seasonal rainfall, at the district level, could be prepared for all districts of the region except the 4 districts of Madhya Maharashtra, namely, Nasik, Pune, Satara and Sangli. For the months of July and September forecast could be prepared for the majority of the districts. For August rainfall forecasting could be possible for the districts of the subdivision of Marathwada only. Forecast for rainfall in the month of June could not be prepared for any of the subdivisions/districts. 
Key Words: Long Range Forecast, South Indian Ocean convergence zone, Southwest monsoon and Maharashtra and Goa.



Cloud Aerosol Interactions and its influence on Cloud Microphysical parameters during Dry and Wet spells of Indian Summer Monsoon using CAIPEEX data 

G.R. Chinthalu*, T. Dharmaraj, M.N. Patil, A.R. Dhakate and Devendraa Siingh
Indian Institute of Tropical Meteorology, Pune 411008 India
*Corresponding author: chintalu@tropmet.res.in

ABSTRACT
The variations of cloud condensation nuclei (CCN), aerosol and cloud particle concentration (PCASP), cloud droplet effective radius (CDPRe), and Liquid water content (LWC) have been measured using instrumented aircraft over Hyderabad, Bengaluru and Bareilly in India during Cloud Aerosol Interactions and Precipitation Enhancement Experiment (CAIPEEX-2009). Three intensive observation periods (IOPs) i.e. 17-22 June and 13 July representing the dry spells, and the IOP during 16-25 August, representing wet spells of Indian summer monsoon were analyzed. Cloud droplet size is highly sensitive to liquid water content and temperature in the cloud environment. The CDPRe and LWC show strong linear correlation during both dry spells and wet spells of ISMR. The mid level clouds CM ~ 2000 meters are more favorable for coalescence of cloud droplets leading to growth of CDPRe > 14 µm required for warm rain formation. 
Key words : Cloud condensation nuclei (CCN), Aerosol and cloud particle concentration (PCASP), Cloud droplet effective radius (CDPRe), Liquid water content (LWC) and Indian Summer Monsoon.


News at a glance 2


10 
In the absence of a robust controlling mechanism Sand mining will be more disastrous compared to Global warming

P.R.Reddy
Director Grade Scientist (Retd), CSIR-NGRI, Hyderabad-500 007
E-mail: parvatarreddy@gmail.com

ABSTRACT
In almost all the international conferences associated with Pollution, monsoon aberrations, environmental issues scientists invariably present their studies covering “Global warming and Climate change”. We hardly come across an international conference that covers studies on sand mining. While fully agreeing that global warming and climate change impacts the land and ocean ecosystem and resultant ill effects on life it is presented in this small write up the necessity to give due importance to steps that would curb illegal sand mining. If we continue to ignore introduction of robust controlling mechanism we will irrevocably suffer due to sand mining resultant permanent negative impact on our environment.
Key words: Sand mining, Global warming, Instream mining, Channel Morphology, National Building Codes.


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Announcement - 20th Convention of the Indian Geological Congress (IGC)