Current Issue

March, 2018   ||  Volume 22 No.2


Critical study on P- and S-waves radiation and computation of earthquake magnitude due to simple crack models

Ajit De
Department of Mathematics, Siliguri College, Siliguri-734001, India

The seismic radiation due to a dynamic crack model has been obtained in frequency domain by considering integral transformed displacement field in an infinite medium. The far field seismic spectra of P- and S-wave arrivals have been computed for the model. Study has also been extended in case of static elliptical shear crack model. Constant far-field displacement spectra have been observed at low frequencies and decay as some power of inverse frequency at high frequencies. Earthquake magnitude or Richter magnitude due to the source model has been computed and a comparative study of different magnitude scales has been presented. The special character of the source model has been compared and discussed with spectral scaling law.
Key words: Earthquake, Seismic radiation, Crack, Fourier transform, Richter magnitude.

Stress Orientation from Image log and Estimation of Shear Wave Velocity using Multiple Regression Model: A Case Study from Krishna-Godavari basin, India

Rima Chatterjee*1 and Dip Kumar Singha2
1Dept. of Applied Geophysics, Indian School of Mines, Dhanbad-826004
2Dept. of Geophysics, Institute of Science, BHU, Varanasi-221005
*Corresponding Author:

Formation Micro Imager (FMI) logs from four boreholes located in the Krishna-Godavari (K-G) basin, covering an area of about 3760sq km onshore, are analyzed to identify natural fractures and breakouts. These features are used to calculate the in-situ maximum and minimum horizontal stress orientation at different depth intervals in the wells. The orientation of maximum principle horizontal stress (SH) obtained from orientations of breakouts and drilling induced fractures varies from N14.540E to N21.840E for the four wells. The dip of natural fracture varies from 4.830 to 29.310 with a dominating mean azimuth N90E. The orientation of SH is in close agreement with the regional NNE trend of the horst-graben, the K-G basin. In addition to stress directions, the mechanical properties of the formations, like Young’s modulus (Y), bulk modulus (K), shear modulus (G), Poisson’s ratio (σ) and unconfined compressive strength (UCS) are estimated from the density and P-and S-wave velocity (Vp and Vs) log data. Further, correlation between Vp and Vs is examined by multiple regression analyses with squared multiple correlation coefficient (R2) varying from 0.92 to 0.96. The models developed by multiple regression analysis for Vs can be used to estimate elastic moduli and rock strength for other wells in the K-G basin.
Key words: FMI log, Breakout, Drilling induced fracture, Natural fracture, Stress orientation, Rock mechanical parameters, Shear wave velocity, Krishna-Godavari basin.

Wavefield decomposition of multi-component OBS data to enhance the seismic signal

N.Satyavani1*, M.Ravi Kumar2 and Kalachand Sain1
1Gas Hydrate Group, CSIR-NGRI, Hyderabad, Telangana
2Institute of Seismological Research, Gandhi Nagar, Gujarat
*Corresponding Author:

The multi-component Ocean Bottom Seismometer (OBS) data captures full wave field by recording on three component geophone and one hydrophone. However, the resultant seismogram includes the free surface multiples that interfere with the recorded wavefield, which has to be removed for further processing. We find that PZ summation, along with the up/down deconvolution is very effective in removing them and renders the multiple-free wavefield. The method is illustrated here, using the OBS data acquired in the Mahanadi basin. In addition to the noise free P wave field, we also obtain the converted (PS) wave field using this approach.
Key words: OBS data, free surface multiples, converted waves, wavefield separation, PP & PS.

Fractal Revaluation of Bottom Depth of Magnetic Sources in Bida Basin, Nigeria from High-Resolution Aeromagnetic Data

Levi I. Nwankwo*1,2, Peter I. Olasehinde 1, and Abayomi J. Sunday 3
1 Department of Geophysics, University of Ilorin, PMB 1515, Ilorin, Nigeria.
2 Department of Physical Sciences, Kampala International University, Uganda.
3 Department of Physics, University of Ilorin, PMB 1515, Ilorin, Nigeria.
* Corresponding Author:  

The recent high-resolution aeromagnetic (HRAM) data for the whole of Bida Basin in north-central Nigeria has been revaluated for depth to bottom of magnetic sources (DBMS) using the modified centroid method for fractal distribution of sources. Analysis of the HRAM map shows magnetic lineations due to tectonic features that may be connected to regional tectonic framework of West and Central Africa Rift Systems. The HRAM data were also divided into 28 overlapping blocks and each block was evaluated to obtain depths to the top and centroid of magnetic sources. Both depth values were consequently used to calculate the DBMS for each block. The results reveal that the DBMS varies between 5.41 and 19.29 km with an average of 12.01 km. Hence, this study would contribute to further explication of the geo-processes and rheology of Bida Basin in north-central Nigeria.
Key words: Basal depth, magnetic sources, fractals, Bida basin, Nigeria

Forecasting aftershocks of major earthquakes

Vinod Kumar* and M. Satya Kumar1
Shyam Bhawan, Ashok Nagar, Road No. 11, Kankarbagh Colony, Patna-800020
1 H. No. 6-3-565, Flat No. 301, Akshaya Apartment, Somajiguda, Hyderabad- 500082
*Corresponding Author:

Aftershocks of highest magnitude of major earthquakes of magnitude ≥ 7.9 can be forecast on certain lunar days when prominent changes are observed in both values of (Ocean) high tides. If main earthquake occurs on the day when both (Ocean) high tides start decreasing or when both high tides are observed as minimum (continue decreasing) then aftershock of maximum magnitude can be forecast during low tide period. If main earthquake occurs on the day when both high tides start increasing or both high tides are observed as maximum (continue increasing) then aftershock of maximum magnitude can be forecast during high tide period.
Key words: Forecasting; aftershocks; major earthquakes, maximum magnitude; Solar-lunar gravitational force, earth tides, Ocean high tides..

Hydrogeological and Geophysical Characteristics of Northern Parts of Eastern Ghat Khondalitic Aquifers

B.Venkateswara Rao
Professor, Centre for Water Resources, IST, JNT University Hyderabad

In this study various concepts pertaining to khondalitic (Garneti Ferrous Sillimanite gneiss) aquifers and their kaolinisation in the Vijayanagaram district of Andhra Pradesh, India is attempted. The hydrogeological and geophysical studies on these aquifers inferred that the khondalites in this region are sedimentary in origin but later metamorphosed and became hard rocks. These rocks were subjected to intense weathering, faulting, fracturing and folding giving way to accumulation of ground water in two different layers mainly in weathered layer and fractured layer with hydraulic continuity among them. Beneath the streams and low-lying areas most of the khondalite became kaolinised and turned out to be low ground water potential zones. This kaolin, which is essentially clay, is acting as a barrier for the ground water movement towards the stream and forcing it to accumulate in the upland areas between the streams and naturally became groundwater potential zones whenever the formation is fractured and intruded with quartz veins. Lack of resistivity contrast between highly weathered khondalite and fractured khondalite has been noticed in the Vertical Electrical Sounding data at few places. This called for Two-Dimensional (2D) and Three-Dimensional (3D) resistivity imaging surveys to delineate the kaolinised zones to avoid well failures. The extended deeper kaolinisation of the aquifer is responsible for failure of wells in this terrain. At failed wells, kaolinisation is not only deeper but also followed by the basement characteristics either with very thin or no aquifer layer immediately below the kaolinised layer. At successful wells not only kaolinised layer is thinner but also aquifers are thicker resulting in presence of basement characteristics only at deeper depths. Layers having resistivities between 25 ­- 65 Ohm-m are identified as aquifer layers, which are composed of moderately weathered and fractured khondalitic suite of rocks. Layers with resistivities greater than 65 Ohm-m are interpreted as granite gneissic basement, while the layers with resistivities less than 25 Ohm - m are interpreted as kaolinised layer. The quality of the ground water in this region is generally good and suitable for both drinking and irrigation purposes except at few pockets where Fluoride and Nitrate is present in excess of permissible limits. Similarly, in downstream areas of major streams high salinity is present.
Key words: Khondalite, Aquifer, Kaolinisation, Resistivity, Groundwater potential

Geochemical and Ore-mineralogical Characterization of Beach placer ilmenite from Srikurmam Deposit, Andhra Pradesh, India

M.Jagannadha Rao1*, J. Venkata Ramana2, Aaron A.Jaya Raj3, G.Raja Rao3 and P.Rajesh4
1-4Department of Geology, Andhra University, Visakhapatnam-530003
1Department of Geosciences, Dr. B.R.Ambedkar University, Etcherla, Srikakulam
*Corresponding Author:

Ilmenite ores from the Srikurmam placer sand deposit were investigated for their geochemistry and ore mineralogy. Studies indicated that the ilmenite of Srikurmam placer has TiO2 content comparable to other placer deposits like Bhimunipatnam in east coast and Ratnagiri in west coast of India. The trace element data indicate that the elements such as Co (315 ppm to 320 ppm), Ni (45 ppm to 49 ppm), Zn (694 ppm to 698 ppm), V (1300 ppm to 1304 ppm) and Cr (648 ppm to 653 ppm) are in higher concentrations. Mn content in the ilmenites of the present study area has significantly low values (0.52 ppm to 0.93 ppm). Ore mineralogical studies indicate that the ilmenite exhibits conspicuous exsolution features. Studies reveal four types of intergrowths; hemo-ilmenite (complex exsolution and lamellar exsolved phase), ilmeno-hematite (Emulsion texture), and irregular exsolved phases exhibiting different grain level textures. Hematite phase in ilmenites incorporates excess iron (average 46.49%) in the structure of ilmenite. Based on the geochemical and ore mineralogical aspects, ilmenites of the Srikurmam placer area is more suitable for pigment-manufacturing. However, the higher concentrations of trace elements may affect the properties of pigment grade oxide. In addition the excess iron may cause environmental problems.
Key words: Beach placer ilmenite, Ore mineralogy, Geochemistry, Srikurmam, Andhra Pradesh..

Ferrosyenites - an overview

K. Sai Krishna and R. Mallikarjuna Reddy* 
Department of Geology, Kakatiya University, Warangal, Telangana-506009
*Corresponding Author:

Through this paper we present an overview on the ferrosyenites. The ferrosyenites are very rare and geologically interesting rocks that are found in North America, Africa, Antarctica, China, Europe, Ukraine, Greenland and India. Mineralogically ferrosyenites are mainly composed of Fe-rich pyroxenes or Fe-rich olivine (fayalite), alkali feldspar minerals. 90% of ferrosyenites occur in association with gabbros in different alkaline complexes of the world, due to their petrogenetic relation. Chronologically ferrosyenites vary widely in age (9.1 ± 0.4 Ma to 1413 ±54 Ma). Along with the mineralogical and chronological diversity, the global distribution and nature of occurrence of the ferrosyenites is presented here.
Key words: Ferrosyenite, mineralogy, correlation, global distribution..

Petrological and Geochemical Characterisation of the Punugodu Granite Pluton Nellore Schist Belt; Implications for Proterozoic Anorogenic Granite Magmatism in the Eastern Dharwar Craton, Southern India

1Ch. Narshimha, 1U.V.B. Reddy, 2V.V. Sesha Sai and 3K.S.V. Subramanyam
1Department of Applied Geochemistry, Osmania University, Hyderabad-500 007, India
2Petrology Division, Geological Survey of India, Southern Region, Hyderabad-500068 – India
3Geochemistry Division, CSIR-NGRI, Hyderabad-500 007, India
*Corresponding Author:

In this paper we present the in-situ field observations along with petrographic and geochemical results of the Punugodu granite pluton of Nellore schist belt, Eastern Dharwar Craton, South India. Located to the South of Podili alkali granite, the Punugodu granite pluton occupies an area of 7 sq. km. Field studies indicate that the Punugodu granite is deformed along the margins. Enclaves of metavolcanics and quartzite of the Nellore schist belt are observed in the pluton indicating its intrusive nature. Petrographically the rock is mainly composed of K-feldspar, with sub ordinate quartz, amphibole, biotite, pyroxene and hypersolvus in nature. Zircon, titanite, fluorite, apatite and opaques are the accessory phases. Geochemical studies reveal that the Punugodu granite indicates the metaluminous nature and exhibits calc-alkaline trend. Punugodu granite is charecterised by high SiO2 contents ranging from 69.62 % to 72.7 %, high Na2O + K2O, relatively low MgO contents ranging from 0.13 % to 0.76 %. The CaO-Na2O-K2O contents range from 10.15 % to11.14 %. Chondrite normalised Rare Earth Elements diagram shows relative enrichment of Light Rare Earth Elements and negative europium anomaly for the Punugodu granite. It is relatively enriched in High Field Strength Elements (HFSE); Zr (85.54 to 311.83 ppm), Y (108.07 to 156.60 ppm), Nb (131.59 to 216.61 ppm) and the (36.38 to 51.62 ppm). In the Y+Nb vs Rb trace element tectonic discrimination diagram Punugodu granite falls in the within plate granite field (WPG). The high SiO2 and Na2O + K2O, relatively low MgO contents along with enriched HFSE and within plate character indicates the anorogenic nature of the fluorite bearing Punugodu granite.
Key words: Punugodu granite, Nellore schist belt, EDC, India

Long range forecast and development of a weak southwest monsoon during 2017- Pt. I: Long range forecast

Onkari Prasad*, O. P. Singh1 and K.Prasad2
*43, Ritu Apartments, A-4 Paschim Vihar, New Delhi-110063
2B44, First Floor, Parshvnath Paradise, Mohan Nagar, Ghaziabad (U.P.)-201007
2D-104, Seema Apartments, Sector 11, Dwarka, New Delhi-110085
*Corresponding Author:

India received below normal rainfall during 2017 southwest monsoon. Formulation of Long Range Forecast (LRF), based on South Indian Ocean Convergence Zone (SIOCZ) model and the results of verification of the forecasts at district and subdivision levels and for India as a whole have been discussed in this part of the study. For the sake of comparison, the forecast from the operational models have also been reproduced. The results of verification have shown that SIOCZ model’s district level forecast was in ‘Excellent’ category in the states of Tamilnadu, Andhra Pradesh, Himachal Pradesh, Maharashtra and Goa and in ‘Very Good’ category in Telangana. At the subdivision level forecast was in ‘Excellent’ category in the months of June, July and August and in ‘Very Good’ category in September. The forecast for bi-monthly rainfall was in ‘Excellent’ category for all the three bi-monthly periods of Jun+ Jul, Jul+ Aug and Aug+ Sep and also for the season as a whole (Jun-Sep). For India as a whole, forecast was in ‘Useful’ category in August and September and during the bi-monthly periods of Jul+ Aug and Aug+ Sep. An Update had been issued in August for improvement of rainfall during the second half of the season. However, the improvement in rainfall did not take place over Central and Northwest India. Instead it remained confined to south Peninsula only.
Key words: Southwest monsoon, South Indian Ocean Convergence Zone model, Long range forecast, Update, Forecast verification..

Defluoridation of water using Mentha longifolia (Mint) as Bioadsorbent

V.Sunitha* and B.Muralidhara Reddy
*Department of Geology, Yogi Vemana University, Kadapa, A.P.
*Corresponding Author:

Excessive fluoride concentrations have been reported in ground waters of 19 states of India. Acute fluorosis is noticed in many problem areas of these states. In spite of several existing physical and chemical defluoridation methods, there is an urgent need to develop cost effective and biodegradable methods to effectively treat high fluoride concentration in ground water. Experiments at room temperature were performed to evaluate the adsorption capacity of Mentha longifolia (Mint) from aqueous solutions. The effect of some major parameters like pH, contact time and amount and particle size of adsorbent and concentration of fluoride ions of the uptake on adsorbent materials is investigated from kinetic viewpoint. Adsorption studies are performed by batch technique to obtain the rate and equilibrium data. The Freundlich and Langmuir sorption isotherms were used to quantify sorption properties. Results show that Mentha longifolia (Mint) is effective in removing fluoride from groundwater samples.
Key words: Defluoridation; Biosorption; Mentha longifolia; pH; Adsorption kinetics.

Feasible Mitigation Options for Air Pollution and Traffic Congestion in Metro Cities

Kopal Verma and Umesh Kulshrestha*
School of Environmental Sciences, Jawaharlal Nehru University, New Delhi 110067 INDIA
*Corresponding Author:

Increasing needs of urban population and exploitation of natural resources are the major concerns for environmental degradation. Growing urbanization and unplanned expansion of large cities, especially in developing countries have led to high levels of air pollution. It has been realized that the megacities are the hot spots of air pollution. The Asian and African megacities such as Cairo, Beijing, Delhi, Mumbai, Bengaluru and Kolkata are some of the examples showing alarming levels of air pollutants. Hence, it is the high time for the policy makers to take urgent and apt initiatives that can mitigate urban traffic congestion and air pollution. This paper highlights the possible options such as introduction of bullet train, more intensive network of metro trains, Odd-Even scheme, work from home, flying cars, transit elevated bus, electric vehicles, bi-cycles, compulsory use of public transport along some highly congested roads and restriction in owning more than one car per family, for congestion reduction and air pollution prevention & control in metro cities.
Key words: Environmental degradation, Air pollution, Traffic congestion, Hydrocarbon emission, Greenbelt

Probing Chemical Heterogeneity of the Mantle Using Open System Isotopic Models of the Silicate Earth

Seema Kumari* and Debajyoti Paul
*Department of Earth Sciences, Indian Institute of Technology Kanpur, Kanpur 208016, Uttar Pradesh, India

The layering and convection within the Earth’s mantle plays a major role in the formation of continental crust as well as tectonic activities and the heat budget of the Earth. The mode of mantle convection (whole versus layered) is still debatable despite concerted geophysical and geochemical studies for the past several decades. This study is an exhaustive numerical approach to develop an open system geochemical model for the Earth comprising bulk continental crust (CC), depleted upper mantle (UM)–source of mid–ocean ridge basalts (MORB), a lower non-chondritic mantle (LM)–source of ocean island basalts (OIB), and an isolated reservoir (IR). The model is solved numerically using fourth-order Runge-Kutta method at 1 Ma time step over the age of the Earth, simulating the evolution of key radioactive isotope systems in terrestrial reservoirs. Coupled Rb–Sr, Sm–Nd, and U–Th–Pb isotope systematics will constrain various aspects related to the Earth’s differentiation processes leading to chemical heterogeneity within the mantle. Various crustal growth scenarios (linear vs. non-linear, early vs. delayed, and continuous vs. episodic growth) and their effects on the evolution of isotope systematics in the silicate reservoirs have been evaluated. The most plausible model-derived solution is the one that produces the present–day concentrations as well as isotopic ratios in the terrestrial reservoirs, constrained from published data. Modeling results suggest that a whole mantle (compositionally similar to the present–day MORB) model fails to satisfy observational constraints. However, a layered mantle model, in which the present–day UM is ~ 60% of total mantle mass and the lower mantle is non–primitive produced the required isotopic ratios and abundances in the terrestrial reservoirs. Modeling also suggests that isotopic evolution in reservoirs is strongly affected by the mode of crustal growth. It is observed that Pb paradoxes result from open system evolution, which allows large-scale mass exchange between reservoirs.
Key words: Mantle convection, open system modeling, crustal growth pattern, Pb paradox.

Dynamics of drought and present status of drought prediction-
an overview

Scientist- G (Retd); CSIR-NGRI, Hyderabad-500007, Telangana State.

News at a glance 2

Proterozoic Orogens of India: A critical window to Gondwana by T.R.K.Chetty,
CSIR-NGRI, Hyderabad- 500 007, pp- 1 to 405, Elsevier publication, ISBN; 978-0-12-804441-4: Book Review by P.R.Reddy.

Short-Term Advanced Warning from Some Large Earthquakes

Indra N. Gupta, B.K. Rastogi* and Robert A. Wagner
Array Information Technology, Greenbelt, Maryland
*Former Director General, Institute of Seismological Research, Gandhinagar, India
*Corresponding Author:

Several recent studies have identified short-term precursory activity before large earthquakes. Ambient seismic noise with spectral peaks at about 0.07 Hz and 0.2 Hz, due to primary and secondary microseisms, respectively, is observed everywhere at stations on hard basement rock. We examined pre-earthquake ambient seismic noise from four large earthquakes recorded at several three-component stations. Spectral characteristics of seismic noise within a narrow frequency range, which includes the larger-amplitude secondary spectral peak frequency, are found to be significantly altered by pre-earthquake activity when monitored by stations near the earthquake epicenter. For the M6 Nevada earthquake of 21 February 2008, spectral ratios of transverse/radial component or T/R observed at two recording stations along nearly orthogonal directions with respect to the epicenter suggest that the pre-seismic energy consists of the lowest frequencies up to about 0.2 Hz and increases in strength as it approaches the earthquake origin time. Moreover, the differences in T/R at the two stations are found to in agreement with regional tectonics, therefore suggesting a mechanism of accelerating movement on pre-existing faults in the region. Analysis of several hours of observed pre-earthquake noise from four large earthquakes, obtained by converting observed data to particle displacement, show the low frequency amplitudes to increase in strength as the earthquake origin time approaches. Moreover, the advanced warning time appears to depend on earthquake magnitude; larger warning times for larger events. Our study appears to provide a method for obtaining advanced warning of a few hours or more before at least some impending large earthquakes.
Key Words: Advanced Warning, Short-term precursory activity, Ambient seismic noise, particle displacement.

54th Annual Convention of Indian Geophysical Union (IGU): A Report