Archived Issue

April, 2016   ||  Volume 20 No.2


Site-specific Next Generation Ground Motion Prediction Models for Darjeeling-Sikkim Himalaya using Strong Motion Seismometry

Manik Das Adhikari and Sankar Kumar Nath*

Department of Geology & Geophysics, Indian Institute of Technology Kharagpur, West Bengal, Pin: 721302, India
*Corresponding Author:

In the perspective of Probabilistic Seismic Hazard Assessment, the ground motion parameters at a site of interest are evaluated by using a ground motion prediction equation that relates a specific strong motion parameter of ground shaking to one or more seismic attributes. In this study, we deliver site-specific Next Generation Prediction (NGP) Models for Darjeeling-Sikkim terrain located in the eastern Himalayan seismogenic province implicating a maximum credible earthquake of magnitude Mw8.3. The NGP models have been developed for three dominant tectonic domains viz. normal, strike-slip and thrust faulting mechanism of earthquake nucleation as per site classes A, B, C & D for different station elevation ranges for Peak Ground Acceleration (PGA) and 5%-damped Pseudo Spectral Acceleration (PSA) at 0.2 and 1.0 sec time period as a function of magnitude, fault rupture distance and site condition. The Extended Finite Fault simulation approach EXSIM is used for ground motion synthesis with the source parameters extracted from the recorded and historical earthquakes reported in the territory. In order to strengthen the ground motion data base, the seismic events of small to moderate magnitude with signal-to-background noise ratio≥ 3 recorded by Darjeeling-Sikkim Strong Motion Array of IIT Kharagpur have been amalgamated with the simulated ones for a wide magnitude range of Mw3.5 to 8.3 at 140 locations at a grid spacing of 0.1º × 0.1º. Altogether 42 ground motion prediction equations have been worked out through a nonlinear regression process of strong ground motion data versus magnitude, distance, and other predictive variables using two classical ground motion attenuation models which predicted 14 coefficients for each of the derived equations depicting zero clustered residuals. The derived NGP models have been used in a logic tree framework for probabilistic seismic hazard assessment of the Darjeeling-Sikkim Himalaya depicting PGA distribution for 10% probability of exceedance in 50 years at surface level varying from 0.293g to 0.807g. The major urban centers viz. Gangtok, Mangan, Singtham, Melli, Jorethang, Uttare and Darjeeling are seen to have enhanced hazard level to the tune of 0.60 - 0.750g placing those to probable Seismic Zone V with the suggested zone factor of 0.75g.
Key words: Next Generation Prediction(NGP), Seismic Source Attributes, Strong Ground Motion Data, Generic Site Amplification, Darjeeling-Sikkim Himalaya.

Heavy Metal Contamination of Groundwater in Nacharam Industrial Area, Hyderabad, India

B. Venkateswara Rao*1, Ch. Kavitha2, N.N. Murthy3 and P. Lakshminarayana4

1Professor of Water Resources
2M.Tech Student, Centre for Water Resources, IST, JNTUH
3Scientist ( Retd ), Environment Geochemistry Division, NGRI, Hyderabad
4Lecturer, CEA & WMT, JNTUH
*Corresponding Author :

Samples of Groundwater, surface water, soil and sediment were collected from the region in and around Peddacheruvu (Irrigation Tank) near Hyderabad City, India. Water samples are analyzed for heavy metals with Inductively Coupled Plasma Mass Spectrometer. Soil and sediment samples were analyzed for heavy metals with X-ray Fluorescence. From the analytical data of heavy metals, it is found that the soil samples are contaminated with heavy metals such as As, Cu, Cr, Pb, Rb, V, Zn and Zr. The high contamination of soils with heavy metals may be due to anthropogenic sources since the country rock of granite does not contain these heavy metals with such high concentration. The contaminated soils have contributed the contamination to both the sediments and groundwater. The sediments have the high concentration of heavy metals such as As, Ba, Cr, Rb, Pb, Zn and Zr, while the groundwater is contaminated with heavy metals such as Al, Mn, Fe, Ni, Zn, Cu and Pb. Interestingly, surface water is less contaminated with heavy metals namely Fe, Mn, Ni and Al when compared to the sediment and groundwater as these heavy metals are deposited on the sediment due to the heavy metal precipitation activity in the water body.
Key words: Heavy Metal contamination, Groundwater, Surface water, Soil and sediment, Nacharam Industrial area, Peddacheruvu, Mass spectrometer, X-Ray Fluorescence.

Geomining Conditions of Seam-I of Godavari Sub-Basin-A Geophysical Study

G. Uday Bhaskar*1, A. Srinivasa Rao2, G. V. S. Prasad2 and K. A. V. L. Prasad3
1DGM (Geophysics), Exploration Division, SCCL, Kothagudem, 507 101
2Superintending Geophysicist, Exploration Division, SCCL, Godavarikhani 505 209
3Superintending Geophysicist, Exploration Division, SCCL, Belampalli 504 251
*Corresponding Author:

Mechanised mining is preferred to extract coals having weak clay roof at Ramagundam and Belampalli regions of Godavari sub-basin located in the state of Telangana, India. The present study has therefore focused on establishing the developmental pattern of one such coal called Seam-I and its overburden strata known as SS-80 using geophysical logs. Development of Seam-I of 4m to 7m thickness took place in a coal swamp spread over the entire Godavari sub-basin. Inundation of coal swamps by the flood basin produced higher amounts of ash of 25% to 40%. The top section of Seam-I contains lesser amounts of ash of 25% to 30%. Dynamism of sub-environments of the fluvial system produced distinct pattern of clay (1.20m thick) and sandstone as the immediate roof of Seam-I in various parts of Godavari sub-basin. Roof rock maps now constructed provide spatial distribution of clay and sandstone, that are useful to plan roof support systems. Very thick to thick (2m to 3m) massive/ graded sandstones make up the 17m to 33m thick overburden of Seam-I. These are low to medium strength and fair to good rocks classified on the basis of uniaxial compressive strength (UCS) of 6MPa to 15MPa and Geophysical Strata Rating (GSR) of 30% to 60% respectively. 1m to 2m thick beds of very low to very high strengths separate very thick beds. UCS and GSR maps provide the spatial distribution of all these beds to predict zones of separation, delamination and periodic weighting. It is also observed that intact strengths of these sandstones are lower than those of Australian and American sandstones for a given range of Vp values.
Key words: Seam-I, SS-80, Vp, UCS, GSR.

Intense Precipitation causing Floods over Himalayan Region of Northern India – A case study on Role of Atmospheric Rivers 

P. Chandrasekhara Rao*, Archana S. Shinde and A. K. Jaswal
India Meteorological Department, Shivajinagar, Pune 411005, INDIA
*Corresponding Author: 

Atmospheric rivers carry a large amount of water vapour and travel long distances in the lower levels of earth’s atmosphere. They are usually found in the mid-latitude region moving up and down, drawing most of the water vapour from the tropical regions when they move up and bringing cold air from the northern regions when they move down. They play an important part in the global water cycle. Climatic changes due to manmade activities disturb the general flow and many a time they are responsible for extreme precipitation and flooding. Northern India receives isolated snow and rainfall due to western disturbances. In the absence of external forces, like atmospheric rivers this activity is rarely vigorous. In this study, an attempt has been made to identify and bring to light the role of the Atmospheric Rivers in triggering sudden extreme precipitation along the Himalayan mountainous regions of North India, under favorable synoptic conditions due to Western disturbances.
Key words: western disturbance, trough, atmospheric river, cloud burst, upper air circulation, precipitable water content.

Delineation of aquifer layer along Anjar-Rapar Corridor, eastern Kachchh basin, Gujarat using electromagnetic investigations

G.Pavan Kumar*, E.Mahender , Y.K.Singh , P.Mahesh and Kapil Mohan
Institute of Seismological Research (ISR), Raisan, Gandhinagar – 382 009
*Corresponding Author:

Kachchh basin is an intraplate region of rifted Precambrian craton in the Gujarat state of the north-western India. The basin is characterized by a thick succession of sedimentary rocks of middle Jurassic to Holocene that overlie the Precambrian basement. Kachchh district is a water scarce region and ground water has become one of the important sources to meet the water requirements of various sectors. Tertiary and Mesozoic formations in general do not form promising aquifer mainly because of the clayey nature and poor groundwater quality. The upper Bhuj (Mesozoic) and Kankawathi (Tertiary) series of formations constitute a relatively good aquifer due to low salinity. We have carried out a time domain electromagnetic (TDEM) survey along the Anjar - Rapar (AR) corridor in the eastern part of the Kachchh basin to map potential aquifer layer in the region. Twelve fixed in-loop TDEM soundings with 100m sided transmitter loop were carried out. The measured transient decay curves are used to delineate the depth and subsurface resistivity of the underlying structures. The modelled 1-D section reveals a 20 to 50m thick conductive layer of 10-15 Ωm resistivity with its top surface at 10-15 m depth. We infer this conductive layer as a probable aquifer comprising saturated sandstone with moderate salinity. At some places along the corridor, we have also obtained a second aquifer layer at deeper levels(150-250m) overlying a relatively low resistive layer probably comprising clay and/or clayey sand. Apart from the first layer, subsequent subsurface formations (up to 200-250m) appear to be heterogeneous in nature and are inferred to be composed of clay (>5 Ωm), Clayey sand/sandy clay/ sandstone with high content of saline water (5-10 Ωm) and shale (20-50 Ωm). The results are integrated with well-log data to better constrain the geophysical inferences.
Key words: Time domain electromagnetic method, Kachchh, resistivity, aquifer mapping, Groundwater.

Landslides and Floods in the Tista Basin (Darjeeling and Jalpaiguri Districts): Historical Evidence, Causes and Consequences 

Raghunath Pal*1 , Sumantra Sarathi Biswas1 , Biswajit Mondal1 and Malay Kumar Pramanik2
1Centre for the Study of Regional Development, Jawaharlal Nehru University, New Delhi-110067.
2Centre for International Politics, Organization and Disarmament,Jawaharlal Nehru University, New Delhi-110067
*Corresponding author:

The Tista basin is one of the most vulnerable among the Himalayan river basins considering the occurrence of landslides and floods. The landslides occurred in 1899, 1950, 1968, 1976, 1991, 1993, 2003, 2004, 2005, 2006, 2009, 2011 and 2015. The floods occurred during 1950, 1968, 1973, 1975, 1976, 1978, 1993, 1996, 2000, 2003 and 2015. Some of the years of landslides and floods are same. This reflects the joint occurrence of the two hazards. Landslides occur in the hilly portion of the basin (Darjeeling Himalaya)whereas floods occur in the plain portion of the basin (Jalpaiguri district) and the flood events occur after the landslides because of topographic variation effect. This in turn indicates the influence of landslides on the floods. The prominent causes of landslides in the basin are torrential rainfall, fragile geology, earthquake and deforestation. The prominent causes of floods are sudden cloud burst, conditional basin surface morphology, landslides and barrage, embankments and guide bunds construction.The record of consequences of these two disasters brings in to focus the severe impact caused on the basin dynamics.
Key words: Landslides, Floods, Historical Evidences, Tista Basin,Darjeeling Himalaya, Jalpaiguri District.

Spatial Characteristics Analysis of Coastal Vulnerability in the Balasore Coastal District, Odisha, India 

Nilay Kanti Barman*1, Soumendu Chatterjee2 and Ashis Kumar Paul3
1Department of Geography, Hijli College, Kharagpur -721306
2Department of Geography, Presidency University, Kolkata- 700073
3Department of Geography and Environment Management, Vidyasagar University, Midnapore-721102
*Corresponding Author:

Climate change related enhanced weather related natural hazards, in the form of frequent high intensity tropical cyclones, storm surges, coastal ecological adverse changes and allied hazards have made Balasore district of Odisha an environmentally degraded coastal vulnerable zone.Since it is paramount to safeguard such vulnerable coastal segments both the scientists and administrators have decided to develop needed maps that bring out vulnerability levels of coastal corridor and inland stretches for arresting further degradation through organised disaster management initiatives. As a part of such an initiative, the present study covenant with the coastal vulnerability for this zone has been carried out by calculating the probability of vulnerability and assigning different levels of vulnerability in the form of weighted score of vulnerability at the Gram Panchayat level in respect of four major resources like land, water, house/shelter and transport in accordance with the dimensional impacts of dominated coastal hazards like cyclone, flood, storm surges, beach erosion, wave action and salinity encroachment. The present study has been conducted among five social groups, as respondent, to recognize the change potential (whether it is enhanced or reduced or no change) of concern resource type subsequent to the hazards occurrence. Nature and composition of such changes may vary from place to place and situation to situation. However, principle of binomial test (as applied in sign test) can be used for determining the probability for each of the variables under every resource type.After getting the vulnerability of probability, it has been multiplied with the respective population to calculate the Coastal Vulnerability Score (CVS) of a particular coastal Gram Panchayat (considered spatial scale to study). This is the first such study that has been undertaken for a part of the Balasore coast. The vulnerability map, prepared for the Balasore coastal district under this study can be used at different coastal stretches to prepare the spatial variability of coastal vulnerability and also formulate the executive management plan.
Key words: probability of coastal vulnerability; coastal vulnerability score; recurring storm flood; Coastal areas.

Modifying Hagen-Poiseullie’s equation for an inclined porous media with varying porosity 

Alabi O.O.* and Olaleye K.O 
Solid Earth Physics Research Laboratory, Department of Physics, Osun State University,Osogbo, Nigeria.(+2348035028760).
*Corresponding Author:

Mode of transport of fluid in soil is the basis for soil environmental engineering especially in transport of contaminants in subsurface groundwater. Volume flux (q) of water through media of different porosities in an inclined pipe for different angles of inclination (α) was determined. The patterns of flow were determined from q-α curve for two forms of porosity change. The porosity change ∆ϕ is positive when moving from aless permeable to amore permeable medium in an inclined pipe, while it is negative when moving from a more permeable medium to aless permeable medium in an inclined pipe. It was observed that (-∆ϕ) acts as a damping factor for turbulent flow, while (+ ∆ϕ) increases the rate of flow vis-à-vis turbulent flow. Also, porosity difference, ∆ϕ was introduced to an already established Hagen-Poiseullie’s equation in order to modify it for an inclined porous media of different porosities.
Key words: Volume flux, inclination angle, porosity, turbulent flow, permeable media.

Subsurface thermal response to increase in air temperature with time dependent recharge 

M. Ravi*1, D. V. Ramana1 and R.N. Singh2
1CSIR-National Geophysical Research Institute, Hyderabad, India
2Former Senior INSA Scientist, NGRI (CSIR), Hyderabad, India
*Corresponding Author:

Kumar et al., (2012) derived a solution to calculate the subsurface thermal response to time dependent air temperature with constant groundwater recharge using a Robin type boundary condition at the earth’s surface relating the air temperature to surface temperature using a heat transfer coefficient. For time dependent recharge, analytical solution would be too complex except in a few simple cases. We thus use a numerical approach based on the finite element method to simulate the changes in the thermal response of subsurface to air temperature change under a step change in recharge. We illustrate the effects of time dependent recharge on the subsurface thermal regime for varying duration and size of step changes in recharge and with a heat transfer coefficient. Numerical results for an example show that the surface temperature rise declines in 6 yrs from the value for recharge of 0.5 m/yr lasting 10 yrs to that of recharge of 0.2 m/yr. This lag is found to be increasing with the duration of higher recharge and the size of the step.
Key words: Shallow subsurface, Temperature, Robin boundary condition, Finite element method, Time dependent recharge, time lag.

Origin and Occurrence of calcretes from Red sediments of Visakhapatnam-Bhimunipatnam coast, East Coast of India 

M.Jagannadha Rao*, Greeshma A.G, B. Sudha Rani, M. Mallikarjuna Rao and U.P.N.Raju1
Department of Geology, Andhra University, Visakhapatnam-530 003
1Department of Geology, M.R.A.College, Vizianagaram-535 002
*Corresponding Author:

The red sediments with calcretes along Visakhapatnam- Bhimunipatnam ( 83° 17.5’-83° 33’N and 17° 41 -17° 59’ E) of Andhra Pradesh state, India is of scientific interest. Morphologically, calcretes are classified as rhizo-concretionary, mottled, massive, corn like structures with micrite cement. The possible mechanism of its formation has been discussed.
Key words: Morophology, Clacretes, Red sediments, Visakhapatnam- Bhimunipatnam coast, Corn like structures.

District level long range forecast of rainfall during southwest monsoon in Andhra Prades 

Onkari Prasad1*, O.P. Singh2 and K. Prasad3
143, Ritu Apartments, A-4 Paschim Vihar, New Delhi-110063
2B44, First Floor, Parshvnath Paradise, Mohan Nagar, Ghaziabad-201007 (U.P.)
3D-104, Seema Apartments, Sector 11, Dwarka, New Delhi-110075
*Corresponding Author:

Long range forecast of rainfall during southwest monsoon season, at spatial resolution of a district, could serve as an important input to the farming community. However, such forecasts are not yet available. It has been shown that making use of South Indian Ocean Convergence Zone (SIOCZ) model, long range forecast of seasonal rainfall and rainfall for bi-monthly periods of July+ August and August+ September could be prepared for all the districts of Andhra Pradesh. Long range forecasts could also be prepared for monthly rainfall in July, August and September for a limited number of districts. Verification results for the real time forecasts the past 2 years (2014-2015), have shown that the performance of the model in Andhra Pradesh is comparable to that in Himachal Pradesh.
Key words: Southwest monsoon, South Indian Ocean Convergence Zone, Activity index, District level long range forecast, Coastal Andhra Pradesh, Rayalaseema.

Basin structure from gravity and magnetic anomalies in the central part of Cauvery basin, India 

D. Bhaskara Rao*1 and T. Annapurna2
Professor of Geophysics (Retd.), Andhra University, Visakhapatnam-530003
2Research Scholar, Dept. of Geophysics, Andhra University,Visakhapatnam-530003
*Corresponding Author:

The gravity and magnetic data along three profiles across the central part of Cauvery basin of India have been collected and interpreted with variable density contrast in order to deduce the structure of the sedimentary basin. The first profile is taken from Vridhachalam to Kilyanjiyur covering a distance of 100 km and the second starts from Niddamangalam and ends at Niybankurichchi covering a distance of 120 km and the third is from Pudukottai to Mallipatnam covering a distance of 50 km. The gravity lows and highs have clearly indicated various sub-basins and ridges. The density logs from ONGC, Chennai, show that the density contrast decreases with depth in the sedimentary basin, and hence, the gravity profiles are interpreted using variable density contrast with depth. From the Bouguer gravity anomaly, the residual anomaly is constructed by graphical method correlating with well data and subsurface geology. The residual anomaly profiles are interpreted using polygon and prismatic models. The maximum depths to the granitic gneiss basement are obtained as 6.41km, 8.70 km and 5.20 km for the first, second and third profiles respectively. These studies are useful to refine the subsurface geological studies.The regional anomaly is interpreted as Moho rise towards coast. The aeromagnetic anomaly profiles are also interpreted for charnockite basement below the granitic gneiss group of rocks using prismatic model.
Key words: Cauvery basin, Gravity, Variable density contrast, Granitic gneiss basement, Magnetic, Charnockite basement.

Observational aspects of life cycle of a distinct squall line over Assam valley

P.A.Kore*1, A.D.Tathe1, H.R.Biswas2 and G.K.Das2
1 Surface Instruments Division, Pune,
2 Regional Meteorological Centre, Kolkata
India Meteorological Department, Ministry of Earth Sciences, Pune-411005
*Corresponding Author:

A squall line of about 180 km in length was observed on 24th April, 2007 over Assam valley with widespread heavy spells of rainfall and wind speed reaching 70 kmph. An attempt is made to analyze life cycle of squall line including genesis, growth and decay explained by synoptic and meso-scale features. The synoptic features like development of low pressure area with embedded cyclonic circulation at lower levels over Assam, adjoining Bangladesh, Gangetic West Bengal and north –south trough across Assam to northwest Bay of Bengal in mid-tropospheric level in the morning hours were found responsible for it. The thermodynamic parameters like LCL, CCL, and LFC were found as precursor for predicting the severe thunderstorm event well in advance on the contrary Showalter index, Total-Total index, SWEAT index, CAPE and CINE were not found use full as the precursor for occurrence of this particular squall line.
Key words: Assam valley, Thunderstorm, Squall line, Life cycle, IPWV, Radar, Synoptic.

Human Induced Severity of Natural Disasters and Extreme Climatic Events

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

This paper presents the status of knowledge about human influence on natural disasters and extreme weather events. It also reports the basic causes and related analyses of data pertaining to warmth of Delhi winters in 2015-16 and the Chennai floods 2015. Recent climate reports have indicated that the majority of the scientists agree upon the human induced climate change due to which the severity and frequency of extreme weather events such as hurricanes, rains, cloud bursts, heat waves, droughts, wildfires and floods have increased. The scientists also agree that certain extreme events have happened due to natural causes as well. In some cases ambiguity persists in classifying various weather related aberrations in to natural or manmade. This is probably because the presently available scientific tools are not capable enough to differentiate the two effects. Hence, more efforts are needed to identify to what extent natural calamities have contribution of manmade activities, such as fossil fuel combustion and land use changes. Frequent cloud bursts as reported in recent past in Himalayan region are probably due to increased human activities such as tourism and land use and land cover change, which emit fine aerosols that act as cloud condensation nuclei and trigger cloud and rain formation. Similarly, the relative warmth in Delhi winters needs an in-depth analysis of various factors. Data analysis showed that during December 2015 only 22.5% days followed the long term average minimum temperature. Monthly mean of actual minimum was 10 0C which was higher than the long term minimum temperature of 7 0C. In 55% cases, daily actual minimum temperature was above the long term average minimum temperature of the month indicating greater frequency of warmer days in Delhi during this winter. Similarly, Chennai floods that occurred during north east monsoon may also be classified under human induced climate change event. Chennai floods can be termed as `The disaster of the year 2015’. Combination of heavy rainfall of 490mm in 24 hrs and water from the Chembarambakkam Lake resulted in drainage system failure, leading to this disaster. In spite of heavy rain forecast, opening of the lake water indicated poor planning, lack of communication and coordination between different agencies responsible for disaster management. Chennai floods suggested that there is a great need- i) to improve inter-agency efforts for effective coordination, ii) to put relevant information on-line so that social networking people can use the data quickly and iii) to provide more precise forecast so that public and concerned authorities trust it and follow the prediction to avoid huge economic and human losses in future.
Key words: Disaster, Chennai floods, extreme events, cloud burst, warmth of Delhi winters.

The 2015 M7.8 Gorkha, Nepal, Earthquake: Possible Implications for Northeastern India

Shane Detweiler*1 and P.R. Reddy2
1U.S. Geological Survey, 345 Middlefield Rd. MS 977, Menlo Park, CA 94025, USA
2National Geophysical Research Institute, Uppal Rd. Hyderabad, India.
*Corresponding Author:

We study the mechanism and pattern of the 25 April, 2015 M7.8 Gorkha, Nepal, earthquake and examine the seismotectonics of the region (including the occurrence of the 28 June, 2015 M5.6 Basugaon earthquake in Assam). We also compare the recent events with historical earthquakes along the Himalayan front, and question whether this present event was typical or if we might expect even larger earthquakes to occur in this region. We conclude that there remains a significant seismic hazard, and that it may be prudent to strengthen close monitoring efforts (focused GPS studies, deployment of state-of-the-art seismic networks and high resolution imaging studies) in anticipation of a future event in Nepal, its surroundings, and northeastern India.
Keywords: Gorkha earthquake, Nepal, Kathmandu Valley, Northeastern India, Thrust faulting, Disaster preparedness.

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