July, 2008

July, 2008   ||  Volume 12 No.3

The assessment of seismic hazard in two seismically active regions in Himalayas using deterministic approach

Kapil Mohan, A.Joshi1 and R.C.Patel2

Institute of Seismological research, Gandhinagar – 382 018
E.mail: kapil_geo@yahoo.co.in
1Department of Earth science, Indian institute of Technology, Roorkee - 247 667
E.mail: anushijos@yahoo.co.in
2Department of Geophysics, Kurukshetra University, Kurukshetra - 136 119
E.mail: patelramesh@rediffmail.com

The long stretch of Himalaya is often visited by many major earthquakes from time to time. The work presented in this paper shows the seismic hazard in the northeast Himalayas and the Uttarakhand Himalayas, India. Seismic hazard estimation in these regions is based on the technique given by Joshi & Patel (1997). In this work, the finite rupture along the lineament has been modeled using the semi empirical technique proposed by Midorikawa (1993) and further modified by Joshi & Midorikawa (2005). The modeling procedure follows the w2 scaling laws, directivity effects and other strong motion properties.
The NE Himalaya has a complex geology. Seismic activities in this region are due to the trijunction of three mountain belts that are Himalayan range, Mishmi Hills and Naga Patkoi range. The huge oil reservoirs and hydroelectric power projects in this area prove its technoeconomic importance and requirement for detailed seismic hazard assessment. The seismic hazard zonation map for magnitude M=6 prepared in this region shows that places like the Tinsukia, North Lakhimpur, Dibrugarh, Ziro, Tezu, Sibsagar, Jorhat, Itanagar, Golaghat, Senapati, Wokha, Imphal and Kohima falls in highly hazardous Zone IV with peak ground acceleration of more than 250 cm/sec2. The places like the Daring, Pasighat, Seppa and Basar, region belongs to Zone III with peak ground accelerations of the order 200–250 cm/sec2.
The region of Uttarakhand Himalaya has witnessed 13 earthquakes of M=6 in last 97 years that indicates the occurrence of one strong earthquake in every 8 years (Rastogi 2000). This region has been visited by two major earthquakes in last one decade. Due to the technoeconomic importance of the region and poor construction practices of building houses, the need for seismic hazard estimation cannot be ruled out in this hilly area. The zonation map prepared for magnitude M ³ 6.0 in this region using present technique shows that the places like the Munsiari, Dharchula, Lohaghat, Pithoragarh, Almora, Nainital, Uttarkashi and Karanparyag falls in Zone V with peak ground acceleration of more than 400 cm/sec2. The places like Sobla and Gopeshwar lies in Zone IV with peak ground acceleration more than 250 cm/sec2. The zonation maps prepared in this work are also compared with the historical past seismicity map of the respective regions and found that many moderate to major earthquakes falls in the identified hazardous zones.


GPS-Geodesy with GNSS Receivers for Indian Plate Kinematics’ studies with the recent plate velocities estimated from GNSS data
E.C.Malaimani, N.Ravi Kumar, A.Akilan and K.Abilash
National Geophysical research Institute, Uppal Road, Hyderabad – 500 606
E.mail : malaimani@gmail.com

Already estimated Indian Plate motion at the rate of 37 ± 0.2 mm/yr towards NNE direction with respect to Eurasian Plate has been revalidated with the new state-of-the art GNSS receivers and a new global network spreading the geographical and azimuthal coverage, which almost includes all the plates surrounding India. 12 years of GPS data from 1995 to 2007 from the Hyderabad IGS GPS Permanent Station (HYDE) have been processed in the global network solution along with the data from other 11 stations. The baseline lengths from Hyderabad to other chosen sites and the rate of changes were also estimated. The angular velocity of Indian plate motion with respect to ITRF 05 reference frame and Indo-Eurasia plate pair have also been estimated. The global network solution has resulted in the estimation of the pole of the angular velocity vector of India with respect to Eurasia to be about a pole of rotation at 29.44 ± 1.2º N, 13.2 ± 7.3º E with an angular velocity of 0.356 ± 0.035º Myr-1. Our results mostly conform to the REVEL-2000 Plate motion model but differs considerably from NUVEL-1A and other earlier studies. This departure could be attributed to the difference in geologic and geodetic estimations. The longer time span of GPS data from the central part of India yields more accurate estimations. This analysis is in the global network solution, which doesn’t take the plate- interior site velocities into account.

10 years of Continuous GPS measurements for geodetic tying of Antarctica and India for geodynamical and strain accumulation studies in the south of Indian Peninsula

N.Ravi Kumar, E.C.Malaimani, A.Akilan and K.Abilash
National Geophysical Research Institute, Uppal Road, Hyderabad – 500 606
E-mail: ravikumar.n@gmail.com

To holistically understand the geodynamical and crustal deformation processes between India and Antarctica, two global networks (IND and ANT) have been chosen. The ultimate objective is to geodetically connect the two continents. The IGS Station at Diego Garcia (DGAR) is the common station between the two networks. 10 years of data from 1997 to 2007 were used. By these global networks’ analyses, the stations HYDE and MAIT are geodetically tied through DGAR. Very long baselines have been estimated from HYDE and also from Kerguelen (KERG) to other chosen IGS stations in and around India and Antarctica. Our analysis and results using ANT network show an increase in the baseline lengths between Kerguelen in Antarctica plate and other stations such as SEY1, DGAR and COCO and shortening of baseline lengths between HYDE in Indian plate and all these above stations using IND network. The analysis using ANT network also shows lengthening of baselines from Kerguelen to the sites Yaragadee (YAR1) and Tidbinbilla (TID2) in Australian plate; and Seychelles (SEY1) in Male plate, COCO in the diffuse plate boundary between India and Australia and DGAR in Capricorn plate at the rates of 5.3cm/yr, 3.8cm/yr, 5.6mm/yr, 3.03 cm/yr and 5.5 cm/yr respectively. The high rate of movement of COCO Island in comparison to Seychelles could be the result of excessive strain accumulation due to the Indo-Australia diffuse plate boundary forces acting upon this region. The estimated elastic strain accumulation shows an increasing trend of 1.27x 10-8 yr-1 in the south of Indian peninsula. Our results show the precision of approximately 3-4mm (North), 5-6 mm (East), and 10-12mm (vertical) for the estimation of site coordinates. These results provide new information on the direction and rate of Indian plate motion, the driving mechanisms of Indian plate and intraplate seismicity of the Indian Ocean on the whole.

Rock Magnetic properties of Proterozoic mafic dykes from the southern margin of Cuddapah Basin
M.R.Goutham, C.V.R.K.Prasad1, K.V.Subbarao2 and V.Damodara Reddy3
Centre of Exploration Geophysics, Osmania University, Hyderabad – 500 007
1AMARARAMA”, 29-12-19, Venkataratnam St., Suryaraopet, Vijayawada - 520 002
2University Center for Earth & Space Sciences, University of Hyderabad, Hyderabad – 500 046
3Department of Geology, Sri Venkateswara University, Tirupati - 517 502
E-mail: gouthammr@rediffmail.com

Seventeen basic dykes of Proterozoic age intruding the Archaean basement from the southern margin of the Cuddapah Basin were studied from five sites for their magnetic characters. NRM intensity (Jn) of the dykes range between 1793 and 57 x 10-3 Am-1 while magnetic susceptibility (c) ranges from 31 to 303 x 10-6 CGS units. Koenigsberger’s ratio (Qn) varies from 1 to 55 for most of the specimens. All the above parameters are indicative of retaining the original magnetization in most of the dykes sampled. Based on the above mentioned rock magnetic properties along with hysterisis studies and low temperature (-196oC) magnetic studies, it is inferred that the main magnetic carrier in these dykes is magnetite in multi domain and mixed domain states. Dykes from Tirupati area seems to be magnetically altered.



Estimation of land surface temperature over Delhi using Landsat-7 ETM+
Javed Mallick, Yogesh Kant1 and B.D.Bharath1

GIS Department, STC-IT-CFS-GIS, Saudi Telecom, Saudi Arabia
1Indian Institute of Remote Sensing (NRSA), Dept. of Space, Govt. of India
4, Kalidas Road, Dehradun – 248 001
E.mail : ykanty@yahoo.com

Land surface temperature (LST) is important factor in global change studies, in estimating radiation budgets in heat balance studies and as a control for climate models. The knowledge of surface temperature is important to a range of issues and themes in earth sciences central to urban climatology, global environmental change, and human-environment interactions. In the study an attempt has been made to estimate surface temperature over Delhi area using Landsat-7 ETM+ satellite data. The variability of these retrieved LSTs has been investigated with respect to different land use / land cover (LU/LC) types determined from the Landsat visible and NIR channels. The classification uncertainties over different land use land cover were assessed and it has been observed that the classification uncertainties were found to be lowest using Minimum Noise Fraction (MNF) components. The emissivity per pixel is retrieved directly from satellite data and has been estimated as narrow band emissivity at the satellite sensor channel in order to have least error in the surface temperature estimation. Strong correlation is observed between surface temperature with Normalized Difference Vegetation Index (NDVI) over different LU/LC classes and the relationship is moderate with fractional vegetation cover (FVC). A regression relation between these parameters has also been estimated indicating that surface temperatures can be predicted if NDVI values are known. The results suggest that the methodology is feasible to estimate NDVI, surface emissivity and surface temperature with reasonable accuracy over heterogeneous urban areas.




Geoscientific Instrumentation in River Valley Projects


Energy Infratech Private Limited, 145-146, Udyog Vihar, Phase –IV, Gurgaon – 122 015

Present day development of the engineering projects, especially river valley development, underground storage chamber and metro rail projects require lot of instrumentation work, many of hydroelectric projects are located in the Himalayan region. Instruments are required in different stages of the project, especially during excavation and in the areas of poor to very poor rock mass. Monitoring of slope in hilly areas and for civil engineering purpose is essential, because of the various regions.
Geotechnical instruments are tools for evaluating performance of the structures during construction as well as later stages. Various types of instruments are used in dam, tunnel, power house and slope. The main objective of the instrumentation program is to measure the reaction of the surrounding rock mass to the excavation process and the installed support system, thereby ensuring the adequacy of the design of the excavation and support system. This can be achieved by measuring various parameters. Based on the data, interpretation of different kinds of instruments are done, further decisions can be made for safety and long life of the structure.
This paper describes purpose & various types of instruments used in river valley projects and how the data indicates the failure of rock mass. In brief case of Parbati hydroelectric project, for the slope failure of surface power house and underground power house data of Malana hydroelectric project are discussed.