Faculty Publications

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Behaviour of large underground cavern during construction in himalayas - a case study
(CAFET INNOVA Technical Society cafetinnova@gmail.com 1-2-18/103, Mohini Mansion, Gagan Mahal Road, Domalguda, Hyderabad 500029, 2014) Naik, S.R.; Sastry, V.R.
Construction of large underground caverns in Himalayas is challenging due to complex geological and insitu stress conditions. Understanding the behaviour of such caverns during construction stage is possible only with extensive instrumentation. A case study of a large cavern under construction in Himalayan region in Bhutan is considered. Results from various types of instruments are discussed in this paper. Instrumentation data shows that Himalayan rock mass particularly with phyllitic quartzite exhibits large deformations thus requiring careful selection of support and excavation methodology. © 2014 CAFET-INNOVA TECHNICAL SOCIETY.
Probabilistic seismic hazard analysis of North and Central Himalayas using regional ground motion prediction equations
(Springer Science and Business Media Deutschland GmbH, 2021) Ramkrishnan, R.; Kolathayar, S.; Sitharam, T.G.
Recently developed region-specific GMPEs are used for a comprehensive seismic hazard analysis (SHA) of the North and Central Himalayas (NCH) using a probabilistic approach considering two source models. Vulnerable seismic sources in the areas are identified based on the Seismotectonic Atlas (Dasgupta et al. 2000), published by the Geological Survey of India. An up to date, homogenized and declustered earthquake catalogue is compiled from various sources, with earthquake data since 250 BC, to create a new digitized seismotectonic representation of the region. Regional seismic zones having similar seismicity are recognized based on the Gutenberg-Richter (GR) parameters and the region is delineated into 5 seismic zones. The study area is divided into grids of size 0.05° × 0.05° and the hazard in terms of Peak Ground Acceleration (PGA) at the centre of each grid point is estimated and presented as hazard maps for individual seismic sources, maximum of all sources, and average of both sources. From the current study, it could be concluded that the PGA estimated in the regions is comparatively higher than what is reported in the codal provisions for seismic zonation and estimation of design horizontal acceleration for the region. © 2021, Springer-Verlag GmbH Germany, part of Springer Nature.
Deterministic seismic hazard analysis of north and central Himalayas using region-specific ground motion prediction equations
(Springer, 2021) Ramkrishnan, R.; Kolathayar, S.; Sitharam, T.G.
Abstract: A comprehensive deterministic seismic hazard assessment (DSHA) of the north and central Himalayas (NCH) is attempted in the current study using recently developed strong-motion data-based region-specific ground motion prediction equations (GMPEs). Two source models, linear and point sources are used for hazard assessment. An updated seismotectonic map of the NCH is developed by identifying and merging the seismic sources from the Seismotectonic Atlas (SEISAT 2000) developed by the Geological Survey of India and recent literature, and a homogenized, declustered up-to-date earthquake catalogue with events since 250 BC. The NCH is divided into grids of size approximately 5 km × 5 km, and the bedrock level peak ground acceleration (PGA) at the center of each grid point is estimated using a region-specific GMPE considering both source models. The PGA values estimated at these points are exported to a GIS platform to develop a seismic hazard map of the region, separately for different sources, average and maximum of both the sources. It is observed from the current study that the PGA estimated is apparently greater than what is recommended in the codal provisions for seismic zonation and estimation of design horizontal acceleration for the NCH. Research highlights: SHA based on the state of the art DSHA technique has been carried out using various source models and recently developed region-specific GMPEs with an updated homogenized and declustered catalogue.Deterministic Seismic Hazard contour maps have been developed representing the bedrock level horizontal acceleration developed using linear and point sources.The newly developed hazard maps for the North and Central Himalayas shows higher PGA in the range of 0.4g to 0.7g towards the plate boundary region and a decreasing trend towards the peninsular shield region and the southern alluvial plains, except at the National Capital Region.The PGA estimated are comparatively higher than the design horizontal acceleration prescribed for these regions in BIS 1893. © 2021, Indian Academy of Sciences.
Ground motion duration predictive models applicable for the Himalayan region
(Springer, 2023) Anbazhagan, P.; Motwani, K.
Several empirical models for the prediction of ground motion duration were developed across the world, but no model has been generated for the Himalayan region in the past. In this study, an attempt is made to study the duration models developed for different regions and compare them with a reference model developed for the Himalayan region for a wide range of magnitudes. The comparison is performed using the log-likelihood method and aims to identify the best duration prediction models based on the developed by Bajaj and Anbazhagan (2019) for the study region. The data support index values along with the weights of the corresponding models across the different distances and magnitude ranges have also been estimated. The study found that the predictive duration relation given by Lee and Green (2014) for Western North America is suitable for M ≤ 5, while the model developed by Ghanat (2011) is suitable for M > 5 for the Himalayan region. The model developed by Afshari and Stewart (2016) is also very close to the reference model. It is always preferable to have a single duration predictive model for a wide range of magnitude and distance range; hence, there is a need to develop a region-specific duration predictive model for the Himalayan region. © 2023, Indian Academy of Sciences.

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