Faculty Publications
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Item 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.Item 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.Item Deterministic seismic hazard and landslide hazard zonation of Arunachal Pradesh(Springer, 2022) Anand, G.; Rahangdale, A.; Mantri, S.S.; Singh, S.; Kolathayar, S.This paper presents a seismically induced landslide hazard assessment for the state of Arunachal Pradesh, India, based on GIS techniques. A comprehensive earthquake catalog was prepared with data from various sources like USGS, ISC, etc., within a rectangular enclosure having a distance of 500 km in four cardinal directions from the Arunachal Pradesh state boundary. The catalog was homogenized in a unified moment magnitude scale. The earthquake data were collected for a period ranging from the 1500s to the year 2020. The earthquakes having a magnitude ≥4 are considered for this study as they are mainly responsible for inducing enough horizontal movement along the slopes for landslides. Considering the linear source model, the deterministic seismic hazard analysis was performed to estimate peak horizontal acceleration (PHA) at the bedrock level. The log-likelihood method was employed to decide the most efficient and reliable ground motion prediction equation (GMPE) for the Arunachal Pradesh region. Then peak ground acceleration (PGA) values generated at the surface due to the shaking of bedrock were calculated using a non-linear site amplification (considering the soil nature as B-type NHERP classification). The PGA values were considered to induce driving force on slopes, thus causing a landslide. The topographical slope map of Arunachal Pradesh was developed from CARTOSAT Digital Elevation Model Data (30m resolution). The study region was divided into 50 × 50 m2 grids. The seismically induced landslide hazard assessment was performed using Newmark’s methodology using PGA values and slope angles at the center of each grid. The critical factor of safety necessary to counter the landslide for corresponding PGA values was determined, and its spatial variation in the state is presented as contour maps. For any grid point in the study region, if the in-situ (available) static factor of safety is higher than the static factor of safety necessary to counter the landslide as predicted in the current study, that slope is regarded to be safe. © 2022, Indian Academy of Sciences.Item Seismic Hazard Assessment and Landslide Vulnerability Mapping for Ladakh, and Jammu & Kashmir Using GIS Technique(Springer, 2023) Bhagyaraj, U.; Kolathayar, S.In the present study, earthquake-induced landslide susceptibility mapping of the two newly formed union territories of India namely Ladakh, and Jammu & Kashmir has been done based on Newmark’s methodology using GIS techniques. The vulnerability of the study area against induced seismic acceleration was estimated in terms of static safety factor (FSc). Terrain slope and Peak Horizontal acceleration (PHA) were taken as the major input for the study. Deterministic Seismic Hazard Analysis (DSHA) was carried out by considering linear seismic source model to obtain PHA at the bedrock level using a MATLAB code developed by authors. The PHA was amplified to the ground surface using appropriate site correction factors considering the B-type site class. GIS technique was employed to get slope value from Digital Elevation Models (DEM). The two union territories were divided into 30m×30m grids and the static factor of safety values required to prevent the landslide for each grid were estimated. It is observed that both Ladakh, Jammu & Kashmir are at risk of landslides caused by earthquakes, as many spots demand a critical safety factor (FSc) of greater than 1.0. It is apparent that the upper western sections of Jammu & Kashmir, which include Muzaffarabad district and parts of Punch district, are severely prone to landslides since they require FSc greater than 2.0. In comparison to other regions, the lower western region of Ladakh, near India’s political border, is demanding a high value of FSc. The map thus developed is an excellent guide to researchers for detailed study and to policymakers for taking remedial actions. © 2023, Geological Society of India, Bengaluru, India.Item Probabilistic Seismic Hazard Assessment and Liquefaction Potential Evaluation for Amaravati Capital Region(Springer, 2024) Kolathayar, S.; Ashrith, M.S.; Rukminikumar, S.The present study aims to evaluate the seismic hazard and liquefaction potential for Amaravati capital region (16° 4?–16° 49? N and 80° 7?–81° 2? E) using the latest earthquake data and in-situ geotechnical data. A state-of-the-art Probabilistic Seismic hazard assessment was carried out for the region, and PGA values were obtained for Maximum Credible Earthquake (MCE) and Design-Based Earthquake (DBE) levels, which are 2% and 10% probability of exceedance for 50 years corresponding to 2475 and 475 return periods, respectively. The maximum PGA values at the bedrock level obtained were 0.084 g and 0.172 g for DBE and MCE levels, respectively. Borehole data from 16 different locations were used in the analysis. Liquefaction potential was evaluated using the Seed and Idriss method considering SPT-N values at the site. Liquefaction hazard maps were developed for 3 m and 6 m depths for both MCE and DBE levels. It is observed that the Factor of safety (FoS) against Liquefaction is lesser for MCE ground motion, whereas FoS is higher for the DBE levels. The region was found to be safe against liquefaction for design-based earthquakes, whereas the liquefaction potential was found to be high for maximum credible earthquakes. © The Author(s), under exclusive licence to Indian Geotechnical Society 2024.Item Deterministic Seismic Hazard Analysis of Sree Padmanabhaswamy Temple, Kerala State(Springer, 2025) Padmanabhan, M.P.H.; Siddhardha, R.; Kolathayar, S.; Hegde, R.; Beekanahalli Mokshanatha, B.M.Deterministic seismic hazard analysis (DSHA) is a technique employed to estimate potential hazards and ground shaking resulting from specific earthquake scenarios at a given location. In the present study, DSHA is conducted for the Sree Padmanabhaswamy Temple, situated in the southernmost district of Kerala, India. This seismic hazard study is crucial due to the temple’s proximity to seismic events such as the 1900 AD Coimbatore earthquake with a magnitude of 6.3 Mw and the 2000 Pala earthquake with a magnitude of 4.7 Mw. This study examines earthquake data within a 500 km radius surrounding the Sree Padmanabhaswamy Temple in Thiruvananthapuram District, Kerala, from 1819 to 2022 AD. The seismic zone of the temple site is III according to the Indian zonation map (IS 1893 (Part 1): 2016), relying on past earthquakes recorded throughout India. The collected earthquake data underwent a homogenization process to determine the moment magnitude (Mw), distinguishing foreshocks and aftershocks from the main shocks. A seismotectonic map was developed comprising of geological discontinuities and 316 earthquakes events with moment magnitudes between 3.0 and 6.3 Mw. The software tools employed for this work include MATLAB, QGIS and ZMAP. The Log-likelihood technique (LLH) was used to choose the ground motion prediction equations (GMPEs) for the location. The GMPEs were then given weights based on the computed values of the data support index (DSI). The study region was partitioned into a grid size of 0.05° × 0.05° (5 km × 5 km). Using MATLAB code, the peak ground acceleration (PGA) was estimated for the site and PGA was found in the center of each grid cell, taking into account all seismic sources within a 500 km radius. In addition, site-specific deterministic spectrum was also developed. The findings show that Sree Padmanabhaswamy Temple has low seismicity, which is defined by weak to moderate earthquakes that have sources close to the temple. © The Author(s), under exclusive licence to Indian Geotechnical Society 2024.