Journal Articles
Permanent URI for this collectionhttps://idr.nitk.ac.in/handle/123456789/19884
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Item Synthesis of Linear JTFA-Based Response Spectra for Structural Response and Seismic Reduction Measures for North-East India(World Scientific, 2020) Devaraj, D.; Ramkrishnan, R.; Prabu, T.; Kolathayar, S.; Sitharam, T.G.North-East India (NEI) has a long history of devastating earthquakes due to the complicated tectonic setting of the region. A shortage of sufficient recorded time-histories from the region calls for a synthesis of accelerograms for dynamic analyses. In this study, a novel Joint Time-Frequency Analysis (JTFA) technique is adopted for the synthesis of accelerograms, considering the non-stationary behavior of earthquake waves. JTFA is used for analyzing the signals in a joint time and frequency domain to better understand its characteristics and synthesize signals without compromising its inherent characteristics like frequency content and amplitude. Synthetic accelerograms are developed using JTFA techniques for different magnitude and distance ranges between 5 to 6.8 and 0-480km and response spectra are developed. Synthesized generalized accelerograms and their response spectra are compared with actual signals in the same magnitude-distance ranges and were found to match. A comparison of the frequency contents of actual and synthetic signals was also carried out using Fourier Transforms and spectrograms (SPs) and was found to be in good agreement. Further, a comparative study of various earthquake reduction measures for NEI is carried out for a scenario earthquake using the synthesized data, and the best suitable structural input for the region is recommended. © 2020 World Scientific Publishing Company.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 Strong Motion Data Based Regional Ground Motion Prediction Equations for North East India Based on Non-Linear Regression Models(Taylor and Francis Ltd., 2022) Ramkrishnan, R.; Kolathayar, S.; Sitharam, T.G.Existing Ground Motion Prediction Equations (GMPE) in practice for North East India have been developed using limited or simulated datasets of recorded ground motions. The current study presents the development of a new GMPE based on a well-established model considering actual recorded ground motion data comprising of acceleration, magnitude, and hypocentral distances. A larger dataset with magnitudes ranging from 4.2 to 6.9 and up to 640 kms, with a total of 204 recordings is used in non-linear multiple-regression. The newly developed GMPE could predict ground acceleration realistically over larger ranges of distance and magnitudes, compared to existing GMPEs. © 2020 Taylor & Francis Group, LLC.