Site-Specific Seismic Hazard Assessment of Northeast India Including Bhutan With Special Emphasis on Microzonation Studies of Imphal City
Description:
Northeast India with complex geology and active tectonics has witnessed several devastating earthquakes viz. 1869 Cachar of MW 7.4, 1897 Shillong of MW 8.1, 1950 Assam of MW 8.7 with maximum MM intensity of VII-X, presenting a serious case for site-specific seismic hazard study. An updated Probabilistic Seismic Hazard at bedrock level with 10% probability of exceedance in 50 years for Northeast India has predicted Peak Ground Acceleration (PGA) variation of 0.19-0.80g. Systematic site-specific response spectral analyses have been performed for the terrain resulting in a site amplification variation of 1.06-2.31. Surface-consistent PGA for a return period of 475 years has been assessed for the study region by convolving the soil/sediment amplification with the PGA at firm rock level, thus predicting a variation of 0.343-1.885g. Imphal, the capital city of Northeast Indian State of Manipur is located within the belt of Indo-Burma Subduction Zone and falls under seismic zone V being frequently affected by moderate to large magnitude earthquakes with the maximum felt MM Intensity of IX. As majority of the state’s population is concentrated within the Imphal valley, with massive infrastructure development and unplanned but rapid urbanization, necessitates comprehensive microzonation studies of this city. A detailed geophysical and geotechnical investigation conducted throughout the city generated effective shear wave velocity (VS30) distribution classifying the City into D2, D3, D4, E and F site classes with predominant frequency distribution of 1.59-5.88Hz thereby conservatively guiding the probabilistic surface-consistent PGA distribution of 0.59-0.83g wherein its compliant Liquefaction Potential Index (LPI) categorized the City into ‘Low’ to ‘Severe’ zones. This comprehensive study provides necessary protocol for its adaptation in carrying out similar exercises and help designing seismic resilient structures in all the cities in this deadliest seismogenic province.
Session: Site-specific Modeling of Seismic Ground Response: Are We Quantitative Enough to Predict? [Poster]
Type: Poster
Date: 4/19/2023
Presentation Time: 08:00 AM (local time)
Presenting Author: Jyothula Madan
Student Presenter: Yes
Invited Presentation:
Authors
Jyothula Madan Presenting Author Corresponding Author madanjyothula@gmail.com Indian Institute of Technology Kharagpur |
Sankar Kumar Nath nath@gg.iitkgp.ac.in Indian Institute of Technology Kharagpur |
Anand Srivastava chitranceanand0104@gmail.com Indian Institute of Technology Kharagpur |
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Site-Specific Seismic Hazard Assessment of Northeast India Including Bhutan With Special Emphasis on Microzonation Studies of Imphal City
Category
Site-specific Modeling of Seismic Ground Response: Are We Quantitative Enough to Predict?