Detailed Seismic Hazard, Disaggregation and Sensitivity Analysis for the Indo-Gangetic Basin

Bajaj, K and Anbazhagan, P (2021) Detailed Seismic Hazard, Disaggregation and Sensitivity Analysis for the Indo-Gangetic Basin. In: Pure and Applied Geophysics, 178 (6). pp. 1977-1999.

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Abstract

Seismic hazard in terms of peak ground acceleration (PGA) and spectral acceleration (SA) for the seismically active Indo-Gangetic Basin (IGB) has been computed using both a fault model and spatially smoothed-grid seismicity model. Seismicity parameters, viz. minimum magnitude, the maximum regional magnitude Mmax, mean seismic activity rate λ, the slope of the frequency�magnitude Gutenberg�Richter relationship, and the β-value (bln(10)), have been estimated spatially. The layered seismogenic source framework based on hypocentral depth distribution, i.e. 0�25, 25�70, and 70�180 km, for the smoothed-grid seismicity model has also been employed. The lowest λ4 and λ5 values for the IGB are 0.05 to 0.02 and 0.015 to 0.005, respectively, in the southern part of the IGB for hypocentral depth variation of 0�25 km. The IGB has a significant variation of seismicity in the entire stretch with noteworthy clustering in the northern side, which gradually decreases towards the south, and the spatial variability of the b-value and Mmax are 0.65�1.15 and 5.0�8.4 Mw, respectively. A ground-motion prediction equation has been selected and weighted by carrying out the efficacy test considering the past earthquakes. The disaggregation process is used for determining the spatial contribution of different magnitudes and distances for the whole IGB. Sensitivity analysis is used for examining the effect of various parameters. The PGA for the IGB varies from 0.06 to 0.54 g for 2 and 0.03 to 0.32 g for a 10 probability of exceedance in 50 years at bedrock condition. The developed average uniform hazard spectra in this study match well with the spectra derived from recorded ground motion. Based on the disaggregation process, dominant magnitude and distance are in the range of 4.7 to 6.0 Mw and 15 to 75 km, respectively, in the case of PGA and change to 5.5�7.2 Mw and 45 to 150 km in the case of 0.5 s and 5.8�7.5 Mw and 70 to 250 km in the case of 2.0 s. Sensitivity analysis suggested that increase in maximum magnitude and distance has an impact on hazard level over a longer period. This is the first time a detailed hazard analysis has been presented for the IGB. © 2021, The Author(s), under exclusive licence to Springer Nature Switzerland AG.

Item Type:	Journal Article
Publication:	Pure and Applied Geophysics
Publisher:	Birkhauser
Additional Information:	The copyright for this article belongs to Birkhauser
Keywords:	Equations of motion; Hazards; Motion estimation; Seismic response; Sensitivity analysis, Ground-motion prediction equations; Indo-Gangetic basin; Maximum magnitudes; Peak ground acceleration; Probability of exceedance; Seismicity parameters; Spatial variability; Spectral acceleration, Earthquakes
Department/Centre:	Division of Mechanical Sciences > Civil Engineering
Date Deposited:	25 Aug 2021 06:31
Last Modified:	25 Aug 2021 06:31
URI:	http://eprints.iisc.ac.in/id/eprint/69368

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