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

Autor: P. Anbazhagan, Ketan Bajaj
Rok vydání: 2021
Předmět:
Zdroj: Pure and Applied Geophysics. 178:1977-1999
ISSN: 1420-9136
0033-4553
Popis: 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 $${M}_{\mathrm{max}}$$ , mean seismic activity rate $$\lambda $$ , 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 $${\lambda }_{4}$$ and $${\lambda }_{5}$$ 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 $${M}_{\mathrm{max}}$$ are 0.65–1.15 and 5.0–8.4 $${M}_{w}$$ , 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 $${M}_{w}$$ and 15 to 75 km, respectively, in the case of PGA and change to 5.5–7.2 $${M}_{w}$$ and 45 to 150 km in the case of 0.5 s and 5.8–7.5 $${M}_{w}$$ 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.
Databáze: OpenAIRE
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