Determination of seismic wave attenuation in Delhi, India, towards quantification of regional seismic hazard

National capital of India, Delhi is under moderate to high seismic hazard due to active regional faults such as the Mahendragarh fault, the Delhi Haridwar fault, the Sohna fault, the Delhi Meerut fault and the Rajasthan boundary fault. In addition, Delhi is also located within 200 km radial distance from Main Boundary Thrust and about 300 km distance from the Main Central Thrust which are active seismic sources in the Himalayan belt. Past studies clearly highlighted the seismic hazard potential and role of local soil for Delhi varying from moderate to very high. The present work manifests the attenuation characteristics of lithosphere up to a depth of 90 km beneath Delhi. These attenuation characteristics are obtained collectively based on the attenuation of P, S and coda wave spectrum from the recorded seismograms during nearby earthquakes (EQs) with focal depths (h) of around 10 km, in terms of the frequency (f)-dependent quality factors (Q). Based on the present analysis, obtained P, S and coda wave attenuations are found as (93±26)f(0.895±0.121)\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ (93 \pm 26)f^{(0.895 \pm 0.121)} $$\end{document}, (162±33)f(0.835±0.088)\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ (162 \pm 33)f^{(0.835 \pm 0.088)} $$\end{document} and (116±16)f(1.029±0.061)\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ (116 \pm 16)f^{(1.029 \pm 0.061)} $$\end{document}, respectively, for Delhi. Seismic wave attenuation determined in this work will be very useful in seismic hazard estimation as well as for development of synthetic ground motion for Delhi for better preparedness during future EQs and thus minimising future EQ damages.