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Validation of strong-motion stochastic model using observed ground motion records in north-east India

We focused on validation of applicability of semi-empirical technique (spectral models and stochastic simulation) for the estimation of ground-motion characteristics in the northeastern region (NER) of India. In the present study, it is assumed that the point source approximation in far field is valid. The one-dimensional stochastic point source seismological model of Boore (1983) (Boore, DM. 1983. Stochastic simulation of high frequency ground motions based on seismological models of the radiated spectra. Bulletin of Seismological Society of America, 73, 1865–1894.) is used for modelling the acceleration time histories. Total ground-motion records of 30 earthquakes of magnitudes lying between MW 4.2 and 6.2 in NER India from March 2008 to April 2013 are used for this study. We considered peak ground acceleration (PGA) and pseudospectral acceleration (response spectrum amplitudes) with 5% damping ratio at three fundamental natural periods, namely: 0.3, 1.0, and 3.0 s. The spectral models, which work well for PGA, overestimate the pseudospectral acceleration. It seems that there is a strong influence of local site amplification and crustal attenuation (kappa), which control spectral amplitudes at different frequencies. The results would allow analysing regional peculiarities of ground-motion excitation and propagation and updating seismic hazard assessment, both the probabilistic and deterministic approaches.