Scientists of the Institute analyzed the strong motion records of recent
Gorkha Nepal earthquake (Mw 7.8), its strong aftershocks and seismic events
of Hindukush region for the estimation of source parameters. The Mw 7.8
Gorkha Nepal earthquake of April 25, 2015 and its six aftershocks of
magnitude range 5.3-7.3 have been recorded at Multi-Parametric Geophysical
observatory (MPGO), Ghuttu, Garhwal Himalaya (India) > 600 km west from the
epicenter of main shock of Gorkha earthquake. The acceleration data of eight
earthquakes occurred in the Hindukush region also recorded at this
observatory which is located > 1000 km east from the epicenter of Mw 7.5
Hindukush earthquake on October 26, 2015. The shear wave spectra of
acceleration record are corrected for the possible effects of anelastic
attenuation at both source and recording site as well as for site
amplification. The strong motion data of six local earthquakes is used to
estimate the site amplification and the shear wave quality factor (Qβ) at
recording site. The frequency dependent Qβ(f) = 124 f 0.98 is computed at
Ghuttu station by using inversion technique. The corrected spectrum is
compared with theoretical spectrum obtained from Brune's circular model for
the horizontal components using grid search algorithm. Computed seismic
moment, stress drop and source radius of the earthquakes used in this work
range 8.20x1016 to 5.72x1020 Nm, 7.1 to 50.6 bars and 3.55 to 36.70 km,
respectively. The results match with the available values obtained by other
agencies.
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