Central Nepal was struck on 25 April 2015 by the Mw 7.8 (ML 7.6) Gorkha earthquake, which initiated about 80 km northwest of Kathmandu and ruptured toward the east along a 140-km-long west-northwest–east-southeast fault segment. Kathmandu basin, located about halfway along the ruptured segment a few kilometers from the southernmost fault tip, was strongly affected. In this article, we present a preliminary analysis of the acceleration-time histories of the 25 April 2015 Mw 7.8 mainshock and the 12 May 2015 Mw 7.3 (ML 6.8) aftershock recorded at the Department of Mines and Geology office building in central Kathmandu valley. We analyze their frequency content using Stockwell et al. (1996) time–frequency decomposition and a polarization analysis (Pinnegar, 2006). We then compute their strong-motion parameters and finally compare their spectral accelerations with the Boore and Atkinson (2008) ground-motion prediction equation.