Ground motion parameters for the 2015 Nepal Earthquake and its aftershocks

The 25th April 2015 Nepal earthquake was the first major event in the Himalayan orogeny to provide a relatively well-recorded dataset. This paper presents a comprehensive analysis of the mainshock and its five major aftershocks through 21 well-established ground motion parameters. The analysis is presented for near-field stations of the Kathmandu basin and far-field stations of the Indo-Ganga Plains, including the site response behavior with varying sediment depths. Moreover, Hilbert-Huang Transform is used to study site amplifications associated with sediment depth and soil class, especially at long periods. In addition, a new ground motion model (GMM) is derived for all 21 parameters using moment magnitude, source-to-site distance, site class and sediment depth as predictor variables. Further, to ensure that the developed GMM is not biased, an inter-event and intra-event residual analysis is performed. Furthermore, the GMM is compared with other well-established prediction models applicable to the study region. The efficacy of the current model is further addressed by the evaluation of ranking indices.