Abstract In the absence of an array of strong motion records, numerical and empirical methods are used to estimate the ground motion during 25th April 2015 Nepal earthquake. Spectral finite element method is used to simulate low frequency displacements. First, the simulated ground displacement is compared with the recorded data at Kathmandu. The good agreement between the comparisons validates the input source and medium parameters. The spatial variation of ground displacement is depicted through peak ground displacement and Ground residual displacement (GRD) contours near the epicentral region. The maximum GRD is of the order of 0.6 m in east–west, 1.8 m in north–south and 0.6 m in vertical (Z) direction respectively. Stochastic finite fault seismological model is used to simulate acceleration time histories. First, the seismological model is calibrated for the region with the available strong ground motion records at Kathmandu. The estimated stress drop for main-event and aftershocks lie in between 50 and 95 bars. Acceleration time histories are simulated at several stations near the epicentral region. Peak ground acceleration (PGA) and spectral acceleration (Sa) contour maps are provided. The estimated PGA near the epicentral region varies from 0.3 to 0.05 g. Another estimate of PGA for the main event is obtained from damage reports. The estimated PGA from simulations and damage reports are observed to be consistent with each other. The average amplification in the Indo-Gangetic plain is estimated to be in the order of 2–6. The simulated results from the study can be used as the basis for the possible ground motion behaviour for a future earthquake of comparable magnitude in the Himalayan region.
"Acta Geodaetica et Geophysica" – Springer Journals
Published: Mar 1, 2017