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.

No abstract

To evaluate the seismic risk associated with infrastructures, site-specific seismic hazard studies are needed to be performed. Further, for nonlinear time history analysis, one requires broadband ground motion. In modern times using physics-based simulations (PBS) for deriving the ground motion for future earthquakes has got due consideration. The PBS helps in decreasing the uncertainties related to the hazard estimation compared to GMPEs. There is a certain threshold to the PBS methods with the limited computational facilities. Hence, certain hybrid methods are required to attain a Broadband spectra for the simulated ground motion. This study uses a new ANN-based model to generate broadband ground motion spectra using the low-frequency spectral acceleration from PBS, source, path, and site parameters as input variables.A detailed parametric study and performance evaluation was made to 1 Springer Nature 2021 L A T E X template 2 ANNHBB identify the optimal input parameters in conjunction with the best-suited ANN architecture. The performance of the ANN model is demonstrated for Iwate (Mw 6.9,2008) earthquake. We found that the predicted values from the developed ANN model are in good agreement with the recorded data. Furthermore, time histories are generated using the spectral ordinate matching technique from the estimated broadband spectra.

No abstract

No abstract