Generation of Site-Dependent Earthquake Ground Motion Parameters

Abstract

The Kathmandu Valley, with many monumental and heritage structures, lies in a zone of high seismic risk. The neo-tectonic activities in the Himalayan region and the unconsolidated soil sediment are the major reasons for the high intensities of the ground motion in the valley. The conservation of the monument zones against the possible future earthquakes has been an issue of global concern. A probabilistic method to simulate the seismic ground motion parameters specific to sites lying in earthquake-prone region with a limited earthquake records is presented. Seismic hazard curves indicating the seismicity of a site is developed, risk consistent spectral shapes and corresponding power spectral density functions are obtained using empirical relationships, and ground acceleration time histories are simulated using Monte Carlo technique. One dimensional wave propagation analysis, with consideration of both linear and nonlinear behaviors of soils, is carried out to obtain the free field ground motion and the input response spectra for the structures. The method is illustrated by determination of site-specific seismic ground motion of three Bhaktapur city sites in the Kathmandu Valley. The significant influence of linear or nonlinear behavior of soil in the free field ground motion is observed in the monument zones.