Abstract
The methods for extracting the relationships between seismic waveforms are often used to investigate ground wave propagation properties because of the complexity of actual ground motions. In this paper, the method of normalized input-output minimization (NIOM) is modified so that the predominant frequency of the modeled ground motions is similar to that of the observed ground motions and so that the band-pass filter can be used. This modified NIOM method is applied to the vertical and horizontal components of seismographs observed at the ground surface during a distant earthquake occurred in Tibet-India border region and recorded worldwide, and the average motion of soil particles is studied. We estimate the direction of wave propagation from that with the largest amplitude obtained by the NIOM method. We find that the estimated direction is similar to the great-circle direction. We also find that the average particle motion modeled by the modified NIOM method is similar to the theoretical particle motion of Rayleigh waves in a semi-infinite medium.
