Evaluation of Deep S-wave Velocity Profiles in Sagaing City, Myanmar from Long-Period Microtremor Array Records

Abstract

For quantitative prediction of strong ground motions, we desperately need precise information of shear wave (S-wave) velocities down to the seismological bedrock for site effect estimation. To determine the deep S-wave velocity profiles in Sagaing City of Myanmar, we have used both single-station and array methods for microtremor records. In this study, we have conducted five microtremor array sites and 100 sites for singlestation measurement. In order to estimate the S-wave velocity profile down to the seismic bedrock (Vs = 3.0 km/s), we extended the radii of the arrays sequentially and we obtained the Rayleigh wave phase velocity in the long-period range. After that, one dimensional S-wave velocity structure models for five array sites were determined. Then, S-wave velocity inversion for all single-station sites were carried out by referencing the five array models. According to the inversion results, we estimated that the engineering bedrock (Vs > 500 m/s) for Sagaing City exists in the range of 10 m to 80 m in depth.