Estimation of Ground Profiles Based on Microtremor Survey in the Bangkok Basin

Bidhya Subedi,Panon Latcharote,Bhuddarak Charatpangoon,Yusuke Ono,Junji Kiyono,Teraphan Ornthammarath,Takafumi Kitaoka,Aiko Furukawa

doi:10.3389/fbuil.2021.651902

Abstract

Multiple earthquakes have been felt in high-rise buildings in Bangkok despite the epicenters being far away. Seismic wave recordings in the Bangkok basin show a low-frequency peak. This study uses horizontal-to-vertical spectral ratio (HVSR) analysis and array analysis of ambient vibration data to find the predominant period of the ground and the shear wave velocity profiles at five sites in Bangkok. The accuracy of the accelerometer used for the ambient data recording was verified by comparing results with velocity-meter results. The estimated predominant period was within 0.68–0.86 s. From the array records, dispersion curves of the Rayleigh-wave phase velocity were extracted and inverted for the deep layers. The results show that the shear-wave velocity of the top clay layer is low (82–120 m/s) at depths of 11–14.3 m. The low-frequency peak in the HVSR of the earthquake data, and the sediment layer with low shear-wave velocity implies that Bangkok is at risk of amplification of long-period earthquake waves.

Highlights

Bangkok, the capital city of the Kingdom of Thailand, is the major economic hub of the region
Papadopoulos et al (2017) compared the horizontal-to-vertical spectral ratio (HVSR) of earthquake records (HVSRE) with HVSR of ambient vibration recorded with a speedometer for the frequency band of 0.2–20 Hz
The ratio of the Thai Meteorological Department (TMD) and SRDT HVSRs of the seismic waves recorded in the 2008 Sichuan Earthquake was used to find the site-effect of the basin (Figure 12A)

Summary

INTRODUCTION

The capital city of the Kingdom of Thailand, is the major economic hub of the region. The horizontal-to-vertical spectrum ratio (HVSR) of a single point measurement in three directions can be used to find the fundamental frequency of a site. This method was proposed by Nogoshi and Igarashi (1970) and was further developed and made widespread by Nakamura (1989). Papadopoulos et al (2017) compared the HVSR of earthquake records (HVSRE) with HVSR of ambient vibration recorded with a speedometer for the frequency band of 0.2–20 Hz. The methods showed good agreement for the lower and higher predominant frequency depending on two main seismic discontinuities for all the sites except the ones near the edge of the basin. For accurate estimation of lower predominant frequency in our study area, sensors with higher corner period need to be used for ambient vibration recordings

Methods for Array Analysis

CONCLUSION

DATA AVAILABILITY STATEMENT