คุณลักษณะของชั้นดินบริเวณที่ตั้งในกรุงเทพมหานครและปริมณฑลจากการตรวจวัดคลื่นขนาดเล็กบนผิวดิน

Abstract

The seismic design standard for buildings in Thailand was recently updated according to improvement of researches.  Among these pertinent tasks, site characterization for evaluation of seismic wave amplification has been primitively investigated.  Owing to this limited information, this research aims to quantitatively investigate site characteristics of subsoils by economical and practical technique of microtremor observations.  The technique of single point observation with Horizontal-to-Vertical spectral ratio (H/V) method to estimate the predominant period and the technique of array observation with Spatial Autocorrelation (SPAC) technique for exploration of shear wave velocity profile down to about 90 m were conducted for 36 sites in approximately 80 km by 80 km area.  The results of shear wave velocity profiles were firstly compared with the available results from previous researches and they were found to be in good agreement.  The average shear wave velocities from the surface to 30-m depth vary from 70 to 200 m/s and the predominant periods are found from 0.4 to 1.1 second.  Site classifications based on the predominant period and the average shear wave velocity are presented and discussed with distribution of thickness of soft clay and geotechnical properties.