การศึกษาคุณลักษณะของชั้นดินบริเวณที่ตั้งด้วยการตรวจวัดคลื่นขนาดเล็กที่ผิวดิน

Abstract

This study quantitatively investigates site effects of subsoils, which govern intensity and characteristics of ground motion, by microtremor observations.  The technique of single point microtremor observation with Horizontal-to-Vertical spectral ratio (H/V) method is applied to estimate the predominant period and the comprehensive technique of array microtremor observation with 2-sites Spatial Autocorrelation (2sSPAC) technique is applied for exploration of shear wave velocity profile.  The sites of investigation are 8 sites in Bangkok, Chiangmai, Chiangrai and Kanchanaburi.  The results of shear wave velocity profiles from 2sSPAC technique are in good agreement when compared with the results from other techniques performed by previous researchers.  Site classifications based on average shear wave velocity reveal that subsoils of Chiangmai, Chiangrai and Kanchanaburi are classified as class D (dense or stiff soil) or class C (very dense soil and soft rock) while all sites in Bangkok are classified as class E (soft soil).  The results of H/V observation show that the predominant periods are about 0.7 second for soft soil and 0.4 second for stiff soil.