Study of local site effects using microtremor survey method

Local site effects are typically characterized by the shear-wave velocity profile of the subsurface layers or the fundamental frequency of the site, which can be obtained by various means. Microtremor survey method is one of the most appropriate methods for urban areas as it is noninvasive and can b...

Full description

Saved in:
Bibliographic Details
Main Author: Zhu, Cheng.
Other Authors: Kusnowidjaja Megawati
Format: Theses and Dissertations
Language:English
Published: 2012
Subjects:
Online Access:http://hdl.handle.net/10356/50586
Tags: Add Tag
No Tags, Be the first to tag this record!
Institution: Nanyang Technological University
Language: English
id sg-ntu-dr.10356-50586
record_format dspace
spelling sg-ntu-dr.10356-505862023-03-03T19:38:38Z Study of local site effects using microtremor survey method Zhu, Cheng. Kusnowidjaja Megawati School of Civil and Environmental Engineering Earth Observatory of Singapore DRNTU::Engineering::Civil engineering::Geotechnical Local site effects are typically characterized by the shear-wave velocity profile of the subsurface layers or the fundamental frequency of the site, which can be obtained by various means. Microtremor survey method is one of the most appropriate methods for urban areas as it is noninvasive and can be carried out easily. Triaxial measurements of microtremors have been carried out at 162 locations in Singapore to investigate the fundamental frequencies of sites underlying different geological conditions. The fundamental frequency of each site is estimated from the Nakamura’s horizontal-to-vertical (H/V) spectral ratio. The site fundamental frequencies estimated are well correlated with the surface geological formations. The frequencies obtained from soft soil sites are typically smaller than 2.5 Hz, whereas those from hard rock formations give higher frequencies or flat H/V spectrum. The site natural frequencies also show good agreement with the N values of the Standard Penetration Test (SPT) at 66 neighbouring boreholes. The relationships between the average shear wave velocity of the upper 30 m soil and topographic slope as well as fundamental frequency are established for site classification, taking into account the uncertainty involved in the estimation. By comparing the fundamental frequency obtained from the H/V spectrum with that of a horizontally layered model based on the SPT data, the maximum effective depth for subsurface soil structure profiling using microtremor measurements is estimated. Additionally, empirical relations are proposed between fundamental frequency and sediment thickness for different shear-wave velocity ranges. Therefore, bedrock mapping is feasible using microtremor survey method for places where site information is not available. Further study on amplification spectrum reveals different impacts by peak ground acceleration (PGA) and underlying soil structure of the site. Master of Engineering 2012-07-11T06:14:09Z 2012-07-11T06:14:09Z 2012 2012 Thesis Zhu, C. (2012). Study of local site effects using microtremor survey method. Master’s thesis, Nanyang Technological University, Singapore. http://hdl.handle.net/10356/50586 en 160 p. application/pdf
institution Nanyang Technological University
building NTU Library
continent Asia
country Singapore
Singapore
content_provider NTU Library
collection DR-NTU
language English
topic DRNTU::Engineering::Civil engineering::Geotechnical
spellingShingle DRNTU::Engineering::Civil engineering::Geotechnical
Zhu, Cheng.
Study of local site effects using microtremor survey method
description Local site effects are typically characterized by the shear-wave velocity profile of the subsurface layers or the fundamental frequency of the site, which can be obtained by various means. Microtremor survey method is one of the most appropriate methods for urban areas as it is noninvasive and can be carried out easily. Triaxial measurements of microtremors have been carried out at 162 locations in Singapore to investigate the fundamental frequencies of sites underlying different geological conditions. The fundamental frequency of each site is estimated from the Nakamura’s horizontal-to-vertical (H/V) spectral ratio. The site fundamental frequencies estimated are well correlated with the surface geological formations. The frequencies obtained from soft soil sites are typically smaller than 2.5 Hz, whereas those from hard rock formations give higher frequencies or flat H/V spectrum. The site natural frequencies also show good agreement with the N values of the Standard Penetration Test (SPT) at 66 neighbouring boreholes. The relationships between the average shear wave velocity of the upper 30 m soil and topographic slope as well as fundamental frequency are established for site classification, taking into account the uncertainty involved in the estimation. By comparing the fundamental frequency obtained from the H/V spectrum with that of a horizontally layered model based on the SPT data, the maximum effective depth for subsurface soil structure profiling using microtremor measurements is estimated. Additionally, empirical relations are proposed between fundamental frequency and sediment thickness for different shear-wave velocity ranges. Therefore, bedrock mapping is feasible using microtremor survey method for places where site information is not available. Further study on amplification spectrum reveals different impacts by peak ground acceleration (PGA) and underlying soil structure of the site.
author2 Kusnowidjaja Megawati
author_facet Kusnowidjaja Megawati
Zhu, Cheng.
format Theses and Dissertations
author Zhu, Cheng.
author_sort Zhu, Cheng.
title Study of local site effects using microtremor survey method
title_short Study of local site effects using microtremor survey method
title_full Study of local site effects using microtremor survey method
title_fullStr Study of local site effects using microtremor survey method
title_full_unstemmed Study of local site effects using microtremor survey method
title_sort study of local site effects using microtremor survey method
publishDate 2012
url http://hdl.handle.net/10356/50586
_version_ 1759858055928872960