Shear wave velocity modelling in crustal rock for seismic hazard analysis

2005 ◽  
Vol 25 (2) ◽  
pp. 167-185 ◽  
Author(s):  
A.M. Chandler ◽  
N.T.K. Lam ◽  
H.H. Tsang
Keyword(s):  
Seismic Hazard ◽  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Hazard Analysis ◽  
Seismic Hazard Analysis ◽  
Crustal Rock

scholarly journals Seismic hazard assessment and local site effect evaluation in Hanoi, Vietnam

2017 ◽  
Vol 17 (4B) ◽  
pp. 82-95
Author(s):  
Nguyen Anh Duong ◽  
Pham Dinh Nguyen ◽  
Vu Minh Tuan ◽  
Bui Van Duan ◽  
Nguyen Thuy Linh
Keyword(s):  
Seismic Hazard ◽  
Shear Wave ◽  
Ground Motion ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Peak Ground Acceleration ◽  
Site Effect ◽  
Local Site Effect ◽  
Ground Acceleration ◽  
Local Site

In this study, we have carried out the probabilistic seismic hazard analysis in Hanoi based on the latest seismotectonic data. The seismic hazard map shows peak ground acceleration values on rock corresponding to the 10% probability of exceedance in a 50-year time period (approximately return periods of 500 years). The calculated results reveal that the maximum ground acceleration can occur on rock in Hanoi is about 0.13 g corresponding to the shaking intensity level of VIII on the MSK-64 scale. The ground motion values calculated on rock vary according to the local site conditions. We have evaluated and corrected the local site effects on ground motion in Ha Dong district, Hanoi by using microtremor and borehole data. The Nakamura’s H/V spectral ratio method has been applied to establish a map of ground dominant periods in Ha Dong with a TS range of 0.6 - 1.2 seconds. The relatively high values of periods indicate that Ha Dong has soft soil and thick Quaternary sediments. The sediment thickness in Ha Dong is calculated to vary between 30 - 75 m based on ground dominant periods and shear wave velocity VS30 = 171 - 254 m/s. The results of local site effect on ground motion show that the 500-year return period peak ground acceleration in Ha Dong ranges from 0.13 g to 0.17 g. It is once again asserted that the seismic hazard in Hanoi is a matter of great concern, due not only to the relatively high ground acceleration, but also to the seismic characteristics of soil (low shear wave velocity, ground dominant period of approximately 1 second).

New Site Coefficients and Site Classification System Used in Recent Building Seismic Code Provisions

2000 ◽  
Vol 16 (1) ◽  
pp. 41-67 ◽  
Author(s):  
R. Dobry ◽  
R. D. Borcherdt ◽  
C. B. Crouse ◽  
I. M. Idriss ◽  
W. B. Joyner ◽  
...  
Keyword(s):  
Seismic Hazard ◽  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Classification System ◽  
Site Amplification ◽  
Site Classification ◽  
Site Class ◽  
Site Classes ◽  
Code Provisions

Recent code provisions for buildings and other structures (1994 and 1997 NEHRP Provisions, 1997 UBC) have adopted new site amplification factors and a new procedure for site classification. Two amplitude-dependent site amplification factors are specified: Fa for short periods and Fv for longer periods. Previous codes included only a long period factor S and did not provide for a short period amplification factor. The new site classification system is based on definitions of five site classes in terms of a representative average shear wave velocity to a depth of 30 m (V¯s). This definition permits sites to be classified unambiguously. When the shear wave velocity is not available, other soil properties such as standard penetration resistance or undrained shear strength can be used. The new site classes denoted by letters A - E, replace site classes in previous codes denoted by S1 - S4. Site classes A and B correspond to hard rock and rock, Site Class C corresponds to soft rock and very stiff / very dense soil, and Site Classes D and E correspond to stiff soil and soft soil. A sixth site class, F, is defined for soils requiring site-specific evaluations. Both Fa and Fv are functions of the site class, and also of the level of seismic hazard on rock, defined by parameters such as Aa and Av ( 1994 NEHRP Provisions), Ss and Sl ( 1997 NEHRP Provisions) or Z ( 1997 UBC). The values of Fa and Fv decrease as the seismic hazard on rock increases due to soil nonlinearity. The greatest impact of the new factors Fa and Fv as compared with the old S factors occurs in areas of low-to-medium seismic hazard. This paper summarizes the new site provisions, explains the basis for them, and discusses ongoing studies of site amplification in recent earthquakes that may influence future code developments.

scholarly journals Estimation of Ground Structure at USM using Microtremor Observation Technique

2018 ◽  
Vol 65 ◽  
pp. 06001
Author(s):  
Kang Chin Tan ◽  
Yi Ben Cheah ◽  
Tze Liang Lau
Keyword(s):  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Hazard Analysis ◽  
Site Amplification ◽  
Circular Array ◽  
Ground Structure ◽  
Earthquake Design ◽  
Component Velocity ◽  
Recorded Data

Determination of ground structure is important for seismic hazard analysis and earthquake design of structures. Different types of ground structure at site, depending on its profile of shear-wave velocity, will amplify seismic wave at different extents. Therefore, structures should be designed accordingly to withstand the expected surface ground motion considering seismic site amplification. Microtremor observations were conducted in this study due to its simplicity, less field effort and economy. Field measurement was carried out at two sites at Universiti Sains Malaysia Engineering Campus where the actual soil profiles were known from the existing borelog data. Two sizes of circular array formed by three three-component velocity sensors along the circumference of circle and a three-component velocity sensor at the center for each array were performed. The recorded data were analysed using Spatial Autocorrelation (SPAC) method. Shear wave velocity profile for the site was then estimated through inversion of phase velocity. To produce convincing estimation of ground structure, the horizontal to vertical (H/V) spectra at the center of the circular array was compared with the computed ellipticity of the fundamental mode of Rayleigh wave. The obtained results were also compared with the borelog data. The accuracy for the estimation of ground structure based on various microtremor array sizes and analysis techniques was assessed.

Shear-Wave Velocity Characteristics of Geologic Units in California

1998 ◽  
Vol 14 (3) ◽  
pp. 533-556 ◽  
Author(s):  
Christopher J. Wills ◽  
Walter Silva
Keyword(s):  
Seismic Hazard ◽  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Site Effects ◽  
Large Scale ◽  
Site Conditions ◽  
Hazard Maps ◽  
Franciscan Complex ◽  
Average Shear

Site conditions can be classified by the average shear-wave velocity to 30 meters (Vs30) and used for estimating site effects in seismic hazard calculations. Large scale seismic hazard maps, which include site effects, may be produced, providing Vs30 can be well correlated with geologic units. Vs30 values for several geologic units can be easily classified into soil profile types of the UBC (ICBO 1997). Most geologic units have wide variations in Vs30 and some extensive geologic units, such as older alluvium, the Franciscan Complex or the Puente Formation cannot be easily classified.

scholarly journals GROUND MOTION IN YOGYAKARTA CITY, YOGYAKARTA SPECIAL PROVINCE, INDONESIA ON DENSELY MICROTREMOR OBSERVATIONS AND SHEAR WAVE VELOCITY

2015 ◽  
Vol 5 (1) ◽  
Author(s):  
Zaw Lin Kyaw ◽  
Subagyo Pramumijoyo ◽  
Salahuddin Husein ◽  
Teuku Faisal Fathani ◽  
Junji Kiyono
Keyword(s):  
Seismic Hazard ◽  
Natural Frequency ◽  
Shear Wave ◽  
Ground Motion ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Amplification Factor ◽  
Geological Engineering ◽  
Single Station ◽  
Yogyakarta City

Microtremor is currently considered the foremost tool in site effect studies. The ground motion is estimated with microtremor observations, meaning that subsoil mechanical properties and geometry are evaluated and from them an estimate of local amplification is computed. Here, the ground motion is studied by the site effects of seismic hazard zonation of urban areas in Yogyakarta City. The main purpose of this paper is zoning the geological engineering features and assessing seismic of the research urban area. In this regard, the microtremors are measured at 274 sites by single station sampling method and Nakamura technique. The microtremors of all over the city are processed by a model of Mitutoyo-GPL-6A3P. The amplification factor generally ranges between 0.70 and 5.56 and the natural frequency normally varies between 0.40 and 3.30 Hz. The information layers are prepared in GMT used for detecting the zonation of potential seismic hazard. The shear wave velocity is calculated in 12 existing drilling sites based on the geotechnical approach of SPT for soil condition. To study the ground motion, geological engineering condition is investigated using amplification factor, natural frequency, shear wave velocity maps which are analyzed using densely single microtremor observation and SPT from existing drilling sites. Keywords: Ground motion, amplification factors, natural frequency; H/V spectral ratio, microtremor observations, Yogyakarta Urban

scholarly journals Spectral Estimation of Site Characteristics of an Earth Quake Prone Region

2021 ◽  
Author(s):  
T. Seshunarayana ◽  
N. Sundararajan
Keyword(s):  
Seismic Hazard ◽  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Earth Quake ◽  
Ambient Noise ◽  
Site Amplification ◽  
Time Data ◽  
Ground Shaking ◽  
Site Characteristics

Abstract The site amplification characteristic is an important part of evaluation of seismic hazard since much of the damage caused by earthquakes may be attributed directly to the ground shaking. Identifying ahead of time such areas which are prone to amplified ground shaking due to earthquake could greatly aid seismic hazard evaluation as well as improved hazard mitigation effects. It is also a well known fact that in most cases site amplification/ shaking is stronger in low shear wave velocity areas. The objective of the present study is to estimate site characteristics of as many as 116 sites in an area of approximately 35 sq.km comprising various geological units including soft alluvial deposits which not only tend to amplify certain frequencies of ground motion but also extend the duration of earth quake that may cause further damage. The basic idea of this study is to decipher the natural ground response during quite period as well as triggered response by spectral analysis. The methodology adopted for the study is modified micro tremor which is based on ambient noise as well as triggered response. Further, the spectral ratio of H/V of ambient noise and triggered data by Nakamura method with short duration data were also estimated. In addition, based on some empirical relations, the site response frequency and amplification were also computed using the shear wave velocity obtained up to a depth of 30 m (VS30) by the method of multichannel analysis of surface wave (MASW) and depth to bed rock estimated through refraction seismic studies. The results of the study has shown that a simple comparison of spectra of quiet time data and triggered time data revealed that in alluvial soils with thick overburden, the signal amplification is more at low frequency (< 10 Hz), whereas in thin overburden the amplification was found to be low at low frequencies. The salient features of the study with merits are presented herein.

scholarly journals Empirical Correlation between Shear Wave Velocity (Vs) and Uncorrected Standard Penetration Resistance (SPT-N) for Dinajpur District, Bangladesh

2021 ◽  
Vol 1 (3) ◽  
pp. 25-29
Author(s):  
Belal Hossain
Keyword(s):  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Seismic Analysis ◽  
Hazard Analysis ◽  
Direct Methods ◽  
Site Effect ◽  
Study Region ◽  
Key Factor ◽  
Vertical Effective Stress

In seismic analysis, shear wave velocity ("V" _"s" ) is a valuable parameter for measuring the site effect of earthquake microzonation. Various methods have been explored to measure this key factor directly. Since measuring shear wave velocity directly is time consuming and expensive, researchers in various regions have been attempting to update empirical relationships between shear wave velocity ("V" _"s" ) and other soil geotechnical properties such as SPT blow count, depth, vertical effective stress and so on. Geophysical tests associated with direct methods are not feasible in developing countries like Bangladesh, so the indirect method is more important. Due to the location of a fault line nearby, the Dinajpur district has previously undergone anomalous earthquakes. As a result, site characterization is important for enhancing seismic design considerations. Focused on an indirect approach, this paper mainly aims to propose a general correlation between shear wave velocity and standard penetration number in 13 upazilas of Dinajpur district for four soil categories (“all soils”, sand, clay, and silt). Finally, an approach was developed to find the overall correlations for the Dinajpur district by combining all of the data. The regression coefficient ("R" ^"2" ) values were observed to vary in between 0.04416-0.6134 for “all soils”, 0.0593-0.668 for sand, 0.5911-0.7149 for clay and 0.5547-0.6794 for silt. The correlations obtained in this study can be used for seismic hazard analysis in both the study region and other areas with identical soil strata.

Sign in / Sign up

Export Citation Format

Share Document