scholarly journals Relationship between Average Shear-Wave Velocity and Site Amplification Inferred from Strong Motion Records at Nearby Station Pairs

2006 ◽  
Vol 6 (1) ◽  
pp. 11-22 ◽  
Author(s):  
Kazuo FUJIMOTO ◽  
Saburoh MIDORIKAWA
Keyword(s):  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Strong Motion ◽  
Site Amplification ◽  
Strong Motion Records ◽  
Average Shear

κ0 for soil sites: Observations from KiK-net sites and their use in constraining small-strain damping profiles for site response analysis

2019 ◽  
Vol 36 (1) ◽  
pp. 111-137 ◽  
Author(s):  
Boqin Xu ◽  
Ellen M Rathje ◽  
Youssef Hashash ◽  
Jonathan Stewart ◽  
Kenneth Campbell ◽  
...  
Keyword(s):  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Site Response ◽  
Strong Motion ◽  
Small Strain ◽  
Site Amplification ◽  
Site Response Analysis ◽  
Response Analysis ◽  
One Dimensional

Small-strain damping profiles developed from geotechnical laboratory testing have been observed to be smaller than the damping inferred from the observed site amplification from downhole array recordings. This study investigates the high-frequency spectral decay parameter ( κ0) of earthquake motions from soil sites and evaluates the use of κ0 to constrain the small-strain damping profile for one-dimensional site response analysis. Using data from 51 sites from the Kiban-Kyoshin strong motion network (KiK-net) array in Japan and six sites from California, a relationship was developed between κ0 at the surface and both the 30-m time-averaged shear wave velocity ( V s30) and the depth to the 2.5 km/s shear wave velocity horizon ( Z2.5). This relationship demonstrates that κ0 increases with decreasing V s30 and increasing Z2.5. An approach is developed that uses this relationship to establish a target κ0 from which to constrain the small-strain damping profile used in one-dimensional site response analysis. This approach to develop κ0-consistent damping profiles for site response analysis is demonstrated through a recent site amplification study of Central and Eastern North America for the NGA-East project.

scholarly journals Vs30Estimate for Southwest China

2016 ◽  
Vol 2016 ◽  
pp. 1-11 ◽  
Author(s):  
Yan Yu ◽  
Walter J. Silva ◽  
Bob Darragh ◽  
Xiaojun Li
Keyword(s):  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Southwest China ◽  
Strong Motion ◽  
Site Classification ◽  
Borehole Data ◽  
Data Set ◽  
Average Shear ◽  
Shear Wave Velocity Profile

Several methods were used to estimateVs30from site profiles with borehole depths of about 20 m for the strong-motion stations located in Southwest China. The methods implemented include extrapolation (constant and gradient), Geomatrix Site Classification correlation with shear-wave velocity, and remote sensing (terrain and topography). The gradient extrapolation is the preferred choice of this study for sites with shear-wave velocity profile data. However, it is noted that the coefficients derived from the California data set are not applicable to sites in Southwest China. Due to the scarcity of borehole profiles data with depth of more than 30 m in Southwest China, 73 Kiknet profiles were used to generate new coefficients for gradient extrapolation. Fortunately, these coefficients provide a reasonable estimate ofVs30for sites in Southwest China. This study showedVs30could be estimated by the time-average shear-wave velocity (average slowness) of only 10 meters of depth. Furthermore, a medianVs30estimate based upon Geomatrix Classification is derived from the results of the gradient extrapolation using a regional calibration of the Geomatrix Classification withVs30. The results of this study can be applied to assignVs30to the sites without borehole data in Southwest China.

Identification of Engineering Bedrock in Taiwan based on Site Amplification and Velocity Structures of Strong-motion Stations

2020 ◽  
Author(s):  
Che-Min Lin ◽  
Jyun-Yan Huang ◽  
Chun-Hsiang Kuo ◽  
Kuo-Liang Wen
Keyword(s):  
Shear Wave ◽  
Ground Motion ◽  
Wave Velocity ◽  
Earthquake Engineering ◽  
Shear Wave Velocity ◽  
Receiver Function ◽  
Ground Surface ◽  
Strong Motion ◽  
Site Amplification ◽  
Velocity Profiles

<p>There are two kinds of bedrocks that are widely used in seismology and earthquake engineering respectively. The seismology field uses the “seismic bedrock” to define an interface that has a practically lateral extent. The strata deeper than this interface is much more homogeneous in comparison with the shallower one. It is common to set the seismic bedrock within the upper crust has 3000 m/sec of the shear wave velocity. In contrast, the earthquake engineering prefers the shallower interface which dominates the main seismic site amplification, especially the predominant frequency of ground motion. The interface is called “Engineering Bedrock”, which the underlying stratum has the shear wave velocity from 300 to 1000 m/sec for different purposes. But, the reference shear wave velocity of the engineering bedrock is mostly defined as 760 m/sec for ground motion prediction and simulation. In Taiwan, the Central Weather Bureau (CWB) constructed and operates a dense strong-motion network called TSMIP (Taiwan Strong Motion Instrument Program), which provides numerous ground motion data for seismology and earthquake engineering. In our previous studies, the shallow shear wave velocity profiles of over 700 TSMIP stations were estimated by the Receiver Function method. The velocity profiles are from the ground surface to the depth with the shear wave velocity of at least 2000 m/sec. It allows us to compare the theoretical site amplification of the velocity profile of TSMIP stations with their observed one from the seismic records. The variance of fitness between theoretical and observed amplifications through shear wave velocity is analyzed to evaluate which reference velocity can appropriately define the depth of engineering bedrock, where the most site amplification occur beneath, in all of Taiwan. The difference between local geology is also discussed. Finally, an engineering bedrock map is proposed for further applications in earthquake engineering.</p>

scholarly journals Nonlinear Site Amplification as Function of 30 m Shear Wave Velocity

2005 ◽  
Vol 21 (1) ◽  
pp. 1-30 ◽  
Author(s):  
Yoojoong Choi ◽  
Jonathan P. Stewart
Keyword(s):  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Active Regions ◽  
Site Amplification ◽  
Site Factors ◽  
Empirical Relationships ◽  
Amplification Factors ◽  
Attenuation Relationships ◽  
Average Shear

We develop empirical relationships to predict nonlinear (i.e., amplitude-dependant) amplification factors for 5% damped response spectral acceleration as a continuous function of average shear wave velocity in the upper 30 m, Vs-30. We evaluate amplification factors as residuals between spectral accelerations from recordings and modified rock attenuation relationships for active regions. Amplification at low- and mid-periods is shown to increase with decreasing Vs-30 and to exhibit nonlinearity that is dependent on Vs-30. The degree of nonlinearity is large for NEHRP Category E (Vs-30<180 m/s) but decreases rapidly with Vs-30, and is small for Vs-30>∼300 m/s. The results can be used as Vs-30-based site factors with attenuation relationships. The results also provide an independent check of site factors published in the NEHRP Provisions, and apparent bias in some of the existing NEHRP factors is identified. Moreover, the results provide evidence that data dispersion is dependent on Vs-30.

scholarly journals Selection of an Appropriate Bedrock for Site Amplification Studies.

2021 ◽  
Author(s):  
Bhavesh Pandey ◽  
Ravi S Jakka
Keyword(s):  
Shear Wave ◽  
Half Space ◽  
Fundamental Frequency ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Reference Site ◽  
Strong Motion ◽  
Site Amplification ◽  
A Site ◽  
Selection Of

Abstract The selection of half-space or reference sites significantly influences site amplification studies. However, there are no well-defined guidelines in the literature. Generally, a layer with a local shear wave velocity (VS) of more than 760 m/s is considered a bedrock/half-space/reference site. This study attempts to formulate a rationale for selecting bedrock stiffness to be used as a half-space/reference site. For this study, VS,30 (average shear wave velocity of top 30-meter soil strata from shear wave velocity measurements) and the site's fundamental frequency (obtained from Horizontal to vertical spectral ratio of ambient vibration records) were used as proxies to study the influence of bedrock/half-space and development of a rationale for their selection. This study uses strong-motion data from India's sixty-two strong motion stations and a few from Japan (Kik-Net). The results suggest that considering a site with a shear wave velocity of 760 m/s may not be suitable as a half-space/bedrock for most geomorphological conditions. The results also recognize a pattern that can help in the development of a mathematical model for determining the bedrock for a site using VS,30 and its fundamental frequency as a proxy.

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