scholarly journals High-Velocity Surface Layer Effects on Rayleigh Waves: Recommendations for Improved Shear-Wave Velocity Modeling

2020 ◽  
Vol 110 (1) ◽  
pp. 279-287
Author(s):  
Gabriel Gribler ◽  
Lee M. Liberty ◽  
T. Dylan Mikesell
Keyword(s):  
Rayleigh Wave ◽  
Shear Wave ◽  
High Velocity ◽  
Site Response ◽  
Soil Classification ◽  
Cost Effective ◽  
Road Surface ◽  
Geologic Hazard ◽  
Soil Stiffness ◽  
Wave Inversion

ABSTRACT Soil stiffness estimates are critical to geologic hazard and risk assessment in urban centers. Multichannel analysis of surface-wave (MASW) data collection along city streets is now a standard, cost-effective, and noninvasive soil stiffness approximation tool. With this approach, shear-wave velocities (VS) are derived from Rayleigh-wave signals. Although the current MASW practice is to neglect the effect of a high-velocity road layer on soil VS estimates, our models show measurable impacts on Rayleigh-wave amplitudes and phase velocities when seismic data are acquired on a road surface. Here, we compare synthetic models with field MASW and downhole VS measurements. Our modeling indicates that a road layer attenuates Rayleigh-wave signals across all frequencies, introduces coherent higher-mode signals, and leads to overestimated VS and VS30 values. We show that VS30 can be overestimated by more than 7% when soft soils underlie a rigid road surface. Inaccurate VS estimates can lead to improper soil classification and bias earthquake site-response estimates. For road-based MASW data analysis, we recommend incorporating a surface road layer in the Rayleigh-wave inversion to improve VS estimate accuracy with depth.

Shear‐wave profiling via SH reflection analysis and rayleigh wave inversion

2005 ◽  
Author(s):  
Giancarlo Dal Moro ◽  
Michele Pipan ◽  
Emanuele Forte ◽  
Paolo Gabrielli ◽  
Monica Sugan ◽  
...  
Keyword(s):  
Rayleigh Wave ◽  
Shear Wave ◽  
Wave Inversion

scholarly journals Vs30 Mapping and Soil Classification in The Southern Part of Kulon Progo Using Rayleigh Wave Ellipticity Inversion

2019 ◽  
Vol 1 (2) ◽  
Author(s):  
Bambang Sunardi
Keyword(s):  
Seismic Hazard ◽  
Rayleigh Wave ◽  
Shear Wave ◽  
Soil Type ◽  
Interpolation Method ◽  
Measurement Data ◽  
Ground Surface ◽  
Soft Rock ◽  
Soil Classification ◽  
Shear Wave Velocities

Shear wave velocity from the ground surface to a depth of 30 meters (Vs30) is a parameter to determine dynamic characteristics of the soil, which can be used to assess the level of seismic hazard. Thus, Vs30 mapping has an important role in seismic hazard mitigation efforts. Vs30 can be determined by Multichannel Analysis of Surface Waves (MASW) and Spatial Autocorrelation (SPAC) methods. A simpler alternative can be done by using Rayleigh wave ellipticity. The main objective of this research is to map Vs30 in the southern part of Kulon Progo using Rayleigh wave ellipticity inversion. In this study, Rayleigh wave ellipticity inversion was performed on 42 microtremor single measurement data, scattered in the southern part of Kulon Progo. The inversion results are used to estimate the value of Vs30 and classify the soil type at the measurement points, referring to SNI 1726:2012. A Vs30 distribution map and soil type classification are obtained by applying the geostatistical interpolation method. The mapping result showed that most of the southern part of Kulon Progo has a relatively low Vs30 value. These values are in the range of 180-342 m/s, which categorized as stiff soil (SD). In this region, some parts located in the hilly and transition zones have relatively high shear wave velocities in the range of 357-578 m/s and included in the category of very dense soil/ soft rock (SC) types

scholarly journals Experimental and analytical study of seismic site response of discontinuous permafrost

2016 ◽  
Vol 53 (9) ◽  
pp. 1363-1375 ◽  
Author(s):  
Behrang Dadfar ◽  
M. Hesham El Naggar ◽  
Miroslav Nastev
Keyword(s):  
Shear Wave ◽  
Site Response ◽  
Free Field ◽  
Frozen Soil ◽  
Shaking Table ◽  
Experimental Program ◽  
Small Scale ◽  
Seismic Site Response ◽  
Discontinuous Permafrost ◽  
Spectral Accelerations

Seismic site response of discontinuous permafrost is discussed. The presence of frozen ground in soil deposits can significantly affect their dynamic response due to stiffer conditions characterized by higher shear-wave velocities compared to unfrozen soils. Both experimental and numerical investigations were conducted to examine the problem. The experimental program included a series of 1g shaking table tests on small-scale models. Nonlinear numerical analyses were performed employing FLAC software. The numerical model was verified using the obtained experimental results. Parametric simulations were then conducted using the verified model to study variations of the free-field spectral accelerations (on top of the frozen and unfrozen soil blocks) with the scheme of frozen–unfrozen soil, and to determine the key parameters and their effects on seismic site response. Results show that spectral accelerations were generally higher in frozen soils than in unfrozen ones. It was found that the shear-wave velocity of the frozen soil as well as the assumed geometry of the blocks and their spacing have a significant impact on the site response.

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