Discussion of “Epistemic Uncertainty in Site Response as Derived from One-Dimensional Ground Response Analyses” by Jonathan P. Stewart and Kioumars Afshari

2021 ◽  
Vol 147 (9) ◽  
pp. 07021018
Author(s):  
Chuanbin Zhu
Keyword(s):  
Site Response ◽  
Epistemic Uncertainty ◽  
Ground Response ◽  
One Dimensional

scholarly journals Two dimensional nonlinear site response analyses

1992 ◽  
Vol 25 (3) ◽  
pp. 222-229
Author(s):  
Tam Larkin ◽  
John Marsh
Keyword(s):  
Material Properties ◽  
Site Response ◽  
Two Dimensional ◽  
Ground Response ◽  
One Dimensional ◽  
Nonlinear Site Response ◽  
Seismic Site Response ◽  
Ground Conditions ◽  
Alluvial Material ◽  
Computer Studies

This paper presents the results of computer studies of the seismic site response of two dimensional alluvial valleys with a variety of geometries and material properties. The alluvial material is modelled as a nonlinear hysteretic solid and results are presented to illustrate the effect of material nonlinearity on surface ground response. Comparative studies with one dimensional analyses are presented and conclusions drawn as to ground conditions that are appropriate to one dimensional site analyses.

Influence of Epistemic Uncertainty in Shear Wave Velocity on Seismic Ground Response Analyses

2019 ◽  
Vol 35 (2) ◽  
pp. 929-954 ◽  
Author(s):  
Federico Passeri ◽  
Sebastiano Foti ◽  
Brady R. Cox ◽  
Adrian Rodriguez-Marek
Keyword(s):  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Site Response ◽  
Epistemic Uncertainty ◽  
Ground Response ◽  
Soil Response ◽  
Linear Elastic ◽  
Seismic Ground Response ◽  
Study Sites

This study aims to evaluate the influence of epistemic uncertainties in shear wave velocity ( VS) on seismic ground response analyses (GRAs). A number of alternative VS profiles obtained from both invasive (i.e., borehole) and noninvasive (i.e., surface waves) testing methods are available for two blind study sites. These profiles are used to estimate epistemic uncertainties in VS, which are then propagated through equivalent linear-elastic GRAs, allowing for the quantification of intramethod uncertainty and intermethod variability in terms of spectral accelerations, amplification functions, and damage parameters (i.e., Arias and Housner intensities). This study demonstrates that nonlinearity of soil response plays a fundamental role in increasing the propagated uncertainty in GRA. Additionally, GRAs were also performed by means of VS upper/lower-range profiles developed from assumptions commonly used to account for epistemic uncertainties. These VS profiles were found to yield unrealistic site response estimates for both low strain (i.e., linear-elastic) and high strain (i.e., nonlinear) levels.

Regional attenuation models in Central and Eastern North America using the NGA-East database

2021 ◽  
pp. 875529302110187
Author(s):  
Jeff Bayless
Keyword(s):  
North America ◽  
Frequency Dependence ◽  
Gulf Coast ◽  
Site Response ◽  
Epistemic Uncertainty ◽  
Amplitude Spectrum ◽  
Active Regions ◽  
Atlantic Coastal Plain ◽  
Eastern North America ◽  
Anelastic Attenuation

The anelastic attenuation term found in ground motion prediction equations (GMPEs) represents the distance dependence of the effect of intrinsic and scattering attenuation on the wavefield as it propagates through the crust and contains the frequency-dependent quality factor, [Formula: see text], which is an inverse measure of the effective anelastic attenuation. In this work, regional estimates of [Formula: see text] in Central and Eastern North America (CENA) are developed using the NGA-East regionalization. The technique employed uses smoothed Fourier amplitude spectrum (FAS) data from well-recorded events in CENA as collected and processed by NGA-East. Regional [Formula: see text] is estimated using an assumption of average geometrical spreading applicable to the distance ranges considered. Corrections for the radiation pattern effect and for site response based on [Formula: see text] result in a small but statistically significant improvement to the residual analysis. Apparent [Formula: see text] estimates from multiple events are combined within each region to develop the regional models. Models are provided for three NGA-East regions: the Gulf Coast, Central North America, and the Appalachian Province. Consideration of the model uncertainties suggests that the latter two regions could be combined. There were not sufficient data to adequately constrain the model in the Atlantic Coastal Plain region. Tectonically stable regions are usually described by higher [Formula: see text] and weaker frequency dependence ([Formula: see text]), while active regions are typically characterized by lower [Formula: see text] and stronger frequency dependence, and the results are consistent with these expectations. Significantly different regional [Formula: see text] is found for events with data recorded in multiple regions, which supports the NGA-East regionalization. An inspection of two well-recorded events with data both in the Mississippi embayment and in southern Texas indicates that the Gulf Coast regionalization by Cramer in 2017 may be an improvement to that of NGA-East for anelastic attenuation. The [Formula: see text] models developed serve as epistemic uncertainty alternatives in CENA based on a literature review and a comparison with previously published models.

Simulation-based site amplification model for shallow bedrock sites in Korea

2021 ◽  
pp. 875529302098198
Author(s):  
Muhammad Aaqib ◽  
Duhee Park ◽  
Muhammad Bilal Adeel ◽  
Youssef M A Hashash ◽  
Okan Ilhan
Keyword(s):  
Linear Models ◽  
Site Response ◽  
Site Amplification ◽  
One Dimensional ◽  
Nonlinear Component ◽  
Nonlinear Site Response ◽  
Simulation Based ◽  
Linear And Nonlinear ◽  
Input Motion ◽  
Nonlinear Components

A new simulation-based site amplification model for shallow sites with thickness less than 30 m in Korea is developed. The site amplification model consists of linear and nonlinear components that are developed from one-dimensional linear and nonlinear site response analyses. A suite of measured shear wave velocity profiles is used to develop corresponding randomized profiles. A VS30 scaled linear amplification model and a model dependent on both VS30 and site period are developed. The proposed linear models compare well with the amplification equations developed for the western United States (WUS) at short periods but show a distinct curved bump between 0.1 and 0.5 s that corresponds to the range of site natural periods of shallow sites. The response at periods longer than 0.5 s is demonstrated to be lower than those of the WUS models. The functional form widely used in both WUS and central and eastern North America (CENA), for the nonlinear component of the site amplification model, is employed in this study. The slope of the proposed nonlinear component with respect to the input motion intensity is demonstrated to be higher than those of both the WUS and CENA models, particularly for soft sites with VS30 < 300 m/s and at periods shorter than 0.2 s. The nonlinear component deviates from the models for generic sites even at low ground motion intensities. The comparisons highlight the uniqueness of the amplification characteristics of shallow sites that a generic site amplification model is unable to capture.

One-Dimensional Dynamic Ground Response Analyses

1982 ◽  
Vol 108 (7) ◽  
pp. 935-952 ◽  
Author(s):  
Philippe P. Martin ◽  
H. Bolton Seed
Keyword(s):  
Ground Response ◽  
One Dimensional

scholarly journals Nonlinear Analysis of Local Site Effects on Seismic Ground Response in New Damietta City, Egypt

2018 ◽  
Vol 7 (4.20) ◽  
pp. 45
Author(s):  
Heba Kamal
Keyword(s):  
Late Holocene ◽  
Direct Method ◽  
Ground Response ◽  
Local Site Effects ◽  
Soil Lead ◽  
One Dimensional ◽  
Local Site ◽  
The City ◽  
Site Period ◽  
Strong Ground

New Damietta City is situated in a locale of moderate notable seismicity about M6.25 have happened. These dangerous tremors started from the Mediterranean subduction zone among African and Eurasian plates and is underlain by soaked late Holocene stores. In this examination, the city of New Damietta was assessed regarding site intensification and site period. Geographical and geotechnical examination including information base of 543 boreholes were gathered from past geotechnical reports and corroborative exhausting logs were executed by the Lodging and Building national Exploration focus. These information were incorporated to decide the variety of the dirt profile and in addition the qualities of the dirt layers inside the investigation site. One dimensional ground response close examination using corresponding straight system and nonlinear procedure have been done. Nonlinear examinations' results were differentiated and those of the indistinguishable direct method, and both of the similarities and differences are discussed. It is assumed that because of nonlinearity of soil under strong ground developments, 1-D parallel direct showing overestimates the strengthening structures the extent that add up to upgrade level, and can't viably speak to full frequencies and hysteric soil lead. Along these lines, more reasonable and suitable numerical strategies for ground reaction examination ought to be reviewed  

Earthquake site response estimation: A weak-motion case study

1992 ◽  
Vol 82 (6) ◽  
pp. 2283-2307
Author(s):  
E. H. Field ◽  
K. H. Jacob ◽  
S. E. Hough
Keyword(s):  
Site Response ◽  
Spectral Ratio ◽  
Large Degree ◽  
One Dimensional ◽  
Loma Prieta Earthquake ◽  
Cross Spectrum ◽  
Downward Bias ◽  
Dimensional Models ◽  
The Cross ◽  
Input Motion

Abstract Using weak-motion recordings of aftershocks of the 1989 Loma Prieta earthquake recorded in Oakland, California, near the failed Nimitz Freeway, two methods have been applied to estimate the site response of an alluvium site and three mud-over-alluvium sites. The first estimate is the traditional spectral ratio, and the second utilizes the cross spectrum. Recordings obtained at a nearby bedrock site are used as estimates of the sediment site input motions. While the two site response estimates produce similar peaks and troughs, there is an approximate factor of 2 difference in amplitudes. This discrepancy is evidence that there is a much greater level of noise than would be expected from the pre-event ambient noise. We interpret this as signal-generated noise produced by scattering from heterogeneities, which causes the true sediment site input to differ significantly from the bedrock site recording. Given this level of noise, the cross-spectrum estimate suffers a severe downward bias (by a factor of 2 in this study) and should probably not be used when the input motion is estimated from a bedrock site recording. The spectral-ratio estimates are relatively unbiased, but the level of noise introduces a large degree of uncertainty. Therefore, inferences about site response from individual spectral ratios should probably be avoided. On the other hand, ensemble averages of the estimates significantly reduce the scatter to reveal resonances that agree quite well in frequency and overall shape with those of one-dimensional models whose parameters were determined independently. A discrepancy of higher observed amplitudes than predicted by theory remains unexplained but most likely results from the effects of boundary layer topography, which are not accounted for by the simple one-dimensional models.

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