Nonlinear site effects on strong ground motion at a reclaimed island

Recently there has been an increased interest in the study of the nonlinearity in soil response for large strains through in situ earthquake observations. In this paper, the downhole array acceleration data recorded at a reclaimed island, Kobe, during the 1995 Kobe earthquake are used to study nonlinear site effects. Particular attention is given to the liquefaction-induced nonlinear effects on the recorded ground motions. By using the spectral ratio and the spectral-smoothing technique, the characteristics of the ground motions are analyzed. It is shown that the peak frequencies in spectral ratios were shifted to lower frequencies when the strongest motions occurred. The increase in the predominant period was caused primarily by a strong attenuation of low-period waves, rather than by amplification of long-period motions. Based on the spectral analyses, the nonlinearity occurring in the shallow liquefied layer during the shaking event is identified, manifested by a significant reduction of the shear modulus. A fully coupled, inelastic, finite element analysis of the response of the array site is carried out. The stress-strain histories of soils and excess pore-water pressures at different depths are calculated. It is suggested that the stress-strain response and the build up of pore pressure are well correlated to the variation of the characteristics of ground motions during the shaking history.Key words: site response, ground motion, nonlinearity, soil liquefaction, array records, Kobe earthquake.

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Site effects of the Denis-Perron dam (SM-3): A case study in Eastern North America

Earthquake Spectra ◽

10.1177/87552930211019439 ◽

2021 ◽

pp. 875529302110194

Author(s):

Daniel Verret ◽

Denis LeBœuf ◽

Éric Péloquin

Keyword(s):

North America ◽

Ground Motion ◽

Site Effects ◽

Transfer Functions ◽

Ground Motions ◽

Published Data ◽

Eastern North America ◽

Ground Acceleration ◽

Large Dams ◽

Moderate Seismicity

Eastern North America (ENA) is part of a region with low-to-moderate seismicity; nonetheless, some significant seismic events have occurred in the last few decades. Recent events have reemphasized the need to review ENA seismicity and ground motion models, along with continually reevaluating and updating procedures related to the seismic safety assessment of hydroelectric infrastructures, particularly large dams in Québec. Furthermore, recent researchers have shown that site-specific characteristics, topography, and valley shapes may significantly aggravate the severity of ground motions. To the best of our knowledge, very few instrumental data from actual earthquakes have been published for examining the site effects of hydroelectric dam structures located in eastern Canada. This article presents an analysis of three small earthquakes that occurred in 1999 and 2002 at the Denis-Perron (SM-3) dam. This dam, the highest in Québec, is a rockfill embankment structure with a height of 171 m and a length of 378 m; it is located in a narrow valley. The ground motion datasets of these earthquakes include the bedrock and dam crest three-component accelerometer recordings. Ground motions are analyzed both in the time and frequency domains. The spectral ratios and transfer functions obtained from these small earthquakes provide new insights into the directionality of resonant frequencies, vibration modes, and site effects for the Denis-Perron dam. The crest amplifications observed for this dam are also compared with previously published data for large dams. New statistical relationships are proposed to establish dam crest amplification on the basis of the peak ground acceleration (PGA) at the foundation.

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An NGA Model for the Average Horizontal Component of Peak Ground Motion and Response Spectra

Earthquake Spectra ◽

10.1193/1.2894832 ◽

2008 ◽

Vol 24 (1) ◽

pp. 173-215 ◽

Cited By ~ 501

Author(s):

BrianS-J. Chiou ◽

Robert R. Youngs

Keyword(s):

Ground Motion ◽

Ground Motions ◽

Hanging Wall ◽

Response Spectra ◽

Horizontal Component ◽

Smooth Functions ◽

Soil Response ◽

New Model ◽

Crustal Earthquakes ◽

Aleatory Variability

We present a model for estimating horizontal ground motion amplitudes caused by shallow crustal earthquakes occurring in active tectonic environments. The model provides predictive relationships for the orientation-independent average horizontal component of ground motions. Relationships are provided for peak acceleration, peak velocity, and 5-percent damped pseudo-spectral acceleration for spectral periods of 0.01 to 10 seconds. The model represents an update of the relationships developed by Sadigh et. al. (1997) and incorporates improved magnitude and distance scaling forms as well as hanging-wall effects. Site effects are represented by smooth functions of average shear wave velocity of the upper 30 m ( VS30) and sediment depth. The new model predicts median ground motion that is similar to Sadigh et. al. (1997) at short spectral period, but lower ground motions at longer periods. The new model produces slightly lower ground motions in the distance range of 10 to 50 km and larger ground motions at larger distances. The aleatory variability in ground motion amplitude was found to depend upon earthquake magnitude and on the degree of nonlinear soil response, For large magnitude earthquakes, the aleatory variability is larger than found by Sadigh et. al. (1997).

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Testing non-linear amplification factors used in ground motion models

10.5194/egusphere-egu21-4829 ◽

2021 ◽

Author(s):

Karina Loviknes ◽

Danijel Schorlemmer ◽

Fabrice Cotton ◽

Sreeram Reddy Kotha

Keyword(s):

Ground Motion ◽

Site Effects ◽

Ground Motions ◽

Site Amplification ◽

Building Codes ◽

Linear Amplification ◽

Motion Models ◽

Earthquake Predictability ◽

Non Linear ◽

Ground Motion Models

Non-linear site effects are mainly expected for strong ground motions and sites with soft soils and more recent ground-motion models (GMM) have started to include such effects. Observations in this range are, however, sparse, and most non-linear site amplification models are therefore partly or fully based on numerical simulations. We develop a framework for testing of non-linear site amplification models using data from the comprehensive Kiban-Kyoshin network in Japan. The test is reproducible, following the vision of the Collaboratory for the Study of Earthquake Predictability (CSEP), and takes advantage of new large datasets to evaluate whether or not non-linear site effects predicted by site-amplification models are supported by empirical data. The site amplification models are tested using residuals between the observations and predictions from a GMM based only on magnitude and distance. When the GMM is derived without any site term, the site-specific variability extracted from the residuals is expected to capture the site response of a site. The non-linear site amplification models are tested against a linear amplification model on individual well-recording stations. Finally, the result is compared to building codes where non-linearity is included. The test shows that for most of the sites selected as having sufficient records, the non-linear site-amplification models do not score better than the linear amplification model. This suggests that including non-linear site amplification in GMMs and building codes may not yet be justified, at least not in the range of ground motions considered in the test (peak ground acceleration < 0.2 g).

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Modeling nonlinear site effects in physics-based ground motion simulations of the 2010–2011 Canterbury earthquake sequence

Earthquake Spectra ◽

10.1177/8755293019891729 ◽

2020 ◽

Vol 36 (2) ◽

pp. 856-879 ◽

Cited By ~ 3

Author(s):

Christopher A de la Torre ◽

Brendon A Bradley ◽

Robin L Lee

Keyword(s):

Wave Propagation ◽

Ground Motion ◽

Site Effects ◽

Ground Motions ◽

Site Amplification ◽

Earthquake Sequence ◽

Response Analysis ◽

Site Specific ◽

Ground Motion Simulations ◽

Empirical Ground

This study examines the performance of nonlinear total stress one-dimensional (1D) wave propagation site response analysis for modeling site effects in physics-based ground motion simulations of the 2010–2011 Canterbury, New Zealand earthquake sequence. This approach explicitly models three-dimensional (3D) ground motion phenomena at the regional scale, and detailed site effects at the local scale. The approach is compared with a more commonly used empirical VS30-based method of computing site amplification for simulated ground motions, as well as prediction via an empirical ground motion model. Site-specific ground response analysis is performed at 20 strong motion stations in Christchurch for 11 earthquakes with 4.7≤ MW≤7.1. When compared with the VS30-based approach, the wave propagation analysis reduces both overall model bias and uncertainty in site-to-site residuals at the fundamental period, and significantly reduces systematic residuals for soft or “atypical” sites that exhibit strong site amplification. The comparable performance in ground motion prediction between the physics-based simulation method and empirical ground motion models suggests the former is a viable approach for generating site-specific ground motions for geotechnical and structural response history analyses.

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Repeatable Source, Path, and Site Effects from the 2019 M 7.1 Ridgecrest Earthquake Sequence

Bulletin of the Seismological Society of America ◽

10.1785/0120200008 ◽

2020 ◽

Vol 110 (4) ◽

pp. 1530-1548 ◽

Cited By ~ 6

Author(s):

Grace A. Parker ◽

Annemarie S. Baltay ◽

John Rekoske ◽

Eric M. Thompson

Keyword(s):

Los Angeles ◽

Ground Motion ◽

Site Response ◽

Ground Motions ◽

Warning System ◽

Site Amplification ◽

Earthquake Sequence ◽

Ground Acceleration ◽

Small Magnitude ◽

Earthquake Early Warning System

ABSTRACT We use a large instrumental dataset from the 2019 Ridgecrest earthquake sequence (Rekoske et al., 2019, 2020) to examine repeatable source-, path-, and site-specific ground motions. A mixed-effects analysis is used to partition total residuals relative to the Boore et al. (2014; hereafter, BSSA14) ground-motion model. We calculate the Arias intensity stress drop for the earthquakes and find strong correlation with our event terms, indicating that they are consistent with source processes. We look for physically meaningful trends in the partitioned residuals and test the ability of BSSA14 to capture the behavior we observe in the data. We find that BSSA14 is a good match to the median observations for M>4. However, we find bias for individual events, especially those with small magnitude and hypocentral depth≥7 km, for which peak ground acceleration is underpredicted by a factor of 2.5. Although the site amplification term captures the median site response when all sites are considered together, it does not capture variations at individual stations across a range of site conditions. We find strong basin amplification in the Los Angeles, Ventura, and San Gabriel basins. We find weak amplification in the San Bernardino basin, which is contrary to simulation-based findings showing a channeling effect from an event with a north–south azimuth. This and an additional set of ground motions from earthquakes southwest of Los Angeles suggest that there is an azimuth-dependent southern California basin response related to the orientation of regional structures when ground motion from waves traveling south–north are compared with those in the east–west direction. These findings exhibit the power of large, spatially dense ground-motion datasets and make clear that nonergodic models are a way to reduce bias and uncertainty in ground-motion estimation for applications like the U.S. Geological Survey National Seismic Hazard Model and the ShakeAlert earthquake early warning System.

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Pitfalls of Deterministic Application of Nonlinear Site Factors in Probabilistic Assessment of Ground Motions

Earthquake Spectra ◽

10.1193/1.3159006 ◽

2009 ◽

Vol 25 (3) ◽

pp. 541-555 ◽

Cited By ~ 15

Author(s):

Christine A. Goulet ◽

Jonathan P. Stewart

Keyword(s):

Site Effects ◽

Site Response ◽

Ground Motions ◽

Site Conditions ◽

Return Periods ◽

Site Factors ◽

Intensity Measures ◽

Site Specific ◽

Nonlinear Site Response ◽

Rock And Soil

It is common for ground motions to be estimated using a combination of probabilistic and deterministic procedures. Probabilistic seismic hazard analyses (PSHA) are performed to estimate intensity measures ( IMs) for reference site conditions (usually rock). This is followed by a deterministic modification of the rock IMs to account for site effects, typically using site factors from the literature or seismic codes. We demonstrate for two California sites and three site conditions that the deterministic application of nonlinear site factors underestimates ground motions evaluated probabilistically for return periods of engineering interest. Reasons for this misfit include different standard deviation terms for rock and soil sites, different controlling earthquakes, and overestimation of the nonlinear component of the site response in the deterministic procedure. This problem is solved using site-specific PSHA with appropriate consideration of nonlinear site response, within the hazard integral.

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Seismic Wave Propagation and Basin Amplification in the Wasatch Front, Utah

Seismological Research Letters ◽

10.1785/0220200449 ◽

2021 ◽

Author(s):

Morgan P. Moschetti ◽

David Churchwell ◽

Eric M. Thompson ◽

John M. Rekoske ◽

Emily Wolin ◽

...

Keyword(s):

Wave Propagation ◽

Ground Motion ◽

Seismic Wave ◽

Seismic Velocity ◽

Site Response ◽

Ground Motions ◽

Seismic Wave Propagation ◽

Velocity Models ◽

Ground Motion Variability ◽

Wasatch Front

Abstract Ground-motion analysis of more than 3000 records from 59 earthquakes, including records from the March 2020 Mw 5.7 Magna earthquake sequence, was carried out to investigate site response and basin amplification in the Wasatch Front, Utah. We compare ground motions with the Bayless and Abrahamson (2019; hereafter, BA18) ground-motion model (GMM) for Fourier amplitude spectra, which was developed on crustal earthquake records from California and other tectonically active regions. The Wasatch Front records show a significantly different near-source rate of distance attenuation than the BA18 model, which we attribute to differences in (apparent) geometric attenuation. Near-source residuals show a period dependence of this effect, with greater attenuation at shorter periods (T<0.5 s) and a correlation between period and the distance over which the discrepancy manifests (∼20–50 km). We adjusted the recorded ground motions for these regional path effects and solved for station site terms using linear mixed-effects regressions, with groupings for events and stations. We analyzed basin amplification by comparing the site terms with the basin geometry and basin depths from two seismic-velocity models for the region. Sites over the deeper parts of the sedimentary basins are amplified by factors of 3–10, relative to sites with thin sedimentary cover, with greater amplification at longer periods (T≳1 s). Average ground-motion variability increases with period, and long-period variability exhibits a slight increase at the basin edges. These results indicate regional seismic wave propagation effects requiring further study, and potentially a regionalized GMM, as well as highlight basin amplification complexities that may be incorporated into seismic hazard assessments.

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Evaluation of stratigraphic effects on seismic site response over large areas: the case study of Italy

10.5194/egusphere-egu21-2014 ◽

2021 ◽

Author(s):

Gaetano Falcone ◽

Gianluca Acunzo ◽

Amerigo Mendicelli ◽

Federico Mori ◽

Giuseppe Naso ◽

...

Keyword(s):

Ground Motion ◽

Site Effects ◽

Risk Mitigation ◽

Site Response ◽

Free Field ◽

Response Spectra ◽

Seismic Intensity ◽

Site Condition ◽

Ground Shaking ◽

Seismic Site Response

Estimation of site effects over large areas is a key-issue for land management and emergency system planning in a risk mitigation perspective. In general, site-conditions are retrieved from available global datasets and the ground-shaking estimation is based on ground motion prediction equations.An advanced procedure to estimate site effects over large areas is here proposed with reference to the Italian territory. Site-condition were defined for homogenous morpho-geological areas in accordance to the borehole logs and the geophysical data archived in the Italian database for seismic microzonation (https://www.webms.it/). Ground motion modifications were determined by means of about 30 milion of one-dimensional numerical simulations of local seismic site response. Correlations between amplification factors (i.e. the ratio between free-field and outcrop response spectra), AF, and site-condition (i.e. harmonic mean of the shear wave velocity in the upper 30&#160;m of the deposit, VS30) were determined for each morpho-geological homogeneous area depending on the reference seismic intensity (i.e. referred to the outcropping stiff rock characterised by VS30&#160;&#8805;&#160;800&#160;m/s). The AF-VS30 correlations were proved to satisfactory forecast the site effects when compared with the results of site specific estimation of local seismic site response.

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Site Effects for the Sacramento-San Joaquin Delta

Earthquake Spectra ◽

10.1193/1.3111087 ◽

2009 ◽

Vol 25 (2) ◽

pp. 301-322 ◽

Cited By ~ 9

Author(s):

Tadahiro Kishida ◽

Ross W. Boulanger ◽

Norman A. Abrahamson ◽

Michael W. Driller ◽

Timothy M. Wehling

Keyword(s):

Seismic Wave ◽

Regression Models ◽

Site Effects ◽

Site Response ◽

Hazard Analysis ◽

Ground Motions ◽

Response Spectra ◽

Organic Soils ◽

Wave Amplification ◽

Seismic Wave Amplification

Seismic site response and site effects models are presented for levees in the Sacramento-San Joaquin Delta where the subsurface soils include thick deposits of highly organic soils. Sources of uncertainty that contribute to the variation of seismic wave amplification are investigated, including variations in the input ground motions, soil profiles, and dynamic soil properties through Monte Carlo simulations of equivalent-linear site response analyses. Regression models for seismic wave amplification for levees in the Delta are presented that range from a function of peak outcrop acceleration alone to a vector of response spectra ordinates and soil profile parameters. The site effects models were incorporated into a probabilistic seismic hazard analysis for a representative location, and the relative impacts of the various models on the computed hazard are evaluated.

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Estimation of seismic ground motions and attendant potential human fatalities from a scenario earthquake on the Sanchiao fault in northern Taiwan

10.5194/egusphere-egu2020-24 ◽

2020 ◽

Author(s):

Kun-Sung Liu ◽

Mei-Rong Yan ◽

Yu-Hua Huang

Keyword(s):

Ground Motion ◽

Active Fault ◽

Site Response ◽

Ground Motions ◽

City Government ◽

Border Area ◽

Scenario Earthquake ◽

Scenario Earthquakes ◽

Taipei City ◽

Northern Taiwan

The purpose of this study is to estimate maximum ground motions in northern Taiwan in the form of ShakeMaps as well as to assess potential human fatalities from a scenario earthquake on the Sanchiao active fault in this area. Analysis of seismic hazard potential becomes necessary in northern Taiwan for the Central Geological Survey (CGS) announced the Sanchiao active fault as Category II. The resultant ShakeMap patterns of maximum ground motion by using ground motion prediction equation (GMPE) method in a case of Mw6.88 show the areas of PGA above 400 gals are located in the regions inside the yellow lines in the corresponding figure. Furthermore, the areas of PGA greater than 637 gal are located in the northern Bali and the border area of Sinjhuang and Shulin. Likewise, the high PGV area greater than 60 cm/s are located in the border area of Sinjhuang, Taishan and Shulin. In addition, seismic hazards in terms of PGA and PGV in the vicinity of the Sanchiao fault are not completely dominated by the Sanchiao fault. The main reason is that some areas located in the vicinity of the Sanchiao fault are marked with low site response amplification values of 0.61 and 0.74 for PGA and PGV, respectively in northwestern Beitou. Finally, from estimation of potential human fatalities from scenario earthquakes on the Sanchiao active fault, it is noted that potential fatalities increase rapidly in people above age 45. Total fatalities reach a high peak in age groups of 55&#8211;64. Another to pay special attention by Taipei City Government is the number and percentage of fatalities above age 85 are more in Taipei City with values 419 and 8.54% than New than Taipei City with values of 319 and 5.02%. In addition, it is surprising that the number and percentage of fatalities are 1234 and 9.75%, respectively in Taoyuan City. Finally, the results of this paper will enable both local and central governments in Taiwan to take notice of potential earthquake threat in these areas, as well as to improve decision making with respect to emergency preparedness, response, and recovery activities for earthquakes in northern Taiwan.

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