Comparison of soil non-linearity (in situ stress-strain relation and G/Gmax reduction) observed in strong-motion databases and modelled in ground motion prediction equations

Philippe Guéguen, Fabian Bonilla, John Douglas

Research output: Contribution to journalArticle

Abstract

Earthquake ground motions are strongly affected by the upper tens of meters of the Earth’s crust and consequently local site effects need to be included in any ground-motion prediction. It is increasingly common in ground motion prediction equations (GMPEs) to account for possible non-linear behavior of near-surface materials (soil). These non-linear site terms adjust observations made on soft soil sites to the ground motion expected on bedrock and hence allow these abundant soil records to be used within the regression analysis for the derivation of empirical GMPEs. These nonlinear site terms also allow rapid predictions of the expected ground motions on soil rather than requiring a site response analysis to be conducted. In this study we compare the signature on observed peak ground acceleration as a function of a strain proxy of non-linear soil behavior within four large strong-motion databases to the predicted signature from four recent GMPEs, three of which explicitly include non-linear site terms. We find that observed non-linearity in the databases, interpreted in terms of strain-stress relationships and reduction of shear modulus, is limited but that even this limited effect is underestimated by the non-linear site terms of the considered GMPEs, which suggests that predictions from these GMPEs could be biased for soft soil sites but also on bedrock. Some of this mismatch could be explained by the use of the average shear-wave velocity in the top 30m (Vs30) to characterize sites as well as errors in these values.
LanguageEnglish
Number of pages28
JournalBulletin of the Seismological Society of America
StateAccepted/In press - 7 Oct 2018

Fingerprint

in situ stress
strong motion
nonlinearity
ground motion
soils
Soils
prediction
predictions
soil
soft soil
bedrock
signatures
comparison
Shear waves
stress-strain relationship
stress-strain relationships
site effect
response analysis
Earth crust
shear modulus

Keywords

  • soil nonlinearity
  • earthquake
  • site response
  • ground-motion prediction
  • engineering seismology
  • geotechnical earthquake engineering

Cite this

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title = "Comparison of soil non-linearity (in situ stress-strain relation and G/Gmax reduction) observed in strong-motion databases and modelled in ground motion prediction equations",
abstract = "Earthquake ground motions are strongly affected by the upper tens of meters of the Earth’s crust and consequently local site effects need to be included in any ground-motion prediction. It is increasingly common in ground motion prediction equations (GMPEs) to account for possible non-linear behavior of near-surface materials (soil). These non-linear site terms adjust observations made on soft soil sites to the ground motion expected on bedrock and hence allow these abundant soil records to be used within the regression analysis for the derivation of empirical GMPEs. These nonlinear site terms also allow rapid predictions of the expected ground motions on soil rather than requiring a site response analysis to be conducted. In this study we compare the signature on observed peak ground acceleration as a function of a strain proxy of non-linear soil behavior within four large strong-motion databases to the predicted signature from four recent GMPEs, three of which explicitly include non-linear site terms. We find that observed non-linearity in the databases, interpreted in terms of strain-stress relationships and reduction of shear modulus, is limited but that even this limited effect is underestimated by the non-linear site terms of the considered GMPEs, which suggests that predictions from these GMPEs could be biased for soft soil sites but also on bedrock. Some of this mismatch could be explained by the use of the average shear-wave velocity in the top 30m (Vs30) to characterize sites as well as errors in these values.",
keywords = "soil nonlinearity, earthquake, site response, ground-motion prediction, engineering seismology, geotechnical earthquake engineering",
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TY - JOUR

T1 - Comparison of soil non-linearity (in situ stress-strain relation and G/Gmax reduction) observed in strong-motion databases and modelled in ground motion prediction equations

AU - Guéguen,Philippe

AU - Bonilla,Fabian

AU - Douglas,John

PY - 2018/10/7

Y1 - 2018/10/7

N2 - Earthquake ground motions are strongly affected by the upper tens of meters of the Earth’s crust and consequently local site effects need to be included in any ground-motion prediction. It is increasingly common in ground motion prediction equations (GMPEs) to account for possible non-linear behavior of near-surface materials (soil). These non-linear site terms adjust observations made on soft soil sites to the ground motion expected on bedrock and hence allow these abundant soil records to be used within the regression analysis for the derivation of empirical GMPEs. These nonlinear site terms also allow rapid predictions of the expected ground motions on soil rather than requiring a site response analysis to be conducted. In this study we compare the signature on observed peak ground acceleration as a function of a strain proxy of non-linear soil behavior within four large strong-motion databases to the predicted signature from four recent GMPEs, three of which explicitly include non-linear site terms. We find that observed non-linearity in the databases, interpreted in terms of strain-stress relationships and reduction of shear modulus, is limited but that even this limited effect is underestimated by the non-linear site terms of the considered GMPEs, which suggests that predictions from these GMPEs could be biased for soft soil sites but also on bedrock. Some of this mismatch could be explained by the use of the average shear-wave velocity in the top 30m (Vs30) to characterize sites as well as errors in these values.

AB - Earthquake ground motions are strongly affected by the upper tens of meters of the Earth’s crust and consequently local site effects need to be included in any ground-motion prediction. It is increasingly common in ground motion prediction equations (GMPEs) to account for possible non-linear behavior of near-surface materials (soil). These non-linear site terms adjust observations made on soft soil sites to the ground motion expected on bedrock and hence allow these abundant soil records to be used within the regression analysis for the derivation of empirical GMPEs. These nonlinear site terms also allow rapid predictions of the expected ground motions on soil rather than requiring a site response analysis to be conducted. In this study we compare the signature on observed peak ground acceleration as a function of a strain proxy of non-linear soil behavior within four large strong-motion databases to the predicted signature from four recent GMPEs, three of which explicitly include non-linear site terms. We find that observed non-linearity in the databases, interpreted in terms of strain-stress relationships and reduction of shear modulus, is limited but that even this limited effect is underestimated by the non-linear site terms of the considered GMPEs, which suggests that predictions from these GMPEs could be biased for soft soil sites but also on bedrock. Some of this mismatch could be explained by the use of the average shear-wave velocity in the top 30m (Vs30) to characterize sites as well as errors in these values.

KW - soil nonlinearity

KW - earthquake

KW - site response

KW - ground-motion prediction

KW - engineering seismology

KW - geotechnical earthquake engineering

UR - https://pubs.geoscienceworld.org/bssa

M3 - Article

JO - Bulletin of the Seismological Society of America

T2 - Bulletin of the Seismological Society of America

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