Ground-motion models for earthquakes occurring in the United Kingdom

John Douglas, Guillermo Aldama-Bustos, Sarah Tallett-Williams, Manuela Davi, Iain J. Tromans

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Abstract

This article presents models to predict median horizontal elastic response spectral accelerations for 5% damping from earthquakes with moment magnitudes 3.5 to 7.25 occurring in the United Kingdom. This model was derived using the hybrid stochastic-empirical method based on an existing ground-motion model for California and a stochastic model for the UK, which was developed specifically for this purpose. The model is presented in two consistent formats, both for two distance metrics, with different target end-users. Firstly, we provide a complete logic tree with 162 branches, and associated weights, capturing epistemic uncertainties in the depth to the top of rupture, geometric spreading, anelastic path attenuation, site attenuation and stress drop, which is more likely to be used for research. The weights for these branches were derived using Bayesian updating of a priori weights from expert judgment. Secondly, we provide a backbone model with three and five branches corresponding to different percentiles, with corresponding weights, capturing the overall epistemic uncertainty, which is tailored for engineering applications. The derived models are compared with ground-motion observations, both instrumental and macroseismic, from the UK and surrounding region (northern France, Belgium, the Netherlands, western Germany and western Scandinavia). These comparisons show that the model is well-centred (low overall bias and with no obvious trends with magnitude or distance) and the branches capture the body and range of the technically defensible interpretations. In addition, comparisons with ground-motion models that have been previously used within seismic hazard assessments for the UK show that ground-motion predictions from the proposed model match those from previous models quite closely for most magnitudes and distances. The models are available as subroutines in various computer languages for ease of use.
Original languageEnglish
Pages (from-to)4265-4302
Number of pages38
JournalBulletin of Earthquake Engineering
Volume22
Issue number9
Early online date9 Jun 2024
DOIs
Publication statusPublished - 1 Jul 2024

Keywords

  • ground-motion models (GMMs)
  • ground motion prediction equations (GMPEs)
  • backbone method
  • stochastic method
  • hybrid empirical-stochastic method
  • United Kingdom (UK)

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