Assessment of ground motion variability and its effects on seismic hazard analysis: a case study for iceland

Teraphan Ornthammarath, John Douglas, Ragnar Sigbjörnsson, Carlo Giovanni Lai

Research output: Contribution to journalArticle

9 Citations (Scopus)

Abstract

Probabilistic seismic hazard analysis (PSHA) generally relies on the basic assumption that ground motion prediction equations (GMPEs) developed for other similar tectonic regions can be adopted in the considered area. This implies that observed ground motion and its variability at considered sites could be modelled by the selected GMPEs. Until now ground-motion variability has been taken into account in PSHA by integrating over the standard deviation reported in GMPEs, which significantly affects estimated ground motions, especially at very low probabilities of exceedance. To provide insight on this issue, ground-motion variability in the South Iceland Seismic Zone (SISZ), where many ground-motion records are available, is assessed. Three statistical methods are applied to separate the aleatory variability into source (inter-event), site (inter-site) and residual (intra-event and intra-site) components. Furthermore, the current PSHA procedure that makes the ergodic assumption of equality between spatially and temporal variability is examined. In contrast to the ergodic assumption, several recent studies show that the observed ground-motion variability at an individual location is lower than that implied by the standard deviation of a GMPE. This could imply a mishandling of aleatory uncertainty in PSHA by ignoring spatial variability and by mixing aleatory and epistemic uncertainties in the computation of sigma. Station correction coefficients are introduced in order to capture site effects at different stations. The introduction of the non-ergodic assumption in PSHA leads to larger epistemic uncertainty, although this is not the same as traditional epistemic uncertainty modelled using different GMPEs. The epistemic uncertainty due to the site correction coefficients (i.e. mean residuals) could be better constrained for future events if more information regarding the characteristics of these seismic sources and path dependence could be obtained.

LanguageEnglish
Pages931-953
Number of pages23
JournalBulletin of Earthquake Engineering
Volume9
Issue number4
Early online date19 Feb 2011
DOIs
Publication statusPublished - Aug 2011

Fingerprint

Iceland
seismic hazard
ground motion
hazards
Hazards
prediction
predictions
Tectonics
Statistical methods
standard deviation
effect
analysis
Uncertainty
stations
site effect
seismic zone
seismic source
coefficients
tectonics

Keywords

  • analysis of variance (ANOVA)
  • GMPEs
  • seismic hazard analysis
  • single-station sigma
  • two-way-fit plot

Cite this

Ornthammarath, Teraphan ; Douglas, John ; Sigbjörnsson, Ragnar ; Lai, Carlo Giovanni. / Assessment of ground motion variability and its effects on seismic hazard analysis : a case study for iceland. In: Bulletin of Earthquake Engineering. 2011 ; Vol. 9, No. 4. pp. 931-953.
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Assessment of ground motion variability and its effects on seismic hazard analysis : a case study for iceland. / Ornthammarath, Teraphan; Douglas, John; Sigbjörnsson, Ragnar; Lai, Carlo Giovanni.

In: Bulletin of Earthquake Engineering, Vol. 9, No. 4, 08.2011, p. 931-953.

Research output: Contribution to journalArticle

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