Accounting for site characterization uncertainties when developing ground-motion prediction equations

Gehl, Pierre and Bonilla, Luis Fabian and Douglas, John (2011) Accounting for site characterization uncertainties when developing ground-motion prediction equations. Bulletin of the Seismological Society of America, 101 (3). pp. 1101-1108. ISSN 0037-1106

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Abstract

Current ground-motion prediction equations invariably assume that site conditions at strong-motion stations, often characterized by the average shear-wave velocity to a depth of 30 m (VS30), are known to a uniform accuracy. This is, however, rarely the case. In this article, we present a regression procedure based on generalized least-squares and maximum-likelihood approaches that take into account the varying uncertainties on VS30. Assuming that VS30s for various groups of stations are known to different accuracies, application of this procedure to a large set of records from the Japanese KiK-net shows that the regression coefficients are largely insensitive to the assumption of nonuniform uncertainties. However, this procedure allows the computation of a site-specific standard deviation (σ) that should be used for sites where VS30 is known to different accuracies (e.g., a site only specified by class or a site with a measured VS profile). For sites with a measured VS profile, this leads to lower sitespecific σ than for a site that is poorly characterized because this technique explicitly models the separation between the epistemic uncertainty in VS30 and the aleatory variability in predicted ground motion.

ORCID iDs

Gehl, Pierre, Bonilla, Luis Fabian and Douglas, John ORCID logoORCID: https://orcid.org/0000-0003-3822-0060;