Uncertainty in Vs30-based site response

Bulletin of the Seismological Society of America
By:  and 



Methods that account for site response range in complexity from simple linear categorical adjustment factors to sophisticated nonlinear constitutive models. Seismic‐hazard analysis usually relies on ground‐motion prediction equations (GMPEs); within this framework site response is modeled statistically with simplified site parameters that include the time‐averaged shear‐wave velocity to 30 m (VS30) and basin depth parameters. Because VS30 is not known in most locations, it must be interpolated or inferred through secondary information such as geology or topography. In this article, we analyze a subset of stations for which VS30 has been measured to address effects of VS30 proxies on the uncertainty in the ground motions as modeled by GMPEs. The stations we analyze also include multiple recordings, which allow us to compute the repeatable site effects (or empirical amplification factors [EAFs]) from the ground motions. Although all methods exhibit similar bias, the proxy methods only reduce the ground‐motion standard deviations at long periods when compared to GMPEs without a site term, whereas measured VS30 values reduce the standard deviations at all periods. The standard deviation of the ground motions are much lower when the EAFs are used, indicating that future refinements of the site term in GMPEs have the potential to substantially reduce the overall uncertainty in the prediction of ground motions by GMPEs.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Uncertainty in Vs30-based site response
Series title Bulletin of the Seismological Society of America
DOI 10.1785/0120150214
Volume 106
Issue 2
Year Published 2016
Language English
Publisher Seismological Society of America
Contributing office(s) Geologic Hazards Science Center
Description 11 p.
First page 453
Last page 463
Online Only (Y/N) N
Additional Online Files (Y/N) N