Reference-Rock Site Conditions for Central and Eastern North America: Part II – Attenuation (Kappa) Definition. 22nd Conference on Structural Mechanics in Reactor Technology San Francisco, California, USA - August 18-23, 2013 Division IV.

摘要

The reference rock site condition is defined by the shear (S)- and compression (P)-wavevelocities, as well as a site attenuation parameter ( 0 ? ). The significance of the reference rock is that itrepresents the site condition for which ground motions will be estimated using semi-empirical groundmotion prediction equations (GMPEs). Moreover, it is the site condition where site amplification arereferenced to (i.e., site amplification is unity for reference rock). This paper presents the recommendationof a reference S-wave velocity, a reference P-wave velocity, and S-wave site attenuation parameter, 0 ? ,associated with a reference rock site condition in Central and Eastern North America (CENA), supportedby results of a comprehensive literature search and additional studies. The work is part of the NextGeneration Attenuation Relationships for Central and Eastern North America (NGA-East) Project. Therecommended S- and P-wave velocities are 3,000 and 5,500 m/sec, respectively. Considering a ? 5%impact on the site amplification, ranges for the reference S- and P-wave velocities of 2,700 to 3,300 m/secand 5,000 to 6,100 m/sec, respectively, are recommended. The recommended reference rock site kappa is0.006 sec. The uncertainty in the site kappa is described using a log-normal distribution with an aleatorystandard deviation of 0.43, and epistemic standard deviations of 0.12, when uncertainty in source, path,and site-amplification effects are included in simulations used to develop ground motion predictionequations, and 0.20, when they are not.