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Accession Number PB2013-108737
Title NGA-West2 Directivity Working Group Final Report.
Publication Date May 2013
Media Count 162p
Personal Author B. Rowshandel B. S. J. Chiou J. R. Bayless J. W. Baker P. Somerville P. Spudich S. K. Shahi
Abstract The 2008 Next Generation Attenuation (NGA-West1) ground motion prediction equations (GMPEs) did not include directivity; it was implemented as a post-facto correction without guidance for its application. The NGA-West2 GMPEs may be developed including the effects of directivity. Four directivity models (DMs) have been developed based on data from the NGAWest2 database and based on numerical simulations of large strike-slip and reverse-slip earthquake. All DMs avoid the use of normalized fault dimension, enabling them to scale up to the largest earthquakes sensibly. Models by Shahi and Baker, Spudich and Chiou, and by Rowshandel are explicitly narrow-band (in which the effect of directivity is maximum at a specific period which is a function of earthquake magnitude). The model by Bayless and Somerville is the only model in this report that predicts directivity for fault-normal and fault parallel motions as well as azimuthally averaged motion. Functional forms and preliminary coefficients of the DMs are presented in this report, but the final coefficients should be produced by including the directivity functional forms ab initio in the development of a GMPE. Also shown is a comparison of maps of the directivity amplification from the various DMs applied to a set of test rupture geometries. This comparison suggests that the directivity model predictions are strongly influenced by effects of their assumptions, and more than one model should be used for site-specific studies of directivity from ruptures dipping less than about 65 degrees.
Keywords Attenuation
Directivity models(DMs)
Ground motion prediction
Next Generation Attenuation(NGA)
Prediction equations

Source Agency US Geological Survey
University of California Earthquake Engineering Research Cent Berkeley
NTIS Subject Category 48F - Geology & Geophysics
63I - Seismic Detection
Corporate Author California Univ., Davis. Dept. of Civil and Environmental Engineering.
Document Type Technical report
Title Note N/A
NTIS Issue Number 1318
Contract Number N/A

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