New PEER Report 2018/07: "An Empirical Model for Fourier Amplitude Spectra using the NGA-West2 Database"

January 8, 2019

PEER has just published Report No. 2018/07: “An Empirical Model for Fourier Amplitude Spectra using the NGA-West2 Database.” It was authored by Jeff Bayless and Norman A. Abrahamson.

Visit the PEER publications page to download a free color pdf of the document.


An empirical ground-motion model (GMM) for shallow crustal earthquakes in California and Nevada based on the NGA-West2 database [Ancheta et al. 2014] is presented. Rather than the traditional response spectrum GMM, this model is developed for the smoothed effective amplitude spectrum (EAS) as defined by PEER [Goulet et al. 2018]. The EAS is the orientation-independent horizontal component Fourier amplitude spectrum (FAS) of ground acceleration. The model is developed using a database dominated by California earthquakes, but takes advantage of crustal earthquake data worldwide to constrain the magnitude scaling and geometric spreading. The near-fault saturation is guided by finite-fault numerical simulations and non-linear site amplification is incorporated using a modified version of Hashash et al. [2018]. The model is applicable for rupture distances of 0–300 km, M 3.0 – 8.0, and over the frequency range 0.1–100 Hz. The model is considered applicable for Vs30 in the range 180–1500 m/sec, although it is not well constrained for Vs30 values greater than 1000 m/sec. Models for the median and the aleatory variability of the EAS are developed. Regional models for Japan and Taiwan will be developed in a future update of the model. A MATLAB program that implements the EAS GMM is provided as an electronic appendix.