PEER has just published Report No. 2016/02 titled “Semi-Automated Procedure for Windowing Time Series and Computing Fourier Amplitude Spectra for the NGA-West2 Database.” It was authored by Tadahiro Kishida, Olga-Joan Ktenidou, Robert B. Darragh, Walter J. Silva.
This document introduces and describes the data processing methods developed for computing Fourier amplitude spectra (FAS) in the NGA-West2 project. The products of this study can be used to estimate high-frequency attenuation, kappa (κ), to estimate site amplification through empirical spectral ratios, as well as to aid in the development of ground-motion models (GMMs) based on FAS. To accommodate different potential user objectives, we selected five-time windows in the acceleration time series (noise, P-wave, S-wave, coda, and the entire record) for which we compute the FAS. The processing starts with the time-aligned, instrument-corrected, tapered, and filtered acceleration time series. The proposed window selection method is developed through trial and error, and tested against a range of ground motions with different magnitudes and hypocentral distances from different regions. This document summarizes the steps for window selection and FAS computation, and describes the output data format. This report will be accompanied by the final products of the PEER NGA-West2 Project, namely, the published report describing the database [Ancheta et al. 2013] and the flat file, which can be downloaded in excel format at: http://peer.berkeley.edu/ngawest2/databases/.