Ground Motion Data from California Vertical Arrays

Developing this dataset was a part of a study on site response in vertical array sites of California. We compiled and processed a dataset of ground motion recordings from California vertical array sites. The data also includes shear-wave velocity profiles and geotechnical logs (if available) for the sites. Unprocessed records for the selected sites and events were downloaded from CESMD and the UCSB NEES websites. Acceleration time series were visually inspected to identify and exclude low-quality noise-dominated records. The data were processed using procedures developed in the NGA-West2 research project (Ancheta et al. 2014) and coded into an R routine (T. Kishida, pers. comm., July 2015). As shown in Figure 7, Fourier amplitude spectra were inspected to identify the limits of flat, noise-dominated frequency intervals using a signal-to-noise ratio of 3, which partially informs the selection of low- and high-cut corner frequencies (the other consideration being the appearance of the displacement time series). Acausal Butterworth filters are used for filtering high- and low-frequency noise in the frequency domain. Baseline correction is also applied as needed. Corner frequencies were manually selected following NGA procedures (i.e., the Ancheta et al. 2014 reference) and the data that was originally accessed was raw (unprocessed). The sites are owned by CSMIP and University of California Santa Barbara (UCSB). The data from vertical arrays help to evaluate observed site response between surface and downhole instruments. The direct observation of site response allows for validation studies on numerical and analytical site response models. This study was a part of Kioumars Afshari's PhD research under supervision of Prof. Jonathan P. Stewart in the Department of Civil Engineering at the University of California Los Angeles in 2017. A readme file included in this publication explains the data and how it is organized.