Summary of the Abrahamson and Gulerce NGA-SUB ground-motion model for subduction earthquakes

Abstract

A set of region-specific ground-motion models (GMMs) for subduction zone earthquakes are developed based on the database compiled by the Pacific Earthquake Engineering Research Center (PEER) Next Generation Attenuation: Subduction project (NGA-SUB). The subset used to develop the GMMs includes 3914 recordings from 113 subduction interface earthquakes with magnitudes between 5 and 9.2 and 4850 recordings from 89 intraslab events with magnitudes between 5 and 7.8. The functional form of the global GMM accommodates the differences in the magnitude, distance, and depth scaling for interface and intraslab earthquakes. In addition to the global model, region-specific GMMs are developed for seven regions: Alaska, Cascadia, Central America, Japan, New Zealand, South America, and Taiwan. The magnitude scaling and the geometrical spreading parameters of the global model are used in all region-specific models, with the exception of the Taiwan region, which has a region-specific geometrical-spreading term. Four region-specific terms are included in the median GMM: the large distance (linear R) scaling, linear site amplification scaling (ln(VS30)), basin depth scaling (for Cascadia and Japan), and the constant term. The aleatory variability is also regionalized with larger aleatory variability at short periods for the Central America, Japan, and South America regions. Estimates of the epistemic uncertainty for the median and aleatory terms for each region are provided. The proposed global and region-specific GMMs are considered to be applicable to sites in the forearc region at distances up to 500 km, magnitudes of 5.0–9.5, and spectral periods from 0 to 10 s. The Cascadia-specific model is applicable to distances of 800 km including the backarc region.