Technical Report, pp.1-241, 2020
A set of global and region-specific ground-motion models (GMMs) for subduction zone earthquakes is developed based on the database compiled by the Pacific Earthquake Engineering Research Center (PEER) Next Generation Attenuation - Subduction (NGA-SUB) project. The subset
of the NGA-SUB database used to develop the GMMs includes 3914 recordings from 113 subduction interface earthquakes with magnitudes varying between 5 and 9.2 and 4850 recordings from
89 intraslab events with magnitudes varying between 5 and 7.8. Recordings in the back-arc region
are excluded, except for the Cascadia region. The functional form of the model accommodates the
differences in the magnitude, distance, and depth scaling for interface and intraslab earthquakes.
The magnitude scaling and geometrical spreading terms of the global model are used for all regions, with the exception of the Taiwan region which has a region-specific geometrical spreading
scaling. Region-specific terms are included for the large distance (linear R) scaling, VS30 scaling,
Z2.5 scaling, and the constant term. The nonlinear site amplification factors used in Abrahamson et al. (2016) subduction GMM are adopted. The between-event standard deviation piece of
the aleatory variability model is region and distance independent; whereas, the within-event standard deviations are both region and distance dependent. Region-specific GMMs are developed
for seven regions: Alaska, Cascadia, Central America, Japan, New Zealand, South America, and
Taiwan. These region-specific GMMs are judged to be applicable to sites in the fore-arc region at
distances up to 500 km, magnitudes of 5.0 to 9.5, and periods from 0 to 10 sec. For the Cascadia region, the region-specific model is applicable to distances of 800 km including the back-arc
region. For the sites that are not in one of the seven regions, the global GMM combined with the
epistemic uncertainty computed from the range of the regional GMMs should be used.