A ground-motion model for the shallow crustal earthquakes in New Zealand

In this study, we propose a new ground-motion model (GMM) for New Zealand (NZ) using a hybrid empirical method (HEM). Only a limited number of GMMs have been developed specifically using the NZ dataset. We utilized HEM to develop a GMM for shallow crustal earthquakes in NZ, aiming to predict PGA (peak ground acceleration) and PSA (pseudo spectral acceleration) at periods ranging from T = 0.01–10 s for moment magnitudes ( M w ) of 4.0 to 8.0, and a rupture distance ( R rup ) of up to 400 km, considering a reference site condition with V S30 = 760 m/s. We considered NZ the target region and Western North America (WNA) the host region. We utilized four GMMs from the NGA-West2 project for ground-motion modeling in WNA. A set of period-dependent adjustment factors were used to convert the GMMs from the host region to the target region. The adjustment factors were developed as the ratio between the stochastically simulated response spectrum in the target and host regions. Seismological parameters are required for stochastically simulating the response spectrum in both the host and target regions. These seismological parameters indicate the differences in source, path, and site effects between the two regions. The seismological parameters for target and host regions are adopted from Zhu et al. and Zandieh et al., respectively.