A New Zealand-Specific Pseudospectral Acceleration Ground-Motion Prediction Equation for Active Shallow Crustal Earthquakes Based on Foreign Models

Abstract

Abstract The applicability of foreign ground‐motion prediction equations (GMPEs) for predicting geometric‐mean pseudospectral acceleration amplitudes from active shallow crustal earthquakes in New Zealand (NZ) is examined. Four different foreign GMPEs were considered, as well as the NZ‐based McVerry et al. (2006) (McV06) model. It was found that the McV06 model exhibited the lowest applicability with a database of 2437 recorded ground motions, and that the Chiou et al. (2010) (C10) modification of the Chiou and Youngs (2008b) (CY08) model was the most applicable. Discrepancies between the C10 model and the NZ database, which were empirically identified and theoretically justified, were used to modify the C10 model for: (1) small magnitude scaling; (2) scaling of short period ground motion from normal faulting events in volcanic crust; (3) scaling of ground motions on very hard rock sites; (4) anelastic attenuation in the NZ crust; and (5) consideration of the increased anelastic attenuation in the Taupo Volcanic Zone. The developed NZ‐specific model therefore contains features as evident from recorded ground motions in NZ and consistent scaling for parameters not well constrained by NZ data. Comparisons with ground motions from the 4 September 2010 Darfield and 22 February 2011 Christchurch earthquakes, which occurred following completion of the NZ‐specific model, illustrate that it provides an empirical prediction with sufficient accuracy and precision.