Applicability of foreign ground motion prediction equations for New Zealand active shallow crustal earthquakes

摘要

The number of instrumental ground motion records in New Zealand (NZ) has increased significantly in recent years due to an increase in thenumber and quality of seismometer throughout NZ. Figure 1 provides a comparison between NGA ground motion database and the NZdatabase developed as part of this study. Despite this increase in instrumental data, it can be seen clearly in Figure 1 that there is a lack ofempirical records from large magnitude events observed at near-source distances. This is even more clear in Figure 2, which plots thecumulative number of records exceeding specific PGA values in the NZ ground motion database. There are only a total of 66 ground motionrecords which have PGA values above 0.1g (28 crustal, 11 interface, and 27 slab). Furthermore, the maximum PGA values recorded are0.39g, 0.31g, and 0.28g for crustal, interface, and slab events, respectively. This lack of ground motion records from large magnitude nearsourcerecords, which typically dominate seismic hazard analyses, makes it difficult to develop robust ground motion prediction equationsused in seismic hazard analysis based on NZ data alone.In this study an alternative approach to empirical ground motion prediction equation development was taken. Firstly, the applicability ofvarious foreign ground motion prediction equations (derived using plentiful data) to NZ were considered. The consideration was based onboth the dependence of the inter- and intra-event residuals as a function of several predictor variables, and also the general predictor variablescaling of the various models. Secondly, the model exhibiting the best applicability to NZ was modified based on theoretical and empirically-drivenconsiderations to better represent the NZ data.