Back to Research Page

Ground Motion Attenuation during M7.1 Darfield and M6.2 Christchurch (New Zealand) Earthquakes and Performance of Global Predictive Models

Margarita Segou, British Geological Survey

Erol Kalkan, U.S. Geological Survey, Menlo Park, ekalkan@usgs.gov

 

Plain English Summary

The M7.1 Darfield earthquake, occurred 40 km west of Christchurch on September 4th 2010, was followed by another M6.2 event on 21st February 2011. These events had disastrous effects in the city’s center and suburbs within the Canterbury region. Processed data, corresponding to peak ground acceleration (PGA) and 5% damped spectral acceleration (SA) values at 0.3, 1, 3 s, were used for evaluating the performance of global ground motion prediction equations (GMPEs) to estimate peak and spectral values. The selected GMPEs are: Graizer and Kalkan (2007 and 2009) (GK07), and Next Generation of Attenuation (NGA) models of Abrahamson and Silva (2008) (AS08), Boore and Atkinson (2008) (BA08), Campbell and Bozorgnia (2008) (CB08), and Chiou and Youngs (2008) (CY08). To rank the relative performance of the GMPEs, we followed a traditional residual analysis and an information theoretic approach, suggested by Scherbaum et al. (2009). For the Darfield earthquake, we observed an overestimation of predicted ground motion at short periods (PGA and SA at 0.3 s) due to faster attenuation of ground motion associated with low Q. The overestimation is evident in the NGA models at 70 km and beyond, and it is very prominent for the case of CB08 model. The GK07 model performs as good as the NGA models. For Christchurch earthquake the overestimation begins almost at 40 km for all GMPEs, and it is less pronounced for the GK07 and CY08. At longer periods (SA at 1 s and 3 s), the overall trend of the overestimation is suppressed, possibly due to large amplitudes of ground motions associated with the basin amplification and Moho reflection. At 1 s, the BA08 and CB08 perform better for distances less than 50 km, whereas for greater distances, their performance gets poorer. The ranking results for both events show that the performance of the GK07, BA08 and CY08 models are equally the same, while the CB08 and AS08 models show relatively poorer performance.

Segou M. and Kalkan E. “Ground Motion Attenuation during M7.1 Darfield and M6.2 Christchurch (New Zealand) Earthquakes and Performance of Global Predictive Models", Seismological Research Letters, pp. 866-874, Nov-Dec, 2011.

Download the flat file of strong motion records of the M7.1 Darfield and M6.2 Christchurch Earthquakes: Appendix.zip (29 Kb)

For Canterbury (New Zealand) region, figure shows the geological conditions defined as shear-­wave  velocity  (unit  =  m/s)  down  to  30  m  derived  from  topographic  slope (also shown are the  location of strong motion stations)

Comparison of PGA values recorded from the M7.1 Darfield earthquake for 16, 50 (median) and 84 percentile predictions of five different ground motion prediction equations.

Comparison of PGA values recorded from the M6.2 Christchurch earthquake for 16, 50 (median) and 84 percentile predictions of five different ground motion prediction equations.