Effects of realistic fault geometry on simulated ground motions in the 2010 Darfield Earthquake, New Zealand

Hoby N. Razafindrakoto, Brendon A. Bradley, & Robert W. Graves

Submitted August 9, 2016, SCEC Contribution #6585, 2016 SCEC Annual Meeting Poster #284

This study investigates the effects of earthquake source information on simulated hybrid broadband ground motions, using the 2010 Darfield Earthquake, New Zealand as a case study. The geometric complexity of the fault for the 2010 Darfield event provides an opportunity to analyse the sensitivity of simulated ground motions to variations in the assumed fault geometry and slip distribution. In the analysis, three different fault geometries were considered, consisting of one, four and six fault segments in which the overall seismic moments are the same. Each of the aforementioned fault geometry cases consider ten different slip distribution realizations.
Simulated ground motions resulting from each earthquake source considered were computed using a hybrid approach, combining low and high frequencies. The simulations were then validated by comparing the simulated ground motions with observed ground motion records. The residual statistical analysis shows that the ground motion variability due to source geometry and slip distribution is larger in the intermediate period range (between 1 and 5s) and for stations near the source. The extent of forward directivity also changes significantly between different source models which is particularly observed at stations located in the Christchurch Basin. Finally, the results reveal that a single fault segment cannot appropriately represent the 2010 Darfield event. The comparison of simulation results for one and four fault segments, for example, shows no significant changes for the stations located to the east of the causative faults, whereas variability of the spectral acceleration residual appears along to the west for intermediate periods (1s and 3s). This, among other observations, implies that appropriate complexity is required, particularly on the west end of the causative fault. The results of this study have implications on the ground motions produced by geometrically complex faults and the seismic hazard in the Canterbury region.

Razafindrakoto, H. N., Bradley, B. A., & Graves, R. W. (2016, 08). Effects of realistic fault geometry on simulated ground motions in the 2010 Darfield Earthquake, New Zealand. Poster Presentation at 2016 SCEC Annual Meeting.

Related Projects & Working Groups
Ground Motion Simulation Validation (GMSV)