Stochastic Source Modelling and Tsunami Hazard Analysis of the 2012 Mw7.8 Haida Gwaii Earthquake

The 2012 M(w)7.8 Haida Gwaii earthquake triggered a tsunami that highlighted the importance of tsunami hazard assessments along Canada's Pacific coast. Stochastic source modelling offers a valuable method to assess future tsunami hazard and has not been previously performed for this region. The stochastic source models characterize the variability of earthquake ruptures by accounting for uncertain fault geometry and slip heterogeneity, allowing the consideration a wide range of possible tsunami scenarios. The model predictions are constrained by observational data and past source inversion studies. A total of 1500 stochastic tsunami models are generated using the stochastic source modelling method to assess tsunami hazard via Monte Carlo tsunami simulations of the target region and conduct sensitivity analyses of tsunami height variability. 500 stochastic models are synthesized by reflecting the key features of the observed tsunami wave profiles as well as ground deformations during the 2012 event, whereas 1,000 stochastic models are generated to represent future potential rupture scenarios of M(w)7.7 to M(w)8.1 in the Haida Gwaii region. The comparison of the offshore tsunami data based on the 2012 observations and the stochastic tsunami simulations matched reasonably well, while the comparison of the run-up measurements with the simulation results showed that the latter is generally smaller than the former. To improve the tsunami simulation, accurate bathymetry and elevation data are necessary. Since the prospective evaluations of regional tsunami hazards using the stochastic source models capture both moderate and extreme tsunami hazard scenarios, the developed models can be used to perform future probabilistic tsunami hazard analysis in this region to promote better-informed risk management decisions.

Automated summary

Stochastic source modelling is a valuable method for assessing future tsunami hazards in the Haida Gwaii region on Canada's Pacific coast. This method accounts for uncertainties in fault geometry and slip heterogeneity, allowing for a wide range of possible tsunami scenarios. By generating multiple stochastic tsunami models, the study provides insights into the variability of tsunami heights and highlights the need for accurate bathymetry and elevation data to improve simulations. The models developed in this study can be used for future probabilistic tsunami hazard analysis and risk management decisions in the region.