Stochastic Source Modelling of the 2002 Denali Earthquake for Fault Displacement Hazard Assessment

The Denali Fault earthquake was one of the largest strike-slip earthquakes with significant surface ruptures that occurred in 2002 in Alaska, United States. Probabilistic fault displacement hazard assessment (PFDHA) plays an important role in post-earthquake disaster management. This is because critical facilities and infrastructures in the vicinity of active faults are prone to major damage, leading to suspension of service due to fault displacement. Hence, in the present study, a PFDHA due to the Denali earthquake is conducted using a new methodology of stochastic source-based fault displacement hazard analysis. In this method, the surface rupture can be evaluated by applying Okada equations to simulated earthquake source models. The main differences between the methodology of the present study with conventional fault displacement assessment practices are to utilize the stochastic source models instead of the empirical predictive relationship of surface fault displacement and to calculate the distribution for surface fault displacement at a site of interest using the Okada equations. The new methodology is more versatile than the existing methods in several characteristics. First, it is applicable to all faulting mechanisms (e.g., strike-slip, normal, and reverse) by specifying different rake angles of the ruptured fault. Second, it has the ability to consider multi-segment fault rupture. Third, the calculation of three translational displacements by the Okada equations for a given location is available. Lastly, it provides physically consistent fault displacement modelling at two locations for a given earthquake scenario, allowing estimating of the differential fault displacement at two sites. Then the capability of the method is evaluated by applying it to the historical case of the 2002 Denali Fault earthquake. The satisfactory match of the modelled fault displacement and the observations, such as surface offset, Global Positioning System (GPS), and Interferometric Synthetic Aperture Radar (InSAR) data, is achieved based on calculating a performance metric. Therefore, more realistic ground deformation assessments can be carried out. Importantly, the obtained results significantly contribute to the hazard in earthquake-prone areas and reduce potential fatality and casualty risks as well as the post-earthquake damage repair costs of the built environment.