2023 – Ground motion modelling updates applicable to seismic hazard assessments for dams in Australia

Jeff Bayless, Paul Somerville, Hong Kie Thio

For all categories of dams, the ANCOLD (2019) guidelines specify how a seismic hazard assessment (SHA) should be performed. One critical component of a SHA is the selection of ground motions models (GMMs), as described in Section 2.5 of ANCOLD (2019), because the SHA results are highly dependent on these models.TheSomervilleetal.(2009;Sea09)GMMs for Australia are due to be improved by taking advantage of ground motions recorded in the past decade-plus. Changes to seismic hazard models with time reflect our increasing knowledge of earthquake source and ground motion characteristics in Australia. This paper describes how the Sea09 ground motion model has changed, and as a result how SHA results for dam projects may be impacted. Comparisons with recently recorded ground motions in Australia have revealed that refinements to the distance and depth scaling components of the model provide a better fit to those data. This update also involves on going earthquake ground motions imulations; these are validated using the recorded ground motion data and are used to extrapolate the model to larger earthquake magnitudes that typically control design ground motions but for which no Australian data are available.

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