Strong Ground Motions Simulations for Dunedin: recent progress

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Kowal, Anna
Stirling, Mark
Gorman, Andrew
Wotherspoon, Liam

We present our on-going QuakeCoRE-funded work on strong motion seismology for Dunedin–Mosgiel area, focusing on ground motion simulations for the Dunedin Central Business District (CBD). Source modelling and ground motion simulations are being carried out using the Southern California Earthquake Center (SCEC) Broadband Simulation Platform (SCEC BBSP). As large earthquakes have not been experienced in Dunedin in the time period of historical observation (since 1840), user-specified scenario simulations need to be developed. The sources considered for ground motion simulations include major active faults near Dunedin that have been the foci of recent paleoseismic studies (Akatore, Titri, Dunstan and Hyde faults), along with the distant Alpine Fault source.

Current work and ongoing goals focus on modelling non-linear site effects. Seismic site effects are related to the amplification of seismic waves in surficial geological layers. We are presently undertaking site response analysis for ground motion simulations via nonlinear total stress and effective stress 1D wave propagation methods.. The simulated, amplified motions are compared against recorded events from strong motion stations in the city centre and southern Dunedin to quantify the amplification characteristics of soil sites relative to rock sites. These recorded events are also being applied to simulation validations. Our work will soon progress to undertaking ground motion simulations that utilize a 3D shear-wave velocity model for the greater Dunedin-Mosgiel area.

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