Preparation of a 3D Dunedin Velocity Model

Abstract

The Akatore Fault is located to the southwest of Dunedin city and is thought to represent the most significant source of seismic hazard for the city. As Dunedin has not experienced a large earthquake in recorded history, modelling is the only way to estimate the likely levels of earthquake shaking that could impact the city in a future Akatore Fault earthquake.

Physics-based ground motion simulations offer an explicit way to model earthquake phenomena not reliant upon past ground motion records. Numerical models that contain the physical properties known to influence seismic wave generation and propagation are critical to the modelling process.

The scope of my study is to undertake groundwork for the development of such models by acquiring, processing and integrating three strategically located land seismic lines with existing borehole data, gravity data, and geological maps in the area to build a 3D seismic velocity model for the geological units of the Dunedin area. Particular focus is given to the near surface in the city, as this is the area of greatest potential human impact

This poster will present:

• The collection and processing of seismic data conducted as a part of this study • The reflection profiles and their interpretation • The P-wave stacking velocity models • The near-surface structures and P-wave velocities determined through refraction modelling • Multichannel analysis of surface waves at inner-city sites. • Preliminary modelling efforts

The present study represents a significant step toward understanding the seismic hazard in Dunedin City.