Institute of Geophysics and Tectonics (IGT) PhD Projects
Exploring the Structure and Dynamics of Subduction Zones with Efficient Full-Waveform Seismic Modelling
Supervisors: Dr Doug Angus
The studentship involves developing and applying advanced seismic forward modelling to test the various hypothesis linking deformation mechanisms, seismic anisotropy and mantle flow. Much of our interpretation of seismic anisotropy and heterogeneity is guided by numerical modelling using ray-based techniques, which, while efficient, are limited to smoothly varying media and fail to model finite-frequency waveform effects and wave coupling. Heterogeneity and anisotropy within the upper mantle exist on a variety of scales, and can vary spatially quite sharply. To constrain observations from real data the ability to accurately simulate wave propagation for these types of media is crucial.
Figure 1. Schematic diagram of a subduction zone.
The elastic one-way wave equation method (Angus et al., 2004; Angus, 2005) is a highly efficient seismic modelling algorithm that simulates finite-frequency waveforms and wavefront evolution in 3D anisotropic and heterogeneous media. Teleseismic waves such as S, ScS and SKS phases, are already possible; in order to model regional S phases from slab earthquakes, the project will extend the technique to allow point and moment tensor source initial conditions. Waveform simulation employing the one-way wave equation and elastic models generated using integrating geodynamical and petrophysical modelling will allow us to test hypotheses of lithospheric structure and evolution, upper-mantle deformation mechanisms, and mantle flow in a much more robust fashion.
Figure 2: Left: modelling shear-wave splitting using an elastic one-way wave equation (Angus et al., 2004). Right: comparison of observed and modelled shear- wave splitting analysis (Hammond et al., 2010).
Group Members
Principal Investigator: Doug Angus
References
Angus, DA; Thomson, CJ; J; Pratt, RG (2004) A one-way wave equation for modelling variations in seismic waveforms due to elastic anisotropy , Geophysical Journal International, 156, pp.595-614.
Angus, DA (2005) A one-way wave equation for modelling seismic waveform variations due to elastic heterogeneity , Geophysical Journal International, 162, pp.882-898.
Hammond, JOS; Kendall, J; Angus, DAC; Wookey, J (2010) Interpreting spatial variations in anisotropy: insights into the Main Ethiopian Rift from SKS waveform modelling , Geophysical Journal International, 181,
p pp.1701-1712.