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Malcolm Sambridge ~ Biography

 



Malcolm Sambridge - Student research project themes




     

    Research projects in Mathematical Geophysics and Computational Seismology


    Background required:

    Most students should have a strong background in Physics, Mathematics, Engineering, Computer Science or Geophysics. The project will be tailored accordingly.


    Project type:

    Projects at Ph.B., honours, and Ph.D. levels are available in the areas below. Most will involve the use of advanced computing facilities of RSES and ANU. for data analysis and development of computational methods.


    Contact:

    If you are interested in any of the projects below, would like further information or are thinking of undertaking post-grad studies in a related area of the earth sciences, contact Malcolm Sambridge or look at his homepage. You might also want to look at what's going on in the
    Seismology group at RSES.


    Computational methods for nonlinear inverse problems

    All of our observations that constrain the Earth's interior structure are made at the surface. Hence there is always an `inverse problem' in making use of indirect observations to perform inferences about the Earth at depth. Inverse problems occur in many areas of the Physical sciences, and it is the subject of on going research of how best to solve them.

    In Geophysics many inverse problems are nonlinear, for example using seismic waveforms or travel times of waves to constrain the structure at depth. Recent research in the seismology group has led to a new fully nonlinear approach to certain types of inverse problem. The figure opposite shows some results. Each point represents an earth model colour code by fit to data. The cross shows the model with best data fit. 


    Important questions include Can we develop new ways of tackling highly nonlinear inverse problems ? How do we deal with uncertainty ? Since inverse problems occur in many areas of teh physical sciences Can we learn form the approaches taken in other fields, or can we export innovations in geophysical inverse problems top those fields ?

    Projects are available in the study of nonlinear inverse problems and methods for their solution. Projects may involve a combination of mathematics, advanced computation, probability theory, statistics, and geophysics. For more information on that nonlinear search algorithm look here

     

    Sampling of a 24-dimensional parameter space using NA
     

    Wave propagation and wavefront tracking in complex media 

    The computational simulation of seismic waves through a complex Earth model is a major focus of seismology research. These calculations have application across many distance scales from that of exploration geophysics to whole earth seismic structure (see below). 

    The current forefront is solving the elastic wave equation in complex 3-D geometries. The figure opposite shows the results of ray tracing calculations for wavefronts through a complex 2-D structure.

    Projects are available in various aspects of theoretical seismology. Current interests are in the development to new approaches to wavefield simulation, and multi-phase wavefront tracking in 3-D.

     

    Wavefronts constructed from raypaths in a 2-D earth model

    Imaging the Earth's interior structure with seismic tomography 

    The last 20 years has seen a huge impact from seismic imaging studies across many areas of geophysics. The figure oposite shows results from 3-D tomography for lateral variations in the Earth's bulk sound speed, carried out by members of the seismology group at RSES. 

    Projects are available in both developing and applying seismic inversion techniques across regional and global scales. These studies often involve enormous travel time or waveform data bases and require the use of sophistical data analysis techniques, computational mathematics, and advanced visualization tools.
    A section through seismic tomoraphy model


    Email Malcolm Sambridge Go to Malcolm's homepage .