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

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.

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.