Research: Observational and Theoretical Studies in Global Seismology

Global seismology maps the Earth's deep interior from the upper mantle to the inner core, elucidating the internal structure and dynamics of our planet. Our goal is to connect seismology with other disciplines such as mineral physics, geodynamic modelling and geochemistry, and determine what causes the heterogeneity found in the Earth. Ultimately, this will provide a consistent picture of the way in which the Earth convects and evolves.

Current Research Projects

  • Mantle discontinuities. An important issue in seismology is the global and regional characteristics of velocity discontinuities in the Earth's mantle. Some of these represent known phase transitions in mantle minerals. The existence and nature of such discontinuities is very important for our understanding of the internal dynamics of the Earth (such as mixing between the upper and lower mantle) and provides the input needed by mineral physicists to connect seismic discontinuities with mineralogical phase changes. We have made the first global map of the Lehmann discontinuity at 220 km depth, and interpreted the observations as most probably being caused by a change in deformation mechanism. We also discovered that the mid-transition zone discontinuity at 520 km depth is 'split' in many regions and provided the first observations of the 660 km discontinuity using PP precursors. These observations can be explained by the combination of phase changes in both olivine and garnet and suggests that the Earth's transition zone is more compositionally heterogeneous than previously thought. We are currently working on extending these projects to the lower mantle and including many different data types.
  • Inner core structure. The core, comprising the innermost parts of the Earth, is one of the most dynamic regions of our planet. The Earth's inner core was discovered more than 65 years ago. The ultimate proof that the innermost Earth is solid would be shear waves traversing the inner core. We made the first unequivocal observations of inner core shear waves by comparing the data with synthetic seismograms for earth models having either a solid or fluid inner core. We are currently studying regional variations in the anisotropic structure of the inner core using compressional body waves and are planning to extend this work to normal mode data.
  • Earth's free oscillations. We are using normal modes, or whole Earth oscillations, to study the large scale structure in the Earth's mantle and inner core. In collaboration with the University of Oxford, research focuses on developing new techniques and theory to compute the normal modes, using coupling in wide frequency bands. Currently the new techniques are being applied to obtain tomographic models of the mantle and determine if it is possible to explain the observations by thermal effects alone. Recently, we have also started to study the anisotropic and attenuation properties of the inner core.
  • Mineral physical reference models. With colleagues at Berkeley and Imperial College London, we have developed a physical reference model that is consistent with seismic data. Currently, this is being used for seismic tomography inversions, which will aid their interpretation in terms of mineral physics.

Older Publications by Dr Arwen Deuss


Publications: 2006-Present

Last updated on 22-Jun-10 09:24