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Stephen Schaeffer

Student

#80 Spencer House
Custom House Square
Lower Mayor Street
Dublin 1

Tel: +353 1 716
Email: 09156828@ucdconnect.ie

Biography

Andrew completed both his B.Sc. and M.Sc. in Geophysics in the Department of Earth and Ocean Sciences at the University of British Columbia, in Vancouver, Canada, with Professor Michael Bostock.
Honours Thesis: Receiver function analysis of teleseismic S-waves applied to the Cascadia subduction zone.
Master Thesis: Nature of a low-velocity zone atop the transition zone in Northwestern Canada.

Andrew is currently a PhD Student jointly between the Dublin Institute for Advanced Studies (DIAS) and the Geophysics Group in UCD since January 2010.

 

Publications

     

Peer Reviewed Journals

A.J. Schaeffer and Bostock, M.G. (2010) 'A low-velocity zone atop the transition zone in northwestern Canada'. Journal of Geophysical Research, . [Details]
P.S. Lipovsky, Evans, S., Clague, J., Hopkinson, C., Couture, R., Babrowsky, P., Ekstrom, G., Demuth, Delaney, K., Roberts, N., Clarke, G.K.C., and Schaeffer, A.J. (2008) 'The July 2007 rock and ice avalanches of Mount Steele, St. Elias Mountains, Yukon, Canada'. LANDSLIDES, . [Details]
C. Kerton, Knee, L., and Schaeffer, A.J. (2006) 'A Intermediate-velocity gas cloud in the Canadian Galactic plane survey'. Astronomical Journal, 131 . [Details]
 

Conference Publications

Schaeffer, A.J. and Lebedev, S. (2012) Anisotropic structure of the upper mantle, imaged with Surface and S waveform tomography (Talk) 55th Irish Geological Research Meeting, UCC, Cork [Details]
E. Neenan, Schaeffer, A.J., Agius, M.R., and Lebedev, S. (2012) The North Anatolian Fault and lithospheric dynamics in eastern Mediterranean: A seismic surface-wave study 55th Irish Geological Research Meeting, UCC, Cork [Details]
P. Lynch, Agius, M.R., Schaeffer, A.J., and Lebedev, S. (2012) Robust shear-velocity profiles within oceanic lithosphere and asthenosphere: Implications for thermal and compositional structure 55th Irish Geological Research Meeting, UCC, Cork [Details]
A.J. Schaeffer and Lebedev, S. (2011) Anisotropic Structure of the upper mantle, image with surface and S waveform tomography (Talk) American Geophysical Union Fall Meeting, San Francisco [Details]
E. Neenan, Schaeffer, A.J., Agius, M.R., and Lebedev, S. (2011) Lithospheric Anisotropy and Deformation in Anatolia, Eastern Mediterranean: A Seismic surface-wave study American Geophysical Union Fall Meeting, San Francisco [Details]
P. Lynch, Agius, M.R., Schaeffer, A.J., and Lebedev, S. (2011) Robust shear-velocity profiles within oceanic lithosphere and asthenosphere: implications for thermal and compositional structure American Geophysical Union Fall Meeting, San Francisco [Details]
S. Lebedev, Agius, M.R., and Schaeffer, A.J. (2011) Shallow-Angle subduction of the Indian plate beneath Tibet: new seismic images and implications for the evolution of the plateau American Geophysical Union Fall Meeting, San Francisco [Details]
A.J. Schaeffer and Lebedev, S. (2011) Global and regional scale seismic tomography using surface and S waveform inversion (Talk) European Geophysical Union Spring Meeting, Vienna [Details]
S. Lebedev, Horan, C., Readman, P., Schaeffer, A.J., Collins, L., Hauser, F., and O'Reilly, B. (2011) Ireland Array: a seismic investigation of Ireland's evolution, seismicity, and new energy resource potential 54th Irish Geological Research Meeting, NUI Galway [Details]
A.J. Schaeffer and Lebedev, S. (2010) Seismic structure of the North American lithosphere and upper mantle imaged using surface and S waveform tomography American Geophysical Union Fall Meeting, San Francisco [Details]
A.J. Schaeffer and Bostock, M.G. (2010) A low-velocity zone atop the transition zone in Northwestern Canada (Talk) 53rd Irish Geological Research Meeting, Belfast [Details]
A.J. Schaeffer and Bostock, M.G. (2010) A low-velocity zone top the transition zone in northwestern Canada Study of the Earth's Deep Interior, 12th Symposium, Sanata Barbara [Details]
T.W. Becker, Crowley, J.W., Gerault, M., Hoink, T., Schaeffer, A.J., Barry, P., Frost, J., Girard, J., Nunez-Valdez, M., Hirschmann, M., Hier-Majumder, S., and O'Connell, R.J. (2010) Deep Water Cycle: its Role in Earth's Thermal Evolution and Plate Tectonics American Geophysical Union Fall Meeting, San Francisco [Details]
A.J. Schaeffer and Bostock, M.G. (2010) The Transition Zone low-velocity zone: properties in Northwestern Canada (Invited Talk) American Geophysical Union Fall Meeting, San Francisco [Details]
A.J. Schaeffer and Bostock, M.G. (2008) Nature of a low-velocity zone atop the transition zone in Northwestern Canada American Geophysical Union Fall Meeting, San Francisco [Details]
A.J. Schaeffer and Bostock, M.G. (2007) Preliminary investigation of shallow-mantle structures beneath western Canada using Sp conversions American Geophysical Union Fall Meeting, San Francisco [Details]
                   

Workshops

A.J. Schaeffer and Lebedev, S. (2012) Isotropic and Anisotropic structure of the upper mantle, imaged with surface and S waveform tomography (Talk). 3rd QUEST Workshop, Tatranska Lomnica, Slovakia: Workshops [Details]
A.J. Schaeffer and Lebedev, S. (2010) Seismic structure of the lithosphere and upper mantle of North America from the inversion of surface and S waveforms. IRIS Annual Workshop, Utah: Workshops [Details]
A.J. Schaeffer and Bostock, M.G. (2010) A low-velocity zone atop the transition zone in Northwestern Canada. Cooperative Institute for Dynamic Earth Research (CIDER), Summer Program, Santa Barbara California: Workshops [Details]
A.J. Schaeffer and Bostock, M.G. (2008) Seismic low-velocity zone beneath the Slave province using P and S receiver functions. IRIS Annual Workshop, Washington: Workshops [Details]
                                                                   

Research

Research Interests

My research is focused on understanding the mechanics and dynamics of the Earth system, in particularly the structure and evolution of the upper mantle and transition zone. How have dynamic processes, both past and present, formed the mechanical, chemical, and thermal structure of the crust, lithosphere, and asthenosphere? What is the nature of the lithosphere-asthenosphere boundary? What role has the transition zone played in modulating the Earth¿s evolution and, in particular, what were its effects on mass transfer and chemical differentiation between the upper and lower mantle?
 
Dynamics of Continental Deformation: I am constructing a global shear-velocity model of the upper mantle, including azimuthal and radial anisotropy, using unprecedentedly large seismic waveform datasets. This is accomplished using automated multimode inversions to accurately and efficiently extract maximum structural constraints from each and every waveform, to be inverted for 3D anisotropic Earth Models. Using this approach, more than one million seismograms have been successfully fit to date, and my most recent tomographic model is constructed using the best almost 600,000. Such models, utilizing maximum available data, will further investigations into the processes associated with lithosphere formation, stabilization, and erosion, through the analysis of both seismic velocity and
anisotropy (radial and azimuthal).
 
Upper Mantle and Transition Zone Structure: In addition to global surface wave techniques mentioned above, I also make use of Receiver Function techniques to investigate the structure of the Earth¿s upper mantle and transition zone. Both P and S RFs yield complimentary information which can be used to learn about the composition and discontinuity structure within the Earth, as well as querying the nature and complexities of the Lithosphere-Asthenosphere Boundary, within both ancient and modern continental environments. I have applied these techniques to several array¿s in north Western Canada to look at the mantle structure immediately overlying the transition zone.

Global Water Cycle: A combination of seismic, petrologic, and geochemical constraints were combined in a geodynamic modelling framework to investigate the effects of varying water (and in general volatile) content on the Earth¿s whole mantle through all geologic time. A simple yet accurate geodynamic model was constructed to simulate Earth¿s evolution to analyse the effects of varying water (and volatiles in general) contents within the Earth¿s mantle.
 
Subduction zone structure and dynamics: Seismic investigation combined with numerical modeling
of wave propagation to characterize the structural elements within the subduction zone and
surrounding environs.