Topography on the Transition Zone Discontinuities
By studying long-period precursors to SS and PP phases, it is possible to map global variations in the topography of the seismic discontinuities in the upper mantle.
Current results are available in the following papers:
Flanagan, M.P. and P.M. Shearer, Global mapping of topography on transition
zone velocity discontinuities by stacking SS precursors, J. Geophys. Res.,
103, 2673-2692, 1998a.
Flanagan, M.P. and P.M. Shearer, Topography on the 410-km seismic velocity
discontinuity near subduction zones from stacking of sS, sP, and pP
precursors, J. Geophys. Res., 103, 21,165-21,182, 1998b.
Flanagan, M.P. and P.M. Shearer, A map of topography on the 410-km discontinuity from PP precursors, Geophys. Res. Lett., 26, 549-552, 1999.
Shearer, P.M., M.P. Flanagan and M.A.H. Hedlin, Experiments in migration processing of SS precursor data to image upper mantle discontinuity structure, J. Geophys. Res., 104, 7229-7242, 1999.
Shearer, P.M. and M.P. Flanagan,
Seismic velocity and density jumps across the 410- and 660-kilometer discontinuities, Science, 285, 1545-1548, 1999.
Shearer, P.M., Upper mantle seismic discontinuities, in Earth's Deep Interior:
Mineral Physics and Tomography from the Atomic to the Global Scale,
AGU Geophysical Monograph 117, 115-131, 2000.
Lawrence, J. F., and P. M. Shearer, A global study of transition zone thickness using receiver
functions, J. Geophys. Res., 111, B06307, doi:10.1029/2005JB003973, 2006.
Lawrence, J.F., and P.M. Shearer, Constraining seismic velocity and density for the mantle
transition zone with reflected and transmitted waveforms, Geochem. Geophys. Geosyst.,
7, Q10012, doi:10.1029/2006GC001339, 2006.
Houser, C., G. Masters, M. Flanagan, and P. Shearer, Determination and analysis of
long-wavelength transition zone structure using SS precursors, Geophys. J. Int., 174, 178-194,
doi: 10.1111/j.1365-246X.2008.03719.x, 2008.
Lawrence, J. F., and P. M. Shearer, Imaging mantle transition zone thickness with SdS-SS
finite-frequency sensitivity kernels, Geophys. J. Int., 174, 143-158,
doi: 10,1111/j.1365-246X.2007.03673.x, 2008.
SS precursor results (Flanagan and Shearer, 1998a), including figures, tables of the spherical harmonic coefficients
for the smoothed topography maps (410, 520, 660, TZ), and a table of the individual depth estimates and travel-times are
available
here.
Click
here
to see maps of discontinuity topography derived from SS precursors
(Plate 2 from Flanagan and Shearer, 1998a).