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.

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 by anonymous ftp at: mahi.ucsd.edu/pub/TOPOTZ.

PP precursor results (Flanagan and Shearer, 1999) including a model of 410 topography are available by anonymous ftp at: mahi.ucsd.edu/pub/TOPOPP.

Near-source 410 topography results (Flanagan and Shearer, 1998b) are available by anonymous ftp at: mahi.ucsd.edu/pub/THE410.

Click here to see maps of discontinuity topography derived from SS precursors (Plate 2 from Flanagan and Shearer, 1998a).