HR: 13:40h
AN: S12D-01 INVITED     [PDF]
TI: 20 years of seismic tomography
AU: * Dziewonski, A M
EM: dziewons@eps.harvard.edu
AF: Department of Earth and Planetary Sciences, Harvard University, 20 Oxford Street, Cambridge, MA 02138
AU: Masters, G
EM: gmasters@ucsd.edu
AF: Institute of Geophysics and Planetary Physics, University of California-San Diego, La Jolla, CA 92093-0225
AB: With the papers by Masters {\it et al.} (1982), Nakanishi and Anderson (1982), Woodhouse and Dziewonski (1984) and Dziewonski (1984), global seismic tomography was well on its way to becoming one of the most important geophysical tools in the investigation of the Earth's interior. These early studies demonstrated the power of the method to discover new, unexpected features, such as the degree-two signal in the transition zone, the ring of fast velocities above the core-mantle boundary, and the Pacific and African megaplumes. Since then, tomography has moved towards higher resolution and the mapping of additional structural details, such as the topography of the internal boundaries and azimuthal and radial anisotropy. Anisotropy, in particular, is turning out to be a property that is likely to map the dynamic history of the Earth's interior. Tomographic studies extend to the very center of the Earth, where the inner core has been found to be anisotropic and, recently, to have an inner-most structure with a 300-km radius, which was discovered by identifying its distinct anisotropic properties. Higher resolution has its limits, and reports of slabs penetrating directly into the lower mantle and the detection of mantle plumes extending from the CMB to the surface remain controversial. An irreplaceable resource that has made this progress possible is the Global Seismographic Network, now transmitting most of the data in nearly real time, as envisioned 20 years ago by a small group of forward-looking seismologists.
DE: 7200 SEISMOLOGY
SC: Seismology [S]
MN: 2003 Fall Meeting