表面波トモグラフィーによる3次元地球内部構造の研究 A Review of Surface Wave Tomography for Three-dimensional Earth Structure
Our understanding of three-dimensional mantle structure has been greatly advanced by surface wave tomography in the last decade. In the upper 300-400km, lateral heterogeneity of seismic wave velocity, attenuation, and seismic anisotropy is correlated well with surface tectonics: Slow velocity and high attenuation beneath island arcs, mountainous regions, and young ocean; fast velocity and low attenuation beneath shield and old ocean. Seismic anisotropy also shows a good correlation with plate motion. Such a correlation diminishes below 300-400km and the amplitude of velocity heterogeneity decreases with depth down to the mid mantle. In the deeper part of the lower mantle, the heterogeneity becomes stronger than that in the mid mantle and is dominated by a long-wavelength pattern: The circum-Pacific region is characterized by a fast velocity which may be cold subducted slabs and the South Pacific and Africa are dominated by low velocities which may represent super hot plumes rising from the core-mantle boundary.
地學雜誌 104(7), 1019-1031, 1995-12-01
Tokyo Geographical Society