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Nature of Mid-Mantle Discontinuity

Hitoshi Kawakatsu

Close inspection of mantle discontinuities is important to understand the geodynamics. We discovered mid-mantle discontinuities at various subduction zones (Kawakatsu & Niu 1994, Niu & Kawakatsu 1997). Depth variation of the mid-mantle discontinuites was also detected beneath Indonesia by short period J-array data (Niu & Kawakatsu 1997), however this feature was not supported by broadband data (Vinnik et al. 2001). Recently very dense and high quality short period array, Hi-Net, was constructed in Japan, and we hope those data will reveal the unknown nature of mantle discontinuities.

References
Niu, F., H. Kawakatsu, and Y. Fukao (2003).
     Seismic evidence for a chemical heterogeneity in the mid-mantle: a strong and slightly dipping seismic reflector beneath the Mariana subduction zone,
     J. Geophys. Res., in press,
Kato, M., M. Misawa, and H. Kawakatsu (2001).
     Small Subsidence of the 660-km Discontinuity Beneath Japan Probed By ScS Reverberations,
     Geophys. Res. Let., 28, 447-450.
Kato, M., and H. Kawakatsu, (2001).
     Seismological in situ estimation of density jumps across the transition zone discontinuities beneath Japan,
     Geophys. Res. Let., 28, 2541-2544.
Vinnik, L., M. Kato, and H. Kawakatsu, (2001).
     Search for seismic discontinuities in the lower mantle,
     Geophys. J. Int., 147 , 41-56.
Vinnik, L., F. Niu, and H. Kawakatsu, (1998).
     Broad-band converted phases from midmantle discontinuities,
     Earth, Planets and Space (OHP special issue), 50, 987-997.
Niu, F., and H. Kawakatsu, (1998).
     Determination of the absolute depths of the mantle transition zone discontinuities beneath China: effect of the stagnant slabs on the mantle transition zone discontinuiteis,
     Earth, Planets and Space (OHP special issue), 50, 965-975.
Niu, F., and H. Kawakatsu, (1997).
     Depth variation of the mid-mantle seismic discontinuity,
     Geophys. Res. Lett., 24, 429-432.
Morita Y (1996).
     The characteristics of J-Array seismograms,
     J PHYS EARTH, 44, 657-668.
Niu, F., and H. Kawakatsu, (1996).
     Complex structure of the mantle discontinuities at the tip of the subducting slab beneath the northeast China: a preliminary investigation of broadband receiver functions,
     J. Phys. Earth, (J-array special issue), 44, 701-711.
Niu, F., and H. Kawakatsu (1995).
     Direct evidence of the undulation of the 660-km discontinuity beneath Tonga: comparison of Japan and US regional array data,
     Geophys. Res. Lett., 22, 531-534.
Kawakatsu, H. and F. Niu (1994).
     Seismic Evidence for a 920km discontinuity in the mantle,
     Nature, 371, 301-305.