第31回ジオダイナミクスセミナー
　　　Geodynamics　Seminar

要　旨

　　An Introduction to the Attenuation (Q)　tomography
　　studies in Japan
　　　　　　　　　　Mr. Mohamed K. Salah

　-Improvement in seismic observations and new developments in computer technology have made it possible to estimate heterogeneous structure of the Earth's interior. For example, several workers have obtained detailed three-dimensional seismic velocity structures beneath the Japan subduction zone (e. g. Hasemi et al. 1984, Obara et al. 1986, Hirahara et al. 1989, Kamiya et al. 1989, Ishida 1992, Yamanaka et al. 1992, Zhao et al. 1992 & 1994). They have shown that seismic velocities are high in the subducting Pacific plate and low in the crust and mantle wedge beneath active volcanoes. In addition to the velocity structure, it is evident that a detailed estimation of the seismic attenuation structure will give us another set of important information about the physical properties and the temperature distribution of the Earth's interior beneath subduction zones.


　　　"Waveform and travel time constraints on the low
　　　 velocitystructure beneath Africa "
　　　　　　　　　　　　Dr. Sidao Ni

We developed a new algorithm to decipher and determine arrival times of seismic phases by matching simulated synthetics to observed waveforms.
This algorithm is applied to analog and digital seismic data along a corridor from South America to Africa and a high-resolution 2-D model is constructed. This model begins with a fast D" beneath South America and transitions into a slow (3%) layer extending 2000 km across the Atlantic, where it rapidly thickens reaching at least 1500 km above the CMB. This large slow column is about 800 km wide and leans towards the east.

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　　　 　　　　　　　　　　　　　　　　E-mail　　inoue@sci.ehime-u.ac.jp