HR: 08:15h
AN: S41C-02    [Abstracts]
TI: Lateral Variations in Attenuation Beneath Japan
AU: * Ishii, M
EM: ishii@eps.harvardr.edu
AF: Dept. Earth & Planetary Sciences, Harvard University, 20 Oxford Street, Cambridge, MA 02138, United States
AB: Improved images of the lateral variations in elastic properties of the mantle in terms of isotropic and anisotropic seismic wave speeds are generated almost routinely by various research groups. These models provide key information on our understanding of the mantle composition and dynamics. Another piece of information that would be very useful in advancing our knowledge of the mantle is constraints on the heterogeneity of anelasticity or attenuation. Lateral variations in attenuation are particularly of interest in subduction zones where complex chemical and dynamical signals, such as presence of water/volatiles, melting, and wedge flow, are directly related to attenuation of seismic waves. Japan is one of the most suitable subduction zones for modelling of attenuation structure. There are numerous local earthquakes with depths ranging from the surface to nearly 600-km depth, and there are dense seismic networks to record signals generated by these events. In particular, the bore-hole instrument network, the High Sensitivity Seismograph Network (Hi-net), provides high- quality data at about 20-km spacing. The first arrivals recorded by the Hi-net array from local earthquakes show strong location dependence in their frequency content. We use relative frequency content and arrival times to model variations in attenuation in the upper mantle beneath Japan. Combined analysis of elastic and anelastic structure of the mantle may shed light on our understanding of subduction processes.
DE: 7203 Body waves
DE: 7208 Mantle (1212, 1213, 8124)
DE: 7240 Subduction zones (1207, 1219, 1240)
DE: 7270 Tomography (6982, 8180)
SC: Seismology [S]
MN: 2007 Fall Meeting