HR: 0830h
AN: S41E-0130    [PDF]
TI: FDM simulation of receiver function_@-laterally heterogeneous model including a subducting slab-
AU: * Hirahara, K
EM: hirahara@eps.nagoya-u.ac.jp
AF: Grad. School Environmental Studies, Nagoya Univ., Furocho, Chikusa, Nagoya, 052-789 Japan
AU: Furumura, T
EM: furumura@eri-u-tokyo.ac.jp
AF: ERI, Univ. of Tokyo, Yoyoi 1-1-1, Bunkyoku, Tokyo, 113-0032 Japan
AU: Tonegawa, T
EM: tonegawa@eps.nagoya-u.acjp
AF: Grad. School Environmental Studies, Nagoya Univ., Furocho, Chikusa, Nagoya, 052-789 Japan
AU: Shibutani, T
EM: shibutan@rcep.dpri.kyoto-u.ac.jp
AF: DPRI, Kyoto Univ., Gokasho, Uji, 611-0011 Japan
AB: We have so far executed receiver function (RF) analyses of teleseismic waveforms observed at a large number of dense F-net, Hi-net and J-array stations to reveal the seismic velocity discontinuities in the crust and the upper mantle beneath the Japan Islands. In these analyses, assuming the phases in RFs are produced by P to S conversion at depths, we use the 1-D reference model of iasp91 to execute depth-migration of RFs. In southwest Japan, the RF images of Conrad, Moho and the upper boundary of dipping Philippine Sea slab are well consistent with those obtained by recent explosion seismological studies. However, in northeast Japan, the Conrad and Moho depths are deeper beneath the low velocity volcanic regions than in tomographic studies. And the negative RF amplitudes of the Sp phase converted at the top of dipping oceanic crust are clearer down a depth of 70km than in southwest Japan, in addition to the positive RF amplitude converted at the boundary between the bottom of oceanic crust and the Pacific slab down to a depth of 200 km. Moreover, the undulation of 410 and 660 km discontinuities are well delineated related to the subducting Pacific slab. Especially, 410 km discontinuity is not clear locally close to or within the slab, which suggests the complex structure of 410 km within the slab due to undulation or metastable state of olivine-spinel transition in a cold slab. These interesting RF features suggest the importance of the use of 3-D heterogeneous reference velocity and Q structures. Our final goal is full-wave tomography of RF to reveal 3-D velocity and Q structure. As a first step toward this goal, we simulate RFs in several 2-D heterogeneous models employing a finite difference method with a frequency content lower than 1 Hz in 0.5 x 0.5 km grids. Referred to existing tomography P, S and Q models provided by Zho and Koketsu, we investigated 1) the effect of lateral heterogeneous velocity and Q structure in the crust on the RF images of the Conrad and the Moho, 2) the effect of heterogeneous velocity and Q structure in the mantle wedge and the dipping slab on the RF image of the dipping slab interface. 3) the existence of dipping oceanic crust above the slab on the RF images, 4) the effect of the undulation and the metastable state of olivine-spinel transition in a cold slab on RF images of 410 km discontinuities around the slab, 5) the effect of the lateral heterogeneous velocity and Q structure in the mantle wedge and the slab on the RF images of 410 and 660 km discontinuities.
DE: 7200 SEISMOLOGY
DE: 7203 Body wave propagation
DE: 7218 Lithosphere and upper mantle
DE: 7260 Theory and modeling
SC: Seismology [S]
MN: 2003 Fall Meeting