HR: 1340h
AN: T13A-0452    [Abstracts]
TI: Lithospheric Shear Velocity Models Beneath Continental Margins in Antarctica Inferred From Genetic Algorithm Inversion for Teleseismic Receiver Functions
AU: * Kanao, M
EM: kanao@nipr.ac.jp
AU: Shibutani, T
EM: shibutan@rcep.dpri.kyoto-u.ac.jp
AB: Seismic shear velocity models of the crust and the uppermost mantle were studied by teleseismic receiver function analyses beneath the permanent stations of the Federation of Digital Seismographic Networks (FDSN) at Antarctic continental margins. In order to eliminate the starting model dependency, a non-linear Genetic Algorithm (GA) was introduced in the time domain inversion of the receiver functions. A plenty of velocity models with an acceptable fit to the receiver function waveforms were generated during the inversion, and a stable model was produced by employing a weighted average of the best 1,000 models encountered in the development of the GA. The shear velocity model beneath the MAW (67.6S, 62.9E) has a sharp Moho boundary at 44 km depth that might have involved in a reworked metamorphic event of adjacent Archaean Napier Complex. A fairly sharp Moho was identified about 28 km depth beneath DRV (66.7S, 140.0E), with a middle grade variation of the crustal velocities that might have been caused by the Early Proterozoic metamorphism. A similar sharp Moho has been found at 40 km beneath SYO (69.0S, 39.6E). Thus Moho depth is consistent with that from refraction / wide-angle reflection surveys around the station. Fairly complicated velocity variations within the crust may have a relationship with lithology of granulite facies metamorphic rocks in the shallow crust associated with Pan-African events. Broadening low velocity zones about 30 km depths with transitional crust-mantle boundary at VNDA (77.5S, 161.9E), might be caused by the rift system besides the Trans Antarctic Mountains. As for the Antarctic Peninsular, very broad Moho was found around 36 km depths around PMSA (64.8S, 64.0W). The evidence of velocity variations within the crust reflects the tectonic histories of each terrain where these permanent stations are located.
UR: http://polaris.isc.nipr.ac.jp/~pseis/
DE: 5462 Polar regions
DE: 7203 Body waves
DE: 7218 Lithosphere (1236)
DE: 8110 Continental tectonics: general (0905)
DE: 9310 Antarctica (4207)
SC: Tectonophysics [T]
MN: Fall Meeting 2005