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TitleSurface wave tomography and azimuthal anisotropy of the Philippine Sea Plate
AuthorYeh, Y -L; Kao, H; Wen, S; Chang, W -Y; Chen, C -H
SourceTectonophysics vol. 592, 2013 p. 94-112,
Alt SeriesEarth Sciences Sector, Contribution Series 20130146
Mediapaper; on-line; digital
File formatpdf
AreaPhilippines; Japan; Taiwan, Province of China
Lat/Long WENS120.0000 150.0000 40.0000 0.0000
Subjectstectonics; geophysics; anisotropy; tectonic environments; tectonic interpretations; tectonic setting; surface wave studies; r waves; deformation; lithosphere; seismic velocities; anomalies; subduction; subduction zones; trenches; Philippine Sea Plate; Philippine Basin; tomography
Illustrationslocation maps
ProgramTargeted Hazard Assessments in Western Canada, Public Safety Geoscience
AbstractLong period and broadband waveform data from 1984 to 2007 extracted mainly from the IRIS Data Center with additional data from 1997 to 2007 extracted from the Ocean Hemisphere Project is used to perform a detailed mapping of Rayleigh wave group velocity and anisotropic structures of the Philippine Sea Plate (PSP). Our results show prominent high Rayleigh wave group velocity anomalies and heterogeneity in three marginal basins of the PSP at period up to 30 s. The convergent boundaries around the PSP are associated with low-velocity anomalies. Heterogeneity of velocity distribution at deep depths along the Ryukyu trench is also observed. Our results indicate that the azimuthal anisotropy in the PSP is depth dependent. The fast direction in the West Philippine Basin and the Shikoku Basin is in NE - SW at shorter periods, which is correlated with fossilized fabric produced by final phase of deformation, whereas the fast direction in the Parece Vela Basin is complex at shorter periods and becomes uniformly NE - SW-oriented at longer periods. At the depths near the lithosphere - asthenosphere boundary, the fast directions become parallel to the absolute plate motion for various parts of the PSP. The fast directions along subduction zones around the PSP are predominately trench-normal. The relatively simple patterns of azimuthal anisotropy may imply that the observed anisotropy originates from the A-type LPO of olivine fabric at shallow depths in the back-arc region and with slab-entrained mantle flow at deep depths.
Summary(Plain Language Summary, not published)
Long-period seismic waveforms from earthquakes around the Philippine Sea plate were collected and analyzed to obtain the seismic velocity structure of the region. The pattern of seismic waves travelling at different speed along different directions (known as the azimuthal anisotropy) was also delineated from the waveform data. Our results indicate that both the velocity structure and azimuthal anisotropy in the 3 marginal basins are significantly different from those along the surrounding subduction zones. The distinctive characteristics are strongly related to the geological evolution history of the region.