HR: 1340h
AN: T43B-1342    [Abstracts]
TI: The tectonic stress field variation along Ryukyu subduction zone
AU: * Lo, C
EM: lo.chungliang@gmail.com
AF: Insititue of Geophysics, NCU, No.300, Jhongda Rd., Jhongli, 32001, Taiwan
AU: Wu, W
EM: 93642002@cc.ncu.edu.tw
AF: Insititue of Geophysics, NCU, No.300, Jhongda Rd., Jhongli, 32001, Taiwan
AU: Chao, B F
EM: bfchao@ncu.edu.tw
AF: Insititue of Geophysics, NCU, No.300, Jhongda Rd., Jhongli, 32001, Taiwan
AU: Hsu, S
EM: hsu@ncu.edu.tw
AF: Insititue of Geophysics, NCU, No.300, Jhongda Rd., Jhongli, 32001, Taiwan
AB: The Ryukyu Trench where the Philippine Sea Plate (PSP) subducts beneath the Eurasian Plate (EP) is distributed from Taiwan to Japan. Behind the Ryukyu Trench, the Okinawa Trough is rifting actively. Hence the convergent and divergent plate boundaries have produced enormous earthquakes. The earthquake behavior is complicated due to the complexity of trench-arc-backarc tectonic system. To better understand the stress field along Ryukyu subduction zone, we apply the damped stress inversion technique (Hardebeck & Michael, 2006). The earthquake catalogue of F-net broadband Seismograph Network of Japan will be used in this study. To avoid the uncertainty of deep earthquakes induced by subduction slab, only earthquake shallower than 35 km deep will be adopted. The preliminary result shows that both σ₁ and σ₃ stress fields display anisotropy along Ryukyu system. Most of σ₁ azimuths in the Ryukyu Trench region have high plunge angles (~ 30° to 60°) and are oblique to trench orientation, however, have near horizontal plunge angles and are parallel to trench orientation at 129.5°E, 24.5°N. Across the Ryukyu Trench, most azimuths of σ₁ in Okinawa Trough display high plunge angle, but also have a perturbation close to 126°E, 26.5°N. Based on the GPS data, both horizontal and vertical velocity fields show that crustal deformations behave different between southern and northern Ryukyu Arc. The combined stress field and crustal velocity fields imply that the Ryukyu subduction zone could be segmented into two parts.
DE: 3040 Plate tectonics (8150, 8155, 8157, 8158)
DE: 7230 Seismicity and tectonics (1207, 1217, 1240, 1242)
DE: 7240 Subduction zones (1207, 1219, 1240)
DE: 8150 Plate boundary: general (3040)
DE: 8164 Stresses: crust and lithosphere
SC: Tectonophysics [T]
MN: 2007 Fall Meeting