HR: 08:15h
AN: G41A-02    [Abstracts]
TI: Microplate Tectonics in East Asia: Evidence from GPS Velocities and Block Modeling
AU: * Apel, E V
EM: apel@seismo.berkeley.edu
AF: University of California, Berkeley, 307 McCone Hall #4767 University of California, Berkeley, Berkeley, CA 94720-4767 United States
AU: B\"{u}rgmann, R
EM: burgmann@seismo.berkeley.edu
AF: University of California, Berkeley, 307 McCone Hall #4767 University of California, Berkeley, Berkeley, CA 94720-4767 United States
AU: Kogan, M
EM: kogan@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory of Columbia University, Lamont-Doherty Earth Observatory of Columbia University 61 Route 9W, Palisades, NY 10964 United States
AU: King, R
EM: rwk@chandler.mit.edu
AF: Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences 81 Massachusetts Ave. Massachusetts Institute of Technology, Cambridge, MA 02139-430 United States
AU: Vasilenko, N F
EM: kogan@ldeo.columbia.edu
AF: Institute of Marine Geology and Geophysics DVO RAN, Institute of Marine Geology and Geophysics DVO RAN 693022, Yuzhno-Sakhalinsk, 693022 Russian Federation
AU: Levin, V I
EM: kogan@ldeo.columbia.edu
AF: KOMSP GS RAN, KOMSP GS RAN 683006, etropavlovsk-Kamchat, 683006 Russian Federation
AU: Steblov, G M
EM: kogan@ldeo.columbia.edu
AF: Geophysical Service, Russian Academy of Sciences, Lenin Str.,189 Kaluga Region, Obninsk, 249020 Russian Federation
AU: Forlov, D I
EM: kogan@ldeo.columbia.edu
AF: Ioffee Institute of Physics and Technology, Russian Academy of Sciences, 26 Polytekhnicheskaya, St Petersburg, 194021 Russian Federation
AU: Ivaschenko, A I
EM: kogan@ldeo.columbia.edu
AF: Institute of Marine Geology and Geophysics DVO RAN, Institute of Marine Geology and Geophysics DVO RAN 693022, Yuzhno-Sakhalinsk, 693022 Russian Federation
AU: Gordeyev, Y I
EM: kogan@ldeo.columbia.edu
AF: KOMSP GS RAN, KOMSP GS RAN 683006, etropavlovsk-Kamchat, 683006 Russian Federation
AB: The possibility of Okhotsk plate motion independent of the North American plate and Amurian plate motion independent of Eurasia were tested rigorously using velocities from 106 GPS sites (58 from within the proposed Okhotsk and Amurian plate boundaries) in order to constrain the plate kinematics of East Asia. A block modeling approach was used to incorporate both rigid block rotation and near-boundary elastic strain accumulation effects in a formal inversion of the GPS velocities. Considered models include scenarios with and without independent Okhotsk and Amurian plate motion. Our modeling favors a scenario with independent Okhotsk plate motion but does not require it, based on the application of F-test statistics. Euler poles, calculated from our optimized inversion, suggest an independent Okhotsk plate rotating 0.206 deg/Myr clockwise with respect to Eurasia about a pole located north of Sakhalin. The plate-motion parameters of the Okhotsk plate are consistent with right-lateral motion in northern Sakhalin and contraction in southern Sakhalin, inferred from focal mechanism solutions. However, subtle changes in block and segment geometry can cause significant changes in the estimated pole of rotation of the Okhotsk plate. This is due, in large part, to the close proximity of essentially all the GPS stations in the Okhotsk region to plate boundaries, such as the Kamchatka-Kurile subduction zone and Sakhalin Island contraction and strike-slip shear zone. GPS velocities on the Kamchatka peninsula capture a complex pattern associated with the locked subduction zone. This locked subduction zone may require a more complex model than a simple elastic dislocation for the rotational signal to be resolvable. We also considered the possible influence of an independent Amurian plate that may also affect the determination of Okhotsk plate existence and motion. Independent Amurian plate motion is more difficult to formally document than Okhotsk plate motion due to the diffuse and uncertain nature of the continental plate boundaries and the small number of GPS sites in the region. Nevertheless, the best-fit plate motion model of an independent Amurian plate is consistent with the overall kinematics of earthquakes and structures in proposed plate boundary zones along the Baikal rift and the Stanavoy mountains range.
DE: 8107 Continental neotectonics
DE: 8110 Continental tectonics--general (0905)
DE: 8158 Plate motions--present and recent (3040)
DE: 1206 Crustal movements--interplate (8155)
DE: 1208 Crustal movements--intraplate (8110)
SC: Geodesy [G]
MN: 2004 AGU Fall Meeting