HR: 0800h
AN: GP41A-0836    [Abstracts]
TI: Relationships Between Seismicity and GPS Determined Velocities in Northeast Asia
AU: * Fujita, K
EM: fujita@msu.edu
AF: Michigan State University, Department of Geological Sciences, East Lansing, MI 48824-1115 United States
AU: Sella, G
EM: sella@earth.northwestern.edu
AF: Northwestern University, Department of Geological Sciences, Evanston, IL 60208 United States
AU: Mackey, K G
EM: mackeyke@msu.edu
AF: Michigan State University, Department of Geological Sciences, East Lansing, MI 48824-1115 United States
AU: Stein, S
EM: seth@earth.northwestern.edu
AF: Northwestern University, Department of Geological Sciences, Evanston, IL 60208 United States
AU: Park, K
EM: kdpark@kookmin.ac.kr
AF: Kookmin University, College of Forest Science, Chongnung-dong, Songbuk-gu, Seoul, 136702 Korea, Republic of
AU: Imaev, V S
EM: imaev@crust.irk.ru
AF: Institute of the Earth's Crust, Siberian Division, Russian Academy of Sciences, Irkutsk, 664033 Russian Federation
AB: Published GPS data are equivocal about the existence of the Okhotsk and Amur plates in northeast Asia. Seismicity data, however, clearly delineate these plates, as well as possible additional blocks. The northern boundary of the Okhotsk plate is separated from both North America and Eurasia by diffuse zones of seismicity in northeast Russia. Seismicity in the Magadan region coincides with faults clearly visible in satellite imagery that are left-lateral based on offset rivers and focal mechanisms. The largest earthquakes (~M 5) are associated with specific faults. Although GPS velocities are generally consistent with the motion of North America, their residual velocity (with respect to North America) shows a gradient across this zone of seismicity with relative displacements increasing towards the Okhotsk plate. The eastern boundary of the Amur plate is generally accepted as lying along Sakhalin Island and bordering the Okhotsk plate. However, several bands of north-south seismicity exist west of this boundary along possible extensions of the Tanlu fault of northeastern China. This seismicity extends the Tanlu to intersect with an east-west striking zone of seismicity separating Amur and Eurasia which connects Lake Baikal and Sakhalin. This seismic extension of the Tanlu implies that a small block may exist between Okhotsk and Amur that extends south to include Korea. Although the events are small, the linear and arcuate trends in seismicity clearly imply active motion along specific faults. However, there is no clear signature of active faulting in the geomorphology or geology. GPS sites in eastern Amur are too close to active to constrain block motions, however, additional blocks may be needed in interpreting GPS results from Amur, Sakhalin, Korea, and northeast China, especially given the low velocities with respect to Eurasia.
DE: 7230 Seismicity and seismotectonics
DE: 8107 Continental neotectonics
DE: 8110 Continental tectonics--general (0905)
DE: 8158 Plate motions--present and recent (3040)
DE: 1206 Crustal movements--interplate (8155)
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2004 AGU Fall Meeting