IASPEI - Picture Gallery

IUGG XXIV General Assembly July 2-13, 2007 Perugia, Italy
(S) - IASPEI - International Association of Seismology and Physics of the Earth's
Interior
JSS014 Oral Presentation 2254
Amurian a nassiance plate: new GPS result supplemented by geological
and geophysical evidence
Prof. Xu Houze
Key Laboratory of Dynamic Geodesy Institutes of Geodesy and Geophysics, CAS IAG
Xiong Xiong, Pil-Ho Park, Teruyuki Kato, Jun Li
The tectonics and plate geometry in northeastern Asia has been a long-standing question, with a major
issue being whether the Amurian plate (AM) is better regarded as part of the Eurasia or as a separate
block. Complicated tectonic features, diffuse seismicity and poor coverage of GPS sites lead to ambiguity
for determining the boundary of the AM. The surprising increment of GPS sites operated in eastern Asia
in recent decade motivated in 2004 the start of a multilateral cooperation between the Institute of
Geodesy and geophysics, Chinese Academy of Sciences, the Earthquake Research Institute, the
University of Tokyo, and the Korea Astronomy and Space Science Institute. The cooperation resulted in
a regional GPS network covering the proposed AM and surrounding areas. The data spanning 6 years
(2000-2005) of 77 GPS sites, including 52 permanent and 25 yearly-surveyed ones, were compiled and
processed by GAMIT/CLOBK software. The obtained velocities combined with published results yielded a
consistent velocity map of the present-day crustal movement in northeast Asia, based on which the
kinematics of the AM was discussed. The Eurasia-fixed Euler vector of AM, which was estimated with
velocities at 12 sites on the stable part of the proposed AM, is located at 121.721.85oE and
60.6530.87oN, with a rate of 0.10210.002 deg/ma taking counterclockwise rotation as positive. The
independence of the Amurian plate from the Eurasia was checked by statistical test. The results
indicated that, in 95% confidence limit, the AM, comprised by the eastern Mongolia, southwest Russia,
northeast China, Korean peninsula, is independent from the Eurasia. The southwest Japan and north
China can be excluded from the AM. The western boundary of AM is defined by a diffuse deformation
zone ranging between Mogolian Altai to the west and Hangay Plateau to the east. The southern
boundary runs along extension basins in front of the south margin of the Yinshan-Yanshan Mts, and
extends along Zhangbei-Shangzhi blind earthquake fracture belt. The kniematic results are consistent
with geological and geophysical evidence, which suggest that the AM is a naissance plate with Stanovoy
range and Baikal Rift zone as matured boundaries to the north and northwest, and developing
boundaries to the south and west.
Keywords: amurian plate, naissance plate, gps