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 Poster presentation 2281
Can Amurian plate be discriminated from Eurasia: results from significance
tests
Mrs. Dongmei Guo
Institute of Geodesy and Geophysics Chinese Academy of Sciences IASPEI
The independence of the Amurian Plate (AM) has been being an important issue of the geodynamics
since the AM was proposed as a microplate within the Northeast Asia. Based on statistical methods, we
conducted significance tests to investigate whether the AM is one part of the Eurasia (EU) or a separate
block which is independent from EU. Furthermore, the ambiguous southern boundary of the AM is
determined by statistical approaches. A consistent velocity field, which was employed as the database
for significance test, was obtained by combining some new results of the ongoing China-Japan-Korea
cooperative project and published ones. The velocities at GPS stations in the eastern Mongolia and
Northeast China, that is believed to be the core stable part of the AM, were used to define the AM-EU
Euler vector, with 55.7074N and 130.7404E as the pole and 0.093o/Ma as rotational rate taking
counterclockwise as positive. The significance test with 2-test method indicated that the AM is
independent from the EU at a confidence level of 95%. In order to define the domain of the AM, we
conducted significance test to check the differential movements between the core part of the AM and
surrounding areas, including North China (NC), South China (SC), Western Mongolia(WM), Southern
Korea (SK) and Southwestern Japan (SWJ). The F-test and 2-test were used to investigate the
differential movements between adjacent plate-pair, while the AIC (Akaike Information Criterion) was
employed to test the independence of blocks within a multi-block system. The significance tests with F-
test、2-test and AIC methods reached the consensus that there is significant relative movements
between the AM and the NC, SC, WM and SWJ, while neglectable relative movement between the AM
and SK. Therefore, we suggested that the SK is one part of the AM, and the others are independent
from the AM. By statistical methods, we tried to define the southern boundary of the AM, which is very
ambiguous due to complicated tectonic features and diffuse seismicity. We selected an area ranging
from 110 oE to 135oE in EW and 36 oN to 50oN in NS, and covering the AM and NC to investigate the
exact location of the southern boundary. Since the AM-NC boundary is almost E-W trending, we
assumed a boundary located at latitude of 36 oN and calculated c2 value. Then, we calculated c2 values
with different locations of the assumed boundaries with and increment of 15′ in latitude. In the c2
values-latitude plot, the latitude corresponding to the minimum value of c2 was suggested to be the
location of the AM-NC boundary, which runs along northern margin of Erdos and Zhangbei earthquake
belt.
Keywords: amurian, significance tests, boundary