042.doc
Application of Multi-Satellite Altimetry Data to Submarine Tectonic and
Geodynamic Study in West Pacific
Gao Jinyao，Jin Xianglong，Sun Peng
2nd Institute of Oceanography & Key Lab of Submarine Geosciences, SOA,
Xixihexia No.9, Hangzhou, Zhejiang, 310012, CHINA.
E-Mail:
jygao@mail.hz.zj.cn.
Phone:
+86-571-88076924-2315.
+86-571-88836690
Fax:
Through synthetic processing of altimetry data from Geosat, ERS-1/2 and
Topex/Poseidon, various kinds of 22 digital models for the Earth gravity field have
been calculated in the West Pacific, located between 0-45N, 100-150E. Compared
with the EGM96 geoid model, high frequency components from the multi-satellite
altimetry geoid is much more sensitive to submarine tectonic features. Within the
Philippine Sea and the South China Sea, short wavelength lineations of the geoid
undulation are found to be parallel or cross to the magnetic lineations and the rifting
ridges. According to geoid residue, gravity anomaly and topography, spreading ridges
can distinguished from common seamount chains. Some trench-arc tectonic trails are
hardly characterized by topography, but they can be discovered by gravity anomaly.
Subducting intensity with its resistant compression are different along different
segment of trench-arcs. The Moho depth among marginal sea basins goes shallow
southward, and their values are close to the Philippine Sea. These evidences mean that
strength of tectonic activities are almost the same in both sides of the
Ryukyu-Taiwan-Philippine arc.
The stress field from small scale of mantle convection is reasonably calculated from
the isostatic geoid undulation. The EGM96 geoid model of harmonic coefficients with
topography/isostatic correction is decomposed to calculate the large and middle scale
of mantle convections, which could be restricted in lower and upper mantle
respectively. Consistent with the rift of the Eurasian plate and the northwestward
spread of the Pacific plate, the stress field from large scale of mantle convection
displays a skeleton of dumbbell shaped with sinistral compresso-shear at the north,
dextral compresso-shear at the south and slip in the middle. Energy converge strong at
the south is attributed to the northward movement of the Indian ocean. The stress
fields from middle and large scales of mantle convection may jointly lead to the
northwestward rifting of Japan, the southeastward rifting of Sea South China Sea, and
specific tectonic features of the Ryukyu and Philippine arcs. Activation of the South
China Sea basin could become stronger and later eastwards. Stress fields from small
scale of mantle convection appear to converge in Okinawa Trough and Mariana
Trough, and such a case may demonstrate the geodynamic process and feature of
basin and trough evolution of marginal seas.
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