HR: 1340h
AN: T43C-1343    [Abstracts]
TI: The Stress Field and Structure-Forming Processes Caused by Density and Topography Variations in the Pacific Continent-Ocean Transition Zone.
AU: * Maslov, L A
EM: leo.maslov@ojc.edu
AF: Computing Center RAS, 65, Kim Yu Chen Str, Khabarovsk, 680000 Russian Federation
AU: Gilmanova, G Z
EM: gulya@as.khb.ru
AF: Pacific Oceanological Institute, 43, Baltyiskaya Str, Vladivostok, 690041 Russian Federation
AU: Sirnekov, D A
EM: sbrbd@mail.ru
AF: Computing Center RAS, 65, Kim Yu Chen Str, Khabarovsk, 680000 Russian Federation
AB: The subduction is considered as one of the most important external forces in modeling structure and activity of the transition zone from continent to ocean, while much less attention is paid to body forces acting inside this zone. Analytic solutions of the following problems have been obtained and analyzed: an elastic layer of variable thickness on an inviscid Newtonian liquid (2D problem); a viscous layer of variable thickness on an inviscid Newtonian liquid (2D problem); thin elastic plate on an inviscid Newtonian liquid (3D problem). Other analytic solutions were applied to study structure and geodynamics of a transition zone (Mindlin and Boussinesque problems) for arbitrary variations of density and surface loads (3D problems). The source of stresses and movements in the above problems is the volumetric forces created by the gravitational field of the Earth. No other forces were taken into consideration. Computer programs were written for calculations of stress field and displacements for the problems listed above. Formulas, relating the outer gravitational field anomalies and stress field components generated by density and topography variations of these layers were obtained. Stress distribution for variations of density and topography typical for a zone of transition, as well as for deep sections of the Earth's crust and the upper mantle in the Eastern part of the Asian continent, the Sea of Japan, and the Philippine Sea have been calculated and analyzed on a base of the above solutions. The common features of those stress fields, typical for all models, were observed. They are: (1) tension in the continental part of the model, (2) compression in the oceanic part of the model and (3) there is a narrow subvertical zone of high shear stresses acting downward under the continental part of the model. Can it be a seismofocal zone? The slope of this zone depends on the degree of isostatic compensation of the crust. The magnitudes of the stresses are high enough to produce fractures in the Earth's crust, forming deep faults and initiating a series of tectonic events. Thus, density and topography variations of the Pacific continent-ocean transition zone are responsible for major structure forming processes within this area. On the other hand, magnitudes of horizontal and vertical rates of displacements produced by density and topography variations of the transition zone are rather low to fit the observed lithospheric plates kinematics. A number of geotectonic models is considered by taking into account the influences of external factors on the crust and upper mantle of the transition zone to receive quantitative conformity of the theoretical to the observable data.
DE: 3210 Modeling
DE: 1212 Earth's interior--composition and state (8105)
DE: 1219 Local gravity anomalies and crustal structure
DE: 1234 Regional and global gravity anomalies and Earth structure
DE: 1236 Rheology of the lithosphere and mantle (8160)
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting