International Geologiical Congress - Oslo 2008

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EIL-06 Seismic anisotropy and deformation of the crust and mantle

 

Anisotropy of elastic properties of rocks, anisotropic wave fields and rhythm of lithospheric tectonic layering

 

Vadim Il'chenko, Geological Institute of the Kola science Centre of RAS (Russian Federation)
 

 

Results of multiple measurements of elastic properties anisotropy of core samples from the Kola Superdeep borehole, Finnish research borehole in Outokumpo area and samples from the surface, studied by means of acoustopolariscopic method, have been analyzed. It is established that variations of anisotropy of elastic properties in the investigated samples have wavy distribution along boreholes and cross-sections. The obtained information confirms previous assumption of the author that wave component takes place in a whole complex of forces responsible for appearance of anisotropy in rock massifs and rhythm in tectonic layering of lithospheric blocks.
The supposed nature of the given phenomenon is caused by constant influence on rocks of anisotropic deformational wave fields. Such fields can result from action of deformational standing waves in lithospheric blocks, caused by dynamic block interaction and the tidal waves arising in the lithosphere because of the Earth rotation and its gravitational planetary (the Sun-Moon flow) interaction. Another situation is also possible which is also caused by variations of geodynamic situations in separate parts (as well as occurrence of standing waves) - appearance of wave fields because of an interference of the deformational waves coming from separate marginal parts of the lithospheric block, which are zones of the most rigid contacts with the next blocks.
The standing wave has a peculiarity which assumed appearance of different parts in a solid medium: so called nodes (without oscillation of particles) and untinodes (where amplitudes of particle oscillation are maximal). As a result of long-term influence of anisotropic deformational-wave field on lithospheric block (which is under its own stress-deformed state caused by gravitation forces and collisional interaction with the next blocks) the tectonic layering inevitably arises in the block caused by distinctions in dynamics of node and untinode zones.
The geometry of systems of tectonic layering of the lithospheric block will depend on its stress-deformed conditions (caused by a geodynamic situation) and interference picture obtained as a result of composition of standing waves acting in the block.
The work is supported by RFBR grants 11 00-05-64057, 03-05-64169, 07-05-00100.

 

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