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
JSS001 Poster presentation 1729
Reconstruction of the complicated stress state of a massif using data of
elastic anisotropy as well as structural and textural measures of rocks
Dr. Valery Korchin
Physical Properties of the Earth's substance S.I.Subbotin Inst. of Geophysics of NASU IASPEI
Burtny Peter, Karnaukhova Elena
The crystalline rocks usually form textures by irreversible changes of mineral matter under the effect of
stress fields, temperature and different geochemical processes. The rocks may "flow" at definite PTparameters
in the deformation process and form here with structures with linear, planar and linearplanar
orientation of crystals, grains, detests. The structural and textural characteristics of rocks are
closely related with elastic anisotropy. According to the character of the anisotropy of the physical
parameters of the textured media, the latter may be differentiated by the classes of symmetry
associated with the history of their formation and by the symmetry of the external effects. Аfter having
defined the elastic symmetry of rock it is not difficult to recover the directions of the fields of the
external effects. But the difficulty of these studies consists in distinguishing the causes of the initial
anisotropy of rocks and the inhomogeneity of the change of their elastic parameters in different
directions caused by non-structural features. These problems can be solved by combined studies of
elastic-anisotropic properties of mineral matter in different thermodynamic conditions. Vp was measured
in 9 oriented polyhedrons of rocks and that Vs in 18 directions under hydrostatic pressure and the
programmed PT-conditions corresponding with rock sampling sites. The elastic anisotropy and the
structural and textural features of samples of a core of rocks of the Krivoy Rog ultradeep borehole from
zones of destruction and non-destructed areas will studied. The effect of paleotectonic and
technological stress in rocks on their destruction in boring is founded. The studies show that in their
geologic evolution the rocks (plagiogranites) formed textured structures with clear-cut elasticanisotropic
characteristics typical of transversely isotropic media. Then, under the effect of recent
tectonic processes characteristic of synclinea, structural transformations of the rock occur that are
detected by petrographic studies as secondary changes of the initial structure or texture and are
marked by elastic anisotropy distortions. The character of the elastic anisotropy of the borehole rocks at
different pressures and temperatures indicates the orientation of the action of tectonic forces not
compensated by lithostatic pressure. Most probable is the orientation of the relaxation of these forces at
an angle of 45 to the borehole shaft. They produce the maximal destructive effect in plagiogranites
when their layering is oriented along the core generant (vertical dip of layering), while the stress is
mainly relaxed in the stratification plane caused by the microckrack orientation and micropore
localization under the effect of recent tectonic stress and movement. In the crushing zone, the rocks
most probably experience the effect of tensile stress (unlike the overlying layers) due to under thrust,
which also favour the borehole shaft destruction during discovering of these horizons by boring.
Keywords: high pressure and temperature, anisotropy