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 2309
Tectonophysical model of Tersko-Sunja segment of East Ciscaucasia based
on seismostomography and lineament analysis.
Mrs. Galina Ivanchenko
Institute of Geospheres Dynamics Researcher IASPEI
The geodynamic situation in East Ciscaucasia in a fragment of the Scythian plate between Pericaspian
rigid lithospheric inclusion and collision zone of the Great Caucasus is determined by horizontal
compression. The area is in high tectonic stress condition and is deformed actively enough. Along the
Caucasian ridge in a sedimentary cover the thrust series of N -Q age are developed. Reversed fault
thrust character is established for Karpinsky Range (inversion structure at southern edge of the East
Europe platform) tectonic boundaries. Intensity and style of deformations appreciably differ in the
different strips of north - northeast (antiCaucasian) trend differentiated by elongated fracture zones.
Usually it is activated fracture zones of the basement. The fragments of these zones are well fixed by
geophysics. Many modern fractures, zones of localization of deformations and structural lines are
established automated space image interpretation on technology LESSA. The area between the
Caucasian ridge and Karpinsky Range is in a condition of strong compression and proceeding folds and
thrust deformations of a sedimentary cover. The analysis and new interpretation of seismic records have
allowed allocating in area Tersko-Sunja zone the set of earthquakes with deep the centers more than 70
kms [Godzikovskaja A.A. 1988]. Presence of such earthquakes, alongside with mantle earthquakes
under the central part of Caspian sea, will be coordinated well to geodynamic model according to which
deep shift or embryonic subduction zone, probably is formed here. We shall note, that it is cut in the
west by an extended cross-Caucasian fracture zone of the north - northeast trend being also border of
blocks with a various seismic mode. Seismotomographic analysis of Tersko-Sunja zone has shown a
presence of structural heterogeneity in a transverse section, interpretive as a underthrust fault under
the Caucasian ridge or thrust of a ridge on the Scythian plate, and heterogeneity of other type in a
section along a ridge, interpretive as segmentation of underthrust fault zone. The presence of highvelocity
anomaly under the Caucasian ridge on depths of 40-70 kms in a zone of the greatest gradients
of a relief also does not contradict the given assumption. A set of thrusts, reversed faults and folds
compensate in a sedimentary cover above the surface of detachment the movement of Transcaucasian-
South-Caspian block (subplate) to Eurasia which is probably realized in depth by embryonic subduction
zone. At least, under the Scythian plate the thickening of the crust compensating to deformation in a
sedimentary cover is not fixed, though subduction or underthrust fault mechanism in continental
conditions is limited enough and cannot accept scales of normal subduction of oceanic crust.
Keywords: seismotomography, lineament, subduction