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[en] Full text: Character of the spread of the plate-tectonic structures of Paleotethys and its oceanic basins including plan and age of the deformation as well as relation between Paleotethys and Mesotethys and the other issues are urgent debatable problems of the Paleozoic-Triassic geology in the region. As a result of complex geologic, magmatic, tectonic, paleo bio geographic, geophysical and cosmotectonic studies in the Caucasus, Zacaspian and Iran there were constructed geo dynamic maps on the paleo tectonic basis for certain time sections starting from the Cambrian transition stage till the Triassic models of Paleotethys evolution for two near-meridional geo traverses Arabian margin of Gondwana and in the north it crosses the East-European platform. In the Cambrian the change of the carbonaceous facies by the arkosicsandstones and quartzites in the Gondwana and in the East-European platforms is associated with the absolute elevation and washout of the Caspian-Caucasian shield. This is a precursor of more significant events and processes. There probably occurred a large structural reconstruction in the boundary of the Cambrian and the Ordovician associated with the beginning of the opening of the Caucasian, Turkestan and Ural pale oceans. As a result of the continental riftogenesis that in the next stage is transformed from the rifting into the spreading of the oceanic crust the double deep-water basins of Paleotethys were separated. The closure of neo-Paleotethys in the late Triassic was preceded by the crack of Gondwana and location of a system of the branching rifting and spreading of Mesotethys
[en] Plate tectonics governs the topography and motions of the surface of Earth, and the loss of heat from Earth's interior, but appears to be found uniquely on Earth in the Solar System. Why does plate tectonics occur only on Earth? This is one of the major questions in earth and planetary sciences research, and raises a wide range of related questions: has plate tectonics ever occurred on other planets in the past? How did plate tectonics start on Earth? Will it ever end? In the absence of plate tectonics, how do planets lose their heat? This article provides a brief introduction to the ways in which planets lose their heat and discusses our current understanding of plate tectonics and the challenges that lie ahead
[en] One of the most efficient methods of great earthquakes prediction is the one based on measurements of the earth surfaces inclination. The efficiency of this method consists in the direct connection between inclination an focal mechanisms occurring previously a to the main shock. Tectonic plates subduction produces rocks deformation which generates very small inclination of the earth surface. (authors)
[en] Global seismic tomography of the subduction zones shows that the subducting slabs could either stagnate around the 660-km discontinuity, or penetrate into the lower mantle. The stagnating slabs also have various morphologies. These are directly related to the interaction between the subducting slabs and the mantle transition zone (MTZ), the dynamics of which are still debated. Using a 2-D thermo-mechanical model, we systematically investigated the modes of subduction in the mantle transition zone and explored the key constraints of various subduction styles. Four basic subduction modes are obtained in the numerical experiments, including one with slab penetrating through the 660-km discontinuity and three other modes with slab stagnating in the MTZ (i.e. folding, lying and rolling-back). The numerical models indicate that the age of subducting oceanic plate, the thickness of overriding continental lithosphere and the convergence velocity play crucial roles in the dynamics of subducting slab and MTZ interaction. In general, the young subducting slab favors the penetration or folding mode, whereas the old subducting slab tends to result in lying or rolling-back mode, although other parameters can also affect. Our models also show a strong correlation between the subduction mode selection and dip angle of the slab tip when reaching the 660-km phase boundary.
[en] Rotating, growing microplates are observed in a wax analogue model of sea-floor spreading. Wax microplates are kinematically similar to sea-floor tectonic microplates in terms of spreading rate and growth rate. Furthermore, their spiral pseudofault geometry is quantitatively consistent with Schouten's oceanic microplate model. These results suggest that Schouten's edge-driven microplate model captures the kinematics of tectonic microplate evolution on Earth. Based on the wax observations, a theory for the nucleation of overlapping spreading centres, the precursors of tectonic microplates, is developed
[en] Our understanding of earthquakes is based on the theory of plate tectonics. Earthquake dynamics is the study of the interactions of plates (solid disjoint parts of the lithosphere) which produce seismic activity. Over the last about fifty years many models have come up which try to simulate seismic activity by mimicking plate plate interactions. The validity of a given model is subject to the compliance of the synthetic seismic activity it produces to the well known empirical laws which describe the statistical features of observed seismic activity. Here we present a review of one such, purely geometric, model of earthquake dynamics, namely The Two Fractal Overlap Model. The model tries to emulate the stick-slip dynamics of lithospheric plates with fractal surfaces by evaluating the time-evolution of overlap lengths of two identical Cantor sets sliding over each other. As we show later in the text, some statistical aspects of natural seismicity are naturally captured by this simple model. More importantly, however, this model also reveals a new statistical feature of aftershock sequences which we have verified to be present in nature as well. We show that, both in the model as well as in nature, the cumulative integral of aftershock magnitudes over time is a remarkable straight line with a characteristic slope. This slope is closely related to the fractal geometry of the fault surface that produces most of thee aftershocks. We also go on to discuss the implications that this feature may have in possible predictions of aftershock magnitudes or times of occurrence.
[en] The temporal seismicity change in two seismically active zones around Hokkaido, northern Japan was investigated using the statistical estimate of the seismicity level (SESL’09) procedure. Hypocenter data provided by the Japan Meteorological Agency from 1960 to 2013 were analyzed. The seismicity of two geographically different zones, formed by Pacific Plate subduction and Amurian Plate convergence, showed different statistical characteristics. Low cross-correlation values between the two zones also suggest independent seismic processes for each area. However, an anomalously high cross-correlation period was identified from 1996 to 2000, with a time lag of 8 weeks. A 6-month seismic quiescence period before the strongest Hokkaido Toho-Oki Earthquake (4 October 1994, Mj 8.2) was observed on the Pacific side.