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11.
A. A. Lukk V. G. Leonova V. I. Shevchenko 《Izvestiya Physics of the Solid Earth》2008,44(12):965-1001
Detailed estimates of seismotectonic strain (STS) characteristics are obtained for the upper crust from focal mechanisms of numerous earthquakes (M ≥ 1) in the northern and axial parts of the Tajik Depression (the Garm area, Tajikistan). It is shown that, in the majority of cases, a close interrelation exists between tectonic structures and the STS type. Changes in the STS characteristics in various areas of the depression admit a reasonable geological interpretation. Based on geological, seismological, and geodetic data, a unified scheme of deformation of layered rocks of the Tajik Depression is presented. The main factor controlling the deformation process is the extrusion of the rocks in the axial part of the depression in the NNW and SSE directions (with the formation of imbricate thrusts) and in the WSW direction. The latter case is characterized by left-lateral motions in fault zones in the south of the depression (including the Darvaz fault) and by right-lateral motions in northern zones (the Peter the First Range) located from seismological data. In our opinion, such expulsion is caused mainly by an increase of the volume of layered rocks in the Tajik Depression, apparently due to deep fluids penetrating into these rocks and supplying additional mineral material. However, it is also possible that the region is influenced, to an extent, by the general subhorizontal N-S compression associated with the convergence of the Indian and Eurasian lithospheric plates in accordance with the concept of plate tectonics. 相似文献
12.
Izvestiya, Atmospheric and Oceanic Physics - A Review of published space geodetic data for Southeast Asia has been used to confirm the assumption that the central part of the region (the Sunda... 相似文献
13.
The available geological, gravimetric, and seismological data suggest that island arcs, deep-sea trenches, and seismofocal zones of Indonesia (as a part of the Alpine-Indonesian mobile belt) differ significantly from structures of the same names of the Pacific ring proper. Thus, seismofocal zones of the ring are characterized by the stress-strain conditions of subhorizontal across-strike compression at depths of 0–400 km. In seismofocal zones of the mobile belt, such conditions exist only in the depth interval ～(0–40) km. At depths of about 40 to 400 km, lengthening (the T axis) is oriented along the dip-updip direction of a zone, whereas shortening (the P axis) is oriented along the strike of a seismofocal zone or, if individual P axes are not well ordered in this depth interval, they are scattered near the plane normal to the lengthening axis. We relate these distinctions to the fact that the mobile belt inherits a geosynclinal, rather than oceanic, basin that cannot be regarded as a huge bay of the paleo-Pacific. The aforementioned data imply that SW Melanesia (the New Guinea Islands, Bismarck Archipelago, and Solomon Islands) includes the recent Bismarck geosynclinal zone located on the strike of the Indonesian segment of the Alpine-Indonesian mobile belt. 相似文献
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Izvestiya, Atmospheric and Oceanic Physics - An example of seven seismogenic regions of the world with different conditions of tectonic deformation confirms the reliability of confinedness of weak... 相似文献
15.
The behavior of the Gutenberg-Richter distribution (the frequency-magnitude relation for the earthquakes) in response to advancing the system of seismic observations and applying various methods for estimation of the Gutenberg-Richter b value is studied. The long highly accurate time series of seismological measurements at the Garm geophysical testing site in Tajikistan is an input for the study. We analyzed the data from the detailed catalogue of earthquakes with magnitude M = 0?C5 that occurred within the test site from 1955 through 1992. It is shown that the changes in the design of measurements both as to the number of observation sites and as to the measurement capacities during the development of the seismic network in 1955?C1966 have strongly affected the content of the catalogue. Our study revealed spatiotemporal changes in the minimum magnitude of completeness, which were associated with advancing the design of observations. We have analyzed the accuracy of the calculation of the b value as a function of the reliability of determining the actual minimal magnitude of completeness (the cutoff magnitude) for the catalogue (Mc), the method of calculation of the b value, and the volume of the spatial sample of the earthquakes used. It is established that the pattern of horizontal distribution of the b value is closely correlated to the tectonic structure of the test area, while its vertical distribution distinctly reflects the crustal waveguide at a depth of 9?C17 km, which has been previously revealed approximately in this depth interval according to other seismological data. This suggests that, in the first approximation, the lateral and vertical variations in the b value observed in our study are caused by the changes in the strength properties of the crustal material, namely, by the increased plasticity of the rocks within a thick sedimentary layer and in the waveguide. 相似文献
16.
V. I. Shevchenko A. A. Lukk M. T. Prilepin R. E. Reilinger 《Izvestiya Physics of the Solid Earth》2014,50(1):38-56
At present, the concept of plate tectonics is predominant in the Earth sciences. However, there are also other, less popular ideas concerning the geodynamics of the Earth’s crust/lithosphere. The highly accurate modern geodetic measurements such as GPS, SLR, and VLBI provide a new framework for assessing different standpoints. The results of global-scale geodetic measurements are in close agreement with the global plate tectonic reconstructions. However, the same measurements of regional networks in the Mediterranean part of the Alpine-Indonesian Mobile Belt yield results that disagree with the plate’s tectonic reconstructions for this region. These measurements show that the belt’s width in many areas of Eurasian and African lithospheric plates’ convergence is not decreasing at present, as follows from the plate reconstructions, but increasing. At the same time, the segments of the belt under consideration are in a state of stress characterized by near-horizontal compression oriented across the strike of the belt. This contradiction can only be explained if it is assumed that the formation of the tectonic structure of the mobile belt is related to the active growth of the volume of the bedded rocks of the belt, i.e., of the plate’s convergence zone. This growth is apparently due to the additional mineral material gained by the ascending mantle fluid flows. This implies that local, autonomous dynamic processes are required in addition to the lithospheric plate’s interactions to account for the tectonic deformations observed in the mobile belt. 相似文献
17.
V. I. Shevchenko A. A. Lukk M. T. Prilepin 《Izvestiya Physics of the Solid Earth》2006,42(12):1018-1037
The Sumatra (Indonesia) earthquake of December 26, 2004 (M w = 9.0?9.3), is among the strongest seismic events (occupying the second to fourth place) recorded in the epoch of instrumental seismological observations. In addition, this earthquake appears to be the first event of such a scale for which results of up-to-date high-precision geodetic measurements are available. Therefore, it is of particular interest for studies of geodynamics of mobile belts, seismogenic zones, and the Earth’s crust as a whole. The available geological, geophysical, and geodetic data for the Mediterranean-Caucasian segment of the Alpine-Himalayan mobile belt, the Greater Caucasus, and the Tajik depression suggest that the tectonic structure, geological zonality, seismicity, and present-day geodynamics of these structural elements of the Earth’s crust are controlled by the interaction of two different mechanisms of tectogenesis. First, this is the mechanism of independent self-development of the aforementioned structural elements and, first of all, the mobile belt as a whole; this mechanism acts through an intense increase in the volume and area of laminated rocks of the crust/lithosphere, apparently, due to the influx of additional mineral material supplied by an ascending flow of deep fluids. The second type of mechanisms is related to the external plate-tectonic action on the mobile belt and the other structural elements due to lateral movements of lithospheric plates. The joint analysis of geological, geodetic (GPS), and seismological data on the Sumatra earthquake area shows that these two mechanisms also act in the Indonesian part of the Alpine-Himalayan mobile belt. However, the Sumatra earthquake itself is a result of an independent (unrelated to plate tectonics) process in the mobile belt rather than the convergence of adjacent lithospheric plates. 相似文献
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19.
Shevchenko V. I. Krupennikova I. S. Lukk A. A. 《Izvestiya Physics of the Solid Earth》2021,57(6):825-833
Izvestiya, Physics of the Solid Earth - Abstract—The leading role in geotectonics is currently played by the neomobilistic plate tectonic concept which is based on the division of the the... 相似文献
20.
The principal seismicity of the Pamirs—Hindu-Kush area is closely related to a high-velocity body in the region. The dimensions of this body, and its relation with the outcrop of a large area of Precambrian shield-like terrain suggest that it may be the rigid downward extension of a piece of old shield, and that the concentration of stress around its eastern extremity is the source of the anomalous intermediate seismic activity of the region. 相似文献