Suchergebnisse

This article describes the fluidolite's breccias which are located in the Darial Gorge of the North Caucasus. Fluidolite's breccias are connected with explosive eruptions in the Late Pleistocene and caused decompressive explosions of high fluidized magma at small depths.

The Qilian Mountains, as the northeastern margin of the Tibetan Plateau, absorbed the crustal shortening and accommodated the left-lateral displacement of the Altun Tagh fault. Detailed geomorphologic study of river valleys on the northern margin of the Qilian Mountains showed that since the late Pleistocene the crustal uplift rate of the northern Qilian Mountains has been greater than the central part. Due to the extension of the Tibetan plateau between the Changma fault and the Yumen fault the latest belt of faults and folds was formed on the northern margin of the Qilian Mountains. The study of the height of river terraces over the past 60 thousand years shows that the rate of vertical displacement along the Changma fault is 0,31±0,06 mm/a and its horizontal crustal shortening rate is 0,11±0,02 mm/a. The rate of vertical displacement along the northernmost Yumen fault is 0,33±0,02 mm/a and its horizontal crustal shortening rate is 0,53±0,03 mm/a. Active faults in the western segment of the northern Qilian Mountains account for 12% of the total crustal shortening in the Qilian Mountains. In addition, the crustal shortening rate of faults in the northern Qilian Mountains is much greater than the crustal shortening rate of faults inside the Qilian Mountains, which further indicates that since the Late Pleistocene the crustal uplift rate of the northern Qilian Mountains has been greater than the central Qilian Mountains.

Longmen Shan fault zone is located in the special joint between the Triassic Songpan-Ganzi orogen of the Qinghai-Tibetan Plateau and the stable Sichuan basin of the Yangtze platform. In this region there are four major active faults and three tectonic nappes. According to the analysis of neotectonics and historical earthquakes the Longmen Shan fault zone is a dangerous earthquake belt. The rupture system of the Wenchuan earthquake is characterized by thrust and dextral strike-slip movement.

The article considers the distribution of different ages volcanic formations of Elbrus volcano, PaleoElbrus and autonomous eruption centers within the modern volcanic structure of Elbrus and its environs. The proposed generation sequence of these volcanogenic formations is shown, which was established using the geomorphological method by the morphology of the lava flows' surface, as well as by the ratio of volcanogenic formations to each other, with Quaternary deposits of other genetic types, and with landforms.

On the basis of new materials this article deals with the structure and origin of a huge (up to 2 km) thick massif of acidic volcanic rocks located in a volcanic-tectonic depression in the Upper Chegem River in the North Caucasus. Discussion on the lava's, rather than pyroclastic, origin of the main part of the rock mass as a result of repeated outpourings of lava flows, which formed the series of acidic volcanic rocks without interruptions with perfectly pronounced columnar jointing in a limited volume of a deep volcanic-tectonic depression, which was forming simultaneously with eruptions in the Late Pliocene. Volcanic rocks formed as a result of boiling silicate meltas the exit from the vent, which could be due to the nature of the phase transition of the supercritical water fluid.

The inefficiency of short-term forecasting of strong earthquakes is obvious. New methods and hypotheses of preparation of seismic events are interesting, but exact and reliable forecasts will not follow. Unpredictability is undoubtedly predetermined by nonlinearity, self-similarity, by a chaotic (not stochastic) and by bifurcations dynamics of seismic process in fractal geomedium. Superdependence of dynamic systems on initial conditions, vagueness of distinctions of background and abnormal structures and conditions, at rigid requirements to adequacy and representativity of forecasts, inevitably lead, to the negative decision of a problem. This article continues the long-standing scientific discussion about earthquake prediction, which was resumed after the our publication [Koronovsky et al., 2019].

The modern conditions, the received results and possible prospects of short-term forecasting of strong earthquakes are analysed. On examples of concrete researches it is shown, that such forecast with a required detail, accuracy and reliability is not carried, and is not expected in the future. It is fundamental consequence of nonlinearity of the seismic geodynamic systems functioning deterministically-chaotically in the fractal geologic medium. Effectiveness of forecasting in the form of attitude of number of successfully predicted earthquakes to number of registered ones on some certain area is not above several percent. Frequent messages about ostensibly reached almost 100%-s' of effective short-term forecasting are denied by absence of adequate reliable methods, and by steady extension of the list of the not predicted seismic catastrophes.