Late Cenozoic faulting and the stress state in the south-eastern segment of the Siberian platform

There is a description of the results of studies of deformation regimes and reconstruction of stress fields of certain time intervals of the Mesozoic – Cenozoic history of the western part of the Tien Shan based on the geological and structural data and earthquake focal mechanisms. The relevance of research is determined by the existing difficulties in the age reference of paleostress fields, which is associated with the retrospective nature of the initial data and the features of geological evolution, as well as the existence of controversial, unresolved issues regarding the development of the western periclinal part of the Tien Shan in the Mesozoic – Cenozoic. The aim of the research is to reconstruct the rank components of paleostresses in the earth’s crust in the western part of the Tien Shan at separate stages of the Mesozoic – Cenozoic development. The time intervals for which the stress field diagrams were obtained represent cyclically manifested phases of the first-rank rhythms, which are characterized by alternation of different deformation modes. The method for reconstructing paleostresses was based on the concept of the formation of superimposed systems of cracks of various generations, which were sequentially manifested at various stages of the development of deformation processes. Analysis of the data showed that with increasing age of rocks the number of different fracture systems actually increases – the earlier systems are superimposed by the later. At the same time, the characteristic elements in Quaternary rocks manifest themselves in different ways in the older rocks. This allows them to be used for the reconstruction of the Late Cenozoic stress field based on mass measurements of fracturing in rocks of earlier Mesozoic – Cenozoic ages. Based on the step-by-step identification of the heterochronous cracks system and determination of a pair of maxima of the fracture density with asymmetric scattering, region-based diagrams of the first-rank stress fields were obtained for different stages of manifestation of Mesozoic – Cenozoic deformation regimes: 1 – from the Permian-Triassic to the Middle Jurassic; 2 – Middle-Late Jurassic; 3 – Late Jurassic – Early Cretaceous; 4 – Late Cretaceous – Paleocene – Eocene; 5 – Oligocene – Quaternary. The results obtained indicate the alternation of compression and extension phases, first-rank for the region, and give an idea of the main trends in its geodynamic evolution. They can be used in the development of a tectodynamic model of the region.

Section: методика определения возрастныхunclassified

Deformation Regimes and Low-Rank Paleotectonic Stresses of the Western Tian Shan in the Mesozoic – Cenozoic

Umurzakov

2023

“…При этом обычно ограничивались лишь изучением скоростного режима опускания земной поверхности, осредненного на многолетней временной базе. Появление методов космической геодезии [Shestakov et al, 2011;Sankov et al, 2017;Timofeev et al, 2019], абсолютной гравиметрии [Ardyukov et al, 2015;Timofeev et al, 2018] и существующий опыт геодинамических исследований позволяют выходить на миллиметровый уровень непрерывного определения 3D-смещений, существенно увеличивать базу измерений и рассматривать движение флюидов в пластах. Так, в последние десятилетия появился 4D-микрогравиметрический метод, позволяющий вести мониторинг процесса заводнения на газовой шапке коллектора месторождения на Аляске (Prudhoe Bay) [Ferguson et al, 2008].…”

Section: некоторые особенности современных техногенных движений земной корыunclassified

“…И СЕЙСМИЧНОСТЬ Известны два региона на юге Сибири, отличаю щиеся природной сейсмичностью, -Байкальский и Алтае-Саянский [Melnikova, Radziminovich, 1998;Sankov et al, 2017;Imaeva et al, 2017;Dobrynina et al, 2019]. Кратко остановимся на некоторых особенностях Алтае-Саянского региона.…”

Section: наблюдения в зоне водохранилищunclassified

Some Features of Current Technogenic Movements of the Earth’s Crust

Тимофеев

Ардюков

Тимофеев

et al. 2021

We describe the history of studying the current crustal movements by various methods and discuss technogenic effects recorded at large water-reservoir zones and mineral deposits in Siberia. Initially, classical surveying techniques aimed to obtain high-accuracy ground-based measurements of height, tilt and direction. Modern geodesy techniques and methods for measuring absolute gravity are now available to investigate displacement, deformation, tilt and other phenomena taking place on the Earth’s surface. These methods are used to estimate kinematic parameters of the crust areas (e.g. rates of subsidence and horizontal movements) and to monitor fluid motions in mineral deposits. Such data are critical for ensuring a proper management of the mineral deposits. In this article, we analyse technogenic processes observed in the Ust Balyk oil-gas field, the Zapolyarny gas deposit, the water-reservoir zone at the Sayano-Shushenskaya hydroelectric power station (SSHPS) on the Yenisei river, and large open-pit mines in the Kuzbass basin. Our analysis is based on surface displacement rates estimated from the data collected in different periods of observations at large man-made facilities. In the study of the hydro technical objects, we estimated the displacement rates at 5.0 mm per year. In the northern areas of the West Siberian petroleum basin, subsidence rates amounted to 20–25 mm per year in the early 2000s. These estimates were supported by the high-accuracy gravity measurements showing an increase up to 6–7 microGal per year in the oil-gas field development areas. We assess a possibility of triggering effects related to weak seismicity due to a high stress accumulation rate (1 KPa per hour) in the SSHPS area. A connection between earth tides and catastrophic events, such as gas emissions in high amounts on mining sites, is discussed. Having analysed the surface monitoring records taken in South Primorye in September 2017, we conclude that underground nuclear explosions in North Korea in this period did not cause any significant displacement of the surface in this most southerly region of the Russian Far East territories.

“…Сведения о разломной тектонике осадочного чехла юга Сибирской платформы представлены на картах и в серии публикаций отечественных геологов [Zolotarev, 1967;Zamaraev et al, 1979;Dubrovin, 1979;Zolotarev, Khrenov, 1979;Khrenov, 1982;Logachev, 1984;Malykh, 1985;Seminsky, Gladkov, 1997;Gladkov et al, 2000;Sizykh, 2001;Arzhannikova, Arzhannikov, 2005;Sankov et al, 2017;и др.]. Они свидетельствуют о существовании в осадочном чехле достаточно редкой сети разрывных нарушений, которая сгущается в пределах Хандинского и Жигаловского валов, располагающихся на востоке и юго-востоке от изучаемой площади.…”

Section: объекты исследованияunclassified

Mapping the internal structures of fault zones of the sedimentary cover: a tectonophysical approach applied to interpret TDEM data (Kovykta gas condensate field)

Семинский

Buddo

Бобров

et al. 2019

The article presents the results of studying the internal structures of platform fault zones with the use of a new tectonophysical approach to processing and interpretation of electrical exploration data obtained by the transient elec‐ tromagnetic method in the near field zone (TEM). In the study of the central part of the Kovykta gas condensate field (East Siberia, Russia), we applied the ideas of tectonophysics envisaging three stages of fault formation, which determine the three‐membered transverse zoning of a fully formed fault zone. Each subzone is characterized by a certain level of rock disturbance and corresponding electrical conductivity. Based on the analysis of electrical conductivity values, the boundaries can be determined between locations differing by the degrees of rock disturbance of the sedimentary stra‐ tum. Using a map of this parameter, it becomes possible to generally establish the boundaries of fault zones and specify internal subzones. The new approach was applied to assess the electrical conductivity of the reservoirs of the Kovykta field. It is established that there are several zones of faulting in the sedimentary stratum, which have not reached a final stage of development when a single fault plane is formed. Currently, these are zones of increased fracturing and dense occurrence of second‐order ruptures that are typical of platform settings due to their relatively weak tectonic activity. The zones are structurally non‐uniform, as evidenced by rheological layering of the sedimentary cover in the vertical cross‐section. A 3D electrical conductivity model of the largest fault zone in the study area shows alternating segments with more or less developed internal structures. Such segments are confined to layers that differ with respect to frac‐ turing. Exploration and development of hydrocarbon deposits can benefit from 3D modeling of large fault zones with the use of the tectonophysical approach for processing and interpretation of the TEM data. The models can provide addition‐ al arguments for improved decision making about locations for trouble‐free well drilling, as well as for selecting more effective methods for drilling sedimentary strata composed of complex horizontal layers.