Latest structure and geodynamics of Western Caucasus (based on decoding of satellite images)

Геодинамический анализ является важнейшим компонентом регио- нальных геологических исследований. Использование дистанционных методов при геологическом кар- тировании закрытых территорий существенно повышает информативность геологической карты и эф- фективность прогнозно-поисковых работ. Цель работы. В работе рассматривается взаимосвязь рельефа с неотектоническими движениями. Обращается внимание на основные морфологические элементы тер- ритории на разных уровнях генерализации цифровой модели рельефа. Методы исследования. Произ- ведено дешифрирование цифровой модели рельефа, выделены линеаменты различных порядков (зоны селективной эрозии) как реакция экзогенных процессов на новейшие тектонические деформации. Дана геодинамическая интерпретация выявленных структур. Проведены палеогеографические реконструкции положения русел основных рек в плиоцен-голоценовый период. Результаты исследования. Установлено правосдвиговое смещение мозаики тектонических блоков на разных уровнях генерализации, нашедшее отражение в современных деформациях рельефа. Об этом свидетельствуют геометрические характери- стики дешифрируемых элементов, кулисообразное расположение периодических серий линеаментов, косое расположение линеаментов относительно линии главного разлома, ориентированных в соответ- ствии с эллипсом деформации, наложение структур друг на друга. Сдвиг по разлому в доплиоценовом фундаменте находит свое отражение в сложном поле напряжений перекрывающего чехла. Деформации соответствуют сколам Риделя, что подтверждается экспериментами, выполненными другими исследова- телями. Активизация тектонических движений привела к образованию тектонических клиньев, создавших естественные дамбы на пути движения водных потоков, что привело к существенной перестройке геомор- фологии и палеогеографии территории. Выявлена миграция русел основных рек в западном направлении в плейстоцен-голоценовый период, их врезание в подстилающие отложения с образованием висячих до- лин. Relevance. Geodynamic analysis is an essential component of regional geological research. The use of remote methods for geological mapping of closed territories significantly increases the information content of the geological map and the effectiveness of forecast and search operations. Aim. The paper considers the relationship of terrain with neotectonic movements. Attention is drawn to the main morphological elements of the territory at different levels of generalization of the digital terrain model. Method of research. The digital terrain model was deciphered and lineaments of various orders (zones of selective erosion) were identified) as a reaction of exogenous processes to the latest tectonic deformations. Geodynamic interpretation of the identified structures is given. Paleogeographic reconstructions of the position of the main riverbeds in the Pliocene- Holocene period were carried out. Results. The right-hand shift of the tectonic block mosaic at different levels of generalization is found, which is reflected in modern relief deformations. This is evidenced by the geometric characteristics of the elements to be decoded, the rocker-like arrangement of periodic series of lineaments, the oblique arrangement of lineaments relative to the main fault line, oriented in accordance with the deformation ellipse, and the superposition of structures on each other. The fault shift in the pre-Pliocene basement is reflected in the complex stress field of the overlapping cover. The deformations correspond to Riedel chips, which is confirmed by experiments performed by other researchers. The activation of tectonic movements led to the formation of tectonic wedges that created natural dams in the path of water flows, which led to a significant restructuring of the geomorphology and paleogeography of the territory. The migration of the main riverbeds in the Western direction during the Pleistocene-Holocene period, their embedding in the underlying sediments with the formation of hanging valleys, was revealed.

Computationally Efficient Thermo-Mechanical Analysis for Predicting Process-Induced Deformations of Composite Structures

This paper presents an innovative numerical model for the calculation of process-induced deformations of composite structures. The capabilities of a refined one-dimensional model, based on the Carrera Unified Formulation, have been exploited to describe the complex displacement field that originates during the curing process of a composite component. The refined kinematic models adopted are able to describe a three-dimensional solution and make it possible to predict the through-thickness deformation that is one of the causes of the origins of the process-induced deformations. The evolution of the material properties during the curing process is evaluated using the software RAVEN and the manufacturing process is simulated using an ‘incrementally elastic’ constitutive model. The results demonstrate the capabilities of the present approach to predict the process-induced deformations including the complex stress field due to thermal and mechanical loads.

Rupture Directivity Analysis of the 2018 Hokkaido Eastern Iburi Earthquake and Its Seismotectonic Implication

ABSTRACT The Mw 6.6 Hokkaido Eastern Iburi earthquake striking southern Hokkaido Island on 5 September 2018 was a disastrous and peculiar event. In contrast to the usually shallow crustal earthquakes, this event occurred at a hypocentral depth about 37 km, close to the Moho discontinuity. To infer the rupture feature of the 2018 Hokkaido earthquake, we determine focal mechanism and centroid depth of the event with inversion of teleseismic waveforms. The result reveals that the centroid (at depth about 26 km) of this thrust earthquake is shallower than the hypocenter, which suggests the upward rupture propagation and dominant rupture in the lower crust. We also investigate the causative fault and rupture directivity based on waveform modeling. The steeply dipping fault (70°) with strike in the north–south direction is preferred to be the causative fault. The total dimension of rupture is estimated to be about 30 km, based on the aftershock distribution and rupture directivity. We propose that a seismogenic model with low temperature and complex stress field in the lower crust above the subduction‐zone interface may explain this event.

An improved failure criterion for biological and engineered staggered composites

High-performance biological materials such as nacre, spider silk or bone have evolved a staggered microstructure consisting of stiff and strong elongated inclusions aligned with the direction of loading. This structure leads to useful combinations of stiffness, strength and toughness, and it is therefore increasingly mimicked in bio-inspired composites. The performance of staggered composites can be tuned; for example, their mechanical properties increase when the overlap between the inclusions is increased. However, larger overlaps may lead to excessive tensile stress and fracture of the inclusions themselves, a highly detrimental failure mode. Fracture of the inclusions has so far only been predicted using highly simplified models, which hinder our ability to properly design and optimize engineered staggered composites. In this work, we develop a new failure criterion that takes into account the complex stress field within the inclusions as well as initial defects. The model leads to an ‘optimum criterion’ for cases where the shear tractions on the inclusions is uniform, and a ‘conservative’ criterion for which the tractions are modelled as point forces at the ends of the overlap regions. The criterion can therefore be applied for a wide array of material behaviour at the interface, even if the details of the shear load transfer is not known. The new criterion is validated with experiments on staggered structures made of millimetre-thick alumina tablets, and by comparison with data on nacre. Formulated in a non-dimensional form, our new criterion can be applied on a wide variety of engineered staggered composites at any length scale. It also reveals new design guidelines, for example high aspect ratio inclusions with weak interfaces are preferable over inclusions with low aspect ratio and stronger interfaces. Together with existing models, this new criterion will lead to optimal designs that harness the full potential of bio-inspired staggered composites.

Research on Stress Corrosion Behavior of In-Service Pipeline in H2S Environment

Stress corrosion test of pressure vessels and piping in H2S environment has been explored extensively, but experimental research closed to the actual stress state of pipelines and the actual operating conditions, especially considered the combined effect of various factors is not common. Stress corrosion test simulated the actual operating conditions is taken in this paper. Four in-service pipes are researched as specimens and complex stress field is built by a specially designed loading device. Specimens are immersed in three different H2S concentration environments. The appearance and expansion of crack is observed regularly and the sensitivity of pipeline on stress corrosion is evaluated by metallographic examination. The result shows that: Intergranular corrosion, transgranular corrosion or micro-crack is not found in H2S corrosive solution (500×10-6, 800×10-6mg/L) after 2160 hours or in saturated H2S corrosive solution (greater than 2000×10-6mg/L) after 360 hours. A surface crack is found in H2S corrosive solution (500×10-6mg/L) after 720 hours and the expression for expansion rate of the crack during 2160 hours is a=16.835e0.0002h.

The geodynamics of Mt. Etna volcano during and after the 1984 eruption

Data concerning M > 2.5 earthquakes that occurred at Mt. Etna volcano (Sicily, Italy) during the period April 15th - October 29th, 1984 are here presented and discussed. Only those events with reliable focal mechanisms (at least eight polarities) have been considered. Instrumental information comes from local seismic networks run by the University of Catania and the CNRS (Grenoble, France). The results obtained support the hypothesis that the seismicity and the volcanic activity at Mt. Etna are related to a complex stress field, due to the combined effects of the tectonics associated with the interaction between the African and Eurasian plates and the movement of magma into the crust. In particular, we hypothesize that the tectonic forces caused the end of the 1984 eruption, by means of a "locking mechanism".