Modeling of the stress-strain state at the Shtokman gas condensate field accounting its block structure

The stress-strain state of the Shtokman gas condensate field has been studied using mathematical modeling and accounting its block structure. It is assumed that the rock mass’s structure has a vertical block structure, which is under the influence of gravity and tectonic force fields. It has been revealed that the stress-strain state of the rocks depends essentially on relationships of initial operating efforts and in-situ gas pressure, which magnitude varies with its production; direction of the maximum forces and dip of angles of fault zones; and elastic characteristics of the main rock mass and fault zones. It has been established that the change in the dip of angle of fault zones and reducing the rocks’ stiffness increases tensile stress in the roof of a horizontal seam and near the sea bottom. A forecast assessment has been performed of the vertical displacement of a rock block contoured with faults relatively to the main rock mass.

Three Dimensional Terrain Modeling for Tectonic Geomorphology of Chinara Anticline, Northern Iraq

Analysis of the terrain using three-dimensional models offers a deep insight view of ground surface topography and terrain representation. The Chinara anticline is one of the main structures of NW-SE trends for the highly folded zone in northeastern Iraq. The objective of this study is to understand the interrelationship between topography and morphotectonic features using three-dimensional models. This research employed fourth generates principal raster derivative products from the DEM using ArcGIS. To understand the undulating of this anticline with the morphotectonic style, the adaptive equation has been suggested to determine the direction and amount of the main tectonic forces, which can be applied to other undulated anticlines. The values of northeastern and southwestern limbs undulating index UI are 11.7 and 7.8 respectively that indicates the strong tectonic force towards the northeast. Two listric faults have been conducted via the field survey that confirmed by remotely sensed interpretation and DEM products. These listric faults had an intensive impact in comparison with concluded strike-slip faults, and then the Chinara anticline would be less structural undulating in a region of vicinity syncline to Perat undulation. The morphotectonic landscapes reveal that the listric fault has branched into two parts, the first one extending to form the anticline and the other comprises the structural dilemma.

New understanding on the principle of earthquake

Earthquake is a natural disaster that causes enormous losses to human society and its prediction is a major scientific challenge widely concerned by the society. However, the mechanism of earthquake is far from clear, and the mainstream view in the international seismology community is that earthquakes are unpredictable. Based on some new concepts and new knowledge developed in physics, this study scrutinizes the incubation and occurrence of earthquake from a novel perspective, and introduces a new understanding of earthquake principle. It is found that the view of earthquake unpredictability originates from the incorrect understanding of both earthquake principle and the self-organized criticality (SOC). That is to say, earthquake is consistent with the laws of SOC, which means it would be impossible to make a medium- or long-term prediction, yet the short-term prediction should still be possible. The preconditions for successful prediction include understanding correctly of earthquake principle, obtaining sufficient characteristic precursory information, and gathering relevant geological data. Traditional seismology is based on the solid continuum mechanics which holds the view that earthquakes are caused by brittle fracture of crustal rocks through the so-called “elastic rebound” mechanism. This point of view is seriously inconsistent with many field observations, cannot account for many seismic phenomena. It therefore cannot obtain and understand the earthquake precursory information correctly, and naturally reach the false conclusion that earthquake is unpredictable. Based on the simple fact that the crust is composed of rock blocks with fault gouges filling in between them, we treat the crust as a discrete system and understand the earthquake incubation process by means of granular physics. The new understanding gained is that the tectonic force propagates through force chains formed by the rock blocks, and the rock blocks move in the manner of stick-slip. Furthermore, by carefully analyzing how the strength of crustal rocks and the distributions of tectonic force vary with depth, we propose that the physical mechanism of earthquake is plastic sliding of rock and a jamming — unjamming transition of rock motion. Our novel theory on the earthquake principle and the earthquake processes can explain many seismological phenomena that could not be understood in terms of traditional seismology, such as the heat-flow paradox and the cause of deep-focus earthquake, etc. Based on this new understanding of earthquake principle, we put forward suggestions on how to obtain the earthquake precursory information correctly, so as to realize the goal of short-term prediction of earthquake.

Mongolian Buddhism in the Early 20th Century

Mongol lands were bastions of Mahāyāna (Mon. yeke kölgen) and Vajrayāna (Mon. vačir kölgen) Buddhist life from the seventeenth to the early twentieth centuries, vast territories of the Buddhadharma deeply twinned with Tibetan traditions but always of local variation and distinct cultural content and purpose. Mongol contact with the Dharma reached its apex in the early decades of the 20th century, a flourishing of Buddhist knowledge, craft, and institutionalism that would soon face the blunt tool of brutal state violence. As the great Eurasian Empires came undone with tectonic force and consequence, Mongol lands along the frontiers of the Qing and Tsarist formations had the highest per capita rate of monastic ordination in the history of Buddhism (up to one in three adult men holding some monastic affiliation). Decades into the revolutionary aftermath of imperial collapse, at the interface of Republican China and Soviet Russia, Mongolian monastic complexes were hubs of cultural, economic, and intellectual life that continued to circulate and shape anew classical Indian and Tibetan fields of knowledge like medicine and astrology, esoteric and exoteric exegesis, material culture, and performance traditions between the Western Himalaya; the northern foothills of the British Raj; the Tibetan plateau; North China; Beijing; all Mongol regions; and Siberia, right to St. Petersburg. In addition to being dynamic centers of production, Mongolian Buddhist communities in the early 20th century provided zones of contact and routes of circulation for persons, ideas, objects, and patronage. Pilgrims, pupils, merchants, diplomats and patrons (and those that were all of these) moved from Mongol hubs such as Urga, Alashan, or Kökeqota to monastic colleges, markets, holy sites (and at this time, universities, parliaments, and People’s Congresses) in Lhasa, Beijing, Wutaishan, France, and St. Petersburg. In the ruins of the Qing and Tsarist empires, to whatever uneven degree these had been felt in local administrative units, Buddhist frames of references, institutions, and technologies of self- and community formation were central in the reimagination of Mongol and Siberian communities. In the decades this article considers, such imperial-era communal and religious references were foundational to new rubrics associated first with the national subject and then the first experiments with state socialism in Asia. In many Mongol regions, Buddhism was at first considered “the very spirit” of revolutionary developments, as the Buryat progressive and pan-Mongolist Ts. Jamsrano once put it. By the late 1930s, however, the economic, social, and political capital of monks (especially monastic officials and khutuγtu “living buddhas”) and their monastic estates were at odds with new waves of socialist development rhetoric. Buddhist clerics and their networks (though not “Buddhism” as such) were tried en masse as counterrevolutionary elements. Able only to speak their crimes under interrogation and in court, monks fell to firing squads by the tens of thousands. All monastic institutions save three were razed to the steppe grasses and desert sands. Any continuity of public religiosity, other than minimal displays of state-sponsored propaganda, was discontinued until the democratic revolution of 1990. Mongol lands and its Buddhism was thus an early exemplar of a pattern that would repeat itself across socialist Asia in the 20th century. From China to Cambodia, Tibet to Vietnam and Korea, counter-imperial and colonial nationalist and socialist movements who were at first aligned with Buddhist institutions would later enact profound state violence against monastics and their sympathizers. Understanding Buddhism in early 20th century Mongolia is thus a key case study to thinking about the broad processes of nationalization, reform, violence, Europeanization, state violence, and globalization that has shaped Buddhism and Buddhists in much of Asia in the recent past.

The mechanism of earthquake

The physical mechanism of earthquake remains a challenging issue to be clarified. Seismologists used to attribute shallow earthquake to the elastic rebound of crustal rocks. The seismic energy calculated following the elastic rebound theory and with the data of experimental results upon rocks, however, shows a large discrepancy with measurement — a fact that has been dubbed as “the heat flow paradox”. For the intermediate-focus and deep-focus earthquakes, both occurring in the region of the mantle, there is not reasonable explanation either. This paper will discuss the physical mechanism of earthquake from a new perspective, starting from the fact that both the crust and the mantle are discrete collective system of matters with slow dynamics, as well as from the basic principles of physics, especially some new concepts of condensed matter physics emerged in the recent years. (1) Stress distribution in earth’s crust: Without taking the tectonic force into account, according to the rheological principle of “everything flows”, the normal stress and transverse stress must be balanced due to the effect of gravitational pressure over a long period of time, thus no differential stress in the original crustal rocks is to be expected. The tectonic force is successively transferred and accumulated via stick-slip motions of rock blocks to squeeze the fault gouge and then exerted upon other rock blocks. The superposition of such additional lateral tectonic force and the original stress gives rise to the real-time stress in crustal rocks. The mechanical characteristics of fault gouge are different from rocks as it consists of granular matters. The elastic moduli of the fault gouges are much less than those of rocks, and they become larger with increasing pressure. This peculiarity of the fault gouge leads to a tectonic force increasing with depth in a nonlinear fashion. The distribution and variation of the tectonic stress in the crust are specified. (2) The strength of crust rocks: The gravitational pressure can initiate the elasticity–plasticity transition in crust rocks. By calculating the depth dependence of elasticity–plasticity transition and according to the actual situation analysis, the behaviors of crust rocks can be categorized in three typical zones: elastic, partially plastic and fully plastic. As the proportion of plastic portion reaches about 10% in the partially plastic zone, plastic interconnection may occur and the variation of shear strength in rocks is mainly characterized by plastic behavior. The equivalent coefficient of friction for the plastic slip is smaller by an order of magnitude, or even less than that for brittle fracture, thus the shear strength of rocks by plastic sliding is much less than that by brittle breaking. Moreover, with increasing depth a number of other factors can further reduce the shear yield strength of rocks. On the other hand, since earthquake is a large-scale damage, the rock breaking must occur along the weakest path. Therefore, the actual fracture strength of rocks in a shallow earthquake is assuredly lower than the average shear strength of rocks as generally observed. The typical distributions of the average strength and actual fracture strength in crustal rocks varying with depth are schematically illustrated. (3) The conditions for earthquake occurrence and mechanisms of earthquake: An earthquake will lead to volume expansion, and volume expansion must break through the obstacle. The condition for an earthquake to occur is as follows: the tectonic force exceeds the sum of the fracture strength of rock, the friction force of fault boundary and the resistance from obstacles. Therefore, the shallow earthquake is characterized by plastic sliding of rocks that break through the obstacles. Accordingly, four possible patterns for shallow earthquakes are put forward. Deep-focus earthquakes are believed to result from a wide-range rock flow that breaks the jam. Both shallow earthquakes and deep-focus earthquakes are the energy release caused by the slip or flow of rocks following a jamming–unjamming transition. (4) The energetics and impending precursors of earthquake: The energy of earthquake is the kinetic energy released from the jamming–unjamming transition. Calculation shows that the kinetic energy of seismic rock sliding is comparable with the total work demanded for rocks’ shear failure and overcoming of frictional resistance. There will be no heat flow paradox. Meanwhile, some valuable seismic precursors are likely to be identified by observing the accumulation of additional tectonic forces, local geological changes, as well as the effect of rock state changes, etc.

Initiation of Triangle Zones by Delamination, Shear, and Compaction at the Front of Fold-and-Thrust Belts

The interest of this paper is to investigate the initiation of triangle zones at the front of fold-and-thrust belts by analyzing the virtual velocity fields in triangle wedges. It allows achieving five collapse mechanisms by delamination, shear, and compaction of competing for the formation of triangle zones as follows. The first mechanism is the classical Coulomb shear thrust. The second is delamination at the frontal part of the décollement with straight back thrust, while the third is delamination with curvy back thrust. The fourth is the combination of ramp with Coulomb shear and shear-enhanced compact fault, while the fifth is the combination of the exchanging motion on the ramp and thrust. The dominating mechanism in the formation of triangle zones relies on the competition of the least upper bound of each mechanism when subjected to tectonic force. The controlling factors of the competition are discovered as follows: (1) the frictional characters and cohesion of horizontal décollements and thrust, (2) the slope of the topography of accretion wedge, and (3) the thickness and rock density of the front toe of accretion wedge.

Passive obduction and gravity-driven emplacement of large ophiolitic sheets: The New Caledonia ophiolite (SW Pacific) as a case study?

The 300 km long allochthonous sheet of oceanic mantle forming the New Caledonia ophiolite displays three specific characters: 1) the ophiolite pile lacks concordant sheeted dykes and pillow basalt layers; 2) the ophiolite, refered to as the Peridotite nappe, is thrusted over the basaltic formations of the Poya terrane which are classicaly thought to originate from a different oceanic environment; 3) The basal contact of the ultramafic sheet is remarkably flat all along New-Caledonia and the Peridotite nappe has not been thickened during obduction, rather it experienced significant extension. This suggests that the peridotites have not been emplaced by a tectonic force applied to the rear. New petrological and geochemical results obtained from mantle rocks finally show that the Poya terrane may originate from the same oceanic basin as the peridotites. In this article, we consider such possible cogenetic links and we propose a simple model for the obduction of the New Caledonia ophiolite in which the Poya basalts represent the original cover of the Peridotite nappe. We infer that continuous uplift of the subducted units buried beneath the oceanic lithosphere in the northern part of New Caledonia drove passive uplift of the ophiolite and led to erosion and to initiation of sliding of the basaltic layer. During the Priabonian (latest Eocene), products of the erosion of the basaltic layer were deposited together with sediments derived from the Norfolk passive oceanic margin. These sediments are involved as tectonic slices into an accretionary wedge formed in response to plate convergence. The volcaniclastic sedimentation ends up with the emplacement of large slided blocks of basalts and rafted mafic units that progressively filled up the basin. Obduction process ended with the gravity sliding of the oceanic mantle sheet, previously scalped from its mafic cover. This process is contemporaneous with the exhumation of the HP-LT units of Pouebo and Diahot. Gravity sliding was facilitated by the occurrence of a continuous serpentine sole resulting from metasomatic hydratation of mantle rocks, which developed during the uplift of the Norfolk basement and overlying Diahot and Pouébo units. Progressive emersion of the obducted lithosphere allowed subsequent weathering under subaerial, tropical conditions.