scholarly journals Arc-parallel shears in collisional orogens: Global review and paleostress analyses from the NW Lesser Himalayan Sequence (Garhwal region, Uttarakhand, India)

2022 ◽  
Author(s):  
Tuhin Biswas ◽  
Narayan Bose ◽  
Dripta Dutta ◽  
Soumyajit Mukherjee
Keyword(s):  
Rock Mass ◽  
Driving Forces ◽  
Regional Scale ◽  
Microstructural Analysis ◽  
Hydrocarbon Exploration ◽  
Plate Interface ◽  
Natural Rock ◽  
Ductile Shear ◽  
The Himalaya ◽  
Shear Planes

Interest in hydrocarbon exploration from the the Lesser Himalayan Sequence (LHS) has recently been revived amongst petroleum geoscientists. Understanding the paleostress regime and the deformation processes are the two important steps to understand the structural geology of any (petroliferous) terrane. Arc-parallel shear is an integral deformation process in orogeny. The scale of the consequent deformation features can range from micro-mm up to regional scale. Unlike orogen-perpendicular shear, different driving forces can produce orogen-parallel shears. We review these mechanisms/theories from several orogens including the Himalaya and compile 44 locations worldwide with reported orogen-parallel shear. Due to continuous crustal shortening by the India-Eurasia collision, the squeezed rock mass at the plate interface has produced the Himalayan Mountain chain. In addition, the rock mass also escapes laterally along the orogenic trend. Tectonic stress-field governs this mass flow. Field study and microstructural analysis in the northwest LHS (India) reveals orogen-parallel brittle and ductile shear movement. Y- and P- brittle shear planes, and the S- and C- ductile shear planes reveal the following shears documented on the ~ NW-SE trending natural rock selections: (i) top-to-NW up, (ii) top-to-SE up, (iii) top-to-NW down, and (iv) top-to-SE down. Our paleostress analysis indicates top-to-SE down and top-to-NW down shears occurred due to stretching along ~ 131°-311° (Dext), whereas top-to-SE up and top-to-NW up shear fabric originated due to shortening along ~133.5°-313.5° (Dcompr). Previous authors considered that the orogen-parallel extension generated ~ 15-5 Ma due to vertical thinning of the Himalaya. The NE-trending Delhi-Haridwar Ridge below the LHS plausibly acted as a barrier to the flowing mass and piled up the rock mass in the form of NW-SE/orogen-parallel compression. The NW-SE compression can be correlated with the D3 of Hintersberger et al. (2011) during ~ 4-7 Ma.

A Review of Soft Computing Methods Application in Rock Mechanic Engineering

2016 ◽  
pp. 1-70 ◽  
Author(s):  
Nurcihan Ceryan
Keyword(s):  
Rock Mass ◽  
Soft Computing ◽  
Rock Mechanics ◽  
Computing Methods ◽  
Rock Material ◽  
Rock Slope Stability ◽  
Rock Mechanic ◽  
Natural Rock ◽  
Soft Computing Techniques ◽  
Soft Computing Methods

Engineering behavior of rock mass is controlled by many factors, related to its nature and the environmental conditions. Determining all the parameters, ranking their weights, and clarifying their relative effects are very difficult tasks to accomplish. To overcome these difficulties, many researchers have employed soft computing methods in rock mechanics engineering. The soft computing methods have taken an important role in rock mechanics, and their abilities to address uncertainties, insufficient information and ambiguous linguistic expressions stand out in treating complex natural rock mass. This chapter briefly will review the development of soft computing techniques in rock mechanics engineering, especially in predicting of rock engineering classification system and mechanical properties of rock material and rock mass, determination weathering degree of rock material, evolution of rock performance, blasting and, rock slope stability. In addition, the future of the development and application of soft computing in rock mechanics engineering is discussed.

scholarly journals Understanding regional-scale structural uncertainty: The onshore Gulf of Corinth rift as a hydrocarbon exploration analogue

2015 ◽  
Vol 3 (4) ◽  
pp. SAC35-SAC53 ◽  
Author(s):  
Alan Wood ◽  
Douglas Paton ◽  
Richard Collier ◽  
Viki O’Connor
Keyword(s):  
Hanging Wall ◽  
Regional Scale ◽  
Hydrocarbon Exploration ◽  
Three Dimensions ◽  
Structural Uncertainty ◽  
3D Space ◽  
Gulf Of Corinth ◽  
Geometric Uncertainty ◽  
Seismic Sections ◽  
2D Data

A major challenge when exploring for hydrocarbons in frontier areas is a lack of data coverage. Data may be restricted to regional-scale 2D seismic lines, from which assumptions of the 3D geometric configuration are drawn. Understanding the limitations and uncertainties when extrapolating 2D data into 3D space is crucial when assessing the requirements for acquiring additional data such as 3D seismic or exploration wells and of assigning geologically reasonable uncertainty ranges. The onshore Gulf of Corinth Rift provides an excellent analog for rift-scale structural uncertainty in the context of hydrocarbon exploration. We have used seismic forward modeling to explore this area of uncertainty. Synthetic seismic sections have been generated across the rift based upon fault geometries mapped in the field. Comparisons that we made of these sections with the mapped geometries allowed quantification of uncertainties encountered when extrapolating 2D data into three dimensions. We have determined how potential column heights may be severely over and underestimated due to trap integrity, spill point depth, and fault seal ambiguities directly related to fault geometric uncertainty. In addition, fault geometries and linkages also controlled the location of hanging wall synrift reservoirs. Hence, gross reservoir volumes and sediment facies distributions were also significantly influenced by how fault geometries were extrapolated along-strike from 2D to 3D.

scholarly journals Calculation of Elastic Modulus for Fractured Rock Mass Using Dimensional Analysis Coupled with Numerical Simulation

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Fengyu Ren ◽  
Jing Zhang ◽  
Zhihua Ouyang ◽  
Hao Hu
Keyword(s):  
Numerical Simulation ◽  
Rock Mass ◽  
Elastic Modulus ◽  
Dimensional Analysis ◽  
Underground Mining ◽  
Fractured Rock ◽  
Continuum Theory ◽  
Equivalent Model ◽  
Fractured Rock Mass ◽  
Natural Rock

Underground mining activities make the fractures in the natural rock mass develop randomly. The elastic modulus of the fractured rock mass Em is changed with the redistribution and development of the fractures. An equivalent model of fractured rock mass is structured to represent the hydraulic conductivity and the rock mass strain because of the continuum theory. Dimensional analysis is very useful to build relationship of the parameters in complex physical phenomena. Based on the engineering phenomenon of groundwater flowing into the goaf along the fracture in the rock mass, a fuzzy expression among parameters such as the parameter Em, the seepage flow Q, and the exposed area of the goaf A is obtained using dimensionless analysis. To calculate the parameter Em, the fuzzy relationship is then characterized by Darcy’s law and numerical simulation. Under the scripting environment of Python, an automated program to realize the numerical simulation of all scenarios is established, which also provides convenience for drawing the dimensionless flux charts. The results show that the parameter Em can be calculated by the dimensional analysis coupled with numerical simulation. In addition, the parameter Em decreases with the increase of the parameter Q, and the integrity of rock mass is also worse. Finally, a mine example is used to verify the feasibility of the method.

scholarly journals High-energy seismic events in Legnica–Głogów Copper District in light of ASG-EUPOS data

2019 ◽  
Vol 107 (1) ◽  
pp. 25-40 ◽  
Author(s):  
Zbigniew Szczerbowski
Keyword(s):  
Rock Mass ◽  
Regional Scale ◽  
Geophysical Methods ◽  
Geodetic Network ◽  
High Energy ◽  
Tectonic Activity ◽  
Baseline Length ◽  
Seismic Events ◽  
Gnss Data ◽  
Mining Tremors

AbstractSeismic events in the area of Poland are related mostly to copper and coal mining, and they are regarded as the most dangerous natural hazard. Although development of geomechanical modelling as the development of geophysical methods determining seismic hazard are evident, low predictability of the time-effect relationship still remains. Geomechanical models as geophysical data analysis highlight the interaction between parts of rock mass or allow to reconstruct the way of rock mass destruction and to understand the processes that take place in the high-energy tremors.However, the association of larger mining tremors with pre-existing geological features has been reported by many investigators; in geomechanical practice, investigations of rock mass condition concentrate on this problem in the local scale. Therefore, the problem of relations between high-energy seismic events in Legnica–Głogów Copper District (LGCD) and regional scale deformations of terrain surface resulting from possible tectonic activity is discussed in this paper. The GNSS data evaluated from the observations of ASG-EUPOS (Active Geodetic Network – EUPOS) stations in the area of LGCD and in the adjacent areas is analysed in this study. Temporal variation of distances between the stations and evaluated on that base so called apparent strain was combined with the occurrence of high-energy tremors. Consequently, after the examination and analysis of occurrences of mining tremors, it is found that high-energy seismic events and periods of strain accumulation evaluated from GPS/GNSS data have temporal relations. Although the seismic events were triggered by mining, nearly all the events with energy E > 108 J occurred in the periods when the analysed stations’ positions demonstrated a decrease in the baseline length.

scholarly journals Short-Term Interaction between Silent and Devastating Earthquakes in Mexico

2020 ◽  
Author(s):  
Víctor Cruz-Atienza ◽  
Josué Tago ◽  
Carlos Villafuerte ◽  
Meng Wei ◽  
Ricardo Garza-Girón ◽  
...  
Keyword(s):  
Seismic Hazard ◽  
Seismic Waves ◽  
Regional Scale ◽  
Slow Slip ◽  
Aseismic Slip ◽  
Short Term ◽  
Plate Interface ◽  
Slow Slip Events ◽  
Large Earthquakes

Abstract Triggering of large earthquakes on a fault that hosts aseismic slip or, conversely, triggering of slow slip events (SSE) by passing seismic waves involves seismological questions with major hazard implications. Just a few observations plausibly suggest that such interactions actually happen in nature. In this study we show that three recent devastating earthquakes in Mexico are likely related to SSEs, describing a cascade of events interacting with each other on a regional scale via quasi-static and/or dynamic perturbations. Such interaction seems to be conditioned by the transient memory of Earth materials subject to the “traumatic” stressing produced by the seismic waves of the great Mw8.2 Tehuantepec earthquake, which strongly disturbed the aseismic beating over a 650 km long segment of the subduction plate interface. Our results imply that seismic hazard in large populated areas is a short-term evolving function of seismotectonic processes that are often observable.

scholarly journals Glacial lakes exacerbate Himalayan glacier mass loss

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Owen King ◽  
Atanu Bhattacharya ◽  
Rakesh Bhambri ◽  
Tobias Bolch
Keyword(s):  
Mass Loss ◽  
Regional Scale ◽  
High Mountain ◽  
Mass Balances ◽  
Glacial Lakes ◽  
Regional Variability ◽  
Glacier Recession ◽  
Minor Portion ◽  
A Minor ◽  
The Himalaya

AbstractHeterogeneous glacier mass loss has occurred across High Mountain Asia on a multi-decadal timescale. Contrasting climatic settings influence glacier behaviour at the regional scale, but high intra-regional variability in mass loss rates points to factors capable of amplifying glacier recession in addition to climatic change along the Himalaya. Here we examine the influence of surface debris cover and glacial lakes on glacier mass loss across the Himalaya since the 1970s. We find no substantial difference in the mass loss of debris-covered and clean-ice glaciers over our study period, but substantially more negative (−0.13 to −0.29 m w.e.a−1) mass balances for lake-terminating glaciers, in comparison to land-terminating glaciers, with the largest differences occurring after 2000. Despite representing a minor portion of the total glacier population (~10%), the recession of lake-terminating glaciers accounted for up to 32% of mass loss in different sub-regions. The continued expansion of established glacial lakes, and the preconditioning of land-terminating glaciers for new lake development increases the likelihood of enhanced ice mass loss from the region in coming decades; a scenario not currently considered in regional ice mass loss projections.

Complex kinematics in a major ductile shear zone, NW Shetland: Evidence of ductile extrusion during Caledonian transpression

2021 ◽  
Author(s):  
Timothy Armitage ◽  
Robert Holdsworth ◽  
Robin Strachan ◽  
Thomas Zach ◽  
Diana Alvarez-Ruiz ◽  
...  
Keyword(s):  
Shear Zone ◽  
Hanging Wall ◽  
Regional Scale ◽  
Shear Zones ◽  
White Mica ◽  
Strike Slip ◽  
Amphibolite Facies ◽  
Lateral Extrusion ◽  
Shear Sense ◽  
Ductile Shear

<p>Ductile shear zones are heterogeneous areas of strain localisation which often display variation in strain geometry and combinations of coaxial and non-coaxial deformation. One such heterogeneous shear zone is the c. 2 km thick Uyea Shear Zone (USZ) in northwest Mainland Shetland (UK), which separates variably deformed Neoarchaean orthogneisses in its footwall from Neoproterozoic metasediments in its hanging wall (Fig. a). The USZ is characterised by decimetre-scale layers of dip-slip thrusting and extension, strike-slip sinistral and dextral shear senses and interleaved ultramylonitic coaxially deformed horizons. Within the zones of transition between shear sense layers, mineral lineations swing from foliation down-dip to foliation-parallel in kinematically compatible, anticlockwise/clockwise-rotations on a local and regional scale (Fig. b). Rb-Sr dating of white mica grains via laser ablation indicates a c. 440-425 Ma Caledonian age for dip-slip and strike-slip layers and an 800 Ma Neoproterozoic age for coaxial layers. Quartz opening angles and microstructures suggest an upper-greenschist to lower-amphibolite facies temperature for deformation. We propose that a Neoproterozoic, coaxial event is overprinted by Caledonian sinistral transpression under upper greenschist/lower amphibolite facies conditions. Interleaved kinematics and mineral lineation swings are attributed to result from differential flow rates resulting in vertical and lateral extrusion and indicate regional-scale sinistral transpression during the Caledonian orogeny in NW Shetland. This study highlights the importance of linking geochronology to microstructures in a poly-deformed terrane and is a rare example of a highly heterogeneous shear zone in which both vertical and lateral extrusion occurred during transpression.</p><p><img src="https://contentmanager.copernicus.org/fileStorageProxy.php?f=gepj.0cf6ef44e5ff57820599061/sdaolpUECMynit/12UGE&app=m&a=0&c=d96bb6db75eed0739f2a6ee90c9ad8fd&ct=x&pn=gepj.elif&d=1" alt=""></p>

scholarly journals Rockfall hazard and risk assessments along roads at a regional scale: example in Swiss Alps

2012 ◽  
Vol 12 (3) ◽  
pp. 615-629 ◽  
Author(s):  
C. Michoud ◽  
M.-H. Derron ◽  
P. Horton ◽  
M. Jaboyedoff ◽  
F.-J. Baillifard ◽  
...  
Keyword(s):  
Rock Mass ◽  
Regional Scale ◽  
Slope Angle ◽  
Swiss Alps ◽  
Cumulative Distribution ◽  
Angle Distribution ◽  
Source Areas ◽  
Hazard And Risk ◽  
Mass Failure ◽  
Rock Mass Failure

Abstract. Unlike fragmental rockfall runout assessments, there are only few robust methods to quantify rock-mass-failure susceptibilities at regional scale. A detailed slope angle analysis of recent Digital Elevation Models (DEM) can be used to detect potential rockfall source areas, thanks to the Slope Angle Distribution procedure. However, this method does not provide any information on block-release frequencies inside identified areas. The present paper adds to the Slope Angle Distribution of cliffs unit its normalized cumulative distribution function. This improvement is assimilated to a quantitative weighting of slope angles, introducing rock-mass-failure susceptibilities inside rockfall source areas previously detected. Then rockfall runout assessment is performed using the GIS- and process-based software Flow-R, providing relative frequencies for runout. Thus, taking into consideration both susceptibility results, this approach can be used to establish, after calibration, hazard and risk maps at regional scale. As an example, a risk analysis of vehicle traffic exposed to rockfalls is performed along the main roads of the Swiss alpine valley of Bagnes.

scholarly journals Carbonate and silicate weathering in glacial environments and its relation to atmospheric CO2 cycling in the Himalaya

2018 ◽  
Vol 59 (77) ◽  
pp. 159-170 ◽  
Author(s):  
Tanuj Shukla ◽  
Shipika Sundriyal ◽  
Lukasz Stachnik ◽  
Manish Mehta
Keyword(s):  
Regional Scale ◽  
Silicate Weathering ◽  
Carbonate Dissolution ◽  
Sea Salts ◽  
Carbonation Reaction ◽  
Sulphide Oxidation ◽  
Silicate Dissolution ◽  
Glacial Environments ◽  
Global Carbon ◽  
The Himalaya

ABSTRACTThis paper presents new insights into the global carbon cycle related to CO2 consumption from chemical denudation in heavily glacierised Himalayan catchments. Data from previous studies of solute concentrations from glacierised catchments were reprocessed to determine the regional scale of CO2 consumption and solute hydrolysis. The results show that ~90% of the SO42− is derived from crustal sulphide oxidation and ~10% from aerosols and sea salts. However, HCO3− flux calculation estimates contribution from sulphide oxidation to carbonate dissolution (SO-CD) (~21%), similar to the contributions from silicate dissolution and simple hydrolysis (~21 and ~20%, respectively). Furthermore, the atmospheric CO2 consumption estimations suggests 10.6 × 104 mole km−2 a−1 (19%) through silicate weathering, 15.7 × 104 mole km−2 a−1 (28%) through simple hydrolysis, 9.6 × 104 mole km−2 a−1 (17%) through SO-CD reaction and 5.9 × 104 mole km−2 a−1 (11%) through carbonate carbonation reaction. Our solute provenance calculations clearly indicate that HCO3− production and CO2 consumption via silicate weathering reactions is balanced by the simple hydrolysis and coupled SO-CD process. This shows a counter mechanism operating in subglacial environments of the Himalaya as a source of CO2 to runoff rather than a sink.

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