scholarly journals Tectonic Structure and Relationship with Sinkhole Harzard in Bang Lung Area, Cho Don District, Bac Kan Province

2021 ◽  
Vol 37 (2) ◽  
Author(s):  
Bui Van Thom ◽  
Tran Quoc Cuong ◽  
Lai Hop phong ◽  
Tran Trung Hieu ◽  
Nguyen Duc Anh
Keyword(s):  
Human Impacts ◽  
Vertical Movement ◽  
Fault System ◽  
Tectonic Activity ◽  
Fracture Zones ◽  
Karst Caves ◽  
Groundwater Fluctuation ◽  
Lung Area ◽  
Unconsolidated Sediment ◽  
Sediment Layers

By integration of remote sensing images analysis, geology, geomorphology, hydrogeology, geophysical method, and drilling data, the paper illustrates the structure tectonics, causes, and initial mechanism of a sinkhole forming in Bang Lung, Cho Don, Bac Kan province. The NE-SW normal slip faults are an essential fault system in the area, which created Bang Lung graben valley. This fault system also forms large fracture zones, creating advantage conditions for the groundwater runoff both vertically and horizontally to eroded and dissolved carbonate rock-forming underground karst caves. These are favorable natural conditions for forming a sinkhole. The sinkhole hazard in the Bang Lung area is initiated by some main factors such as tectonic activity, thickness, and characteristics of unconsolidated sediment layers, groundwater fluctuation, karst caves, and human activities. The most human impacts are mining exploitation and agricultural cultivation that promote sinkholes occurring faster and earlier. The horizontal and vertical movement of groundwater dragged the material on the ceiling karst caves into ground spaces. Thereby, weakening the cohesion of the unconsolidated sediment above caves leads to gravitational unbalance and creates a sinkhole. This study has also shown potential sinkhole areas in Bang Lung, which helps the authorities and local people in sinkhole prevention and mitigation mission.  

scholarly journals Application of observations of recent tectonic activity in the Świebodzice Depression (the Sudetes, SW Poland) in assessing seismic hazard in the Fore-Sudetic Monocline

2018 ◽  
Vol 55 ◽  
pp. 00001 ◽  
Author(s):  
Marek Kaczorowski ◽  
Damian Kasza ◽  
Ryszard Zdunek ◽  
Roman Wronowski
Keyword(s):  
Vertical Movement ◽  
Rock Massif ◽  
Fault System ◽  
Tectonic Activity ◽  
Regional Tectonic ◽  
Sw Poland ◽  
Tidal Signal ◽  
Representative Function ◽  
Low Activity

Tiltmeter observations with application of horizontal pendulums have been carried out for 40 years in the Geodynamic Laboratory in Książ. Long-term observations have not indicated any correlation of these data with meteorological or seasonal phenomena. Following an epoch of fast azimuth changes, a gradual compensation process took place, excluding the effect of gravitational creep of the rock massif. An assumption was made that the observed large changes of the equilibrium azimuths of the horizontal pendulums that result from tectonic tilt of the foundation blocks. Multiannual tiltmeter observations allowed to determine the temporal characteristics and amplitude tectonic effects. Intervals of strong tectonic activity in the rock massif of the Świebodzice Depression last from several days to over ten weeks and are separated by several tens of hours of low activity. Amplitude of the rock massif deformation reaches values from over ten to several tens of amplitudes of the tidal signal, i.e. up to several hundreds of micrometres. Water-tube tiltmeters (WT) launched in 2003 have confirmed the characteristics of tectonic effects and their incidental occurrence. Beside the tilt effects, WT have enabled to confirm vertical movement of the foundation blocks. Geological investigations in the Świebodzice Depression have indicated the presence of a numerous faults separating particular blocks in the rock massif. The presence of this fault system favours the dislocation of foundation blocks, which results in a quake-less relaxation of tectonic stresses and absence lack of seismic activity in the Świebodzice Depression. Foundation blocks separated by faults combined with the multiscale measurement system of WTs form a natural detector of regional tectonic activity, allowing to determine with micrometric resolution the representative function of tectonic activity in the rock massif of the Świebodzice Depression.

Hydrofractures and crustal-scale fluid flow

2021 ◽  
Author(s):  
Paul D. Bons ◽  
Tamara de Riese ◽  
Enrique Gomez-Rivas ◽  
Isaac Naaman ◽  
Till Sachau
Keyword(s):  
Fluid Flow ◽  
Large Scale ◽  
Low Flow ◽  
Fault System ◽  
Tectonic Activity ◽  
Field Evidence ◽  
Dehydration Reactions ◽  
Matrix Flow ◽  
Matrix Porosity ◽  
Fluid Sources

<p>Fluids can circulate in all levels of the crust, as veins, ore deposits and chemical alterations and isotopic shifts indicate. It is furthermore generally accepted that faults and fractures play a central role as preferred fluid conduits. Fluid flow is, however, not only passively reacting to the presence of faults and fractures, but actively play a role in their creation, (re-) activation and sealing by mineral precipitates. This means that the interaction between fluid flow and fracturing is a two-way process, which is further controlled by tectonic activity (stress field), fluid sources and fluxes, as well as the availability of alternative fluid conduits, such as matrix porosity. Here we explore the interaction between matrix permeability and dynamic fracturing on the spatial and temporal distribution of fluid flow for upward fluid fluxes. Envisaged fluid sources can be dehydration reactions, release of igneous fluids, or release of fluids due to decompression or heating.</p><p> </p><p>Our 2D numerical cellular automaton-type simulations span the whole range from steady matrix-flow to highly dynamical flow through hydrofractures. Hydrofractures are initiated when matrix flow is insufficient to maintain fluid pressures below the failure threshold. When required fluid fluxes are high and/or matrix porosity low, flow is dominated by hydrofractures and the system exhibits self-organised critical phenomena. The size of fractures achieves a power-law distribution, as failure events may sometimes trigger avalanche-like amalgamation of hydrofractures. By far most hydrofracture events only lead to local fluid flow pulses within the source area. Conductive fracture networks do not develop if hydrofractures seal relatively quickly, which can be expected in deeper crustal levels. Only the larger events span the whole system and actually drain fluid from the system. We present the 10 square km hydrothermal Hidden Valley Mega-Breccia on the Paralana Fault System in South Australia as a possible example of large-scale fluid expulsion events. Although field evidence suggests that the breccia formed over a period of at least 150 Myrs, actual cumulative fluid duration may rather have been in the order of days only. This example illustrates the extreme dynamics that crustal-scale fluid flow in hydrofractures can achieve.</p>

Karst Caves

2017 ◽  
Author(s):  
Mario Parise
Keyword(s):  
Human Impacts ◽  
Mediterranean Area ◽  
Karst Aquifers ◽  
Karst Hydrogeology ◽  
Diffuse Flow ◽  
Karst Caves ◽  
Cave Sediments ◽  
Classical Studies ◽  
Mechanical Erosion ◽  
Areas Of Protection

Karst refers to the processes of chemical dissolution and mechanical erosion acting on soluble rocks (mainly carbonates and evaporites), and to the surface and subsurface landforms thus produced. In their book Karst Hydrogeology and Geomorphology, Derek Ford and Paul Williams state that about 20 percent of the emerged Earth’s surface is karst, with caves representing a typical and well-known expression (see Ford and Williams 2007, cited under Karst Hydrogeology: The Importance of Karst Aquifers). Together with caves, karst lands are characterized by underground drainages and by scarce presence of water running at the surface. Water, rather than flowing on the ground as watercourses and rivers, rapidly infiltrates underground through networks of fissures and conduits, which combine to the diffuse flow in recent carbonates, giving origin to the complex systems of karst caves. Karst environments and caves have been of interest to humans since the earliest civilizations—for water supply, as settlements or areas of protection, or to bury the dead. Some of the more ancient testimonies of art are within caves, such as those in several caverns of the Mediterranean area (including, to mention the most remarkable, Lascaux and Chauvet in France, Altamira in Spain, and Porto Badisco in Italy). Karst research, which is linked to caving exploration, had a great impulse in the second half of the 20th century. Caves have been recognized as a very precious and peculiar environment, where traces of the past, in terms of sediments (see Sasowsky and Mylroie 2004, cited under Cave Deposits) or evidence of paleoclimate (see Fairchild and Baker 2012, cited under Contribution to Paleoclimatic Studies), have been preserved, often in great detail, in contrast to what occurs at Earth’s surface, where most of it is being destroyed, canceled, or covered by later processes. As a consequence, the classical studies about speleogenesis (that is, the origin of caves) and on geomorphology of the underground settings have developed in integration with those by researches in other disciplines, covering, among others, cave sediments, biospeleology and microbiology, and dating of speleothems for paleoclimatic and paleoenvironmental studies. Further, the expansion of built-up environments and construction in karst lands resulted in the interaction among natural hazards in karst and society, as pointed out in Parise and Gunn 2007 (under Karst Hazards), and Gutiérrez, et al. 2014 (under Human Impacts and Land Management in Karst), bringing to general attention the issue of fragility of karst, due to its peculiar hydrologic and hydrogeological features. As a matter of fact, Goldscheider and Drew 2007 (under Karst Hydrogeology: The Importance of Karst Aquifers) documents that karst aquifers are of high quality and represent between 20 and 25 percent of the world’s drinking resources, but that they are also extremely vulnerable and potentially threatened by a variety of forms of pollution.

How syn-rift sedimentation promotes the formation of hyper-extended margins

2020 ◽  
Author(s):  
Susanne Buiter
Keyword(s):  
Sedimentary Basins ◽  
Surface Processes ◽  
Tectonic Activity ◽  
Tectonic Deformation ◽  
Continental Margins ◽  
Rifted Margins ◽  
Continental Rifts ◽  
Break Up ◽  
Mountain Belts ◽  
Sediment Layers

<p>Seismic observations show that some rifted continental margins may have substantial amounts of offshore sediments. For example, sediment layers of several kilometres thick are found on the margins of Mid Norway, Namibia and Angola. Intriguingly, these margins are wide, being characterised by distances of several hundreds of kilometres from typical continental crustal thicknesses of 30-40 km to clearly identifiable oceanic crust. On the other hand, some margins that are sediment-starved, such as Goban Spur, Flemish Cap and Northern Norway, have short onshore-to-offshore transitions. Variations in the amount of sediments not only impact the development of offshore sedimentary basins, but the changes in mass balance by erosion and sedimentation can also interact with extensional tectonic processes. In convergent settings, such feedback relationships between erosion and tectonic deformation have long been highlighted: Erosion reduces the elevation and width of mountain belts and in turn tectonic activity and exhumation are focused at regions of enhanced erosion. But what is the role played by surface processes during formation of rifted continental margins?</p><p>I use geodynamic finite-element experiments to explore the response of continental rifts to erosion and sedimentation from initial rifting to continental break-up. The experiments predict that rifted margins with thick syn-rift sedimentary packages are more likely to form hyper-extended crust and require more stretching to achieve continental break-up than sediment-starved margins. These findings imply that surface processes can control the style of continental break-up and that the role of sedimentation in rifted margin evolution goes far beyond the simple exertion of a passive weight.</p>

scholarly journals Late Quaternary Tectonic Activity of the Udine-Buttrio Thrust, Friulian Plain, NE Italy

Geosciences ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 84
Author(s):  
Andrea Viscolani ◽  
Christoph Grützner ◽  
Manuel Diercks ◽  
Klaus Reicherter ◽  
Kamil Ustaszewski
Keyword(s):  
Late Quaternary ◽  
Tectonic Setting ◽  
Surface Expression ◽  
Vertical Surface ◽  
Fault System ◽  
Tectonic Activity ◽  
Morphological Evidence ◽  
Seismic Reflection Data ◽  
Reflection Data ◽  
Ne Italy

The NW-SE trending Udine-Buttrio Thrust is a partly blind fault that affects the Friulian plain southeast of Udine in NE Italy. It is part of a wider fault system that accommodates the northward motion of the Adriatic plate. Although seismic reflection data and morphological evidence show that the fault was active during the Quaternary, comparably little is known about its tectonic activity. We used high-resolution digital elevation models to investigate the surface expression of the fault. Measured vertical surface offsets show significant changes along strike with uplift rates varying between 0 and 0.5 mm/yr. We then analyze a topographic scarp near the village of Manzano in more detail. Field mapping and geophysical prospections (Georadar and Electrical Resistivity Tomography) were used to image the subsurface geometry of the fault. We found vertical offsets of 1–3 m in Natisone River terraces younger than 20 ka. The geophysical data allowed the identification of deformation of the fluvial sediments, supporting the idea that the topographic scarp is a tectonic feature and that the terraces have been uplifted systematically over time. Our findings fit the long-term behaviour of the Udine-Buttrio Thrust. We estimate a post-glacial vertical uplift rate of 0.08–0.17 mm/yr recorded by the offset terraces. Our results shed light on the Late Quaternary behaviour of this thrust fault in the complicated regional tectonic setting and inform about its hitherto overlooked possible seismic hazard.

Hydrofractures and crustal-scale fluid flow

2020 ◽  
Author(s):  
Paul D. Bons ◽  
Tamara de Riese ◽  
Enrique Gomez-Rivas ◽  
Isaac Naaman ◽  
Till Sachau
Keyword(s):  
Fluid Flow ◽  
Large Scale ◽  
Low Flow ◽  
Fault System ◽  
Tectonic Activity ◽  
Field Evidence ◽  
Dehydration Reactions ◽  
Matrix Flow ◽  
Matrix Porosity ◽  
Fluid Sources

<p>Fluids can circulate in all levels of the crust, as veins, ore deposits and chemical alterations and isotopic shifts indicate. It is furthermore generally accepted that faults and fractures play a central role as preferred fluid conduits. Fluid flow is, however, not only passively reacting to the presence of faults and fractures, but actively play a role in their creation, (re-) activation and sealing by mineral precipitates. This means that the interaction between fluid flow and fracturing is a two-way process, which is further controlled by tectonic activity (stress field), fluid sources and fluxes, as well as the availability of alternative fluid conduits, such as matrix porosity. Here we explore the interaction between matrix permeability and dynamic fracturing on the spatial and temporal distribution of fluid flow for upward fluid fluxes. Envisaged fluid sources can be dehydration reactions, release of igneous fluids, or release of fluids due to decompression or heating.</p><p> </p><p>Our 2D numerical cellular automaton-type simulations span the whole range from steady matrix-flow to highly dynamical flow through hydrofractures. Hydrofractures are initiated when matrix flow is insufficient to maintain fluid pressures below the failure threshold. When required fluid fluxes are high and/or matrix porosity low, flow is dominated by hydrofractures and the system exhibits self-organised critical phenomena. The size of fractures achieves a power-law distribution, as failure events may sometimes trigger avalanche-like amalgamation of hydrofractures. By far most hydrofracture events only lead to local fluid flow pulses within the source area. Conductive fracture networks do not develop if hydrofractures seal relatively quickly, which can be expected in deeper crustal levels. Only the larger events span the whole system and actually drain fluid from the system. We present the 10 square km hydrothermal Hidden Valley Mega-Breccia on the Paralana Fault System in South Australia as a possible example of large-scale fluid expulsion events. Although field evidence suggests that the breccia formed over a period of at least 150 Myrs, actual cumulative fluid duration may rather have been in the order of days only. This example illustrates the extreme dynamics that crustal-scale fluid flow in hydrofractures can achieve.</p>

Cyclicity of paleofluid infiltration in the active Mount Morrone Fault System (central Apennines, Italy) constrained by carbonate concretions

2020 ◽  
Author(s):  
Gianluca Vignaroli ◽  
Valentina Argante ◽  
Federico Rossetti ◽  
Lorenzo Petracchini ◽  
Michele Soligo ◽  
...  
Keyword(s):  
Regional Scale ◽  
Active Faults ◽  
Fluid Pressure ◽  
Fault System ◽  
Tectonic Activity ◽  
Middle Pleistocene ◽  
Recurrence Time ◽  
Seismic Cycle ◽  
Central Apennines ◽  
Carbonate Concretions

<p>Active faults are characterized by creation/destruction of secondary (tectonic) permeability in response to a continuous interplay between deformation and fluid pressure fluctuations during the seismic cycle. The study of the paleofluid circulation in fault rocks can thus provide insights into the hydraulic and mechanical behavior of the seismogenic crust.</p><p>This work integrates data from field geology with geochemical and geochronological constraints to understand the spatio-temporal evolution of the paleofluid circulation in the Mount Morrone Fault System (MMFS), a ~25 km-long tectonic structure activated during the extensional Quaternary phase of the central Apennines (Italy). The MMFS cuts through a Mesozoic-Cenozoic multilayer carbonate succession for a cumulative stratigraphic offset of about 2 km. Fluvio-lacustrine and slope deposits (Middle-Late Pleistocene) occur at its hanging wall and are variably involved by faulting. The MMFS is currently classified as a silent seismic fault, with an estimated Mw= 6.5-7.0 potential magnitude and recurrence time at 2.4 ka for an expected earthquake.</p><p>The structural survey focused on the western strand of the MMFS cutting through a succession of Sinemurian dolomitized limestones. A composite network of NW-SE-striking, SW-dipping fault surfaces defines the structural architecture of the MMFS in the study outcrops, with high angle (dip > 55°) faults that systematically cut and displace medium-to-low angle (dip in the order of 30°-50°) faults. Both fault systems are characterized by dominant dip-slip movement and normal kinematics. Lenses of cm-thick cataclasites often occur along the slip surfaces. Cataclasites are made by sub-angular to sub-rounded carbonate clasts (up to 1 cm-wide) dispersed in a very fine-grained matrix. Layers of cm-thick carbonate concretions occur associated with the cataclasites, testifying for pulses of fluid discharge along the fault surface during the tectonic activity of the MMFS. Microstructural investigations document that: (i) carbonate concretions show an internal texture of fibrous vein having fiber growth direction roughly perpendicular to the vein wall, and (ii) the basal portions of the carbonate concretions are fractured and incorporated within the underlying cataclasites through the deposition of a new calcite cement. The geochemical (δ<sup>13</sup>C and δ<sup>18</sup>O stable isotope) analyses on selected samples attest for a progressive chemical shift of the mineralizing fluid from marine (in host rock and in cataclasites) to meteoric waters (in carbonate concretions). The U-Th dating of carbonate concretions and calcite slickenfibers constrains the fault-controlled fluid circulation to the Middle Pleistocene, with ages spanning from 270 to 180 ka. Significantly, the dating of carbonate concretions documents a 12-kyr cyclicity of the fluid infiltration in the fault zone.</p><p>The development of the secondary permeability in the MMFS thus corresponds to a combination of faulting and tensile fracturing, in response to a cyclic increasing of the shear stress and the pore pressure during the seismic cycle. The polyphasic deformation system of the MMFS constitutes a record of fault activation and reactivation episodes that could contribute to define the recurrence model of seismic events on regional-scale faults.</p>

scholarly journals Evolution of a long-lived continental arc: a geochemical approach (Arequipa Batholith, Southern Peru)

2019 ◽  
Author(s):  
Sophie Demouy ◽  
Mathieu Benoit ◽  
Michel de Saint-Blanquat ◽  
Jérôme Ganne
Keyword(s):  
Fractional Crystallization ◽  
Thermal State ◽  
Early Stage ◽  
Evolutionary Model ◽  
Vertical Movement ◽  
Fault System ◽  
Large Variability ◽  
Magmatic Arc ◽  
Southern Peru ◽  
Trace Element Contents

Abstract. Batholith emplacements within a continental margin may bear witness of a magmatic input lasting for several million years. Consequently, the geochemical signatures of such sections are complex, and their understanding in terms of petrological processes, is crucial. The Arequipa section of the Coastal Batholith of Southern Peru was discontinuously constructed during several periods of magmatic activity, from the Jurassic to the Paleocene (200–175 Ma, and 90–60 Ma). Thermobarometric data on amphiboles indicates two main levels of emplacement at the batholith scale, the deepest between 5 and 7 km in depth and the second around 3.5 km. The present day outcropping of these different units at the same elevation argue for a large vertical movement along the Lluclla Fault System between 76 and 68 Ma. Both major/trace element contents and Nd-Sr isotopes show a large variability that is not random. The data dispersion is consistent with a two-staged evolutionary model of the magmatic arc, inspired by the MASH model: (i) an early stage dominated by hybridization and fractional crystallization processes, (ii) a late stage in which magmas were homogenized and mainly evolved by fractional crystallization. The change from one stage to another is controlled by the thermal state of the crustal arc section, especially the Deep Crustal Hot Zone.

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