Thermal effects of normal faulting during rifted basin formation, 2. The Lugano-Val Grande normal fault and the role of pre-existing thermal anomalies

ABSTRACT Oceanic plate seismicity is generally dominated by normal and strike-slip faulting associated with active spreading ridges and transform faults. Fossil structural fabrics inherited from spreading ridges also host earthquakes. The Indian Oceanic plate, considered quite active seismically, has hosted earthquakes both on its active and fossil fault systems. The 4 December 2015 Mw 7.1 normal-faulting earthquake, located ∼700 km south of the southeast Indian ridge in the southern Indian Ocean, is a rarity due to its location away from the ridge, lack of association with any mapped faults and its focal depth close to the 800°C isotherm. We present results of teleseismic body-wave inversion that suggest that the earthquake occurred on a north-northwest–south-southeast-striking normal fault at a depth of 34 km. The rupture propagated at 2.7 km/s with compact slip over an area of 48×48 km2 around the hypocenter. Our analysis of the background tectonics suggests that our chosen fault plane is in the same direction as the mapped normal faults on the eastern flanks of the Kerguelen plateau. We propose that these buried normal faults, possibly the relics of the ancient rifting might have been reactivated, leading to the 2015 midplate earthquake.

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Excellent Ductility in the Extruded AZ61 Magnesium Alloy Tube Induced by Electropulsing Treatment during Tension

Metals ◽

10.3390/met11050813 ◽

2021 ◽

Vol 11 (5) ◽

pp. 813

Author(s):

Bo Jiang ◽

Dongdong Zhang ◽

Hong Xu ◽

Yongbing Liu ◽

Zhanyi Cao ◽

...

Keyword(s):

Magnesium Alloy ◽

Thermal Effects ◽

Average Amplitude ◽

Serrated Flow ◽

Flow Phenomenon ◽

Az61 Magnesium Alloy ◽

Alloy Tube ◽

Electropulsing Treatment ◽

Electron Wind

In this work, we reported the high ductility of an extruded AZ61 magnesium alloy tube achieved by electropulsing current-assisted tension. The elongation of the alloy reached up to about 45%, which is largely superior to the majority of AZ61 wrought Mg alloys. We found that the hardening capacity of the alloy seemed to slightly increase as the electropulsing frequency increased. Furthermore, electropulsing can arouse the serrated flow phenomenon. Here we proposed an equation describing the correlation between the average amplitude and frequency: Aa = C − 6 × 10−3f, where Aa is the average amplitude, f is the frequency, and C is the constant. In addition, introducing electropulsing current pronouncedly reduced the tendency of twinning, but the twinning fraction seemed to fail depending on the electropulsing frequency. Based on microstructure analysis, we concluded that the outstanding ductility of the studied alloy was mainly due to the combined role of the thermal effects from Joule heating, the athermal effects from electron wind, and the magnetic effects from the electropulsing current. The serrated flow phenomenon occurred along stress–strain curves after electropulsing treatment, and the underlying reasons also were uncovered.

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Role of Thermal Effects on Magnetic Interactions in Stacked Magnetic Layers With Perpendicular Anisotropy

IEEE Magnetics Letters ◽

10.1109/lmag.2014.2370612 ◽

2014 ◽

Vol 5 ◽

pp. 1-4

Author(s):

S. N. Piramanayagam ◽

Hang Khume Tan ◽

Binni Varghese

Keyword(s):

Thermal Effects ◽

Magnetic Interactions ◽

Perpendicular Anisotropy ◽

Magnetic Layers

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The role of frictional plasticity in the evolution of normal fault systems

Journal of Structural Geology ◽

10.1016/j.jsg.2012.03.001 ◽

2012 ◽

Vol 39 ◽

pp. 122-137 ◽

Cited By ~ 5

Author(s):

David E. Dempsey ◽

Susan M. Ellis ◽

Julie V. Rowland ◽

Rosalind A. Archer

Keyword(s):

Normal Fault ◽

Fault Systems

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Seismic-Scale Evidence of Thrust-Perpendicular Normal Faulting in the Western Outer Carpathians, Poland

Minerals ◽

10.3390/min11111252 ◽

2021 ◽

Vol 11 (11) ◽

pp. 1252

Author(s):

Jan Barmuta ◽

Krzysztof Starzec ◽

Wojciech Schnabel

Keyword(s):

Large Scale ◽

Fault Plane ◽

Normal Fault ◽

Normal Faulting ◽

Seismic Profiles ◽

Horizontal Movement ◽

Outer Carpathians ◽

Differential Uplift ◽

Seismic Scale ◽

Detachment Surface

Based on the interpretation of 2D seismic profiles integrated with surface geological investigations, a mechanism responsible for the formation of a large scale normal fault zone has been proposed. The fault, here referred to as the Rycerka Fault, has a predominantly normal dip-slip component with the detachment surface located at the base of Carpathian units. The fault developed due to the formation of an anticlinal stack within the Dukla Unit overlain by the Magura Units. Stacking of a relatively narrow duplex led to the growth of a dome-like culmination in the lower unit, i.e., the Dukla Unit, and, as a consequence of differential uplift of the unit above and outside the duplex, the upper unit (the Magura Unit) was subjected to stretching. This process invoked normal faulting along the lateral culmination wall and was facilitated by the regional, syn-thrusting arc–parallel extension. Horizontal movement along the fault plane is a result of tear faulting accommodating a varied rate of advancement of Carpathian units. The time of the fault formation is not well constrained; however, based on superposition criterion, the syn -thrusting origin is anticipated.

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Normal Faulting and Volcanism in the Kora 3D Seismic Volume

10.26686/wgtn.17060582 ◽

2021 ◽

Author(s):

◽

Ian Hurst

Keyword(s):

New Zealand ◽

Causal Relationship ◽

Petroleum Industry ◽

Local Stress ◽

3D Seismic ◽

Normal Faulting ◽

New Information ◽

Basin Formation ◽

Geologic Uncertainty ◽

Local Tectonics

The spatial and temporal relationship between normal faulting and volcanism in offshore Western North Island, New Zealand can be used to gain insight into basin formation, hydrocarbon resources, regional tectonics, and large subduction processes. It is hypothesised that there is a causal relationship between volcanic activity and faulting, however, within the Taranaki Kora 3D seismic volume (survey) this relationship has not yet been explored. The overall aim of this thesis was to map and identify whether there is a relationship between volcanism and normal faulting within the Kora 3D survey. A causal relationship in location and timing between volcanic processes and fault activity was discovered in this study. Two novel models were created to explain the creation of the local stress leading to this causal relationship. The first model uses intrusive magma build up and the second extrusive cone building to explain the changes in local stress. These models not only support the causal relationship between volcanism and faulting activity but also provide a new understanding into how Kora volcanic cone activity may have influenced active faulting in the Kora 3D survey. Application of this new information will allow innovative insights into basin formation, regional and local tectonics, and subducting plate geometry in the Taranaki Basin. This research could be utilized to increase knowledge for prospecting and reduce geologic uncertainty, which is of importance for the New Zealand petroleum industry at this northern end of the Taranaki Basin.

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The Schneeberg Normal Fault Zone: Normal faulting associated with Cretaceous SE-directed extrusion in the Eastern Alps (Italy/Austria)

Tectonophysics ◽

10.1016/j.tecto.2005.02.005 ◽

2005 ◽

Vol 401 (3-4) ◽

pp. 143-166 ◽

Cited By ~ 42

Author(s):

Helmuth Sölva ◽

Bernhard Grasemann ◽

Martin Thöni ◽

Rasmus Thiede ◽

Gerlinde Habler

Keyword(s):

Fault Zone ◽

Normal Fault ◽

Eastern Alps ◽

Normal Faulting

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Validation of Coupled FDM-DEM Approach on the Soil-Raft Foundation Interaction Subjected to Normal Faulting

10.5194/egusphere-egu21-9783 ◽

2021 ◽

Author(s):

Fang Ru-Ya ◽

Lin Cheng-Han ◽

Lin Ming-Lang

Keyword(s):

Active Fault ◽

Ground Deformation ◽

Numerical Models ◽

Hanging Wall ◽

Normal Fault ◽

Small Scale ◽

Foot Wall ◽

Normal Faulting ◽

Raft Foundation ◽

Overburden Soil

Recent earthquake events have shown that besides the strong ground motions, the coseismic faulting often caused substantial ground deformation and destructions of near-fault structures. In Taiwan, many high-rise buildings with raft foundation are close to the active fault due to the dense population. The Shanchiao Fault, which is a famous active fault, is the potentially dangerous normal fault to the capital of Taiwan (Taipei). This study aims to use coupled FDM-DEM approach for parametrically analyzing the soil-raft foundation interaction subjected to normal faulting. The coupled FDM-DEM approach includes two numerical frameworks: the DEM-based model to capture the deformation behavior of overburden soil, and the FDM-based model to investigate the responses of raft foundation. The analytical approach was first verified by three&#160; benchmark cases and theoretical solutions. After the verification, a series of small-scale sandbox model was used to validate the performance of the coupled FDM-DEM model in simulating deformation behaviors of overburden soil and structure elements. The full-scale numerical models were then built to understand the effects of relative location between the fault tip and foundation in the normal fault-soil-raft foundation behavior. Preliminary results show that the raft foundation located above the fault tip suffered to greater displacement, rotation, and inclination due to the intense deformation of the triangular shear zone in the overburden soil. The raft foundation also exhibited distortion during faulting. Based on the results, we suggest different adaptive strategies for the raft foundation located on foot wall and hanging wall if the buildings are necessary to be constructed within the active fault zone. It is the first time that the coupled FDM-DEM approach has been carefully validated and applied to study the normal fault-soil-raft foundation problems. The novel numerical framework is expected to contribute to design aids in future practical engineering.Keywords: Coupled FDM-DEM approach; normal faulting; ground deformation; soil-foundation interaction; raft foundation.

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Timing of post–Karoo alkaline volcanism in southern Namibia

Geological Magazine ◽

10.1017/s001675680001517x ◽

1990 ◽

Vol 127 (5) ◽

pp. 427-433 ◽

Cited By ~ 18

Author(s):

D. L. Reid ◽

A. F. Cooper ◽

D. C. Rex ◽

R. E. Harmer

Keyword(s):

Crustal Structure ◽

Surface Expression ◽

Alkaline Magmatism ◽

Precambrian Basement ◽

African Plate ◽

Age Progression ◽

Thermal Anomalies ◽

Igneous Activity ◽

Tectonic Boundaries

AbstractNew radiometric age data are reported for alkaline centres in southern Namibia, and are discussed together with published age data in terms of models put forward to account for post-Karoo (Mesozoic–Recent) alkaline magmatism within the African plate. Agreement between K–Ar and Rb–Sr ages indicate emplacement of the Dicker Willem carbonatite in southern Namibia at 49 ± 1 Ma. Alkaline rocks associated with the Gross Brukkaros volcano show a discordant radiometric age pattern, but the best estimate for the age of this complex is 77 ± 2 Ma, similar to that obtained for the neighbouring Gibeon carbonatite-kimberlite province. The Dicker Willem carbonatite is therefore younger than the Luderitz alkaline province (133 ± 2 Ma), and the Gross Brukkaros volcano, but is older than the Klinghardt phonolite field (29–37 Ma). The new age data argue against a distinct periodicity in alkaline igneous activity in southern Africa, thereby ruling out possible controls by episodic marginal upwarping of the subcontinent. Although the available age data do not appear to be consistent with the passage of one or even two hotspots under southern Namibia, it is argued that the surface expression of hotspots under continents may be so large and overlapping that within-plate magmatism attributed to these thermal anomalies need not necessarily be confined to narrow linear belts or show an age progression. The role of hotspots in continental alkaline magmatism is most likely one of melt generation, while local crustal structure probably controls the distribution and timing of eruption. Major tectonic boundaries in the Precambrian basement underlying southern Namibia seem to have controlled the development of Tertiary alkaline centres in that region.

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