Width Of Deformation Zone Research Articles

The 2023 Pazarcık (Kahramanmaraş, Türkiye) earthquake (M w 7.7): implications for surface rupture dynamics along the East Anatolian Fault Zone

Southern Türkiye faced widespread catastrophic destruction by two devastating earthquakes on the same day. As the earthquakes occurred at 04:17 (M w = 7.7, Pazarcık, Kahramanmaraş) and 12:30 (M w = 7.6, Elbistan, Kahramanmaraş) on 6 February 2023, neighbouring active fault systems were broken in succession between the Hatay and Malatya provinces in the region. The first earthquake, one of the largest earthquakes in this region during the last century, caused major fatalities and widespread damage to infrastructure and buildings, and produced large-scale seismo-gravitational surface deformation such as landslides, lateral spreading, liquefaction and extensional cracks. Here, we present the surface rupture geometry and coseismic displacement characteristics of the fault systems, determined by field observations immediately after the 6 February 2023 Pazarcık (Kahramanmaraş, Türkiye) earthquake (M w = 7.7). Preliminary results show that the total rupture length ( L max ) is 270 ± 10 km on the Karasu, Pazarcık and Erkenek segments of the East Anatolian Fault Zone. Left-lateral strike-slip faulting developed with a maximum horizontal displacement ( D max ) of 7.30 m and an average displacement ( D avg ) of 3.00 m. Although the surface rupture generally exhibits a narrow deformation zone width of 2–5 m, this expands to 50 m in some sections of the faults. The implications for rupture dynamics suggest that fracture development started on a secondary fault (Narlı Fault), transferred to the main fault and triggered the breaking of asperities on the Pazarcık segment, which exhibits a long period of accumulation of stress, to initiate the major rupturing. Supplementary material: Figures S1–S12 with details on coseismic displacement are available at https://doi.org/10.6084/m9.figshare.c.6487245

Crack growth path of high-strength steel with different toughness under monotonic and cyclic loadings

In this paper, the crack growth path of 4340 steel with different toughness was studied in quasi-in-situ testing by scanning electron microscopy and X-ray technology. The crack growth behavior under monotonic loading shows that the critical load and crack growth distance increase with the fracture toughness. The angles between the crack growth direction and loading direction are 43.07° for 180 °C tempered steel, 28.36° for 350 °C tempered steel and 34.69° for 500 °C tempered steel, respectively. The crack grows synchronously in high fracture toughness steel, demonstrating high crack resistance and large energy consumption. The severe deformation zone width of 4340 steel after first unloading increases from 7.5 μm to 28.1 μm with fracture toughness. On the other hand, the crack growth behavior under cyclic loading displays that the surface roughness in high fracture toughness steel is higher than those in low fracture toughness steel. The fatigue cycle of high fracture toughness steel is nearly twice higher than that of low fracture toughness steel. Macro/micro crack bifurcation, crack growth uniformity, crack surface roughness and plastic deformation complexity play significant roles in the crack resistance of materials. These findings would provide an in-depth understanding for the damage tolerance design of high-strength steel.

Wall thickness control in multi-stage hydroforming of multiwave seal ring with small diameter

Thinning rate is a crucial factor in forming quality of the thin-walled seal ring with complex features. To control the excessive thinning by altering the stress state during the material deformation, a new multi-stage three-dimensional (3D) hydroforming technology was proposed in this work. Based on the characteristics of the seal ring and the used superalloy strip, a multi-stage internal pressure forming process was established through finite element analysis (FEA) and forming experiment verification. In addition, the distribution of wall thickness in every stage was discussed. And the influence of the width of deformation zone and the pressure loading path in the cavity on the wall thickness of the part in each step was studied. Finally, the optimal forming parameters of each step that can achieve a stable state of metal flow were obtained. The experimental results demonstrated that the developed 3D hydroforming technology can accurately control the material flow in the multi-stage forming of the multi-wave seal ring with small-diameter and ultrathin wall thickness. For the optimized parameter combination, the blank dimensions of deformation zone are 8 mm in the first step and 18 mm in the second step, while the pre-bulging pressure is 9 ~ 12 MPa and the maximum pressure is 100 MPa in the two steps.

Stress-strain state of metal in deformation zone during production of steel section billets on the unit of combined continuous casting and deformation. Report 2

Stress state of metal in deformation zone during introduction of the separating collars of the grooved die into continuously casted steel slab was calculated for production of section billets on the unit of combined continuous casting and deformation. Calculation of axial, tangential and equivalent stresses arising in deformation zone of metal was made in four sections of deformation zone and its results are presented in specific points and lines. View of the section of deformation zone and location of specific points are provided. The stress state of metal in zone of cyclic deformation at formation of three steel section billets from continuously cast slab by separating collars of grooved die on the unit of combined continuous casting and deformation was determined by solving extensive problem of elasticity with the finite element method using the ANSYS package. The results of calculation of axial, tangential and equivalent stresses according to Mises in deformation zone are given in form of graphs and tables for working surfaces in four cross sections. The values and regularities of distribution of these stresses along the length and width of deformation zone were determined. The character of axial stresses distribution by characteristic lines located along the length of deformation zone is shown. Values of the highest compressive and tensile axial stresses arising in deformation zone during introduction of separating collars of grooved were obtained for the unit of combined continuous casting and deformation.

Laboratory Model Test of EPB Shield Tunneling in a Cobble-Rich Soil

Model tests and field measurements were carried out to study the mechanical behavior of cobble-rich soil in response to shield tunneling. In particular, an experimental investigation was carried out using a laboratory-scale model. The model used includes a miniature shield machine that can approximate real tunnel construction, replicating the in-situ methods of excavation and support. The surface settlement and subsurface deformation were analyzed, and these data were compared with predictions based on previous studies. The results confirm that the model tests can effectively simulate the principal operations of a real earth-pressure-balance machine. The observed surface settlement troughs in both the transverse and longitudinal directions were found to be narrower than in clay or sandy soils. With respect to subsurface deformation, the deformation zone width decreases almost linearly as a function of depth.

Centrifuge modeling of reverse fault rupture propagation through single-layered and stratified soil

Many buildings have been built over active faults. Surface faulting as a main effect of earthquakes can cause damage such buildings. Properties of material over bedrock affect the pattern of rupture propagation through deposits and the width of the rupture zone on ground surface. Several researchers have primarily studied fault rupture propagation patterns on single-layered granular soil; however, natural geologic deposits are rarely homogeneous and uniform, but mostly consist of different layers. In this study, centrifuge model tests were conducted to investigate the patterns of reverse fault rupture propagation through single and double-layered soil stratum. It was observed that the soil type and sequence of layers affected the fault rupture propagation pattern as well as the surface rupture zone. The results show that the width of deformation zone tends to decrease in stiffer soil in compare to softer soil. These findings may help to produce a framework for predicting the occurrence and geometry of surface fault rupture zone that, can help us to define a setback zone, which is a major concern in building codes.

Effects of spall edge profiles on the edge plastic deformation for a roller bearing

A clear understanding of the plastic deformations at the spall edges is a primary task for the edge propagation predictions in rolling element bearings. This work proposed an elastic–plastic two-dimensional finite element model for calculating the contact stress and plastic deformation between the rolling element and raceway. This model includes a rolling element and one raceway. The rectangular plane strain solid elements are used to formulate the finite element model. The Coulomb model is used to formulate the friction force between the rolling element and raceway. A bilinear kinematic hardening material model is used in the finite element model, which can formulate the elastic–plastic deformations. The studied spall edge profiles are assumed to be sharp and cylindrical ones. To validate the finite element model, the contact deformations between the rolling element and the raceway from the proposed model and Hertzian contact theory are compared. Effects of spall edge profiles on the edge plastic deformations at the edge are analyzed, as well as the edge plastic deformation zone width. Based on the numerical results, the relationship between the edge plastic deformation and the spall edge profile, and that between the edge plastic deformation zone width and the spall edge profile are established. The results show that the edge plastic deformation is significantly influenced by the spall edge profiles, as well as the edge plastic deformation zone width. This paper provides a clear understanding of the effects of the edge profiles on the plastic deformations and propagation at the spall edge.

Salt diapir reactivation and normal faulting in an oblique extensional system, Vulcan Sub-basin, NW Australia

Oblique extension and salt diapirism have their own distinct mechanisms that control the geometry and kinematics of structures. In this study, we document a geological phenomenon from the Vulcan Sub-basin in NW Australia that combines these processes: a salt diapir reactivated in an oblique extensional system. Detailed structural analysis of this natural example, with a focus on normal fault systems, allows characterization of the oblique extensional system and investigation of how the pre-existing structural fabrics and salt diapir control deformation, and interact with each other under oblique extension. After comparison with forward modelling results and using constraints from geological evidence, our fault strike analysis indicates that the Neogene flexural extension orientation in the oblique extensional system is around 347°, revealing a perpendicular relationship between extension direction and fault strikes from the deformation zone. The salt diapir, reactivated during Neogene extension, strongly influences local structure in the oblique extensional system by altering fault strikes, stepping patterns, deformation zone width and fault density, indicative of a ‘stress–strain concentration’ effect of the salt diapir owing to its extremely low strength. These results provide valuable insights into the understanding of oblique extensional systems, the geomechanical role of salt during extension, and the Neogene tectonic evolution of NW Australia. Supplementary material : Dominant seismic frequency analysis, uninterpreted seismic profiles, additional structural and isochron maps, a 3D view of fault systems, and original measurements of the fault system are available at http://doi.org/10.6084/m9.figshare.c.3148321 .

Off-fault damage and acoustic emission distributions during the evolution of structurally complex faults over series of stick-slip events

Variations in fault structure, for example, surface roughness and deformation zone width, influence the location and dynamics of large earthquakes as well as the distribution of small seismic events. In nature, changes in fault roughness and seismicity characteristics can rarely be studied simultaneously, so that little is known about their interaction and evolution. Here, we investigate the connection between fault structure and near-fault distributions of seismic events over series of stick-slip cycles in the laboratory. We conducted a set of experiments on rough faults that developed from incipient fracture surfaces. We monitored stress and seismic activity which occurred in the form of acoustic emissions (AEs). We determined AE density distributions as a function of fault normal distance based on high-accuracy hypocentre locations during subsequent interslip periods. The characteristics of these distributions were closely connected to different structural units of the faults, that is, the fault core, off-fault and background damage zone. The core deformation zone was characterized by consistently high seismic activity, whereas the off-fault damage zone displayed a power-law decay of seismic activity with increasing distance from the fault core. The exponents of the power-law-distributed off-fault activity increased with successive stick-slip events so that later interslip periods showed a more rapid spatial decay of seismic activity from the fault. The increase in exponents was strongest during the first one to three interslip periods and reached approximately constant values thereafter. The relatively rapid spatial decay of AE events during later interslip periods is likely an expression of decreasing fault zone complexity and roughness. Our results indicate a close relationship between fault structure, stress and seismic off-fault activity. A more extensive mapping of seismic off-fault activity-decay has the potential to significantly advance the understanding of fault zone properties including variations in fault roughness and stress.

Joining Porous and Compact Titanium by Laser Welding and Plastic Deformation

Joining porous elements (40-45% porosity) prepared by compaction and sintering of titanium powder (PTKh2-1) with compact titanium (VT1-0 and VT-6) by laser welding and plastic deformation is studied. Welding is accomplished by a pulsed-periodic laser Nd:YAG (λ = 1.06 μm). It is shown that prior mechanical treatment of porous surfaces improves welded joint quality. A joint may be obtained without the use of filler or consumable materials. Optimum welding regimes are determined. A permanent joint may also be prepared by local plastic deformation of an enveloping porous article and “flow” of its material into the groove of a compact article. Optimum production and structural parameters are determined: the level of relative deformation, deformation zone width, and relative groove height.

Tectonic evolution of the Niksar and Tasova–Erbaa pull-apart basins, North Anatolian Fault Zone: their significance for the motion of the Anatolian block

The Tasova–Erbaa and Niksar basins are two adjacent pull-apart basins along the North Anatolian Fault Zone (NAFZ). Within the Tasova–Erbaa basin, sedimentary lithofacies of the Upper Pontus Formation (Plio-Pleistocene) are asymmetrically distributed, with laterally derived alluvial fans, coarse braid plain deposits, and axial braided stream deposits dominating the northern and western parts of the basin. The basin has gently dipping sediments locally affected by pervasive extensional (T) faulting. Isolated compressional structures are associated with master faults (deformation zone width ≤500 m). Pervasive extensional faults (T and R?) and late-stage PDZ-parallel compressional faults are also present. An additional set of extensional faults trends perpendicular to the PDZ, accommodating secondary pull-apart stretching within the basin. The distribution of sedimentary facies and structural styles is consistent with that predicted by models for pull-apart basins. The adjacent Niksar basin is an active pull-apart basin, possibly as young as 0.5–1 Ma. Its modern drainage and sedimentary facies are symmetrically arranged. Adding the lengths of the Tasova–Erbaa and Niksar basin suggests ∼80 km total displacement along the North Anatolian fault, which is consistent with Seymen (ITU Ph.D. Thesis, 1975), Sengor [J. Geol. Soc. 136 (1979) 269–282] and Armijo et al. [Tectonophysics 243 (1999) 135–154], who observed about 85±5 km total displacement along the North Anatolian fault. The change in course of the North Anatolian fault, marked by the formation of the Niksar–Ezinepazari segment, and this new geometry suggest that the Anatolian block is rotating anticlockwise by having two separate poles: one located near Damascus and the other occurring north of the Sinai peninsula. This change may also mark the transfer of the Anatolian triple junction from Erzincan to Karliova about 1 Ma ago. Furthermore, it appears that while the fault shortcuts the older basin, a new generation of pull-apart basins is formed due to changes of boundary conditions along the fault zone.

Ascent of a granitoid diapir in a temperature varying medium

A relationship for the ascent velocity of a granitoid diapir is derived and used in conjunction with a crustal heat flow model which incorporates a depth‐dependent temperature to predict emplacement histories. Ascent rate is strongly dependent on the width of a deformation layer of variable viscosity that is formed by the transfer of heat to the country rock and on the buoyancy force which propels the diapir through it. Ascent velocity is described by the expression U∞ = 2Δρgd3Z/μ0R, where Δρ is the density contrast between diapir and country rock, g is gravitational acceleration, d is the deformation zone width, Z is a parameter which describes the increase in viscosity across the zone, μ0 is the country rock viscosity at the contact, and R is the diapir radius. The width of the deformation zone, as dictated by the temperature distribution and rheological function, is the point at which the viscosity increases by a factor F from the contact value. Although ascent rates vary with choice of this parameter, ascent distances are not strongly dependent on F. Results of simulations which incorporate a spectrum of input parameters reveal that ascent distance is strongly dependent on both the rheology and ambient temperature of the encompassing rock, but only weakly dependent on the initial diapir temperature. Ascent velocity varies with the diapir size, with larger bodies moving more slowly and ascending for longer periods relative to smaller plutons. As a result of the proportionately larger amount of thermal energy available for ascent, larger bodies will rise greater distances than smaller diapirs. However, the additional ascent appears nominal relative to the contrast in available energy. Modeling diapirs using a no‐slip boundary condition decreases ascent velocity by a factor of about 3 relative to results incorporating a stress‐free boundary condition. The time scale of granitoid diapirism over crustal distances cannot be less than 104 years, due to the rate limiting effect of thermal conduction above the body, and not greater than ∼105 years, reflecting solidification times of kilometer‐sized plutons. A consequence of ascent by a deformation zone mechanism is the generation, following emplacement, of a mechanically weakened crust which extends from beneath the diapir to near the source, perhaps explaining the relatively common occurrence of synmagmatic to postmagmatic mafic dikes within granites believed to be derived from interaction of basalt with the lower crust.