Propagation Arrest Research Articles

Sequential phreatomagmatic eruptions during the lateral propagation of giant dyke swarms

Giant dyke swarms are widely developed on Earth, Venus, and Mars and form by lateral propagation of constituent dykes over hundreds to thousands of kilometers. The failure of these dykes to erupt magma at surface partly accounts for their long-range propagation. However, the lack of preservation of the upper regions of most terrestrial dykes is a barrier to fully explaining the reasons for this upward arrest below ground level. Here we use 3-D seismic and well data to document the near surface expression of dykes comprising the Mull Dyke Swarm from the southern North Sea (UK). The upper tips of these dykes are overlain by linear arrays of craters with deeply eroded bases. Craters are flanked by a tephra apron comprising reworked chalky sediments. The well data allow us to exclude crater forming mechanisms based on collapse into a void but are consistent with those linked to phreatomagmatic eruption. We propose that the rapid cooling of dyke magma during the phreatomagmatic eruptive process was an important contributory factor in the upward arrest of dyke propagation, preventing surface extrusion and hence promoting lateral propagation.

Crack propagation arrest by the Joule heating in micro/nano-sized structures

The Joule heating technique is utilized to arrest the crack propagation so to protect some important structures being further damaged. In this approach there are created compression stresses at the crack tip vicinity due to a specific temperature distribution induced by the electric current. The Joule heating is amulti-physical problem which is applied here to micro/nano-sized structures. The size-effects are considered for description of both the elastic and the thermal fields. The heat conduction can’t be well described by classical Fourier’s law in nano-sized structures. A novel gradient theory is developed in such structures adopting the size effect of heat conduction. Besides, the strain gradients and double stresses are introduced into the constitutive laws. Then, the governing equations are given by partial differential equations with order of derivatives being higher than in classical theory. The principle of virtual work is the base of weak formulation and derivation of the discretized finite element equations for ageneral 2d boundary value problem with cracks. The collocation mixed FEM with large strain gradients is developed for numerical solution, where the C0 continuous approximation is applied independently to displacements and strains and also to temperature and temperature gradients. Kinematic constraints between strains and displacements are satisfied by the collocation method at selected interior points. The collocation mixed FEM is applied to solve 2D crack problems with Joule heating.

Crack Propagation Arrest by the Joule Heating in Micro/Nano-Sized Structures

The concept of crack arrest design is proposed to enhance the safety of structures reducing the probability of crack propagation. The goal of crack arrest methods is to create compression stresses at the crack tip vicinity to stop the crack propagation. The thermal field at the crack tip vicinity can create such compression stresses. If a cracked electrically conductive structure is subjected to an electric load, a high temperature is induced by the Joule heating effect in regions subjected to higher electric current densities. A reliable computational method based on gradient theory is developed in the present paper. Due to a high concentration of electro-thermal-mechanical fields at the crack tip vicinity, the size effects are considered for both mechanical equation and the thermal transport. The strain gradients are included into the constitutive equations for the double stress tensor and electric displacements. Due to occurrence of higher order derivatives in governing equations of gradient theories it is needed to develop the collocation mixed FEM. The collocation mixed FEM is applied to our multiphysical problem with size effects for mechanical and thermal fields, where the C° continuous approximations are applied independently to displacements and strains and also to temperature and temperature gradients.

Megathrust reflectivity reveals the updip limit of the 2014 Iquique earthquake rupture

The updip limit of seismic rupture during a megathrust earthquake exerts a major control on the size of the resulting tsunami. Offshore Northern Chile, the 2014 Mw 8.1 Iquique earthquake ruptured the plate boundary between 19.5° and 21°S. Rupture terminated under the mid-continental slope and did not propagate updip to the trench. Here, we use state-of-the-art seismic reflection data to investigate the tectonic setting associated with the apparent updip arrest of rupture propagation at 15 km depth during the Iquique earthquake. We document a spatial correspondence between the rupture area and the seismic reflectivity of the plate boundary. North and updip of the rupture area, a coherent, highly reflective plate boundary indicates excess fluid pressure, which may prevent the accumulation of elastic strain. In contrast, the rupture area is characterized by the absence of plate boundary reflectivity, which suggests low fluid pressure that results in stress accumulation and thus controls the extent of earthquake rupture. Generalizing these results, seismic reflection data can provide insights into the physical state of the shallow plate boundary and help to assess the potential for future shallow rupture in the absence of direct measurements of interplate deformation from most outermost forearc slopes.

Intermittent lab earthquakes in dynamically weakening fault gouge.

Large and destructive earthquakes on mature faults in Earth's crust occur as slip in a layer of a fine granular material-fault gouge-produced by comminution during sliding1,2. A range of insights into the frictional resistance of faults-one of the main factors controlling earthquake nucleation, dynamic propagation and arrest, and hence the destructive ground shaking of earthquakes2,3-has been obtained in experiments with spatially uniform slip imposed in small samples2,4-21. However, how various features of gouge friction combine to determine spontaneous progression of earthquakes is difficult to study in the lab owing to substantial challenges with sample sizes and adequate imaging22. Here, using lab experiments, we show that spontaneously propagating dynamic ruptures navigate a fault region with fine rock gouge through complex, intermittent slip processes with dramatic friction evolution. These include repeated arrest of rupture propagation caused by friction strengthening at lower slip rates and dynamic earthquake re-nucleation enabled by pronounced rapid friction weakening at higher slip rates consistent with flash heating8,12,23. The spontaneous repeated weakening and strengthening of friction in fine rock gouge highlights the fundamental dependence of friction on slip rate and associated processes, such as shear heating, localization and delocalization of shear, and dilation and compaction of the shear layer6,7,9-21. Our findings expand experimental support9,11 of the concept that co-seismic weakening may enable earthquake rupture to break through stable fault regions24,25, with substantial implications for seismic hazard.

Internal architecture and earthquake rupture behavior of a long-lived intraplate strike–slip fault: A case study from the Southern Yangsan Fault, Korea

Deciphering the internal composition of large-scale fault zones helps to better understand the various geologic factors that govern their seismic rupture behavior. We used new detailed geologic, structural, and geomorphic map of an excellent natural laboratory in the Southern Yangsan Fault (SYF) in the southeastern part of the Korean Peninsula to elucidate the fault zone architecture and its controls on the rupture processes of neotectonic earthquakes. The Yangsan Fault is a major strike–slip fault, and a subsidiary fault within the fault zone ruptured during the 2016 ML 5.8 Gyeongju earthquake which is the largest instrumental record in the intraplate Korean Peninsula. The 12-km-long study area in the SYF shows along-strike variations in wall rock lithology and fault zone architecture. At the south of the study area, the fault zone surrounded by crystalline rocks consists of a single major fault core. In contrast, at the north, the fault zone is sandwiched between crystalline rocks and sedimentary rocks and exhibits multiple major fault cores bounding broken-up wall rock blocks. The width of the across-fault damage zone, which was estimated from the cumulative fracture frequency with the distance from the major fault core, widens northward, indicating the distributed deformation of the northern fault zone over a long history of fault evolution. The geometry of paleoearthquake surface ruptures traced by the geomorphic and stratigraphic evidence of deformed young deposits diverge to multiple strands in the northern fault zone but converge to a single strand in the southern fault zone, directly reflecting its internal architecture. We propose that the long-lived rupturing patterns have been primarily controlled by intrinsic discontinuity- and mineralogy-dependent deformation processes in terms of strain-hardening vs. strain-weakening, along with propagation arrest and rupture tip damage due to a fault-bend geometry (geometric barrier) and an abrupt change in wall rock lithology (relaxation barrier).

Unstable fracture phenomenon of welded joints with weld residual stresses

Residual stress variations were determined through small- and large-scale specimen welds using neutron diffraction to evaluate the effect of residual stress on the brittle crack propagation path. The results revealed that significant tensile stresses accelerated brittle crack propagation, while compressive stresses obstructed the brittle crack propagation path. The evaluations were performed using small scale specimens, such as CT specimens. To assess the brittle crack propagation arrest toughness, tests with full-scale specimens were performed. The objective was to clarify the mechanism of brittle crack propagation arrest in welds and to establish the basic theory of a welding technique that uses compressive residual stress to prevent brittle fracture.

Propagation of microwave surface-wave-sustained discharge in air

The propagation dynamics of the gas microwave discharge front in a quartz tube filled with air is studied experimentally. The discharge is initiated and sustained by the dipolar mode (m = 1) of the propagating surface electromagnetic wave (SEW). The discharge front propagation regime was experimentally discovered, which is characterized by the arrest of propagation of the discharge front, the plasma decay and the subsequent resumption of the translational motion, but at a lower propagation velocity. The distributions of the SEW electric field and the integrated discharge luminosity along the plasma column are measured. The mean plasma density in the tube was estimated using data on the measured SEW wavelengths and the dispersion relation.

Consideration on the toughness difference depending on the direction of brittle crack propagation in very thick steel

In recent years, the steel plates used in large structures such as container ships have become extremely thick, and their strength is increasing. Since the risk of brittle fracture increases as the steel plate thickness increases (T. Ishikawa et al, 2004), it is important to properly stop brittle cracks generated from the viewpoint of ensuring safety. In the discussion about fracture safety of large container ships from the viewpoint of arrest in these ten years, two fracture safety scenarios were established. Recently an important experimental fact that the brittle crack stopping toughness Kca is lower in scenario 1 than in scenario 2 was found, but the cause has not revealed yet. In order to clarify the cause of this experimental fact, the authors carried out the three-sided slitted Charpy test and the DWTT test in which the propagation direction of the crack was devised. Parameters such as mis-orientation between neighbour grains and fracture surface roughness were calculated, and the correlation with brittle crack propagation arrest properties was examined.

Current-Induced Ductility Enhancement of a Magnesium Alloy AZ31 in Uniaxial Micro-Tension Below 373 K.

The size effects in metal forming have been found to be crucial in micro-scale plastic deformation or micro-forming processes, which lead to attenuation of the material’s formability due to the increasing heterogeneity of the plastic flow. The use of an electric field during micro-scale plastic deformation has shown to relieve size effects, enhance the material’s formability, modify the microstructure, etc. Consequently, these electric-assisted (EA) micro-forming processes seem to bring many potential benefits that need to be investigated. Accordingly, here we investigated the influence of an electric field on the size effects to describe the fracture behavior in uniaxial micro-tension tests of an AZ31 alloy with various grain sizes. In order to decouple the thermal-mechanical and microstructure changes, room temperature (RT), oven-heated (OH), air-cooled (AC), and EA uniaxial micro-tension tests were conducted. The size effects contribution on the fracture stress and strain showed a similar trend in all the testing configurations. However, the smallest fracture stresses and the largest fracture strains were denoted in the EA configuration. EBSD examination shows that current-induced dynamic recrystallization (DRX) and texture evolution could be negligible under the studied conditions. The kernel average misorientation (KAM) maps give the larger plastic deformation in the EA specimens due to the reduction of plastic micro-heterogeneity. Finally, the fracture morphology indicates that the current-induced ductility enhancement may be attributed to the arrest of micro-crack propagation and the inhibition of void initiation, growth, and coalescence caused by lattice melting and expansion.

Mechanical behavior of mallow fabric reinforced polyester matrix composites

Woven fabrics made of a natural lignocellulosic mallow fiber have been used for a long time in common clothes. Recently, these fabrics are being considered as reinforcement for engineering composites. This work investigates the basic mechanical behavior of polyester composites reinforced with up to 40vol% of mallow fabric. Room temperature tensile tests allow the evaluation of properties, such as the ultimate strength, elastic modulus, resilience and total strain. An improvement in these properties was found with increasing amount of mallow fabric in the composite. Indeed, a significant increase in strength, modulus and resilience occurred up to 40vol% of fabric reinforcement. A slight increase was also observed in the total strain. Fracture analysis by scanning electron microscopy revealed that this improved performance of the reinforced composites might directly be associated with arrest of cracks propagation in the brittle polyester matrix by the mallow fibers in the fabric.

Research of the crack development process in a nickel heat-resistant alloyin the process of testing

A method of direct observation of the process of low-cycle fatigue crack development during bend loading directly in the chamber of a scanning electronic microscope is described in the paper. It was found that the presence of slip bands near the apex of the crack is the determining factor of crack development in a specimen made of a nickel heat-resistant alloy with a monocrystalline structure. The fracture in the area of the crack apex was found to be of a brittle nature. In the case of crack propagation arrest before an obstacle an area of plastic deformation forms at some distance from the apex of the crack, with branches from the main crack.  Crystallographic orientation of the specimen was determined using the X-ray structure analysis and the Shmid factor was calculated for glide planes along which the fracture took place and secondary cracks were formed. The prevailing direction of the crack development was determined by slip systems with the value of Shmid factor maximum for the given conditions. It is shown that the described method of observation of the material structure and crack propagation under low-cycle fatigue makes it possible to obtain unique information about the fracture pattern and the impact of the material’s structure on its characteristics. The results can be used to determine the choice of the most favorable crystallographic orientation of the monocrystalline structure of the material of gas turbine engine blades relative to their geometry.

Research of the crack development process in a nickel heat-resistant alloyin the process of testing

A method of direct observation of the process of low-cycle fatigue crack development during bend loading directly in the chamber of a scanning electronic microscope is described in the paper. It was found that the presence of slip bands near the apex of the crack is the determining factor of crack development in a specimen made of a nickel heat-resistant alloy with a monocrystalline structure. The fracture in the area of the crack apex was found to be of a brittle nature. In the case of crack propagation arrest before an obstacle an area of plastic deformation forms at some distance from the apex of the crack, with branches from the main crack. Crystallographic orientation of the specimen was determined using the X-ray structure analysis and the Shmid factor was calculated for glide planes along which the fracture took place and secondary cracks were formed. The prevailing direction of the crack development was determined by slip systems with the value of Shmid factor maximum for the given conditions. It is shown that the described method of observation of the material structure and crack propagation under low-cycle fatigue makes it possible to obtain unique information about the fracture pattern and the impact of the material’s structure on its characteristics. The results can be used to determine the choice of the most favorable crystallographic orientation of the monocrystalline structure of the material of gas turbine engine blades relative to their geometry.

Experimental investigation of hydraulic fracture propagation in fractured blocks

Natural fractures in reservoirs can be the cause of many adverse effects during hydraulic fracturing treatment. In the present paper, hydraulic fracturing tests are used to investigate the interaction of a propagating hydraulic fracture with a natural fracture in the fractured blocks. Systematic experiments were designed and performed on the cement blocks with different pre-existing fracture strikes and dips (30°, 60° and 90°). The effect of horizontal stress difference on the propagation of hydraulic fractures was also determined through a series of experiments with different values for Δσ, which were 5 and 10 MPa, respectively. Propagation arrest of the hydraulic fracture and crossing the pre-existing fracture were two dominating fracture behaviors at horizontal stress differences of 5 and 10 MPa, respectively. It was observed that both the magnitude of differential stress and the pre-existing fracture geometry can magnify the effect of a pre-existing fracture on hydraulic fracture propagation. When the horizontal differential stress is low (5 MPa), the hydraulic fracture crosses the pre-existing fracture at a high pre-existing fracture dip (90°) and at an intermediate to high pre-existing fracture strike (60°–90°), while hydraulic fracture is arrested by the opening of the pre-existing fracture at a pre-existing fracture strike (30°). Meanwhile, when the pre-existing fracture dip is low to intermediate (30°–60°) and its strike is low to high (30°–90°), hydraulic fracture is arrested by the opening and shear slippage of the pre-existing fracture in this situation. However, at a high horizontal differential stress (10 MPa), when the pre-existing fracture dip is low to high (30°–90°), the hydraulic fracture crosses the pre-existing fracture at the strike of the pre-existing fracture of 60°–90°, and when it is decreased to 30°, the hydraulic fracture is arrested by th eopening and shear slippage of the pre-existing fracture. Therefore, the pre-existing fracture’s strike and dip play a significant role in the propagation of hydraulic fracture at a low horizontal stress difference, while the role of the pre-existing fracture dip at a high horizontal stress difference is less than the pre-existing fracture strike on the propagation of hydraulic fracture.

The phenomenon of self-trapping of a strongly nonlinear wave

Self means here an effect of a wave on itself. Several self-action phenomena are known in nonlinear wave physics. Among them are self-focusing of beams, self-compression of light pulses, self-channeling, self-reflection (or self-splitting) waves with shock fronts, self-induced transparency, and self-modulation. These phenomena are known for weakly nonlinear waves of different physical origin. Our presentation at ASA meeting in Montreal [POMA 19, 045080 (2013)] was devoted to strongly nonlinear waves having no transition to the linear limit at infinitesimally small amplitudes. Such waves can demonstrate particle-like properties. Self-trapping consists of the arrest of wave propagation and in the formation of a localized state. In particular, the model generalizing the Heisenberg' ordinary differential equation to spatially distributed systems predicts periodic oscillations but no traveling waves. Different models for strongly nonlinear waves will be considered and some unusual phenomena will be discussed. Preliminary results were published in Ac. Phys. 59, 584 (2013) and Physics-Uspekhi (Adv. Phys. Sci.) 183, 683 (2013). [This work was supported by the Megagrant No.11.G34.31.066 (Russia) and the KK Foundation (Sweden).]

Nucleation and arrest of dynamic slip on a pressurized fault

Elevated pore pressure can lead to reactivation of slip on pre‐existing fractures and faults when the static Coulomb failure is reached locally. As the pressurized region spreads diffusively, slip can accumulate quasi‐statically (paced by the pore fluid diffusion) or dynamically. In this work, we consider a prestressed fault with a locally peaked, diffusively spreading pore pressure field to study (1) conditions leading to the escalation of slip and nucleation of dynamic rupture and (2) rupture run‐out distance before it is arrested. Nucleation appears in this model when the fault friction decreases from its peak value with slip, while arrest of dynamic propagation is imminent on aseismic faults (i.e., such that prestressτb is less than the residual fault strength τrat ambient conditions). When fluid overpressure is a small‐to‐moderate fraction of the ambient value of normal effective stress (and prestress is large enough for fault slip to be activated by overpressure), dynamic rupture always nucleates, and the nucleation length increases with decreasing prestress practically independently of the overpressure value. Transition from the ultimately unstable (τb > τr) to the ultimately stable (τb < τr) fault loading is marked by a strong increase of the nucleation length (∝1/(τb − τr)2) as τb approaches τr from above. For aseismic faults (τb < τr), no dynamic rupture is nucleated at large fluid overpressures for all but the smallest values of prestress. The largest run‐out distances of dynamic slip on aseismic faults correspond to overpressure/prestress just sufficient for slip activation. In such cases, the dynamically accumulated slip can lead to enhanced, dynamic fault weakening, resulting in a sustained dynamic rupture and generating a large earthquake. This is consistent with field observations when the largest injection‐induced seismicity occurred after fluid injection ended.

Transient dike propagation and arrest near the level of neutral buoyancy

Abstract We present a finite difference/perturbation method to investigate transient dike propagation from a magma chamber 1–2 km below the level of neutral buoyancy in oceanic crust and explore the role of density gradation in dike propagation arrest. The dike is modeled as a magma-filled blade crack and the host rock is assumed to be a linear elastic medium with graded mass density. An integral equation approach is used to obtain the dike propagation velocity and stress intensity factor at the propagating dike tip. The finite difference/perturbation method is applicable generally to mafic dikes with ηV less than 50 Pa-m, where η is the magma viscosity and V the dike propagation velocity. Numerical results show that dike propagation velocity initially increases with dike length, reaches a peak value when the dike tip reaches a position well above the level of neutral buoyancy and then rapidly decreases to zero after the dike propagates further into the region above the level of neutral buoyancy, which indicates that density gradation is an effective mechanism for dike arrest. The effects of host-rock fracture toughness and magma chamber depth relative to the level of neutral buoyancy are also discussed.

Conditions for the arrest of a vertical propagating dyke

Magma ascent towards the Earth’s surface occurs through dyke propagation in the vast majority of cases. We investigate two purely mechanical effects unrelated to cooling or solidification that lead to the arrest of propagation, so that no eruption occurs. The first is that the input of magma from the source is not maintained continuously, such that a fixed volume of magma is released. Laboratory experiments show that, in this case, the dyke stops at a finite distance from the source. This behaviour is specific to the fracturing process in 3-D. We derive a relationship for the minimum magma volume required for an eruption as a function of magma buoyancy and source depth. When large magma volumes are available, eruption may also be prevented by a thick low density layer in the upper crust. Numerical studies of dyke propagation show that the dyke continues to rise even though it is negatively buoyant. Magma accumulates in a swollen nose region at the interface between the low density layer and the dense basement. Magma overpressure is largest at this interface and increases with increasing penetration into the upper layer. It may become large enough to induce horizontal fractures in the dyke walls and lateral intrusion of a sill, which prevents eruption. This requires that the thickness of the low density layer exceeds a threshold value that depends on the density contrast between magma and host rock. If the magma volume is smaller than a threshold value, neither sill intrusion nor eruption are possible and magma gets stored in a horizontal blade-shaped dyke straddling the interface. Scaling laws for variations of ascent rate and for the minimum magma volume allow diagnosis of a failed eruption.

Eruption versus intrusion? Arrest of propagation of constant volume, buoyant, liquid‐filled cracks in an elastic, brittle host

When a volume of magma is released from a source at depth, one key question is whether or not this will culminate in an eruption or in the emplacement of a shallow intrusion. We address some of the physics behind this question by describing and interpreting laboratory experiments on the propagation of cracks filled with fixed volumes of buoyant liquid in a brittle, elastic host. Experiments were isothermal, and the liquid was incompressible. The cracks propagated vertically because of liquid buoyancy but were then found to come to a halt at a configuration of static mechanical equilibrium, a result that is inconsistent with the prediction of the theory of linear elastic fracture mechanics in two dimensions. We interpret this result as due to a three‐dimensional effect. At the curved crack front, horizontal cracking is necessary in order for vertical propagation to take place. As the crack elongates and thins, the former becomes progressively harder and, in the end, impossible to fracture. We present a scaling law for the final length and breadth of cracks as a function of a governing dimensionless parameter, constructed from the liquid volume, the buoyancy, and host fracture toughness. An important implication of this result is that a minimum volume of magma is required for a volcanic eruption to occur for a given depth of magma reservoir.

Interaction between Epsomite Crystals and Organic Additives

A number of phosphonates and carboxylates were tested as potential crystallization inhibitors for epsomite (MgSO4·7H2O). Epsomite nucleation is strongly inhibited in the presence of amino tri(methylene phosphonic acid) (ATMP), diethylenetriaminepentakis (methylphosphonic acid) (DTPMP), and poly(acrylic acid) sodium salt (PA). These additives also act as habit modifiers promoting the growth of acicular crystals elongated along the [001] direction. Environmental scanning electron microscopy (ESEM), Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), and molecular modeling of additive adsorption on specific epsomite (hkl) faces are used to identify how these additives inhibit epsomite crystallization. Additives attach preferentially on epsomite {110} faces, at edges of monolayer steps parallel to [001]. Step pinning and the eventual arrest of step propagation along ⟨110⟩ directions account for the observed habit change. Hydrogen bonding between the functional groups of additive mol...