Influence of Shear Heating and Thermomechanical Coupling on Earthquake Sequences and the Brittle‐Ductile Transition

2021 ◽  
Author(s):  
Kali L. Allison ◽  
Eric M. Dunham
Keyword(s):  
Thermomechanical Coupling ◽  
Brittle Ductile Transition ◽  
Shear Heating ◽  
Earthquake Sequences

On brittle-ductile strain localization

2020 ◽  
Author(s):  
Yury Podladchikov
Keyword(s):  
Strain Localization ◽  
Shear Bands ◽  
Shear Zones ◽  
Thermal Runaway ◽  
Spontaneous Generation ◽  
Principal Stresses ◽  
Earth Planet ◽  
Brittle Ductile Transition ◽  
Shear Heating

<p>The classification of the strain localization modes is attempted around brittle-ductile transition. The stresses are high. The are a number of suspects: earthquake-like thermal runaway (Braeck et al. 2009), stable sliding as shear heating zones oriented 45 degrees to the principal stresses (Kiss et al. 2019), brittle faults/shear bands oriented ca. 30 degrees to the maximum compressive principal stress and mode 1 fracture. The coupling to the porous fluid hydrology is accounted for.  High resolution numerical simulations are compared to classical and newly derived composite asymptotic solutions.</p><p><strong>References</strong></p><p>Braeck, S., Podladchikov, Y., & Medvedev, S., 2009. Spontaneous dissipation of elastic energy by self-localizing thermal runaway, Phys. Rev. E , 80, 046105, doi:10.1103/PhysRevE.80.046105.</p><p>Kiss, D., Podladchikov, Y., Duretz, T., & Schmalholz, S., 2019. Spontaneous generation of ductile</p><p>shear zones by thermal softening: Localization criterion, 1D to 3D modelling and application to the</p><p>lithosphere, Earth Planet. Sci. Lett., 519, 284–296, doi:10.1016/j.epsl.2019.05.026.</p>

scholarly journals Aseismic transient slip on the Gofar transform fault, East Pacific Rise

2020 ◽  
Vol 117 (19) ◽  
pp. 10188-10194 ◽  
Author(s):  
Yajing Liu ◽  
Jeffrey J. McGuire ◽  
Mark D. Behn
Keyword(s):  
East Pacific Rise ◽  
Rupture Propagation ◽  
Slow Slip ◽  
Aseismic Slip ◽  
Transform Faults ◽  
Brittle Ductile Transition ◽  
East Pacific ◽  
Seismic Swarms ◽  
Underlying Mechanisms ◽  
Earthquake Sequences

Oceanic transform faults display a unique combination of seismic and aseismic slip behavior, including a large globally averaged seismic deficit, and the local occurrence of repeating magnitude (M) ∼6 earthquakes with abundant foreshocks and seismic swarms, as on the Gofar transform of the East Pacific Rise and the Blanco Ridge in the northeast Pacific Ocean. However, the underlying mechanisms that govern the partitioning between seismic and aseismic slip and their interaction remain unclear. Here we present a numerical modeling study of earthquake sequences and aseismic transient slip on oceanic transform faults. In the model, strong dilatancy strengthening, supported by seismic imaging that indicates enhanced fluid-filled porosity and possible hydrothermal circulation down to the brittle–ductile transition, effectively stabilizes along-strike seismic rupture propagation and results in rupture barriers where aseismic transients arise episodically. The modeled slow slip migrates along the barrier zones at speeds ∼10 to 600 m/h, spatiotemporally correlated with the observed migration of seismic swarms on the Gofar transform. Our model thus suggests the possible prevalence of episodic aseismic transients in M ∼6 rupture barrier zones that host active swarms on oceanic transform faults and provides candidates for future seafloor geodesy experiments to verify the relation between aseismic fault slip, earthquake swarms, and fault zone hydromechanical properties.

scholarly journals Deep decoupling in subduction zones: Observations and temperature limits

Geosphere ◽  
2020 ◽  
Vol 16 (6) ◽  
pp. 1408-1424 ◽  
Author(s):  
Geoffrey A. Abers ◽  
Peter E. van Keken ◽  
Cian R. Wilson
Keyword(s):  
Subduction Zone ◽  
Shear Zone ◽  
Subduction Zones ◽  
Thermal Structure ◽  
Shear Zones ◽  
Seismic Attenuation ◽  
Plate Interface ◽  
Brittle Ductile Transition ◽  
Wide Range ◽  
Shear Heating

Abstract The plate interface undergoes two transitions between seismogenic depths and subarc depths. A brittle-ductile transition at 20–50 km depth is followed by a transition to full viscous coupling to the overlying mantle wedge at ∼80 km depth. We review evidence for both transitions, focusing on heat-flow and seismic-attenuation constraints on the deeper transition. The intervening ductile shear zone likely weakens considerably as temperature increases, such that its rheology exerts a stronger control on subduction-zone thermal structure than does frictional shear heating. We evaluate its role through analytic approximations and two-dimensional finite-element models for both idealized subduction geometries and those resembling real subduction zones. We show that a temperature-buffering process exists in the shear zone that results in temperatures being tightly controlled by the rheological strength of that shear zone’s material for a wide range of shear-heating behaviors of the shallower brittle region. Higher temperatures result in weaker shear zones and hence less heat generation, so temperatures stop increasing and shear zones stop weakening. The net result for many rheologies are temperatures limited to ≤350–420 °C along the plate interface below the cold forearc of most subduction zones until the hot coupled mantle is approached. Very young incoming plates are the exception. This rheological buffering desensitizes subduction-zone thermal structure to many parameters and may help explain the global constancy of the 80 km coupling limit. We recalculate water fluxes to the forearc wedge and deep mantle and find that shear heating has little effect on global water circulation.

scholarly journals Modelling thermomechanical ice deformation using a GPU-based implicit pseudo-transient method (FastICE v1.0)

2019 ◽  
Author(s):  
Ludovic Räss ◽  
Aleksandar Licul ◽  
Frédéric Herman ◽  
Yury Y. Podladchikov ◽  
Jenny Suckale
Keyword(s):  
Numerical Models ◽  
Time Integration ◽  
Three Dimensional ◽  
Three Dimensions ◽  
Thermomechanical Coupling ◽  
Transition Zones ◽  
Distributed Memory Machines ◽  
Basal Sliding ◽  
Shear Heating ◽  
Matrix Free

Abstract. Accurate predictions of future sea level rise require numerical models that capture the complex thermomechanical feedbacks in rapidly deforming ice. Shear margins, grounding zones and the basal sliding interface are locations of particular interest where the stress-field is complex and fundamentally three-dimensional. These transition zones are prone to thermomechanical localisation, which can be captured numerically only with high temporal and spatial resolution. Thus, better understanding the coupled physical processes that govern these boundaries of localised strain necessitates a non-linear, full Stokes model that affords high resolution and scales well in three dimensions. This paper’s goal is to contribute to the growing toolbox for modelling thermomechanical deformation in ice by levering GPU accelerators’ parallel scalability. We propose a numerical model that relies on pseudo-transient iterations to solve the implicit thermomechanical coupling between ice motion and temperature involving shear-heating and a temperature-dependant ice viscosity. Our method is based on the finite-difference discretisation, and we implement the pseudo-time integration in a matrix-free way. We benchmark the mechanical Stokes solver against the finite-element code Elmer/Ice and report good agreement among the results. We showcase a parallel version of the solver to run on GPU-accelerated distributed memory machines, reaching a parallel efficiency of 93 %. We show that our model is particularly useful for improving our process-based understanding of flow localisation in the complex transition zones bounding rapidly moving ice.

Thermomechanical Coupling of a Hyper-viscoelastic Truck Tire and a Pavement Layer and its Impact on Three-dimensional Contact Stresses

2021 ◽  
pp. 036119812110171
Author(s):  
Angeli Jayme ◽  
Imad L. Al-Qadi
Keyword(s):  
Contact Stress ◽  
Contact Area ◽  
Three Dimensional ◽  
Interaction Model ◽  
Rolling Resistance ◽  
Contact Stresses ◽  
Thermomechanical Coupling ◽  
Temperature Profiles ◽  
Near Surface ◽  
Truck Tire

A thermomechanical coupling between a hyper-viscoelastic tire and a representative pavement layer was conducted to assess the effect of various temperature profiles on the mechanical behavior of a rolling truck tire. The two deformable bodies, namely the tire and pavement layer, were subjected to steady-state-uniform and non-uniform temperature profiles to identify the significance of considering temperature as a variable in contact-stress prediction. A myriad of ambient, internal air, and pavement-surface conditions were simulated, along with combinations of applied tire load, tire-inflation pressure, and traveling speed. Analogous to winter, the low temperature profiles induced a smaller tire-pavement contact area that resulted in stress localization. On the other hand, under high temperature conditions during the summer, higher tire deformation resulted in lower contact-stress magnitudes owing to an increase in the tire-pavement contact area. In both conditions, vertical and longitudinal contact stresses are impacted, while transverse contact stresses are relatively less affected. This behavior, however, may change under a non-free-rolling condition, such as braking, accelerating, and cornering. By incorporating temperature into the tire-pavement interaction model, changes in the magnitude and distribution of the three-dimensional contact stresses were manifested. This would have a direct implication on the rolling resistance and near-surface behavior of flexible pavements.

scholarly journals Fault reactivation and strain partitioning across the brittle-ductile transition

Geology ◽  
2019 ◽  
Vol 47 (12) ◽  
pp. 1127-1130 ◽  
Author(s):  
Gabriel G. Meyer ◽  
Nicolas Brantut ◽  
Thomas M. Mitchell ◽  
Philip G. Meredith
Keyword(s):  
Fault Slip ◽  
Fault Reactivation ◽  
Ductile Deformation ◽  
Tectonic Deformation ◽  
Gradual Change ◽  
Bulk Rock ◽  
Total Deformation ◽  
Bulk Strain ◽  
Brittle Ductile Transition ◽  
Ductile Flow

Abstract The so-called “brittle-ductile transition” is thought to be the strongest part of the lithosphere, and defines the lower limit of the seismogenic zone. It is characterized not only by a transition from localized to distributed (ductile) deformation, but also by a gradual change in microscale deformation mechanism, from microcracking to crystal plasticity. These two transitions can occur separately under different conditions. The threshold conditions bounding the transitions are expected to control how deformation is partitioned between localized fault slip and bulk ductile deformation. Here, we report results from triaxial deformation experiments on pre-faulted cores of Carrara marble over a range of confining pressures, and determine the relative partitioning of the total deformation between bulk strain and on-fault slip. We find that the transition initiates when fault strength (σf) exceeds the yield stress (σy) of the bulk rock, and terminates when it exceeds its ductile flow stress (σflow). In this domain, yield in the bulk rock occurs first, and fault slip is reactivated as a result of bulk strain hardening. The contribution of fault slip to the total deformation is proportional to the ratio (σf − σy)/(σflow − σy). We propose an updated crustal strength profile extending the localized-ductile transition toward shallower regions where the strength of the crust would be limited by fault friction, but significant proportions of tectonic deformation could be accommodated simultaneously by distributed ductile flow.

Brittle-ductile transition: semi-brittle behavior

1989 ◽  
Vol 167 (1) ◽  
pp. 75-79 ◽  
Author(s):  
John V. Ross ◽  
Peter D. Lewis
Keyword(s):  
Brittle Behavior ◽  
Brittle Ductile Transition
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