Transient creep in subduction zones by long‐range dislocation interactions in olivine

2022 ◽  
Author(s):  
David Wallis ◽  
Mike Sep ◽  
Lars N. Hansen
Keyword(s):  
Long Range ◽  
Subduction Zones ◽  
Transient Creep ◽  
Dislocation Interactions

scholarly journals Dislocation interactions in olivine control postseismic creep of the upper mantle

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
David Wallis ◽  
Lars N. Hansen ◽  
Angus J. Wilkinson ◽  
Ricardo A. Lebensohn
Keyword(s):  
Upper Mantle ◽  
Stress Transfer ◽  
Transient Creep ◽  
Slip Systems ◽  
Stress Distributions ◽  
Correlation Lengths ◽  
Mantle Viscosity ◽  
Dislocation Interactions ◽  
Different Temperatures ◽  
New Generation

AbstractChanges in stress applied to mantle rocks, such as those imposed by earthquakes, commonly induce a period of transient creep, which is often modelled based on stress transfer among slip systems due to grain interactions. However, recent experiments have demonstrated that the accumulation of stresses among dislocations is the dominant cause of strain hardening in olivine at temperatures ≤600 °C, raising the question of whether the same process contributes to transient creep at higher temperatures. Here, we demonstrate that olivine samples deformed at 25 °C or 1150–1250 °C both preserve stress heterogeneities of ~1 GPa that are imparted by dislocations and have correlation lengths of ~1 μm. The similar stress distributions formed at these different temperatures indicate that accumulation of stresses among dislocations also provides a contribution to transient creep at high temperatures. The results motivate a new generation of models that capture these intragranular processes and may refine predictions of evolving mantle viscosity over the earthquake cycle.

scholarly journals Investigating the signatures of long-range persistence in seismic sequences along Circum-Pacific subduction zones

2019 ◽  
Vol 37 (4) ◽  
pp. 407
Author(s):  
Daniel Freitas ◽  
George França ◽  
Thais Scherrer ◽  
Carlos Vilar ◽  
Raimundo Silva
Keyword(s):  
Long Range ◽  
Subduction Zones ◽  
Active Fault ◽  
Long Term Memory ◽  
Seismic Sequences ◽  
Rescaled Range ◽  
The Pacific ◽  
Q Index ◽  
National Earthquake Information Center

AbstractIn the present paper, we analyze the signatures of long-range persistence in seismic sequences along Circum-Pacific subduction zones, from Chile to Kermadec, extracted from the National Earthquake Information Center (NEIC) catalog. This region, known as the Pacific Ring of Fire, is the world’s most active fault line, containing about 90% of the world’s earthquakes. We used the classical rescaled range (R/S) analysis to estimate the long-term persistence signals derived from a scaling parameter called the Hurst exponent, H. We measured the referred exponent and obtained values of H > 0.5, indicating that a long-term memory effect exists. We found a possible fractal relationship between H and the bs(q)-index, which emerges from the non-extensive Gutenberg-Richter law as a function of the asperity. Therefore, H can be associated with a mechanism that controls the level of seismic activity. Finally, we concluded that the dynamics associated with fragment-asperity interactions can be classified as a self-affine fractal phenomenon.Keywords: Applied geophysics; Fault and Fracture Analysis; Mathematics applied to geohysics; Seismology; Statistics;geostatistics ResumoNo presente artigo, analisamos as assinaturas de persistência long-range nas sequências sísmicas ao longo das zonas de subducção Circum-Pacific, do Chile até Kermadec, extraídas do catálogo do Centro Nacional de Informações sobre Terremotos (NEIC). Esta região, conhecida como Anel de Fogo do Pacífico, é a linha de falhas mais ativa do mundo, contendo cerca de 90% dos terremotos do mundo. Usamos a análise clássica R / S para estimar a assinatura de persistência a longo prazo derivada do parâmetro de escalonamento chamado expoente de Hurst, H. Como principal objeto de estudo}, medimos o referido expoente e obtivemos todos os valores de H> 0,5, indicando que existe um efeito de memória de longo prazo. A principal contribuição do nosso artigo foi encontrar uma possível relação entre H e o índice bs (q) - que emerge da lei de Gutenberg-Richter não-extensiva como uma função da aspereza, isto é, H pode estar associado ao mecanismo que controla o nível de atividade dos terremotos. Finalmente, concluímos que a dinâmica associada às interações fragilidade-aspereza pode ser classificado como um fenômeno fractal auto-afim.Palavras-chaves: Geofisica Aplicada; Analise de falhas e fraturas; Matematica Aplicada a Geofisica; Sismologia; Estatistica;geoestatistica

Observations of dislocation interactions with recrystallized grain boundaries

1988 ◽  
Vol 46 ◽  
pp. 628-629
Author(s):  
C. W. Price
Keyword(s):  
Dislocation Density ◽  
Grain Boundary ◽  
Strain Rate ◽  
Grain Boundaries ◽  
Dislocation Structure ◽  
Hot Deformation ◽  
Static Recrystallization ◽  
High Dislocation Density ◽  
High Angle ◽  
Dislocation Interactions

Little evidence exists on the interaction of individual dislocations with recrystallized grain boundaries, primarily because of the severely overlapping contrast of the high dislocation density usually present during recrystallization. Interesting evidence of such interaction, Fig. 1, was discovered during examination of some old work on the hot deformation of Al-4.64 Cu. The specimen was deformed in a programmable thermomechanical instrument at 527 C and a strain rate of 25 cm/cm/s to a strain of 0.7. Static recrystallization occurred during a post anneal of 23 s also at 527 C. The figure shows evidence of dissociation of a subboundary at an intersection with a recrystallized high-angle grain boundary. At least one set of dislocations appears to be out of contrast in Fig. 1, and a grainboundary precipitate also is visible. Unfortunately, only subgrain sizes were of interest at the time the micrograph was recorded, and no attempt was made to analyze the dislocation structure.

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