Wallis D, Hansen LN, Wilkinson AJ, Lebensohn RA. Dislocation interactions in olivine control postseismic creep of the upper mantle.
Nat Commun 2021;
12:3496. [PMID:
34108476 PMCID:
PMC8190305 DOI:
10.1038/s41467-021-23633-8]
[Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2020] [Accepted: 05/05/2021] [Indexed: 12/03/2022] Open
Abstract
Changes 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.
Models of the viscosity evolution of mantle rocks are central to analyses of postseismic deformation but constraints on underlying physical processes are lacking. Here, the authors present measurements of microscale stress heterogeneity in olivine suggesting that long-range dislocation interactions contribute to viscosity evolution.
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