Year: 2026
Type: article
Abstract: Transformational faulting in olivine has been widely invoked as a possible triggering mechanism for deep‐focus earthquakes, yet its dynamics remain debated. It is unclear whether it requires the combined effects of heat release, volume change and mechanical strength contrast, or whether it can be triggered by any one of these alone. Here, we tested if transformational faulting can be caused solely by a large volume change, through deformation experiments on novaculite during the quartz‐coesite transition. Under sluggish reaction kinetics, acoustic emissions and microstructural observations indicate strain localization and fault plane formation. Under fast kinetics, deformation was distributed and associated with fewer, lower‐magnitude events. b ‐values of ∼1 and ∼3 reflect these two regimes. Our results provide the first evidence of transformational faulting during the quartz‐coesite transition, suggesting that volume change is the primary driver of brittle failure at high pressure, broadening the range of mineral transitions generating deep and intermediate‐depth earthquakes.
Source: Geophysical Research Letters
DOI: 10.1029/2026gl124806
Institutions: Heidelberg University, University of Pavia, Université Paris Sciences et Lettres, École Normale Supérieure - PSL, Laboratoire de Géologie de l’École Normale Supérieure, Deutsches Elektronen-Synchrotron DESY, Centre National de la Recherche Scientifique, Géosciences Rennes, Université de Rennes
Language: English
Subfield: Geophysics
Field: Earth and Planetary Sciences
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $3,190
OpenAlex ID: W7225430441