Transformation shear instability and the seismogenic zone for deep earthquakes

Chris J. Marone, Ming Liu

Research output: Contribution to journalArticle

5 Citations (Scopus)

Abstract

We use a numerical model for olivine-spinel transformation to study deep earthquake nucleation and to delineate the seismogenic region within a subducting slab. The model includes laboratory-derived flow laws, latent heat release, and phase transformation kinetics. We calculate deformation, transformation state, grain growth, and rheology for several paths within a subducting slab. Strain rate perturbations are imposed to define the necessary conditions for instability. Strain rate perturbations decay for ξ < a critical value ξc, and thus the coldest, interior portion of the metastable wedge deforms stably. For ξ≥ξc, strain rate perturbations grow, shear strength decreases with strain, and the system is potentially unstable. The instability condition is mapped to delineate the seismogenic zone within a subducting slab. The model seismogenic zone is bounded by ξc, and, at larger percent transformations, by coarsening of spinel grains and saturation of the transformation weakening effect. The model predicts a narrow seismogenic region along the outer edges of the metastable wedge and thus a "double seismic" zone, consistent with some seismic observations. Several simplifying assumptions are required due to lack of thermo-kinetic data and incomplete knowledge of constituent mineralogy and rheology. However, the model provides a quantitative definition of the instability condition and a framework for testing the hypothesis of transformation-induced instability.

Original languageEnglish (US)
Article number97GL01851
Pages (from-to)1887-1890
Number of pages4
JournalGeophysical Research Letters
Volume24
Issue number15
DOIs
StatePublished - Jan 1 1997

Fingerprint

earthquakes
shear
earthquake
strain rate
slabs
slab
rheology
perturbation
wedges
spinel
shear strength
kinetics
latent heat
mineralogy
olivine
seismic zone
phase transformations
nucleation
saturation
decay

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Earth and Planetary Sciences(all)

Cite this

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title = "Transformation shear instability and the seismogenic zone for deep earthquakes",
abstract = "We use a numerical model for olivine-spinel transformation to study deep earthquake nucleation and to delineate the seismogenic region within a subducting slab. The model includes laboratory-derived flow laws, latent heat release, and phase transformation kinetics. We calculate deformation, transformation state, grain growth, and rheology for several paths within a subducting slab. Strain rate perturbations are imposed to define the necessary conditions for instability. Strain rate perturbations decay for ξ < a critical value ξc, and thus the coldest, interior portion of the metastable wedge deforms stably. For ξ≥ξc, strain rate perturbations grow, shear strength decreases with strain, and the system is potentially unstable. The instability condition is mapped to delineate the seismogenic zone within a subducting slab. The model seismogenic zone is bounded by ξc, and, at larger percent transformations, by coarsening of spinel grains and saturation of the transformation weakening effect. The model predicts a narrow seismogenic region along the outer edges of the metastable wedge and thus a {"}double seismic{"} zone, consistent with some seismic observations. Several simplifying assumptions are required due to lack of thermo-kinetic data and incomplete knowledge of constituent mineralogy and rheology. However, the model provides a quantitative definition of the instability condition and a framework for testing the hypothesis of transformation-induced instability.",
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Transformation shear instability and the seismogenic zone for deep earthquakes. / Marone, Chris J.; Liu, Ming.

In: Geophysical Research Letters, Vol. 24, No. 15, 97GL01851, 01.01.1997, p. 1887-1890.

Research output: Contribution to journalArticle

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