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The Role of Fabric in Frictional Properties of Phyllosilicate-Rich Tectonic Faults
Published on: November 6, 2021
Mantle phase changes and deep-earthquake faulting in subducting lithosphere
Science (New York, N.Y.)
|April 12, 1991
Summary
Deep earthquakes, occurring 350-690 km deep, are explained by transformational faulting. This process involves shear instability linked to phase transformations in olivine-rich peridotite within subducting tectonic plates.
Area of Science:
- Geophysics
- Seismology
- Mineral Physics
Background:
- Subduction zones exhibit inclined earthquake zones, with a distinct deep population (350-690 km).
- Traditional faulting mechanisms (brittle fracture, frictional sliding) are not expected at these extreme depths.
- Understanding deep earthquakes requires novel geophysical and geodynamic concepts.
Purpose of the Study:
- To explain the occurrence and characteristics of deep earthquakes below 350 km.
- To test the hypothesis of transformational faulting as the mechanism for deep earthquakes.
- To correlate deep earthquake distribution with mantle phase transitions.
Main Methods:
- Review and synthesis of experimental geophysics data on mineral phase transformations.
- Theoretical modeling of shear instability under nonhydrostatic stress conditions.
- Analysis of global earthquake catalogs and seismic data for deep events.
Main Results:
- Transformational faulting, a shear instability during phase transformations, is identified as a viable mechanism.
- Deep earthquakes are hypothesized to occur in metastable olivine-rich peridotite wedges.
- The proposed model aligns with observed global and regional deep earthquake distributions and characteristics.
Conclusions:
- Transformational faulting provides a consistent explanation for deep earthquakes in subduction zones.
- The persistence of metastable olivine explains earthquake occurrence down to 690 km.
- Mantle phase changes play a critical role in the generation and depth limits of deep seismic events.
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