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Striations, duration, migration and tidal response in deep tremor.
1Department of Earth and Planetary Science, University of Tokyo, Hongo 7-3-1, Bunkyo, Tokyo 113-0033, Japan. ide@eps.s.u-tokyo.ac.jp
Nature
|July 16, 2010
Summary
Deep tremor in subduction zones, linked to plate movement, is controlled by persistent interface properties. These properties influence tremor duration, tidal stress sensitivity, and migration patterns, offering insights into earthquake processes.
Area of Science:
- Geophysics
- Seismology
- Tectonics
Background:
- Deep tremor in subduction zones originates from slow slip events on the plate interface, approximately 30 km deep.
- This phenomenon provides crucial data on deep plate motion and stress buildup preceding megathrust earthquakes.
- Previous research suggested tremor exhibits regular intervals, variable migration, and tidal modulation.
Purpose of the Study:
- To investigate the controlling factors of deep tremor behavior in subduction zones.
- To analyze the relationship between tremor characteristics and plate interface properties.
- To understand the long-term evolution of these interface properties.
Main Methods:
- Precise location of tremor sources and analysis of event durations in the Nankai subduction zone, Japan.
- Correlation of tremor behavior (tidal sensitivity, migration) with inferred interface properties.
- Modeling of diffusive migration and estimation of diffusivity.
Main Results:
- A time-invariant interface property controls tremor behavior, influencing duration and migration.
- Shorter tremor durations correlate with higher tidal stress sensitivity and inhibited migration.
- Longer tremor durations exhibit diffusive migration with a constant diffusivity of 10^4 m^2 s^-1.
- Interface properties, potentially related to brittle/ductile ratios influenced by serpentinization, show striated spatial variations aligned with subduction directions.
Conclusions:
- Deep tremor behavior is governed by stable, spatially varying interface properties.
- These properties are likely shaped over millions of years by the subduction of geological structures like seamounts.
- Understanding these properties is key to deciphering deep plate motion and seismic hazard in subduction zones.
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