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A scaling law for slow earthquakes
Satoshi Ide1, Gregory C Beroza, David R Shelly
1Department of Earth and Planetary Science, University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033, Japan. ide@eps.s.u-tokyo.ac.jp
Nature
|May 4, 2007
Summary
Unusual seismic events like tremors and slow slips are unified by a new scaling law. This finding reveals they are a distinct earthquake category, differing from regular earthquakes.
Area of Science:
- Seismology
- Earthquake Science
- Geophysics
Background:
- Recent discoveries include deep episodic tremor, low-frequency earthquakes, very-low-frequency earthquakes, slow slip events, and silent earthquakes.
- These phenomena arise from shear slip, similar to regular earthquakes, but have longer durations and emit less seismic energy.
Purpose of the Study:
- To demonstrate a unified scaling relationship for various slow seismic events.
- To differentiate the behavior of slow seismic events from regular earthquakes.
- To establish a new category for these unified seismic phenomena.
Main Methods:
- Analysis of seismic moment and characteristic duration.
- Examination of moment rate function and spectral high-frequency decay.
- Investigating the scale dependence of rupture velocity.
Main Results:
- Slow seismic events follow a unified scaling relationship: seismic moment is proportional to characteristic duration.
- Their moment rate function is constant with a spectral high-frequency decay of f(-1).
- This behavior distinguishes them from regular earthquakes and suggests they are different manifestations of the same phenomenon.
Conclusions:
- A new earthquake category encompassing diverse slow seismic events is proposed.
- The observed scaling laws can be explained by either a constant low-stress drop or a diffusional constant-slip model.
- This unified scaling law may enhance understanding of plate subduction and large earthquake generation.
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