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| Titel |
Slip-dependent weakening on shallow plate boundary fault in the Japan subduction zone: shallow coseismic slip facilitated by foreshock afterslip |
| VerfasserIn |
Yoshi Ito, Matt Ikari, Kohtaro Ujiie, Achim Kopf |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250139840
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| Publikation (Nr.) |
 EGU/EGU2017-3153.pdf |
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| Zusammenfassung |
| Understanding of role of slow earthquakes as they relate to the occurrence of both
megathrust earthquakes and tsunami earthquakes is necessary to mitigate these
disasters in the near future. Laboratory shearing experiments is one of important
approach to evaluate these relationships. Here, we use powdered gouge samples from
JFAST (IODP Expedition 343) Hole C0019E, core sample 17R-1, which is the plate
boundary fault zone in the Japan Trench subduction zone. In this region, both large
coseismic slip during the 2011 Tohoku-Oki earthquake as well as discrete slow
slip events (SSE) have occurred. Experiments were conducted in a single-direct
shear apparatus under normal stress of 16 MPa, with total shear displacements
of up to 16 mm. We evaluate the slip-dependence of friction by extracting the
velocity-dependent friction parameters a, b, and Dc , and also measure the rate of
change in friction coefficient with shear displacement as the slip-dependence of
friction.
We report that in friction experiments using the Tohoku fault zone samples, an increase in
sliding velocity exceeding that of earthquake afterslip can induce a change from steady-state
frictional strength or slip hardening friction to slip-weakening frictional behavior. Our
results show that the slip weakening is observed when the slip velocity exceeds
3.7 × 10−6
m/s during our experiments, while steady-state frictional strength or slip hardening is
observed below 1 × 10−6
m/s. In the Japan Trench region, two slow events prior to the mainshock were observed in the
mainshock area with a coseismic slip exceeding 30 m . One event is an episodic SSE with a
slip velocity of 0.1 × 10−6
, and the other is afterslip after the largest Tohoku earthquake foreshock with a slip velocity
exceeding 2 × 10−6
m/s. Our experiments show that slip-weakening friction should be expected at the
afterslip rate, suggesting that the afterslip may have facilitated the large coseismic slip
during the mainshock on the plate boundary fault of the Tohoku-Oki earthquake. |
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