IASPEI - Picture Gallery

IUGG XXIV General Assembly July 2-13, 2007 Perugia, Italy
(S) - IASPEI - International Association of Seismology and Physics of the Earth's
Interior
JSS004 Poster presentation 1903
Variation of slip velocity of repeating earthquakes and its dependence on
focal depths
Dr. Keisuke Ariyoshi
DONET (JAMSTEC) Seismological Sciety of Japan, AGU IASPEI
Toru Matsuzawa, Ryota Hino, Akira Hasegawa, Yoshiyuki Kaneda
We investigated depth dependence of the slip velocity of small repeating earthquakes using 3-D
numerical simulations of a subduction zone involving large and small asperities based on a rate- and
state-dependent friction law. Our results reveal that the postseismic slip of a large earthquake trigger
slow slip (with slip velocity lower than that of the spontaneous rupture of the small asperity) rupture of
the small asperity located at a depth of 45 km [Ariyoshi et al., 2007, GRL], whereas rapid slip (with
higher slip velocity) one at a depth of 5 km. Uchida et al. [2003, GRL] showed that the repeating
earthquakes in the NE Japan subduction zones occur constantly, conforming to the rate of the plate
convergence for the depth range of > ~40 km. On the other hand, the shallow (< ~10 km) focus
repeating earthquakes tend to be activated only for the postseismic period of large interplate
earthquakes and cumulative slip estimated by them is less than that expected from the plate
convergence rate. Considering that frictional instability of asperities in shallower part is less than those
deeper due to low effective normal stress, most of the observed shallow repeating earthquakes may be
rapid slip events triggered by the postseismic slip of the neighboring large asperities, and the
corresponding small asperities give rise to (aseismic) slow slip events otherwise.
Keywords: effective normal stress, repeating earthquake, rate and state dependent law