On the biannually repeating slow‐slip events at the Ryukyu Trench, southwestern Japan

[1] Global positioning system data show that about 20 slow-slip events occurred during 1997–2007 in the southwestern part of the Ryukyu Arc, Japan, where large interplate thrust earthquakes are not known to have occurred in spite of relatively fast plate convergence. They recur fairly regularly on one patch of the subduction fault, which is as deep as 20–40 km and mechanically isolated in an uncoupled subduction zone. They have time constants of a month or so and release seismic moment equivalent of Mw 6.6 on average. This is one of the best recorded sequences of repeating fault slips, with enough events for statistical analyses. They have fairly constant recurrence interval of ∼0.5 year but do not show preferred months of occurrence in a year, suggesting that they are not controlled by seasonal forcing. The correlation between intervals and amounts of fault slip show statistically significant time-predictable recurrences. There is one significant disruption in the rhythm, but the stress perturbations due to nearby earthquakes do not appear to play a significant role. This part of the fault might be an altered asperity that used to rupture fast but now slips only slowly because of the increased ambient temperature.

[1]  Kosuke Heki,et al.  Crustal velocity field of southwest Japan: Subduction and arc‐arc collision , 2001 .

[2]  Takashi Nakata,et al.  Time‐predictable recurrence model for large earthquakes , 1980 .

[3]  Tim Melbourne,et al.  Periodic Slow Earthquakes from the Cascadia Subduction Zone , 2002, Science.

[4]  J. Vidale,et al.  Tidal Modulation of Nonvolcanic Tremor , 2008, Science.

[5]  Manabu Hashimoto,et al.  A rigid block rotation model for the GPS derived velocity field along the Ryukyu arc , 2004 .

[6]  Kelin Wang,et al.  Geodetic and seismic signatures of episodic tremor and slip in the northern Cascadia subduction zone , 2004 .

[7]  Shui-Beih Yu,et al.  GPS observation of crustal deformation in the Taiwan‐Luzon Region , 1999 .

[8]  G. Beroza,et al.  A scaling law for slow earthquakes , 2007, Nature.

[9]  Kenji Satake,et al.  Time and size of a giant earthquake in Cascadia inferred from Japanese tsunami records of January 1700 , 1996, Nature.

[10]  Y. Okada.  Internal deformation due to shear and tensile faults in a half-space , 1992, Bulletin of the Seismological Society of America.

[11]  M. Nakamura.  Source Fault Model of the 1771 Yaeyama Tsunami, Southern Ryukyu Islands, Japan, Inferred from Numerical Simulation , 2006 .

[12]  Zheng‐Kang Shen,et al.  Pole-Tide Modulation of Slow Slip Events at Circum-Pacific Subduction Zones , 2005 .

[13]  A. Sangawa.  Research on Paleoearthquakes Using Traces Discovered at Archaeological Sites , 1993 .

[14]  S. Miyazaki,et al.  A slow thrust slip event following the two 1996 Hyuganada Earthquakes beneath the Bungo Channel, southwest Japan , 1999 .

[15]  Akira Hasegawa,et al.  Characteristic small‐earthquake sequence off Sanriku, northeastern Honshu, Japan , 2002 .

[16]  Masayuki Kikuchi,et al.  Co‐seismic slip, post‐seismic slip, and largest aftershock associated with the 1994 Sanriku‐haruka‐oki, Japan, earthquake , 2003 .

[17]  Makoto Murakami,et al.  Detection and Monitoring of Ongoing Aseismic Slip in the Tokai Region, Central Japan , 2002, Science.

[18]  Kazushige Obara,et al.  Nonvolcanic Deep Tremor Associated with Subduction in Southwest Japan , 2002, Science.

[19]  Kelin Wang,et al.  A Silent Slip Event on the Deeper Cascadia Subduction Interface , 2001, Science.

[20]  S. Sekine,et al.  Slow Earthquakes Coincident with Episodic Tremors and Slow Slip Events , 2007, Science.

[21]  Hiromichi Tsuji,et al.  Silent fault slip following an interplate thrust earthquake at the Japan Trench , 1997, Nature.

[22]  Kristine M. Larson,et al.  A large silent earthquake in the Guerrero seismic gap, Mexico , 2003 .

[23]  V. Popov.  Earthquakes and Friction , 2010 .

[24]  B. Deffontaines,et al.  Okinawa trough backarc basin: Early tectonic and magmatic evolution , 1998 .

[25]  Manabu Hashimoto,et al.  GPS observation of the first month of postseismic crustal deformation associated with the 2003 Tokachi-oki earthquake (MJMA 8.0), off southeastern Hokkaido, Japan , 2004 .

[26]  M. Kikuchi,et al.  Asperity map along the subduction zone in northeastern Japan inferred from regional seismic data , 2004 .

[27]  Hitoshi Hirose,et al.  Repeating short- and long-term slow slip events with deep tremor activity around the Bungo channel region, southwest Japan , 2005 .

[28]  A. Lowry.  Resonant slow fault slip in subduction zones forced by climatic load stress , 2006, Nature.

[29]  H. Hirose,et al.  Episodic slow slip events accompanied by non‐volcanic tremors in southwest Japan subduction zone , 2004 .

[30]  C. Scholz.  Earthquakes and friction laws , 1998, Nature.

[31]  H. Suito,et al.  Occurrence of quasi-periodic slow-slip off the east coast of the Boso peninsula, Central Japan , 2007 .

[32]  T. Dixon,et al.  16. Secular, Transient, and Seasonal Crustal Movements in Japan from a Dense GPS Array Implication for Plate Dynamics in Convergent Boundaries , 2007 .

[33]  K. Larson,et al.  Transient fault slip in Guerrero, southern Mexico , 2001 .

[34]  S. Miyazaki,et al.  Characteristic silent earthquakes in the eastern part of the Boso peninsula, Central Japan , 2003 .

[35]  Richard G. Gordon,et al.  No-net-rotation model of current plate velocities incorporating plate motion model NUVEL-1 , 1991 .

[36]  T. Sagiya.  Interplate Coupling in the Kanto District, Central Japan, and the Boso Peninsula Silent Earthquake in May 1996 , 2004 .

[37]  H. Dragert,et al.  Episodic Tremor and Slip on the Cascadia Subduction Zone: The Chatter of Silent Slip , 2003, Science.

[38]  T. Okada,et al.  Comparison of source areas of M4.8±0.1 repeating earthquakes off Kamaishi, NE Japan: are asperities persistent features? , 2003 .