Episodic slow slip events accompanied by non‐volcanic tremors in southwest Japan subduction zone

Abstract

Episodic slow slip events have been recognized by means of tilt changes in the western Shikoku area, southwest Japan. The crustal tilt deformation was observed repeatedly with a recurrence interval of approximately six months coincident with the occurrences of major non‐volcanic deep tremor activities in this area. Observed tilt changes can be explained by slow slip events occurring around the source area of tremors. In each episode, the source of the slow slip event and tremor migrate simultaneously. The spatial and temporal coincidence of tremors and slow slip events indicates that they both may be coupling phenomena reflecting the stress accumulation process at the subducting plate.

Scaling Relationships of Source Parameters for Slow Slip Events

“…There are two sources for the dataset used in this study: source parameters inferred directly from the slip distributions of Schmidt and Gao (2010) for the Cascadia subduction zone and source parameters reported in the literature for other subduction zones (e.g., Obara et al, 2004;Brown et al, 2005;Douglas et al, 2005;Hirose and Obara, 2005;Wallace and Beavan, 2006;Ito and Obara, 2006;Hirose and Obara, 2006;CorreaMora et al, 2008CorreaMora et al, , 2009Hirose and Obara, 2010;Sekine et al, 2010; see references in Ⓔ Table S1, available in the electronic supplement to this paper). Additionally, we also include documented aseismic slip on the San Andreas fault (Linde et al, 1996) and Hawaii's south rift zone (Segall et al, 2006;Montgomery-Brown et al, 2009).…”

“…Abundant fluids may facilitate low effective stress and conditionally stable behavior on subduction zones. The lack of tremor associated with shallow aseismic slip in Hawaii (Montgomery-Brown et al, 2009) and the San Andreas fault (Zhang et al, 2010) may indicate that pore pressures are not as high in these regions as on those subduction zones where nonvolcanic tremor and SSEs are colocated (Rogers and Dragert, 2003;Obara et al, 2004). In addition to their different tectonic environments, the depths at which the events occur are strikingly different, which may be a factor.…”

Spatial and temporal evolution of the long-term slow slip in the Bungo Channel, Japan

“…By contrast, we use the phrase 'short-term slow slip' to mean aseismic slip that has a moment magnitude of roughly 6 and lasts for only several days as detected using a tiltmeter (Obara et al, 2004).…”

Tilt records prior to the 2011 off the Pacific coast of Tohoku Earthquake

“…The Hi-net tiltmeters have successfully detected the tilt deformations caused by slow slip events (SSE) in the southwest Japan subduction zone (e.g., Obara et al, 2004;Hirose and Obara, 2005). The typical tilt change of ∼0.1 μrad is observed when a M w ∼ 6.0 SSE occurs at around 30 km depth.…”