18:15 〜 19:30
[SSS30-P06] 東北沖浅部断層の低～高速摩擦特性を考慮したスロースリップと地震性すべりのモデル化
キーワード：東北沖, 浅部プレート境界, 低～高速摩擦特性, スロースリップ, 地震性すべり
Ikari et al. (2013) examined low to high speed frictional properties of fault zone material from the shallow plate boundary in the Tohoku region obtained by the IODP Expedition 343 (JFAST). They found velocity-weakening frictional behavior at slip velocities slower than 10-6 m/s and velocity-strengthening at higher slip velocities. This frictional property is considered to be a mechanism that causes slow slip events and stress accumulation during the period between slow slip events. We investigate the effects of this frictional property on generation of slow slip events and megathrust events.
We use a rate- and state-dependent friction law with cut-off velocity to an evolution effect to represent this frictional behavior. Based on the experimental results (Ikari et al., 2013), we set the cut-off velocity at 10-6 m/s. We also consider dynamic weakening due to thermal pressurization at high slip velocity. We perform three-dimensional quasi-dynamic modeling of slip processes. Numerical results show the occurrence of slow slip events at intervals of several ten years at the shallow plate boundary. During the period between slow slip events, stress accumulation proceeds. When an earthquake nucleates at the deeper region, coseismic slip propagates into this region, which results in larger slip compared to the case where a simple velocity-strengthening friction law is considered.
Ito et al. (2012) detected slow slip events in the Japan subduction zone before the 2011 Tohoku-Oki earthquake. Shallow very low frequency earthquakes off Tohoku were detected by Matsuzawa et al. (2012). In addition, along the shallow plate boundary off Tokachi, sequential activity of very low frequency earthquakes occurs at intervals of several years (Asano et al., 2008). These observations suggest that the transitional friction behavior investigated by Ikari et al. (2013) occurs along the shallow plate boundary off Tohoku.
We use a rate- and state-dependent friction law with cut-off velocity to an evolution effect to represent this frictional behavior. Based on the experimental results (Ikari et al., 2013), we set the cut-off velocity at 10-6 m/s. We also consider dynamic weakening due to thermal pressurization at high slip velocity. We perform three-dimensional quasi-dynamic modeling of slip processes. Numerical results show the occurrence of slow slip events at intervals of several ten years at the shallow plate boundary. During the period between slow slip events, stress accumulation proceeds. When an earthquake nucleates at the deeper region, coseismic slip propagates into this region, which results in larger slip compared to the case where a simple velocity-strengthening friction law is considered.
Ito et al. (2012) detected slow slip events in the Japan subduction zone before the 2011 Tohoku-Oki earthquake. Shallow very low frequency earthquakes off Tohoku were detected by Matsuzawa et al. (2012). In addition, along the shallow plate boundary off Tokachi, sequential activity of very low frequency earthquakes occurs at intervals of several years (Asano et al., 2008). These observations suggest that the transitional friction behavior investigated by Ikari et al. (2013) occurs along the shallow plate boundary off Tohoku.