日本地球惑星科学連合2019年大会

講演情報

[E] ポスター発表

セッション記号 S (固体地球科学) » S-CG 固体地球科学複合領域・一般

[S-CG48] Science of slow earthquakes: Toward unified understandings of whole earthquake process

2019年5月29日(水) 10:45 〜 12:15 ポスター会場 (幕張メッセ国際展示場 8ホール)

コンビーナ:井出 哲(東京大学大学院理学系研究科地球惑星科学専攻)、廣瀬 仁(神戸大学都市安全研究センター)、氏家 恒太郎(筑波大学生命環境系)、波多野 恭弘(東京大学地震研究所)

[SCG48-P44] Unified description of fast and slow earthquakes using velocity strengthening patches

*小澤 創1波多野 恭弘1 (1.東京大学地震研究所)

キーワード:スロー地震、速度状態依存摩擦

In a prevalent view, seismicity in subduction zones is governed by the distribution of the frictional properties of the plate interface. Regions with velocity-weakening (VW) friction generate earthquakes, whereas velocity-strengthening (VS) regions creep aseismically. Although most models consider isolated VW regions (patches) from the idea of asperities (e.g. Dublanchet et al., 2013), isolated VS patches also would exist given the frictional properties on faults are inferred to be complex and hierarchical. Therefore, the role of VS patches is to be studied.

Here we perform 3-D numerical simulation of the seismic cycle of faults governed by the rate and state friction law with the aging law. We distribute randomly circular VS patches on a VW background. We mainly focus on the effect of the ratio of VS and VW areas.

In our preliminary simulation, we identified two important effects. First, the VS patches act as the “stability barriers” during dynamic rupture propagation, which makes the rupture process more complicated than a single propagating crack. Rupture decelerates by encountering a stability barrier, followed by reacceleration due to overcoming the barrier. Such a process gives rise to multiple rupture fronts in the slipping area.

Second, dynamic rupture is inhibited by increasing the number of VS patches, and the fault slips aseismically with strong fluctuation in slip velocity. This is because there are no enough VW regions to accelerate the slip to dynamic rupture. Although a similar mechanism for slow earthquakes is proposed by Skarbek et al. (2012) and Yabe & Ide (2017), our 3-D modeling enables detailed studies on the spatiotemporal evolution of slip. In the presentation, we further discuss our results in the context of the dynamic scaling of rupture growth and the phenomenological law of slow earthquakes.