日本地球惑星科学連合2019年大会

講演情報

[J] 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-CG61] 変動帯ダイナミクス

2019年5月28日(火) 15:30 〜 17:00 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:深畑 幸俊(京都大学防災研究所)、竹下 徹(北海道大学大学院理学院自然史科学専攻)、岩森 光(海洋研究開発機構・地球内部物質循環研究分野)

[SCG61-P15] 2018年北海道胆振東部地震の動的破壊シミュレーション:非平面断層形状の役割

*久河 竜也1安藤 亮輔1 (1.東京大学)

The 2018, Hokkaido Eastern Iburi, Japan, earthquakeis an event characterized by complexity of rupture process, which may involve both reverse and strike slip depending on the locations on the fault surface. We perform dynamic rupture simulations based on simple physical laws and conditions for stressing and fault friction, taking complexity of the fault into account. The complex fault geometry is numerically treated by the boundary integral equation method accelerated by the fast domain portioning method. We search in a small number of parameter spaces for the stress ratio of the regional stress field and the frictional coefficients assumed to be the same over the fault area, rather than assigning heterogeneous distributions of the stress drop on the fault, to evaluate to what extent relatively simple forward models accounting for realistic fault geometry can explain the characteristics of coseismic observations. The fault geometry is constrained based on the aftershock distribution (NIED, 2018) and characterized primarily by the combination of three fault planes. As the result, we are able to reproduce several observed features of the event including the spatial variation of the fault slip direction, which is inferred from the seismological inversion (Okuwaki and Yagi, 2018), and the ground surface displacement observed by GEONET. The results suggest that the complex rupture event can be reproduced by a relatively simple physical model to some extent if the geometrical complexity of the faults is properly taken into account.