JpGU-AGU Joint Meeting 2017

講演情報

[EE] ポスター発表

セッション記号 S (固体地球科学) » S-SS 地震学

[S-SS04] [EE] Subduction zone dynamics from regular earthquakes through slow earthquakes to creep

2017年5月24日(水) 15:30 〜 17:00 ポスター会場 (国際展示場 7ホール)

コンビーナ:金川 久一(千葉大学大学院理学研究科)、小原 一成(東京大学地震研究所)、Demian M Saffer(Pennsylvania State University)、Wallace Laura(University of Texas Institute for Geophysics)

[SSS04-P03] Stress drops of earthquakes on the Pacific plate off south-east of Hokkaido, Japan: Implications for the spatial heterogeneity of frictional properties

*山田 卓司1齋藤 悠2谷岡 勇市郎3河原 純1 (1.茨城大学理学部、2.北海道大学大学院理学院、3.北海道大学大学院理学研究院附属地震火山研究観測センター)

キーワード:Stress drop, Frictional properties on the Pacific plate, Spatial heterogeneity

We analyzed stress drops of 721 earthquakes with the magnitude of 4.0 to 5.0 off south-east of Hokkaido, Japan and investigated the spatial heterogeneity of the difference of shear strength and dynamic stress level on the Pacific plate. We deconvolved observed P and S waves with those of collocated small earthquakes and derived the source effect of the earthquakes. We then estimated corner frequencies of the earthquakes and calculated stress drops by using a circular fault model. The values of stress drop showed a spatial pattern consistent with slip distributions of historical large earthquakes. This suggests that frictional properties on the plate interface show little temporal change and their spatial pattern can be monitored by stress drops of moderate-sized earthquakes. The spatial heterogeneity would give clues for estimating the slip pattern of a future large earthquake and discussing a policy for the disaster mitigation, especially for regions where slip patterns of historical large earthquakes are unclear.