[S-GL37] 地域地質と構造発達史

[SGL37-08] ハフ変換逆解法を用いた小断層すべりデータによる秋田県出羽丘陵の古応力解析

村田 淳一¹、*西川 治²、佐藤 活志³ (1.秋田大学工学資源学部、2.秋田大学鉱業博物館、3.京都大学大学院 理学研究科)

キーワード：ハフ変換、古応力解析、小断層、出羽丘陵

Paleostress analysis was conducted using Hough-transform based inversion method (HIM; Sato, 2006) from slip data of mesoscale faults in the Dewa Hills, Akita, where both pre- and post-lift deposits are widely exposed. The Dewa Hills has been uplifting under E-W compression stress field since late Neogene, and shows a regional variety in deformation intensity and structure. Low angle faults with reverse sense are dominant in the Iwaki coastal area, where an intense shortening occurred showing N-S trending folds and thrusts associated with the activity of the Kitayuri thrust fault. Orientations of σ₁ and σ₃ are detected in E-W and nearly vertical, respectively. In the Toyokawa area at the hinge of the anticlinorium and the northeast part of the Dewa hills without intense deformation, high angle normal faults mainly occur. Stress states of relatively strong σ₁s in vertical and σ₃s diffused widely in NW-SE are obtained from the stress analyses. These are different from the regional stress field, and infer that mesoscale faults in these areas provide signals of later stage of uplifting. Under a limited influence of the regional stress state, the effect of equalization of crustal topography would be apparent. Normal faulting probably occurred resulted from the gravitational spreading (e.g., Ikeda and Yamaji, 2008) towards the structural low away from the high.