Propagation history of the Osaka-wan blind thrust, Japan, from trishear modeling

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• 作者：Pamela R. Grothe ; Nestor Cardozo ; Karl Mueller ; Tatsuya Ishiyama
• 关键词：Osaka Bay ; Osaka-wan fault ; High-resolution seismic profiles ; Fault propagation folding ; Growth strata ; Trishear
• 刊名：Journal of Structural Geology
• 出版年：January, 2014
• 年：2014
• 卷：58
• 期：Complete
• 页码：79-94
• 全文大小：6721 K

文摘

Mapping the nucleation and 3D fault tip growth of the active Osaka-wan blind thrust provides an opportunity to asses how reactivated thrusts build slip from preexisting faults and the threat they pose as sources of large earthquakes. Analysis of folded growth strata, based on 2D trishear inverse modeling allows a range of best-fit models of the evolution of slip and propagation of the fault to be defined. The depth of the fault tip at 1200聽ka varies between 鈭?.5-4.5聽km, suggesting the fault grew upward from high in the crust, and that it is reactivated. From its onset at 鈭?500聽ka, the fault grew rapidly along strike in 鈭?00聽ky, and upwards with a P/S ratio of 2.5-3.0, but variable fault slip in space and time. Shallower depths of the fault tip at initiation and thinner basin fill correlates with slower propagation with time, contradicting models that argue for sediments as inhibitors of fault growth. Results also suggest the displacement profile of the currently active thrust is offset from its predecessor, assuming shallower depths to the original fault correlate with greater displacement in its prior history. These results suggest reactivated faults may accrue slip differently than newly developed ones, based on the history of upward fault propagation.