17:15 〜 19:15
[SGL23-P01] 3次元反射法地震探査に基づく広尾海脚の地質構造発達史
キーワード：反射法地震探査、広尾海脚、十勝沖
A 3D marine seismic reflection survey was conducted offshore Tokachi covering the Hiroo Spur under the National Program for Oil and Gas Prospecting (Kokunai Kisochosa). The survey area is currently subjected to the ongoing compression caused by the westward collision of the Kuril forearc sliver (Kimura, 1986). The Hiroo Spur is an anticline located approximately 50 km offshore Hiroo Town, elongating about 40 km in NW-SE direction. The strike direction suggests that its formation is related to the collision of the Kuril forearc sliver (e.g., TuZino, 2011). Although the Hiroo Spur is a well-recognized bathymetric structure, its detailed structural development history is still unknown. Using a broadband depth-migrated 3D seismic reflection data, we interpreted the spatial variations of thickness and reflection termination patterns of the post-Paleogene intervals to address the evolution process of the Hiroo Spur and its surrounding paleo structures as well as distributions of potential reservoir sandstones.
Temporal variations and spatial distributions of sediment thickness from the Middle Miocene to Pleistocene infer that the uplift of the Hiroo Spur is most likely to have started since the early Late Miocene. The uplift continued intermittently until the present day as indicated by onlap reflectors and growth strata observed in proximity to the crest in several different units. The fold-axis direction of the Hiroo Spur was initially trending NNW-SSE and has gradually rotated to the current NW-SE direction since the end of the Late Miocene. Although the change of the fold-axis was not addressed in previous studies (e.g., TuZino, 2011), the 3D seismic data revealed regional/local change in the stress field.
We also identified a subsurface anticline and a depositional center lying nearly parallel to the Hiroo Spur. In the presentation, we will further discuss the properties and spatial distributions of the post-Paleogene potential reservoir sandstones localized by the paleo topography. Also, the geohistory prior to the uplift of those anticlines will be addressed.
Acknowledgement:
This survey was conducted as a part of the National Program for Oil and Gas Prospecting (Kokunai Kisochosa) led by the Agency for Natural Resources and Energy, Ministry of Economy, Trade and Industry. We would like to express our gratitude to the Agency for permission to use the survey data.
Reference:
Kimura (1986). Oblique subduction and collision: Forearc tectonics of the Kuril arc. Geology, 14(5), 404-407
TuZino (2011). Explanatory notes of geological map offshore of Kushiro. Marine Geology Map Series, 73, Geological Survey of Japan, AIST
Temporal variations and spatial distributions of sediment thickness from the Middle Miocene to Pleistocene infer that the uplift of the Hiroo Spur is most likely to have started since the early Late Miocene. The uplift continued intermittently until the present day as indicated by onlap reflectors and growth strata observed in proximity to the crest in several different units. The fold-axis direction of the Hiroo Spur was initially trending NNW-SSE and has gradually rotated to the current NW-SE direction since the end of the Late Miocene. Although the change of the fold-axis was not addressed in previous studies (e.g., TuZino, 2011), the 3D seismic data revealed regional/local change in the stress field.
We also identified a subsurface anticline and a depositional center lying nearly parallel to the Hiroo Spur. In the presentation, we will further discuss the properties and spatial distributions of the post-Paleogene potential reservoir sandstones localized by the paleo topography. Also, the geohistory prior to the uplift of those anticlines will be addressed.
Acknowledgement:
This survey was conducted as a part of the National Program for Oil and Gas Prospecting (Kokunai Kisochosa) led by the Agency for Natural Resources and Energy, Ministry of Economy, Trade and Industry. We would like to express our gratitude to the Agency for permission to use the survey data.
Reference:
Kimura (1986). Oblique subduction and collision: Forearc tectonics of the Kuril arc. Geology, 14(5), 404-407
TuZino (2011). Explanatory notes of geological map offshore of Kushiro. Marine Geology Map Series, 73, Geological Survey of Japan, AIST