5:15 PM - 7:15 PM
[SCG61-P04] Study of stress fields on the sedimentary succession in the Eastern Fram Strait from borehole resistivity images obtained in IODP Exp.403
Keywords:In-situ stress, Mid-ocean ridge, Glacial cycles, Methane seepage
The Fram Strait, the unique deep passage from the Arctic Ocean to the other ocean, is located between Greenland and Svalbard. The eastern part of the region is subjected to tectonic stress fields induced by a cluster of mid-ocean ridges and transform faults as well as to glacial stresses associated with the evolution of the Svalbard-Barents Sea Ice Sheet especially for the eastside of the mid-ocean ridges. In addition, active seafloor methane seepage has been observed on the sedimentary succession in the region, originating from the warm current along the continental slope. Thus, it is expected to elucidate the complex stress field and the controlling mechanisms on the hydrology and evolution of faults and chimney in the sediments.
Studies over the last decade have shown that seafloor methane seepage is impacted by the spatiotemporal evolution of the aforementioned stress factors in the crust. However, they have suffered from some uncertainties and difficulties in extrapolating to the sedimentary sequence. Additionally, the in-situ stress measurements from the area have been lacking to constrain stress regime inferences from geophysical data and stress models.
During International Ocean Discovery Program (IODP) Expedition 403, borehole resistivity images were obtained and observed in two sites. These are the first actual data of in-situ stress measurements in the region containing borehole failures from which the maximum and minimum principal horizontal stress orientations can be determined. For U1618B (located on the eastern Vestnesa ridge, an active seafloor seepage system), we have recognized very scarce borehole compressive failures, implying weak horizontal compression by normal stress regime. The azimuth of maximum horizontal stress axis was northwest-southeast. For U1623D (located offshore the Bellsund fjord), we have recognized multiple borehole failures with large fluctuations of azimuth possibly due to presence of local stress or small differential stress. Our results provide the first in-situ stress field constrain stress fields in the Eastern Fram Strait. In combination with existing model-based studies, our results advance understanding of the effect of the stress regime on fluid dynamics and seafloor seepage in the region.
Studies over the last decade have shown that seafloor methane seepage is impacted by the spatiotemporal evolution of the aforementioned stress factors in the crust. However, they have suffered from some uncertainties and difficulties in extrapolating to the sedimentary sequence. Additionally, the in-situ stress measurements from the area have been lacking to constrain stress regime inferences from geophysical data and stress models.
During International Ocean Discovery Program (IODP) Expedition 403, borehole resistivity images were obtained and observed in two sites. These are the first actual data of in-situ stress measurements in the region containing borehole failures from which the maximum and minimum principal horizontal stress orientations can be determined. For U1618B (located on the eastern Vestnesa ridge, an active seafloor seepage system), we have recognized very scarce borehole compressive failures, implying weak horizontal compression by normal stress regime. The azimuth of maximum horizontal stress axis was northwest-southeast. For U1623D (located offshore the Bellsund fjord), we have recognized multiple borehole failures with large fluctuations of azimuth possibly due to presence of local stress or small differential stress. Our results provide the first in-situ stress field constrain stress fields in the Eastern Fram Strait. In combination with existing model-based studies, our results advance understanding of the effect of the stress regime on fluid dynamics and seafloor seepage in the region.