TY - JOUR
T1 - Stress constraints from shear-wave analysis in shallow sediments at an actively seeping pockmark on the W-Svalbard margin
AU - Singhroha, Sunny
AU - Schramm, Bettina
AU - Plaza-Faverola, Andreia
AU - Domel, Przemyslaw
AU - Dannowski, Anke
AU - Cooke, Frances
AU - Bünz, Stefan
N1 - Publisher Copyright:
© 2023 The Authors. Earth and Space Science published by Wiley Periodicals LLC on behalf of American Geophysical Union.
PY - 2023/10
Y1 - 2023/10
N2 - Mechanisms related to sub-seabed fluid flow processes are complex and inadequately understood. Petrophysical properties, availability of gases, topography, stress directions, and various geological parameters determine the location and intensity of leakage which change over time. From tens of seafloor pockmarks mapped along Vestnesa Ridge on the west-Svalbard margin, only six show persistent present-day seepage activity in sonar data. To investigate the causes of such restricted gas seepage, we conducted a study of anisotropy within the conduit feeding one of these active pockmarks (i.e., Lunde Pockmark). Lunde is ∼400–500 m in diameter, and atop a ∼300–400 m wide seismic chimney structure. We study seismic anisotropy using converted S-wave data from 22 ocean-bottom seismometers (OBSs) located in and around the pockmark. We investigate differences in symmetry plane directions in anisotropic media using null energy symmetries in transverse components. Subsurface stress distribution affects fault/fracture orientations and seismic anisotropy, and we use S-wave and high-resolution 3D seismic data to infer stress regimes in and around the active seep site and study the effect of stresses on seepage. We observe the occurrence of changes in dominant fault/fracture and horizontal stress orientations in and around Lunde Pockmark and conclude minimum (NE-SW) and maximum (SE-NW) horizontal stress directions. Our analysis indicates a potential correlation between hydrofractures and horizontal stresses, with up to a ∼32% higher probability of alignment of hydrofractures and faults perpendicular to the inferred minimum horizontal stress direction beneath the Lunde Pockmark area.
AB - Mechanisms related to sub-seabed fluid flow processes are complex and inadequately understood. Petrophysical properties, availability of gases, topography, stress directions, and various geological parameters determine the location and intensity of leakage which change over time. From tens of seafloor pockmarks mapped along Vestnesa Ridge on the west-Svalbard margin, only six show persistent present-day seepage activity in sonar data. To investigate the causes of such restricted gas seepage, we conducted a study of anisotropy within the conduit feeding one of these active pockmarks (i.e., Lunde Pockmark). Lunde is ∼400–500 m in diameter, and atop a ∼300–400 m wide seismic chimney structure. We study seismic anisotropy using converted S-wave data from 22 ocean-bottom seismometers (OBSs) located in and around the pockmark. We investigate differences in symmetry plane directions in anisotropic media using null energy symmetries in transverse components. Subsurface stress distribution affects fault/fracture orientations and seismic anisotropy, and we use S-wave and high-resolution 3D seismic data to infer stress regimes in and around the active seep site and study the effect of stresses on seepage. We observe the occurrence of changes in dominant fault/fracture and horizontal stress orientations in and around Lunde Pockmark and conclude minimum (NE-SW) and maximum (SE-NW) horizontal stress directions. Our analysis indicates a potential correlation between hydrofractures and horizontal stresses, with up to a ∼32% higher probability of alignment of hydrofractures and faults perpendicular to the inferred minimum horizontal stress direction beneath the Lunde Pockmark area.
KW - S-wave analysis
KW - stress
KW - ocean-bottom seismometer (OBS)
KW - anisotropy
KW - converted shear (PS) waves
KW - fluid seepage
KW - fault analysis
UR - http://www.scopus.com/inward/record.url?scp=85173521503&partnerID=8YFLogxK
U2 - 10.1029/2023EA003068
DO - 10.1029/2023EA003068
M3 - Article
SN - 2333-5084
VL - 10
JO - Earth and Space Science
JF - Earth and Space Science
IS - 10
M1 - e2023EA003068
ER -