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Medientyp:
E-Artikel
Titel:
Horizontal compressive stress regime on the northern Cascadia margin inferred from borehole breakouts
Beteiligte:
Riedel, Michael
[Verfasser:in];
Malinverno, A.
[Verfasser:in];
Wang, K.
[Verfasser:in];
Goldberg, D.
[Verfasser:in];
Guerin, G.
[Verfasser:in]
Anmerkungen:
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Beschreibung:
During Integrated Ocean Drilling Program Expedition 311 five boreholes were drilled across the accretionary prism of the northern Cascadia subduction zone. Logging-while-drilling borehole images are utilized to determine breakout orientations to define maximum horizontal compressive stress orientations. Additionally, wireline logging data at two of these sites and from Site 889 of Ocean Drilling Program Leg 146 are used to define breakouts from differences in the aperture of caliper arms. At most sites, the maximum horizontal compressive stress SHmax is margin-normal, consistent with plate convergence. Deviations from this trend reflect local structural perturbations. Our results do not constrain stress magnitudes. If the margin-normal compressional stress is greater than the vertical stress, the margin-normal SHmax direction we observe may reflect current locking of a velocity-weakening shallow megathrust and thus potential for trench-breaching, tsunamigenic rupture in a future megathrust earthquake.