1. Variable In Situ Stress Orientations Across the Northern Hikurangi Subduction Margin
- Author
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McNamara, D. D., Behboudi, E., Wallace, L., Saffer, D., Cook, A. E., Fagereng, A., Paganoni, M., Wu, Hung‐Yu, Kim, G., Lee, H., Savage, H. M., Barnes, P., Pecher, I., LeVay, L. J., and Petronotis, K. E.
- Abstract
We constrain orientations of the horizontal stress field from borehole image data in a transect across the Hikurangi Subduction Margin. This region experiences NW‐SE convergence and is the site of recurrent slow slip events. The direction of the horizontal maximum stress is E‐W at an active splay thrust fault near the subduction margin trench. This trend changes to NNW‐SSE in a forearc trench slope basin on the offshore accretionary wedge, and to NE‐SW in the onshore forearc. Multiple, tectonic, and geological processes, either individually or in concert, may explain this variability. The observed offshore to onshore stress rotation may reflect a change from dominantly compressional tectonics at the deformation front, to a strike‐slip and/or extensional tectonic regime closer to the Taupo Volcanic Zone, further inland. In addition, the offshore stress may be affected by topography and/or stress rotation around subducting seamounts, and/or temporal stress changes during the slow slip cycle. Using geophysical images captured from the inside of boreholes drilled across the Hikurangi Subduction Margin, an area that experiences slow earthquakes, we describe variability in the direction of modern day maximum horizontal tectonic forces (stress) at this collisional plate boundary. Changes in the direction of maximum horizontal stress occur as you move from the plate boundary toward the onshore region of New Zealand's North Island. We suggest a range of possible tectonic and geological processes that either individually or in concert may explain our observed stress direction variations. This includes changing tectonic regimes as you move away from the plate boundary, topography, and effects on the stress field caused by the presence of subducting seamounts, and changing stress conditions related to the intermittent activity of slow earthquakes. Maximum horizontal stress directions vary in a transect across the Hikurangi Subduction MarginStress orientations suggest a change occurs moving from offshore to onshore associated with changing dominant tectonic regimeOffshore stress variation may be caused by a number of specific tectonic and geological causes Maximum horizontal stress directions vary in a transect across the Hikurangi Subduction Margin Stress orientations suggest a change occurs moving from offshore to onshore associated with changing dominant tectonic regime Offshore stress variation may be caused by a number of specific tectonic and geological causes
- Published
- 2021
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