Slab tearing and segmented subduction termination driven by transform tectonics
Subduction may terminate when a mid-ocean ridge approaches a trench, introducing buoyant lithosphere that resists subduction, leading to slab detachment and plate boundary reconfiguration. Yet, the spatial and temporal dynamics of slab tearing remain enigmatic due to a lack of modern examples. Here, we integrate new seismic images with regional seismicity to investigate an actively fragmenting subduction system at northern Cascadia's ridge-trench-fault triple junction where subduction termination is imminent. Our analyses reveal a broad shear-zone initiated at ~4 Ma by exploiting ridge-parallel fabrics of nascent oceanic lithosphere and progressively localized into a mature trench-perpendicular transform boundary. This process severed an oceanic microplate and enabled its diminished subduction relative to adjacent subducting lithosphere. Downdip, we image trench-parallel slab tears offset by the transform, suggesting lateral tear propagation was intersected by the transform boundary, facilitating efficient decoupling of the microplate while allowing adjacent subduction to continue. We propose a 4D model where transform boundaries drive laterally diachronous slab fragmentation and subduction termination.
Authors
- M. R. Nedimović (ORCID: https://orcid.org/0000-0003-0327-5192)
- S. M. Carbotte (ORCID: https://orcid.org/0000-0001-9471-700X)
- Anne Bécel (ORCID: https://orcid.org/0000-0001-7803-5949)
- B. Boston (ORCID: https://orcid.org/0000-0002-0647-4018)
- Geneviève Savard (ORCID: https://orcid.org/0000-0001-5464-3384)
- Harold Tobin (ORCID: https://orcid.org/0000-0002-1447-6873)
- Geena Littel (ORCID: https://orcid.org/0000-0001-5432-325X)
- Brandon Shuck (ORCID: https://orcid.org/0000-0003-2543-721X)
- J. P. Canales (ORCID: https://orcid.org/0000-0003-3066-7888)
- Jeffrey W. Beeson (ORCID: https://orcid.org/0000-0002-7396-237X)
- Jesse Hutchinson (ORCID: https://orcid.org/0000-0003-1781-0977)
- N. C. E. Miller (ORCID: https://orcid.org/0000-0003-3271-2929)
- Shuoshuo Han (ORCID: https://orcid.org/0000-0002-2904-3659)
- Reid Merrill (ORCID: https://orcid.org/0000-0003-1337-782X)
- Pinar Gurun
Institutions
- University of Geneva (CH)
- Louisiana State University (US)
- United States Geological Survey (US)
- Dalhousie University (CA)
- National Oceanic and Atmospheric Administration (US)
- Oregon State University (US)
- University of British Columbia (CA)
- Lamont-Doherty Earth Observatory (US)
- University of Washington (US)
- University of Victoria (CA)
- NOAA Pacific Marine Environmental Laboratory (US)
- Ocean Networks Canada Society (CA)
- Broadcom (Canada) (CA)
- Woods Hole Oceanographic Institution (US)
- Columbia University (US)
- Auburn University (US)
- The University of Texas at Austin (US)
Publication Details
- Journal
- Science Advances
- Published
- 2025-09-24
- DOI
- https://doi.org/10.1126/sciadv.ady8347
- Citations
- 1
- Primary Topic
- Geological and Geophysical Studies
- Type
- article
- Field-Weighted Citation Impact
- 2.35