Bathymetric highs on the ocean floor ultimately sink into highly seismic subduction zones, raising vigorous debates on their potential to trigger or arrest large earthquakes (Mw > 7.5). Many geophysical and seismological studies addressing this problem meet penetration and/or resolution issues and deal with only the most recent earthquakes. We herein present the missing piece of the puzzle with the time-integrated field and petrographic record of a unique, almost intact subducted seamount cropping out along a fossil subduction interface. We document seamount buildup and subduction down to ∼30 km, and we show that this seamount did not behave as a large earthquake asperity and may have acted as a barrier.

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