Intraslab Seismicity Near Subducted Seamounts Induced by the 2019 Large Slow Slip Event Offshore the Northern Hikurangi Subduction Zone, New Zealand

At the northern Hikurangi subduction zone, New Zealand, large slow slip events (SSEs) occur every 18–24 months. During the large 2019 SSE, ocean‐bottom seismometers were deployed directly above the main slip region. To analyze seismicity related to this event, we used machine learning and template matching techniques, along with a detailed velocity model, to generate a high‐resolution earthquake catalog that spans before, during, and after this SSE. This catalog reveals a significant increase in seismicity located near a subducted seamount after the peak slip of the SSE. This seismicity is predominantly located within the subducting slab and is interpreted as reactivation of pre‐existing tensional faults, driven by stress perturbations from the SSE and potentially facilitated by fluid migration. Notably, this active intraslab seismicity was not observed in the preceding SSE in the same area, likely due to variations in slip location or local plate stress state. Our results provide further evidence of the intriguing relationship between slow slip on the plate interface and faults in the slab, as previously demonstrated by the Mw 6.7 Gisborne normal faulting earthquake in 2007 that triggered a SSE on the plate interface. Comparative analysis with earlier studies highlights the important influence of subducted seamounts and fluid presence in governing the spatial and temporal patterns of SSE‐related seismicity, as well as the interactions between intraslab and plate interface earthquakes.