OBS Data Mining Reveals Seismic Structure and Dynamics of the Oceanic Blanco Transform Fault, Northeast Pacific

Deformation along oceanic transform faults is partitioned between seismic and aseismic slip, controlled by lithology, thermal structure, and fluid circulation. We analyze one year of data from a 54‐station ocean bottom seismometer network deployed across the Blanco Transform Fault (BTF), Northeast Pacific. Using machine‐learning pickers and high‐precision location methods, we construct a high‐resolution microseismicity catalog with over 30,000 earthquakes. Comparison with three independent catalogs shows that earthquake depth estimates vary with velocity models, phase association, and location strategies. Our enhanced catalog reveals strong along‐strike variations in seismicity, including depth extent, density, and moment release. Seismicity concentrates near structural step‐overs, which host ∼2.4 times more earthquakes than intervening transform segments, indicating segmentation of the fault system. Four‐dimensional spatiotemporal patterns highlight marked contrasts between transforms and step‐overs. Extension at step‐overs likely enhances fluid circulation within networks of normal faults, sustaining high microearthquake rates and seismic bursts. Comparison with three‐dimensional thermal models constrains the nature and thermal state of the BTF step‐overs, classifying them as intra‐transform spreading centers (ITSCs) or amagmatic pull‐apart basins. Along the Blanco Ridge segment, we compare space–time patterns of microseismicity with relocated earthquakes from 1992 to 2019. Three rupture barriers exhibit distinct levels of microearthquake activity, while active seismic bursts in the mantle are concentrated beneath locked M6 patches and one rupture barrier. A crustal northeastward fault bending is observed on the edge of a locked M6 patch. Our results highlight how fault geometry, thermal structure, and fluid‐related processes jointly control seismicity patterns and slip behavior on oceanic transform faults.