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PACSAFE LEG2: Investigating Seismicity in the Northern Segment of the Queen Charlotte Triple Junction Using a Year-long OBS Deployment

Description: 

The Pacific Coast Seismic Assessment for Faults and Earthquakes (PACSAFE) multi-year OBS program aims to investigate the earthquake hazards offshore BC, with the goal of improving the characterization of seismicity and fault structure in the region. This study examines data from the second leg of the PACSAFE program (LEG2), in which 23 OBS were deployed in the northern segment of the Queen Charlotte Triple Junction, mainly covering the region between the Revere–Dellwood Fault Extension (RDFE) and the south end of the Queen Charlotte Fault (QCF/paleo-QCF), for a one-year period (July 2024–Aug 2025). Of the deployed instruments, two stations self-released prematurely; therefore, our analysis is based on data from the remaining 21 OBS.
We carried out preliminary seismic analyses of the one-year long continuous LEG2 seismic data in the northern segment of the Queen Charlotte Triple Junction . We applied OBSTransformer, a deep learning–based phase picker, to the continuous waveform data. Only high-confidence picks (probability ≥ 0.3) were retained for phase association, yielding 17,500 candidate events. We subsequently conducted both absolute and relative earthquake relocations, producing a final seismicity catalog containing over 14,000 double-difference–relocated events with depths predominantly shallower than 20 km, but extending to ~40 km offshore southern Haida Gwaii. The abundance of earthquakes with high-resolution locations clearly delineates the detailed active fault structure of the region. Lineated seismicity is observed along the RDFE rather than the QCF or paleo-QCF, with a major conjugate shear zone connecting the RDFE to the QCF/paleo-QCF that accommodates most earthquakes observed during the study period, including the aftershocks of the recent 2024 M 6.5 earthquake, whose mainshock hypocenter is located at the intersection of the Tuzo–Wilson Volcanic Field and the QCF. Through further seismological analyses and multidisciplinary integration, the research team anticipates gaining a better understanding of deformation mechanisms and associated seismic hazards in the region.

Session: Linking Subduction Zone Processes and Cascading Hazards in Alaska, Cascadia, Chile and Beyond [Poster]

Type: Poster

Date: 4/16/2026

Presentation Time: 08:00 AM (local time)

Presenting Author: Adnan Barkat

Student Presenter: No

Invited Presentation: 

Poster Number: 123

Authors