Endeavour Extend

This project is a collaborative effort involving scientists from the University of Washington, Dalhousie University, the Geological Survey of Canada, Ocean Networks Canada and the University of Victoria, funded by awards from the NSF, NSERC Ship Time Fund, and MEOPAR. It seeks to take advantage of a rare opportunity for a preemptive enhanced seismic response to a diking spreading sequence that is anticipated on the Endeavour segment of the Juan de Fuca Ridge (JdFR) based on observations of escalating seismicity. Such a sequence will likely occur only once in the 25-year design lifetime of the Ocean Networks Canada (ONC) NEPTUNE observatory. Except for Axial Seamount, which is a hotspot volcano with two rifts and not a ridge segment with enhanced magma supply at the center, there is nowhere else on the 80,000-km-long global network of oceanic spreading centers with the cabled infrastructure in place to anticipate such events and make the multidisciplinary observations necessary to link a detailed geophysical understanding of diking to its impact on vigorous hydrothermal systems and biological communities. Dike injection is the fundamental process that creates the upper oceanic crust and, except at the slowest spreading rates, accounts for the bulk of plate boundary extension. Submarine diking along mid-ocean ridges is most easily detected using hydroacoustic observations of swarm seismicity. In previous studies, hydroacoustic datasets have tracked the propagation speeds of dikes, identified the locations of likely eruptions, and facilitated rapid response efforts to observe their impacts on the seafloor. Yet, much more can be learned about the deformation associated with dike injection if local seismic networks are in place to record the high levels of precursory seismicity when the crust is critically stressed and the rupturing that accompanies dike injection. Beyond volcanic eruption monitoring, this dataset provides valuable submarine seismic data that offer a unique opportunity to investigate marine mammals, including endangered blue whale, by analyzing their behaviours and migration patterns. Seismicity monitoring will also contribute to understanding of major geohazards on the Pacific Coast, with results incorporated in seismic hazard and tsunami prediction models used to protect public safety and coastal infrastructure. A network of 20 Aquarius broadband ocean-bottom seismometers (OBS) from the National Facility for Seismological Investigations (Dalhousie University) will be deployed in August 2025 for a period of approximately 1 year to supplement the existing cabled NEPTUNE observatory during the time period when the Endeavour segment is most likely to rupture. A dense cluster of 16 OBS will be deployed near the center of the segment to cover the footprint of previously observed seismicity, with 2 OBS at either end to fully characterize off-axis seismicity. Continuing deployments of 5 OBS (3 central and 2 at southern end) per year are planned for 2026-2029.

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