Collaborative Research: Follow on to Seafloor Optical Fiber Strainmeters for the Detection of Slow Slip Events in Cascadia

The Cascadia subduction zone lies offshore Oregon and Washington. This region is known for slow-slip events, where the plates gradually slip past each other slowly over days, weeks, or months. Onshore instrumentation can detect slow slip, but seafloor instrumentation is needed to monitor the full subduction zone. This is important because slow slip may increase the chance of triggering a great megathrust earthquake and tsunami. This project will extend a time series of seafloor optical fiber strainmeters that detect slow slip off the coast of Oregon. The results could allow for more precise timing of earthquake forecasts for the region. The project supports two graduate students and a post-doctoral scholar. Two orthogonal seafloor optical fiber strainmeters were deployed off the coast of Oregon in 2022. Early results show a signal that is interpreted as an offshore slow slip event that is near simultaneous with onshore slow slip. This project will extend the deployment of the seafloor instruments for two additional years. Capturing more events should help clarify the relative timing of slip in the shallow and deep patches. A primary scientific question is how two slow slip zones, with a gap separating them, are mechanically linked so that they slip nearly simultaneously. This project will also further the real-world use of the seafloor optical fiber strainmeters, a relatively new type of seafloor geodetic instrument which has unique capabilities for capturing offshore slow slip. This project is the first to deploy these instruments over a multi-year time frame. Detecting and monitoring offshore slow slip at the base of the locked zone is important for understanding earthquake hazards in this coastal region. The project will provide training in seafloor geodesy techniques and instrumentation for graduate students and a post-doctoral scholar. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.