Maps of study region and graphs from the paper.
Left: The 2021 Mw 8.2 Chignik, Alaska, earthquake was recorded by the instruments of the Ocean Networks Canada's NEPTUNE observatory. Right: seafloor (blue) and sub-seafloor borehole (orange) fluid pressure records at Holes 1027C and 1364A show ocean tides (top) and the seismic waves and tsunami from the earthquake (bottom, “de-tided”), revealing the loading efficiency of the rock formation. Credit: Sun and Davis [2022], Figure 1(a,c) and Figure 8(a,b)
Editors’ Highlights are summaries of recent papers by AGU’s journal editors.
Source: Geochemistry, Geophysics, Geosystems

The 2021 Mw 8.2 Chignik, Alaska, earthquake was recorded by Ocean Networks Canada’s cabled, ocean-floor observatory NEPTUNE (North-East Pacific Time-series Undersea Networked Experiments). Its seismometers and high-rate seafloor and borehole fluid pressure sensors recorded signals in a very broad frequency range, including tides, short- and long-period seismic waves, and the tsunami generated by the earthquake.

Using this unique dataset, Sun and Davis [2022] offer new insights into the pressure variations at and below the seafloor and the dynamic coupling between the ocean and the crust. By capturing incoming waveforms of tsunamis in detail, such data can contribute to the modeling of their runup. For tsunami early warning, the real-time recordings from the diverse ocean-floor instruments can come 15 to 20 minutes prior to those from coastal tidal gauges. The seismic and seafloor pressure observations also quantify the surface-wave amplification controlled by the sediment layer thickness, which is important for the assessment of hazards caused by offshore slope failures due to intense ground shaking. 

Citation: Sun, T., & Davis, E. (2022). Monitoring the 2021 Mw 8.2 Alaska Earthquake by an Offshore Seismic and Fluid Pressure Observation Network and Implications for Ocean-Crust Dynamic Coupling. Geochemistry, Geophysics, Geosystems, 23, e2022GC010540.

—Sergei Lebedev, Associate Editor, Geochemistry, Geophysics, Geosystems

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