Building and Maintaining a global seismic network in the oceans

Abstract:

During the past decade the deployment of broadband seismic networks and arrays in the oceans has become increasingly common (e.g., Kohler et al., 2020). It is now common to deploy broadband networks to operate in the oceans (e.g. Lynn et al., 2016) although a permanent, global seismic network remains elusive. The cost of research ships to deploy and recover instruments and associated batteries is high even for a minimal global distribution of 20 seismometers or local arrays. In the recent past an investment in autonomous surface gliders has allowed near-real-time telemetry of data to shore possible while using acoustic telemetry signals to maintain long-term accuracy of clocks (Berger et al.,2016). A key to long-term deployments is the use of autonomous ships with no personnel aboard. The U.S. Navy has developed, tested and commissioned the Sea Hunter that is capable of unmanned operations at sea including a recent round trip between San Diego and Pearl Harbor. There are several ships operating in the Baltic, which are wholly autonomous. A small (120’), low speed autonomous ship capable of deploying and recovering seafloor seismographs is within reach. Given that an autonomous ship requires no facilities for supporting personnel (e.g., staterooms, bridge, galley, heads, sanitation tanks), the costs of construction and maintenance are greatly decreased. Furthermore, while at sea, the ship could be used to map the seafloor at high accuracy. The UN Decade of Ocean Science for Stainable Development (2021-2030) believes that it will be impossible to achieve the targeted level of sustainable development without a comprehensive map of the ocean floor. There are many applications for a few new, inexpensive oceanographic autonomous ships capable of a variety of tasks. New LEO communications satellites are being tested to increase ship or glider to land rates to Gbps rather than the current geosynchronous systems operating at Mbps speeds (e.g. HiSeasNet).

Berger, J., G. Laske, J. Babcock, and J. Orcutt (2016). An ocean bottom seismic observatory with near real-time telemetry, Earth Space Sci. 3, 68-77, doi: 10.1002/2015EA000137.

Lynn, P.-Y. P., J. B. Gaherty, G. Jin, J.A. Collins, D. Lizarralde, R. L. Evens, and G. Hirth (2016) High- resolution seismic constraints on flow dynamics in the oceanic asthenoshpere, Nature 535, 538-541, doe: 10.1038/nature18012.

Kohler, M. D., Hafner, K., Park, J., Irving, J. C. E., Caplan-Auerbach, J., Collins, J., et al. (2020). A Plan for a Long-Term, Automated, Broadband Seismic Monitoring Network on the Global Seafloor. Seismological Research Letters, 91(3), 1343–1355. http://doi.org/10.1785/0220190123