ARI: The Hawaii-2 Observatory: A Deep Ocean Geoscience Facility Re-using the Hawaii-2 Telephone Cable

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This ARI award provides funding to convert the AT&T Hawaii-2 undersea co-axial telephone cable, a retired cable that stretches from Hawaii to southern California, into a long-term geophysical observatory. The Hawaii-2 Observatory (H2O) will be created by cutting the cable approximately mid-way between Hawaii and California and inserting a junction box with eight underwater-mateable connectors. Power will be supplied to the junction box and any instruments attached to it from the AT&T Makaha cable station on the island of Oahu. A landline from the cable station to the Univ. of Hawaii at Manoa will allow scientists to monitor data from the ocean bottom observatory in real-time and modify the software contained in the junction box and instruments. The first instrument the PI's propose to deploy at the H2O is a seismometer because the proposed site of the junction box optimizes coverage of a strategic area for the IRIS Global Seismic Network (GSN), an international network of seismic stations. Observations from GSN stations are constrained by the location of the stations, which are all on continents or islands. This biased distribution of seismic stations introduces spatial alias and substantial uncertainties into earth studies, particularly tomographic studies of the Earth's structure and studies of earthquake source location, focal mechanism, and rupture process. Ocean floor observatories are necessary to complete the network. Oceanographers have initiated an international effort to establish an Ocean Seismic Network as a subset of the GSN. They have identified 20 areas of the ocean floor where seismic coverage is a high priority; H2O would offer coverage of one of these areas. In addition to advances in seismic studies, H2O could be used to advance studies of geomagetism, tsunamis, polar motion, gravity and geodetic studies. Geomagnetic data also are biased by the distribution of observatories, which are mainly located on continents in the northern hemisphere. A recent NRC task group re port has described the scientific rationale for a more balanced global geomagnetic network and proposed the addition of 8 seafloor sites, including one in the vicinity of H2O. Tsunami studies are hampered by a lack of open-ocean data and would be greatly enhanced by deployment of a pressure sensor at the H2O site. Real-time access to the data would improve the ability of existing tsunami warning systems to predict wave height. Ocean bottom pressure is also an indicator of large scale horizontal water motions, which affect the Earth's axis of rotation, vertical and horizontal deformation of the earth's crust, and fluctuations in surface gravity. The H2O site would allow real-time studies of these geophysical systems.