HUGO:The Hawaii Undersea Geo-Observatory

The Hawaii Undersea Geo-Observatory, HUGO, was installed with the intent of supplying infrastructure for researchers interested in studies of undersea volcanism and associated phenomena at Loihi, the newest volcano of the Hawaiian chain. Much like an astronomical observatory, HUGO is a facility where scientists can perform experiments while sharing resources with others. The main components of HUGO are the shore station, supplying power to the observatory and recording data; the main cable-an electro-optical cable connecting the shore station to the summit of Loihi; the Junction box-the power distribution and data collection center on Loihi; multiplexing (mux) nodes-secondary distribution points; and experiments supplied by scientists. HUGO can potentially supply electrical power, command capability and real-time data service to more than 100 instruments connected and removed on the ocean floor by submersible or ROV. HUGO was installed on October 11, 1997, but the main cable developed an electrical short circuit to sea water on April 26, 1998, and a new cable must be obtained and installed before routine operations can continue. Despite the failure, several important tasks have been accomplished, including: 1) the successful small-ship lay of the 47-km electro-optical cable from the Island of Hawaii to the summit of Loihi submarine volcano; 2) installation and servicing of the Junction box; 3) successful operation of electro-optical connectors on the ocean floor by submersible; 4) installation and removal of experiments on the ocean floor; 5) transmission of power and commands from shore to experiments installed at HUGO; 6) transmission of high-rate, high-fidelity data from the summit of Loihi to shore in real time; and 7) recording of volcanic, earthquake, biological, ocean wave and ship noises for a period of three months. This paper provides a general description of the HUGO system and its history of operation

Mid-ocean microseisms

Author Posting. © American Geophysical Union, 2005. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry Geophysics Geosystems 6 (2005): Q04009, doi:10.1029/2004GC000768.The Hawaii-2 Observatory (H2O) is an excellent site for studying the source regions and propagation of microseisms since it is located far from shorelines and shallow water. During Leg 200 of the Ocean Drilling Program, the officers of the JOIDES Resolution took wind and wave measurements for comparison with double-frequency (DF) microseism data collected at nearby H2O. The DF microseism band can be divided into short period and long period bands, SPDF and LPDF, respectively. Comparison of the ship’s weather log with the seismic data in the SPDF band from about 0.20 to 0.45 Hz shows a strong correlation of seismic amplitude with wind speed and direction, implying that the energy reaching the ocean floor is generated locally by ocean gravity waves. Near-shore land seismic stations see similar SPDF spectra, also generated locally by wind seas. At H2O, SPDF microseism amplitudes lag sustained changes in wind speed and direction by several hours, with the lag increasing with wave period. This lag may be associated with the time necessary for the development of opposing seas for DF microseism generation. Correlation of swell height above H2O with the LPDF band from 0.085 to 0.20 Hz is often poor, implying that a significant portion of this energy originates at distant locations. Correlation of the H2O seismic data with NOAA buoy data, with hindcast wave height data from the North Pacific, and with seismic data from mainland and island stations, defines likely source areas of the LPDF signals. Most of the LPDF energy at H2O appears to be generated by high amplitude storm waves impacting long stretches of coastline nearly simultaneously, and the Hawaiian Islands appear to be a significant source of LPDF energy in the North Pacific when waves arrive from particular directions. The highest DF levels observed at mid-ocean site H2O occur in the SPDF band when two coincident nearby storm systems develop. Mid-ocean generated DF microseisms are not observed at interior continental sites, indicating high attenuation of these signals. At near-coastal seismic stations, both SPDF and LPDF microseism levels are generally dominated by local generation at nearby shorelines.This work was supported by the U.S. Science Support Program (User Reference: 418920-BA372; Task Order F001602) associated with the Ocean Drilling Program and is sponsored by the National Science Foundation and the Joint Oceanographic Institutions, Inc. Additional support was provided by the California Energy Commission and the California Department of Boating and Waterways as part of their program to improve boating facilities, access, safety, and education. Support for Ralph Stephen was also provided by the National Science Foundation under Grant #OCE-0424633

Wind, waves, and acoustic background levels at Station ALOHA

Author Posting. © American Geophysical Union, 2012. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 117 (2012): C03017, doi:10.1029/2011JC007267.Frequency spectra from deep-ocean near-bottom acoustic measurements obtained contemporaneously with wind, wave, and seismic data are described and used to determine the correlations among these data and to discuss possible causal relationships. Microseism energy appears to originate in four distinct regions relative to the hydrophone: wind waves above the sensors contribute microseism energy observed on the ocean floor; a fraction of this local wave energy propagates as seismic waves laterally, and provides a spatially integrated contribution to microseisms observed both in the ocean and on land; waves in storms generate microseism energy in deep water that travels as seismic waves to the sensor; and waves reflected from shorelines provide opposing waves that add to the microseism energy. Correlations of local wind speed with acoustic and seismic spectral time series suggest that the local Longuet-Higgins mechanism is visible in the acoustic spectrum from about 0.4 Hz to 80 Hz. Wind speed and acoustic levels at the hydrophone are poorly correlated below 0.4 Hz, implying that the microseism energy below 0.4 Hz is not typically generated by local winds. Correlation of ocean floor acoustic energy with seismic spectra from Oahu and with wave spectra near Oahu imply that wave reflections from Hawaiian coasts, wave interactions in the deep ocean near Hawaii, and storms far from Hawaii contribute energy to the seismic and acoustic spectra below 0.4 Hz. Wavefield directionality strongly influences the acoustic spectrum at frequencies below about 2 Hz, above which the acoustic levels imply near-isotropic surface wave directionality.Funding for the ALOHA Cabled Observatory was provided by the National Science Foundation and the State of Hawaii through the School of Ocean and Earth Sciences and Technology at the University of Hawaii-Manoa (F. Duennebier, PI). Donations from AT&T and TYCOM and the cooperation of the U.S. Navy made this project possible. The WHOI-Hawaii Ocean Time series Station (WHOTS) mooring is maintained by Woods Hole Oceanographic Institution (PIs R. Weller and A. Plueddemann) with funding from the NOAA Climate Program Office/Climate Observation Division. NSF grant OCE- 0926766 supported R. Lukas (co-PI) to augment and collaborate on the maintenance of WHOTS. Lukas was also supported during this analysis by The National Ocean Partnership Program “Advanced Coupled Atmosphere-Wave-Ocean Modeling for Improving Tropical Cyclone Prediction Models” under contract N00014-10-1-0154 to the University of Rhode Island (I. Ginis, PI).2012-09-1