Ocean Drilling at the Hawaii-2 Observatory (H2O)

Ocean Drilling at the Hawaii-2 Observatory (H2O) Horizontal component spectrogram for the broadband Guralp sensor (HH1) at the Hawaii-2 Observatory (H2O) during drilling operations from JD 350/2001 to 27/2002 (16 December, 2001 to 27 January, 2002). Large earthquakes are indicated as horizontal red lines in the band 0.01 to 0.1Hz. Variations in the magnitude of the microseisms from 0.1 to 0.3Hz correlate with sea state in the North Pacific (Bromirski et al, 2005). Sediment resonances at 1.1 and 2 Hz dominate even the microseism peak. The red blotches in the frequency band from 2 to 60 Hz correspond primarily to drilling activities. Color, as defined in the bar on the right, indicates energy content in decibels relative to m2/s2Hz.

On ODP Leg 200 a borehole was drilled at the Hawaii-2 Observatory in preparation for the installation of a high quality broadband borehole seismometer similar to the system deployed on the Ocean Seismic Network Pilot Experiment (OSNPE) (Stephen et al, 2003). The drilling at H2O provided a unique opportunity to observe drilling-related noise from the JOIDES Resolution on a seafloor seismometer in the frequency band from 0.001 to 60Hz. H2O, located on the seafloor midway between Hawaii and California, uses a retired trans-oceanic telephone cable to provide continuous, real-time data transmission to the Makaha cable station on Oahu. At H2O, the University of Hawaii operates a shallow-buried ocean bottom seismometer composed of a Guralp CMG-3T three-component broadband seafloor seismometer and a conventional 4.5-Hz three-axis geophone (Duennebier et al., 2000, 2002). Data are acquired continuously and are made available to scientists worldwide through the IRIS Data Management System in Seattle.

The figure shows a broadband horizontal component spectrogram for the duration of ODP Leg 200. Seismic signal levels can be associated with wind speed, sea state, shear resonance effects in the sediments, whales, water gun shooting, earthquakes, passing ships, and drilling-related activities such as bit noise and running pipe.

Bromirski, P. D., F. K. Duennebier, and R.A. Stephen. “Mid-ocean microseisms.” Geochemistry, Geophysics, Geosystems, 6: doi:10.1029/2004GC000768, 2005.

Duennebier , F. K., D. W. Harris, J. Jolly, J. Babinec, D. Copson, and K. Stiffel., “The Hawaii-2 observatory seismic system.” IEEE Journal of Oceanic Engineering, 27: 212-217, 2002.

Stephen, R.A., F.K. Duennebier, D. Harris, J. Jolly, S.T. Bolmer, and P.D. Bromirski. Data Report: Broadband seismic observations at the Hawaii-2 Observatory during ODP Leg 200. In Kasahara, J., R.A. Stephen, G.D. Acton, and F. Frey (Eds.), Proc. ODP, Sci. Results, 200 (CD-ROM). Available from: Ocean Drilling Program, Texas A&M University, College Station, TX 77845-9547, USA, inpress.

Stephen, R.A., J. Kasahara, G.D. Acton, et al., Proc.ODP. Init. Repts., 200 (C-ROM). Available from: Ocean Drilling Program, Texas A&M University, College Station, TX 77845-9547, USA, 2003.

Stephen, R.A., F.N. Spiess, J.A. Collins, J.A. Hildebrand, J.A. Orcutt, K.R. Peal, F.L. Vernon, and F.B. Wooding, 4 (10), 1092, Ocean seismic network pilot experiment, Geochem. Geophys. Geosyst., 4 (10), 1092, doi:10.1029/2002GC000485, 2003.


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