Figure F1. Artist's renderings of deepwater Dynamics of Earth and Ocean Systems (DEOS) observatory buoys resulting from (A) 2001 United States (US) National Science Foundation (NSF)-supported DEOS design study and (B) 2001 United Kingdom (UK) Natural Environment Research Council (NERC)-supported DEOS design study. Both buoys and mooring systems are designed to provide stable, multiyear to decadal-scale support for long-term observatory measurements at the air/sea interface, within the water column, on the seafloor, and below. They are designed to maintain better than 95% quality of service of continuous medium bandwidth bidirectional satellite telemetry to shore stations and, through them, the Internet. They also generate 1.52.0 kw of continuous electrical power at the sea surface using (A) multiple diesel and (B) diesel or fuel-cell technologies. The US design is a spar buoy with three-point mooring optimized for deepwater deployment in tropical through temperate climates. The UK design is a hybrid design with two-point mooring optimized for deepwater deployment in particularly harsh extreme northern and southern latitudes.
Figure F2. Location of Site 1243 (Ocean Seismic Network [OSN]-2; star) is shown superimposed on a free-air gravity-anomaly map derived from Geosat and ERS-1 data (courtesy of David Sandwell and Walter Smith). Other sites shown are the Hawaii-2 Observatory (H2O; diamond), where an observatory hole was drilled during Leg 200 (Hole 1224D) (the OSN-1 observatory), where a hole was drilled and cased during Leg 138 (Hole 843B), and the notional site (circle) proposed by International Ocean Network (ION)/OSN documents to fill a coverage gap west of the Galapagos Islands. Hole 1243A replaces the notional site and fills the gap for the region. Additional second priority ION/OSN notional sites lie between Sites H2O and OSN-2.
Figure F3. The proposed drilling site for Leg 203 (solid circle) superimposed on a tectonic map of the world.
Figure F4. Deployment of a borehole seismometer within a cased ODP hole with a reentry cone using a wireline reentry system.
Figure F5. Generalized circulation of the eastern equatorial Pacific showing surface currents (solid arrows), subsurface currents (dashed arrows), California Current (CAC), North Equatorial Current (NEC), North Equatorial Countercurrent (NECC), Equatorial Undercurrent (EUC), South Equatorial Current (SEC), Chile Current (CHC), and Peru Current (PC). Shaded areas illustrate the general latitudinal extent of the SEC and NEC. Solid circles = Leg 138 sites (Site 1243A is very near Site 852). Modified from figure 1 of Shipboard Scientific Party (1992).
Figure F6. A, B. Dynamic sea height from satellite altimetry superimposed upon the wind field for a recent period. The residual shows the different current regimes.
Figure F7. A. Ekman velocity from satellite scatterometer measurements. B. Geostrophic currents from Topex/Poseidon. C. The sum of the currents box superimposed upon sea-surface temperature anomalies (SSTA). The surface currents in the vicinity of Site 1243 (OSN-2) are ~1 kt. The Equatorial Countercurrent is well to the south. QuikSCAT data courtesy of M. Bourassa, Center for Ocean-Atmospheric Prediction Studies/Florida State University. Topex/Posiedon sea surface height (SSHgt) analysis courtesy of L. Miller, NOAA. Sea-surface temperature data courtesy of R. Reynolds, NOAA. Surface velocity calculation courtesy of G. Lagerloef and J. Gunn, Earth and Space Research (www.esr.org).
Figure F8. Sediment thickness along the 110°W transect collected during the Thomas Washington Venture I cruise. The locations of the various drill sites shown in Figure F9 are superimposed. TWT = two-way traveltime.
Figure F9. Vertical component spectra from the seafloor, buried, and borehole installations at Ocean Seismic Network (OSN)-1 are compared with the spectra from the buried installation at Hawaii-2 Observatory (H2O) and the Kipapa, Hawaii (KIP) GSN station on Oahu. Site H2O has extremely low noise levels above 5 Hz and near the microseism peak from 0.1 to 0.3 Hz. Site H2O has high noise levels below 50 mHz. Otherwise, Site H2O levels are comparable to the OSN borehole and KIP levels. The sediment resonances at Site H2O near 1 and 3 Hz are very prominent.
Figure F10. Horizontal component spectra from the seafloor, buried, and borehole installations at Ocean Seismic Network (OSN)-1 are compared with the spectra from the buried installation at Hawaii-2 Observatory (H2O) and the Kipapa, Hawaii (KIP) GSN station on Oahu. The sediment resonance peaks in the 0.38 Hz band are up to 35 dB louder than background and far exceed the microseism peak at 0.10.3 Hz. The fact that the resonant peaks are considerably higher for horizontal components than for the vertical component is consistent with the notion that these are related to shear wave resonances (Scholte modes).
Figure F11. Track chart for the Ocean Seismic Network (OSN)-2 site survey. WP = way point.
Figure F12. Lines 56 (see Fig. F11) from the site survey, migrated, showing the locations of Holes 1243A and 1243B. UTC = Universal Time Coordinated.
Figure F13. Schematic representation of Hole 1243A.
Figure F14. Basement lithology from Hole 1243B. T.D. = total depth.
Figure F15. Physical properties of basalt samples recovered from Hole 1243B. A. Wet bulk density vs. porosity. B. Porosity vs. grain density. C. Wet bulk density vs. grain density. D. Sonic velocity vs. wet bulk density. E. Sonic velocity vs. porosity. F. Sonic velocity vs. grain density.
Figure F16. Composite plot of downhole measurements in the sediment and basement section of Hole 1243B. The core lithology has been shifted down 6.3 m to match the logging-derived depths. gAPI = American Petroleum Institute gamma ray units, IDPH = deep induction phasor-processed resistivity, IMPH = medium induction phasor-processed resistivity, SFLU = spherically focused resistivity measurement, DTCO = Delta-T P-wave, DTSM = Delta-T S-wave.
Figure F17. Porosities and measured sonic velocities in basalt samples recovered from Hole 1243B, plotted with the downhole sonic log and interval velocities computed from the WST survey. Also shown is the lithostratigraphy column. Logging and Well Seismic Tool (WST) depths have been adjusted to the coring depths. s.e. = standard error, T.D. = total depth.
Figure F18. Downhole caliper log from Hole 1243B.
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