Figure Captions

Figure 1. Location map of seismic station coverage in the northwest Pacific. Solid circles = land seismic stations; open circles = current (Sites 1150, 1151, and 1179) and proposed (site WP-1) seafloor borehole observatories; and shaded circle (at HCH) = a presently inactive land seismic station. Note that the few borehole stations effectively complement and expand the existing network. YSS = Yuzhno Sakhalinsk, Russia; NMR = Nemuro, Japan; HCH = Hachijo-shima, Japan; PHN = Pohang, Korea; OGS = Chichi-jima, Japan; MCSJ = Minami-tori-shima, Japan; ISG = Ishigaki, Japan; TGY = Tagaytay, Philippines; PATS = Ponsei, Mictonesia; and PMG = Port Moresby, Papua New Guinea.

Figure 2. Location of Site 1179 relative to circum-Pacific and other earthquakes for the period 1992-1996. Distances from Site 1179 are shown (thick lines) in 5000-km intervals.

Figure 3. Site 1179 location relative to magnetic lineations in the northwest Pacific. The map shows predicted bathymetry and magnetic lineations. Sites 1180/1181 and 1182 are the hard rock reentry system test sites.

Figure 4. Site 1179 location relative to magnetic lineations in the northwest Pacific. Thick lines show magnetic lineations and fracture zones. Thin lines show 500-m bathymetry contours (from Sager et al., 1999; Nakanishi et al., 1989). Proposed sites SR-1 and SR-2 (open circles) are the proposed hard rock reentry system test sites on Shatsky Rise.

Figure 5. Comparison of stratigraphic columns at Site 1179 and other DSDP and ODP boreholes in the northwest Pacific. The numbers at the top give site designations. Biostratigraphic ages are along the left side of each column. The distance from Site 1179 is shown at the bottom.

Figure 6. Schematic of the NEREID-191 seismic borehole observatory. PCS = power control system; ROV = remotely operated vehicle; DL = data logger; and BIA = borehole instrument assembly.

Figure 7. Multiaccess expandable gateway system controller attached to the riser/hanger assembly prior to installation.

Figure 8. Power access terminal (PAT) battery frame being lowered through the moonpool. The PAT was hung on the logging line by a bridle assembly consisting of wire cables, nylon straps, three glass ball floats, and a redundant acoustic release.

Figure 9. Snapshot from the VIT/subsea TV camera showing the PAT landed properly on top of the Hole 1179E reentry cone.

Figure 10. Schematic of the borehole seismic observatory installation in Hole 1179E. PAT = power access terminal; and ROV = remotely operated vehicle.

Figure 11. Magnetic lineations in the vicinity of Site 1179. Thin, curved lines show magnetic anomalies, which are shaded where positive. Anomaly identifications are after Nakanishi et al. (1999). The location of Site 1179 is shown by the cross at the center of the figure. Dashed lines = magnetic lineation correlations.

Figure 12. Lithologic summary column for Site 1179. Core recovery is shown in left columns, with solid blocks indicating the amount of recovered core. Lithology and lithologic unit columns show generalized stratigraphy. Lightly shaded bands in Unit I lithology denote ash layers. Color reflectance, magnetic susceptibility, and natural gamma-ray columns show data measured on the archive multisensor track (color reflectance) and multisensor track (others). Curves in the far right column are from downhole logs. Magnetic polarity is shown by black (normal polarity) and white (reversed polarity) bands. Chron age designations are given next to the polarity column. (Continued on next two pages.)

Figure 13. Comparison of the multichannel seismic reflection profile from the site survey (Hakuho Maru cruise 96-3-1), the lithologic column developed from coring at Site 1179, and depths predicted for lithologic boundaries. The lithologic column was scaled to the seismic section using the velocity-depth relationship of Carlson et al. (1986) to calculate the two-way traveltime of unit boundaries and ash layers derived from core observations. In the lithologic column, solid lines = unit boundaries; dotted lines = ash layers. Lithologic boundary depths are given in meters next to the column.

Figure 14. Closeup photograph of the typical clay- and radiolarian-bearing diatom ooze of Unit I (interval 191-1179B-4H-5, 88-120 cm).

Figure 15. Closeup photograph of typical clay-rich, diatom-bearing radiolarian ooze of Unit II (interval 191-1179C-20H-6, 30-50 cm).

Figure 16. Closeup photograph of brown pelagic clay found in Unit III (interval 191-1179C-24H-5, 72-92 cm).

Figure 17. Closeup photograph of chert fragments recovered from Unit IV (interval 191-1179D-6R-1, 80-110 cm).

Figure 18. Closeup photograph of basalt from Unit V. Lighter areas are interpillow sediments

(interval 191-1179D-11R-1, 74-102 cm).

Figure 19. Summary of igneous units in the basaltic basement section (lithologic Unit V).

Figure 20. Age-depth curve for Site 1179 developed from biostratigraphic data.

Figure 21. Age-depth curve for Site 1179 from magnetostratigraphic interpretations of paleomagnetic data. The magnetic polarity reversal time scale is from Cande and Kent (1995). Black bands = normal polarity; white bands = reversed polarity.

Figure 22. Summary figure showing velocity, density, and porosity vs. depth at Site 1179. The lithologic column is shown at the left. Solid circles in the bottom plots represent measurements taken in the basaltic basement. Plots at the top show measurements taken in the sedimentary section. Open triangles and circles show data from discrete measurements, whereas solid dots show MST-derived data.