FIGURE CAPTIONS

Figure 2. Schematic cross section through the Mariana system showing various types of associations of serpentine mud volcanoes with faulting in the forearc wedge. Strike-slip faulting associated with along-strike extension and vertical tectonics related to seamount subduction both play a part in the tectonic deformation of the forearc and provide avenues for egress of slab-derived fluids and fault gouge from both the décollement and the lithosphere of the overriding plate. Decarbonation reactions in the downgoing plate probably take place between ~15 and 20 km (Fryer et al, in press).

Figure 3. Bathymetry of the Southern Mariana forearc (250-m contour intervals). The location of all forearc seamounts sampled thus far are labeled. The South Chamorro Seamount is targeted for drilling during Leg 195. Map gives shaded bathymetric relief.

Figure 4. HMR-1 sidescan imagery of South Chamorro Seamount showing the location of six channel seismic reflection profiles listed in the "Site Summary" section (A-A' and B-B').

Figure 5A. Location map of seismic station coverage in the northwest Pacific showing additional stations needed. At least five major plates with consuming boundaries interact in the northwest Pacific, causing subduction, back-arc opening, slab collisions, terrane accretion, and island arc development. Solid circles indicate land seismic stations, whereas open circles are current and proposed seafloor borehole observatories. Note that a few borehole stations effectively complement and expand the existing network. YSS = Yuzhno Sakhalinsk, Russia, 46.9583°N, 142.7610°E; NMR = Nemuro, Japan, 36.1525°N, 145.7430°E; PHN = Pohang, Korea, 36.03°N, 129.36°E; HCH = Hachijo-shima, Japan, Reserved; OGS = Chichi-jima, Japan, 27.0570°N, 142.2030°; MCSJ = Minami-tori-shima, Japan, 24.290°N, 153.978°E; ISG = Ishigaki, Japan, 24.3793°N, 124.2347°E; PATS = Ponsei, Micronesia, 6.8367°N, 158.3125°E; PMG = Port Moresby, Papua New Guinea, 9.41°N, 147.16°E; TGY = Tagaytay, Philippines, 14.10°N, 120.94°E. B. Location of proposed Site WP-1B in relation to global seismicity. M = magnitude.

Figure 6. Location map showing Deep Sea Drilling Project Sites 290, 294, 295, and 447 and proposed Site WP-1B in the Philippine Sea.

Figure 7. Photograph of the Japan Marine Science and Technology Center's (JAMSTEC) ROV, the Kaiko. All seafloor assembly electrical connections, the data storage unit, and the data handling and control unit (see Fig. 9A, Fig. 9B) can be removed and replaced by such a ROV. The Kaiko will visit Site WP-1B to activate the borehole observatory after Leg 195.

Figure 8. Noise spectra from the borehole seismometer at Site JT-1 (Leg 186) off Sanriku, Japan (from Suyehiro et al., 1999). The noise level is positioned at a satisfactory level between the high noise model and the low-noise model. The rise of noise around 0.01 Hz is known to be infragravity wave noise induced from a long-period surface wave in the ocean. At Site WP-1, the borehole seismometer will be installed in the basement so that such serious noise should be sufficiently suppressed. The seismometer in Hole 1150D (proposed Site JT-1C; Leg 186) has a vertical (V) and two horizontal components that are perpendicular to each other. The direction of the horizontal components H1 and H2 could not be determined during installation of the instrument. dB = decibels.

Figure 9A. Schematic block diagram of the seismic observatory components. B. Schematic configurations of the instrument package for broadband seismometry. All the equipment in this assembly is accessible to an ROV. Cables from the sensors grouted at ~500 mbsf terminate in a four-way underwater-mateable connector block. The data control unit (MEG) plugs into this connector block. A single output from the top of this package is coupled (by ROV) to the battery/recorder unit (PAT) installed after the sensors are grouted. A data recording unit (SAM) can be retrieved by an ROV when required. MEG = multiple-access expandable gateway. PAT = Power supply access terminal. SAM = storage acquistion module.

Figure 10. Schematic of the seafloor assembly with expected lithologies extrapolated from Leg 185. PAT = Power supply access terminal.

Figure 11. Approximate path of the Kuroshio Current in the area of Site KS-1. Stippled areas indicate upwelling.