Ocean Drilling Program Scientific Prospectus No. 100 (August 2001)

Distribution: Electronic copies of this publication may be obtained from the ODP Publications homepage on the World Wide Web at: http://www-odp.tamu.edu/publications

This publication was prepared by the Ocean Drilling Program, Texas A&M University, as an account of work performed under the international Ocean Drilling Program, which is managed by Joint Oceanographic Institutions, Inc., under contract with the National Science Foundation. Funding for the program is provided by the following agencies:
Australia/Canada/Chinese Taipei/Korea Consortium for Ocean Drilling
Deutsche Forschungsgemeinschaft (Federal Republic of Germany)

Institut National des Sciences de l'Univers-Centre National de la Recherche Scientifique

(INSU-CNRS; France)

European Science Foundation Consortium for Ocean Drilling (Belgium, Denmark,

DISCLAIMER
Any opinions, findings, and conclusions or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the views of the National Science Foundation, the participating agencies, Joint Oceanographic Institutions, Inc., Texas A&M University, or Texas A&M Research Foundation.

This Scientific Prospectus is based on precruise JOIDES panel discussions and scientific input from the designated Co-chief Scientists on behalf of the drilling proponents. The operational plans within reflect JOIDES Planning Committee and thematic panel priorities. During the course of the cruise, actual site operations may indicate to the Co-chief Scientists and the Operations Manager that it would be scientifically or operationally advantageous to amend the plan detailed in this prospectus. It should be understood that any proposed changes to the plan presented here are contingent upon approval of the Director of the Ocean Drilling Program in consultation with the Science and Operations Committees (successors to the Planning Committee) and the Pollution Prevention and Safety Panel.

Within the Ocean Drilling Program (ODP) and marine geology and geophysics communities, there has been considerable interest in the past few years in long-term seafloor observatories that include a borehole installation. Prototype long-term borehole and seafloor experiments almost exclusively use battery power and internal recording. Data are only available after a recovery cruise. One exception to this is the Columbia-Point Arena ocean bottom seismic station (OBSS), which was deployed on an offshore cable by Sutton and others in the 1960s (Sutton et al., 1965; Sutton and Barstow, 1990). For the foreseeable future, the most practical method for acquiring real-time continuous data from the seafloor will be over cables (Chave et al., 1990). The H2O project provides this opportunity.

On a cable like Hawaii-2, there are repeaters every 20 nmi to compensate for attenuation on the cable. The repeater boxes are ~0.2 m in outside diameter and 1 m long. The H2O junction box has been located between two of these repeater boxes. Experiments should be carried out within a kilometer or two of the junction box. The borehole should be no closer than ~500 m.

Geological Setting
The Hawaii-2 cable runs south of the Moonless Mountains between the Murray and Molokai Fracture Zones (Fig. 1) (Mammerickx, 1989). Between 140° and 143°W, water depths along the cable track are typical for the deep ocean (4250-5000 m); the crustal age varies from 45 to 50 Ma (Eocene), and the sediment thickness varies to within the available resolution (~100 m or less). Prior to our cable survey cruise in August 1997, sediment thickness was not well resolved along the cable track (Winterer, 1989).

Tectonically, the cable runs across the "disturbed zone" south of the Murray Fracture Zone, between magnetic isochrons 13 and 19 (Atwater, 1989; Atwater and Severinghaus, 1989). In the disturbed zone, substantial pieces of the Farallon plate were captured by the Pacific plate in three discrete ridge jumps and several propagating rifts. To avoid this tectonically complicated region and to be well away from the fracture zone to the south of the disturbed zone, the H2O observatory was situated west of isochron 20 (45 Ma) at ~140°W. The crust west of 140°W was formed between the Pacific and Farallon plates under "normal" spreading conditions at a "fast" half-rate of about 7 cm/yr (Atwater, 1989; Cande and Kent, 1992). At the time this crust was formed, the Farallon plate had not split into the Cocos and Nazca plates, and the ridge that formed this crust was the same as the present day East Pacific Rise. The water depth at the junction box is 4979 m. The maximum relief between sites proposed for the borehole observatory is 40 m.

Between 140° and 143°W, the Hawaii-2 cable lies in the pelagic clay province of the North Pacific (Leinen, 1989). The sediments here are eolian in origin, consisting primarily of dust blown from Asia. They are unfossiliferous red clays. Deep Sea Drilling Project (DSDP) Leg 5 drilled a transect of holes in the pelagic clay province along longitude 140°W (McManus, Burns, et al., 1970). DSDP Site 39 is north of the cable at latitude 32°48.28'N with an age of 60 Ma. It has a sediment thickness of only 17 m. DSDP Sites 40 and 41 are near the same latitude at 19°50'N with an age of about 67 Ma. DSDP Site 40 was drilled in an area of ponded sediments at the base of a large abyssal hill. Basement was not reached and drilling terminated at a chert bed at 156 m. The acoustic basement, the deepest horizon identified on the seismic reflection profiles, corresponded to the chert beds. DSDP Site 41 was drilled 15 km from Site 40 but was considered to be more representative of the sediments in the general area. Basaltic basement was encountered at 34 meters below seafloor (mbsf) but there were no cherts. Site 39 is north of the Murray Fracture Zone, and Sites 40 and 41 are south of the Molokai Fracture Zone. The actual "ribbon" of crust on which the cable lies is between the two fracture zones and was not drilled during Leg 5.

Site 172 (31°32.23'N, 133°22.36'W) was drilled on DSDP Leg 18 between the Molokai and Murray Fracture Zones, penetrating basement with an estimated age of 35 Ma that lies east of 140°W and is in the "disturbed" zone (Kulm, von Huene, et al., 1973). Sediment thickness above the basaltic basement was 24 m. The sediment thickness from seismic reflection profiles had been interpreted as 90-105 m. The discrepancy was attributed to "reverberations and thin sediment cover."
Cable Survey Cruise in August 1997
In August 1997, we carried out a survey of the Hawaii-2 cable between 140° and 143°W (Stephen et al., 1997). Our survey strategy consisted of two phases. First, we collected SeaBeam bathymetry, magnetics, and single-channel seismic profiles along the cable track starting at 140°W and heading west. Our site criteria were (1) to have 100 m of sediment thickness for setting the reentry cone; (2) to be in relatively undisturbed "normal" crust in a plate tectonic sense; and (3) to optimize drilling penetration by selecting sites with well-consolidated basement, not rubble or highly altered zones. As a second phase, we carried out a survey in a 20 km by 20 km area around each of three drill sites to map bathymetry, sediment thickness, basement morphology, and magnetics in the vicinity (e.g., Fig. 3).

Figure 4 shows the H2O junction box location with respect to the tracklines for the Revelle during the site survey in 1997. The actual site is to the southwest of a well-surveyed block but is bracketed by two parallel single-channel seismic (SCS) lines (Fig. 5). Figures 6 and 7 show the tracklines, annotated in SCS shot numbers and Julian time, respectively, for the SCS and 3.5-kHz data. Circles at 1-, 2-, and 3-km radius from the site and the specific proposed drill locations are also indicated. Although cross-tie seismic lines are not available, the parallel seismic lines are sufficiently close together that contiguous structure can be identified across the lines.

Figures 8 and 9 are the latest 3.5-kHz examples from lines north and south, respectively, of the H2O area. This 3.5-kHz data was acquired on the Revelle in August 1997 at the same time as the SCS data. Unmigrated and migrated SCS profiles from this site are shown in Figures 10 and 11, respectively, for the north line and in Figures 12 and 13, respectively, for the south line. A tenth of a second two-way traveltime corresponds to about 75 m.

We know there are chert layers in this part of the Pacific from early drilling during DSDP (Legs 5 and 18). On these 3.5-kHz records, there is a clean, single pulse followed 10 ms later by a diffuse event. Our interpretation is that the clean event is the seafloor and that the diffuse event is the chert layer. Ten ms of two-way traveltime corresponds to ~8 m thickness of soft sediments. The 3.5 kHz data image nothing coherent below the "chert layer." This was also the experience in the 1960 surveys where "acoustic basement" turned out to be chert.

There is a continuous midsediment reflector at ~0.03 s below seafloor, or ~25 m depth, which does not correspond to the chert layer identified on the 3.5-kHz records. If we interpret the diffraction events at ~0.06 s below seafloor in the SCS data as occurring at the sediment/basement boundary, we get a very uniform sediment thickness of ~50 m. This may get as thick as 75 m in some areas, but in no area did we identify 100-m sediments.

The Ocean Seismic Network
Drilling at the H2O area would address both teleseismic, whole-Earth seismic studies, and regional studies. The site is located in a region on the Earth's surface where there is no land in a 2000-km2 area. For uniform coverage of seismic stations on the surface of the planet, which is necessary for whole-Earth tomographic studies, a seafloor seismic observatory is required. This site is one of three high-priority prototype observatories for the OSN (Butler, 1995a; Butler, 1995b; Purdy, 1995). Global seismic tomography (GST) provides three-dimensional images of the lateral heterogeneity in the mantle and is essential in addressing fundamental problems in subdisciplines of geodynamics such as: mantle convection, mineral physics, long wavelength gravimetry, geochemistry of ridge systems, geomagnetism, and geodesy. Specific problems include the characteristic spectrum of lateral heterogeneity as a function of depth, the anisotropy of the inner core, the structure of the core/mantle boundary, the role of oceanic plates and plumes in deep mantle circulation, and the source rupture processes of Southern Hemisphere earthquakes, which are among the world's largest (Forsyth et al., 1995).

The culturally important earthquakes in California are only observed at regional distances on land stations in North America, which restricts the azimuthal information to an arc spanning about 180°. To observe California earthquakes at regional distances to the west requires seafloor stations. Regional observations are used in constraining earthquake source mechanisms. Since the Site H2O data will be available in real time, data will be incorporated into focal mechanism determinations within minutes of California earthquake events. Other problems that can be addressed with regional data from Californian and Hawaiian earthquakes are the structure of the 400-, 525-, and 670-km discontinuities in the northeastern Pacific, the variability of elastic and anelastic structure in the Pacific lithosphere from Po and So and pure-path oceanic surface wave studies, and improved locations for Juan de Fuca Ridge earthquakes from T-phase arrivals (Butler, 1995a, 1995b).

In 1998 at the OSN pilot experiment site established in seafloor west of Hawaii, we deployed seafloor, buried, and borehole broadband seismometers to compare the performance of different styles of installation (Fig. 14). Figures 15 and 16 summarize for vertical and horizontal component data, respectively, the improvement that we expect to see in ambient seismic noise on placing a sensor in basement rather than on or in the sediments. Above the 0.3 Hz, the seafloor, buried, and borehole spectra at the OSN-1 site show the borehole to be 10 dB quieter on vertical components and 30 dB quieter on horizontal components (Collins et al., 2001). Shear wave resonances (or Scholte modes) are the physical mechanism responsible for the higher noise levels in or on the sediment. The resonance peaks are particularly distinct and strong at the H2O site. Note the 15-dB peak on the vertical component and the 35-dB peak on the horizontal components near 1 Hz on the H2O spectra. By placing a borehole seismometer in basement at H2O, we expect to eliminate these high ambient noise levels.

Basement Drilling on the Pacific Plate
There are no deep boreholes (>100 m) in the Pacific plate, the largest modern tectonic plate. Table 1 summarizes the boreholes drilled on "normal" crust on the Pacific plate that have >10 m of basement penetration and crustal ages <100 Ma. Holes in seamounts, plateaus, aseismic ridges, and fracture zones were not included. Holes with crustal ages >100 Ma are not included because they would be affected by the mid-Cretaceous super plume (Pringle et al., 1993). In 30 years of deep ocean drilling and more than 1000 holes world wide, there have been only 12 holes with >10 m penetration into "normal" igneous Pacific plate: only one hole during ODP, no holes with >100 m penetration, and no holes in crust with ages between 29 and 72 Ma. Furthermore, there are no boreholes off axis in "very fast" spreading crust. At the latitude and age of the H2O area, the spreading rate was 140 mm/yr (full rate). Having a reference station in "normal" 45- to 50-Ma ocean crust will constrain geochemical and hydrothermal models of crustal evolution.

Although fast-spreading ridges represent only about 20% of the global ridge system, they produce more than half of the ocean crust on the surface of the planet, almost all of it along the East Pacific Rise. Most ocean crust currently being recycled back into the mantle at subduction zones was produced at a fast-spreading ridge. If we wish to understand the Wilson cycle in its most typical and geodynamically significant form, we need to examine ocean crust produced at fast-spreading ridges. We have also known for more than 40 yr that crust created by fast seafloor spreading is both simple and uniform, certainly so in terms of seismic structure (Raitt, 1963; Menard, 1964). Successful deep drilling of such crust at any single location is thus likely to provide fundamental information that can be extrapolated to a significant fraction of the Earth's surface (Dick and Mével 1996).

There are three important characteristics for a broadband borehole seismic installation:

(1)The hole should penetrate well below the sediment/basement contact so that true basement vibration is observed. The OSN Pilot Experiment hole was only drilled ~20 m into basement, and after installation the top of the sonde was still protruding out of basement and into the sediment. Therefore, it is difficult to say conclusively that the seismometer was responding to true basement motion.

(2)The sides and bottom of the hole must be sealed to hydrothermal circulation with the formation. Water circulation around the sonde generates undesirable "installation noise." If the bottom of the hole is composed of unconsolidated and fractured basalt, this means that the hole must be cased to total depth and sealed at the bottom with a cement plug.

(3)To ensure good coupling of the sonde to the Earth, the hole should be in as consolidated a section of basalt as possible and the casing should be cemented to the formation. It is impossible to predict the seismic response of rubble, and it is impossible to couple the sonde and/or casing to rubble. When cementing in poorly consolidated rock, the cement will flow mostly into the formation rather than up the annulus around the casing, so proper coupling of the casing to the formation cannot be obtained.

Our strategy will be to probe the sediment at each site in an attempt to locate the site with the deepest sediment above the chert (Table 2). This will be accomplished by conducting a jet-in test at each site using the jets on the rotary core barrel (RCB) bit to wash down through the upper part of the sedimentary section. We will also attempt to wash through and possibly sample the chert layer to determine how solid it is. In some areas, chert layers are rubble zones that can be washed through when installing the reentry cone. The deepest sediment may be in a fault zone where the basement is highly fractured (e.g., Site H2O-3 in Fig. 9 or Site H2O-1 in Fig. 8), and it may be difficult to drill. The best strategy, if we have the option, may be to select a site high on the block (e.g., Site H2O-4 in Fig. 8) or a midblock site (such as Site H2O-2 in Fig. 9).

Estimating that there may be somewhere between 8 to 25 m of soft sediment above the chert layer, we plan on setting a reentry cone with ~25 m of 20-in casing. We will then RCB core from 25 to ~325 mbsf (meters below seafloor), which will include the deeper sedimentary horizons and ~250 m of basement penetration. The core will be available for a broad spectrum of shipboard and shore-based analyses, and it will give us positive confirmation of the degree of rubble and fracturing in the upper basalts. Though we will likely encounter progressively more consolidated material down to the proposed 250 m of basement penetration, we expect that the bottom of the hole will still be fractured. If the bottom of the hole consists of unconsolidated material, we will plan to core deeper until we reach a more consolidated material or until the allotted time for coring is exhausted (see Tables 2 and 3 for time estimates). We will then run the triple combination (triple combo) tool and Formation MicroScanner/dipole sonic shear imager (FMS/sonic) in the 9-7/8-in hole to get a continuous record of the well up to 25 mbsf. The hole will then be reamed to ~85 mbsf (~10 m into basement) and 16-in casing will be installed and cemented to this depth. The hole will then be reamed to the total depth (TD) for installation and cementing of 10-3/4-in casing. A borehole compensated sonic log (also called a cement bond log) will be run to check the integrity of the cement behind the casing.

Our original target depth was 400 m of basement penetration, which was a conservative estimate to get into consolidated basalts based on the drilling experience at Hole 504B. The allotted time for Leg 200 will unlikely be sufficient for us to reach this depth. At Hole 504B, sonic logs and resistivity measurements indicate poorly consolidated basalt down to 600 mbsf. If we are fortunate enough to set a reentry cone and casing and reach the current target depth of 250 m of basement penetration ahead of schedule, we will plan to continue drilling until we are in consolidated basalt. A hole that penetrates further into basement will acquire good-quality basalt samples for geochemical studies, will provide adequate penetration into Layer 2 for paleomagnetic analyses, and will provide good hole conditions for in situ experiments.

If the reentry hole is completed before the end of the allotted time on site, there are a number of options, depending on how much time is left (Table 3). If we have less than 24 hr, we suggest repeating the vertical seismic profile (VSP) in the cased hole. If we have a few days left, we plan to core one or more holes at one or more of the H2O sites with the advanced piston corer (APC) and extended core barrel (XCB). The additional holes around the observatory will characterize the lateral heterogeneity of the sediment, confirm the depths to basement, and provide additional observations that can be tied to sites being cored during Leg 199, which is a Paleogene equatorial coring transect aimed at studying the evolution of the equatorial Pacific current and wind system. The information gained would also be useful in interpreting seafloor heat-flow measurements that may be made at the site in the future and provide useful background information for further drilling at the site in the future. If we have roughly a week left, we plan to core other alternate sites proposed for Leg 199 that may not be completed during that leg (e.g., Site PAT-13C, see the Leg 199 Scientific Prospectus at http://www-odp.tamu.edu/publications/prosp/199_prs/199toc.html).

The triple combo tool string includes the natural gamma ray sonde (NGS) to measure radioactivity, the accelerator porosity sonde (APS) to measure porosity, the hostile environment lithodensity sonde (HLDS) to measure density, and the dual induction tool (DIT-E) to measure resistivity. The Lamont-Doherty Earth Observatory temperature tool (TLT) is also attached to the triple combo string. Temperature logs will be emphasized for identification of permeable zones and inflow/outflow from both drilling-induced and natural fractures in the holes.

The FMS/sonic string includes the Formation MicroScanner (FMS) and the dipole shear sonic imager (DSI). The high-resolution (centimeter scale) FMS image log can help to identify large- and small-scale lithologic units and tectonic features (presence of fractures and faults, their orientations, and their degree of alteration). Comparison of fractures detected from these log images could provide information on the lateral extension of the fracture system beyond the borehole and the significance of borehole-induced features vs. natural fractures. The FMS caliper log could also be used for hole size estimation. The DSI tool provides both compressional and shear wave data.

WST (or WST-3 if available) will be used to provide normal incident VSP data for the proposed objectives. However, its deployment depends upon the time constraints and the hole penetration. The BHC sonic log will be used for the cased interval of basement to obtain the acoustic properties of the formation through casing and to check the integrity of the cement.

During Leg 200, we expect to recover <400 m of basalt and <100 m of sediment. All sample frequencies and sample volumes taken from the working half of the core must be justified on a scientific basis and will be dependent on core recovery, the full spectrum of other requests, and the cruise objectives. All sample requests must be made on the standard Web sample request form and approved by the SAC. Leg 200 shipboard scientists may expect to obtain as many as 100 samples of no more than 15 cm3 in size from basement cores. Additional samples may be obtained upon written request onshore after initial data are analyzed. Depending on the penetration and recovery during Leg 200, the number of samples taken may be increased by the shipboard SAC. For example, studies requiring only small sample volumes of 1 cm3 or less (e.g., veins, fluid inclusions, etc.) may require >100 samples to characterize a long section of core. The SAC will review the appropriate sampling interval for such studies as the cores are recovered. Samples larger than 15 cm3 may also be obtained with approval of the SAC. Request for large samples must be specified on the sample request form. Sample requests may be submitted by shore-based investigators as well as the shipboard scientists. Based on sample requests received two months precruise, the SAC will prepare a temporary sampling plan, which will be revised on the ship as needed. Some redundancy of measurement is unavoidable, but minimizing redundancy of measurements among the shipboard party and identified shore-based collaborators will be a factor in evaluating sample requests.

If some critical intervals are recovered (e.g., glass, fault gauge, veins, etc.), there may be considerable demand for samples from a limited amount of cored material. These intervals may require special handling, a higher sampling density, reduced sampling size, or continuous core sampling by a single investigator. A sampling plan coordinated by the SAC may be required before critical intervals are sampled.

Figure 2. Hydrosweep bathymetry around the H2O area acquired from the Thompson in September 1999. The site is on a relatively benign ribbon of "normal" oceanic crust. Total relief varies by ~40 m across the region within 2 km of the junction box.

Figure 3. The location of the H2O junction box is shown on the SeaBeam bathymetry acquired during the site survey in August 1997. The locations of the repeaters (AT&T waypoints) on the cable are also shown (filled triangles).

Figure 4. The tracklines during the 1997 site survey cruise on Revelle (KIWI02) are shown with the location of the H2O junction box.

Figure 5. A detail of the track chart shows that the H2O junction box lies between two parallel tracklines southwest of a well-surveyed area.

Figure 6. The locations of the four possible drill sites (Sites H2O-1 through -4) are shown with the tracklines of the 1997 survey. The tracklines are annotated with SCS shot numbers for comparison with the seismic data in Figures 10-13. Circles were drawn at 1-, 2-, and 3-km radius from the junction box. Sites should be beyond a 1-km radius to avoid conflicts with other experiments at the observatory. They should be within a 2-km radius to minimize the effort in running cable to the junction box.

Figure 7. This figure is similar to Figure 6, except the tracklines are annotated with Julian day and time for comparison with the 3.5-kHz data in Figures 8 and 9.

Figure 8. The 3.5-kHz data for the line north of the site shows about 8-10 m of sediment above the first reflector, which we interpret to be a chert layer.

Figure 9. The 3.5-kHZ data for the line south of the site shows similar sediment thickness to the north line (Fig. 8).

Figure 10. The unmigrated single-channel seismic (SCS) line north of the site shows relief of about 40 m. Site H2O-1 is at the bottom of a fault block, and Site H2O-4 is at the top.

Figure 11. The migrated SCS line north of the site does not improve the resolution of sediment thickness.

Figure 12. The unmigrated SCS line south of the site shows smooth relief within 2 km of the junction box. Site H2O-3 is at the bottom of a fault block, and Site H2O-2 is in the middle of a block.

Figure 13. The migrated SCS line south of the site does not improve the resolution of sediment thickness.

Figure 14. The Ocean Seismic Network site (OSN-1) is 225 km southwest of Oahu at a water depth of 4407 m. The Hawaii-2 Observatory (H2O) is halfway between Hawaii and California on the retired Hawaii-2 telecommunications cable and is at a water depth of 4970 m.

Figure 15. Vertical component spectra from the seafloor, buried, and borehole installations at OSN-1 are compared with the spectra from the buried installation at H2O and the KIP GSN station on Oahu. H2O has extremely low noise levels above 5 Hz and near the microseism peak from 0.1 to 0.3 Hz. H2O has high noise levels below 50 mHz. Otherwise H2O levels are comparable to the OSN borehole and KIP levels. The sediment resonances at H2O near 1 and 3 Hz are very prominent.

Figure 16. Horizontal component spectra from the seafloor, buried, and borehole installations at OSN-1 are compared with the spectra from the buried installation at H2O and the KIP GSN station on Oahu. The sediment resonance peaks in the band 0.3-8 Hz are up to 35 dB louder than background and far exceed the microseism peak at 0.1-0.3 Hz. 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 (or Scholte modes). Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 6 Fig. 7 Fig. 8 Fig. 9 Fig. 10 Fig. 11 Fig. 12 Fig. 13 Fig. 14 Fig. 15 Fig. 16 Table 1. Summary of holes drilled in "normal crust" on the Pacific Plate with an age <100 Ma and penetration into basement >10 m. Table 2. Operations plan and time estimates for Leg 200. Table 3. Time estimates for secondary operations that may be conducted if extra time is available.

Priority: 1
Position: 27°53.928´N, 141°59.544´W
Water Depth: 4980 + 40 m
Sediment Thickness: 50-75 m
Target Drilling Depth: 350 mbsf
Approved Maximum Penetration: Unlimited
Seismic Coverage: SCS with a generator-injector (GI) gun acquired on Revelle cruise KIWI02 (August 1997). 3.5-kHz data acquired on Revelle cruise KIWI02. SeaBeam bathymetry acquired on Revelle cruise KIWI02. Hydrosweep bathymetry acquired on the Thompson (September 1999).

Objectives: The objectives of Site H2O-1 if selected as the primary observatory site are to

1.Drill a reentry hole into basement for a permanent broadband borehole seismograph at the H2O area;

2. Provide a borehole at the H2O area for other long-term borehole measurements; and

3.Provide a "reference site" with in situ igneous samples in normal, fast-spreading (140 mm/yr full rate), 45- to 50-Ma ocean crust to constrain geochemical and hydrothermal models of crustal evolution.

Drilling Program: Jet-in test. If this becomes the primary observatory site, set a reentry cone with 20 in casing to ~25 mbsf, RCB core from 25 to 325 mbsf, log with the triple-combo and FMS/sonic tool strings, WST for normal-incidence VSP if time permits, open hole and set 16-in casing ~10 m into basement, open hole and set 10-3/4-in casing TD, and log hole with the BHC sonic tool.

Logging and Downhole: Triple-combo, FMS/sonic, WST for normal-incidence VSP, and BHC sonic for cement bond log

Nature of Rock Anticipated: Fractured pillow basalt

See Figure 10 for the seismic line and Figure 6 for the trackline. Site: H2O-2

Priority: 2
Position: 27°52.002´N, 141°59.802´W
Water Depth: 4980 + 40 m
Sediment Thickness: 50-75 m
Target Drilling Depth: 350 mbsf
Approved Maximum Penetration: Unlimited
Seismic Coverage: SCS with a GI gun acquired on Revelle cruise KIWI02 (August 1997). 3.5 kHz data acquired on Revelle cruise KIWI02. SeaBeam bathymetry acquired on Revelle cruise KIWI02. Hydrosweep bathymetry acquired on the Thompson (September 1999).

Objectives: The objectives of Site H2O-2 if selected as the primary observatory site are to

1.Drill a reentry hole into basement for a permanent broadband borehole seismograph at the H2O area;

2. Provide a borehole at the H2O area for other long-term borehole measurements; and

3.Provide a "reference site" with in situ igneous samples in normal, fast-spreading (140 mm/yr full rate), 45- to 50-Ma ocean crust to constrain geochemical and hydrothermal models of crustal evolution.

Drilling Program: Jet-in test. If this becomes the primary observatory site, set a reentry cone with 20 in casing to ~25 mbsf, RCB core from 25 to 325 mbsf, log with the triple-combo and FMS/sonic tool strings, WST for normal-incidence VSP if time permits, open hole and set 16-in casing ~10 m into basement, open hole and set 10-3/4-in casing TD, and log hole with the BHC sonic tool.

Logging and Downhole: Triple-combo, FMS/sonic, WST for normal-incidence VSP, and BHC sonic for cement bond log

Nature of Rock Anticipated: Fractured pillow basalt

See Figure 12 for the seismic line and Figure 6 for the trackline. Site: H2O-3

Priority: 3
Position: 27°52.398´N, 141°59.142´W
Water Depth: 4980 + 40 m
Sediment Thickness: 50-75 m
Target Drilling Depth: 350 mbsf
Approved Maximum Penetration: Unlimited
Seismic Coverage: SCS with a GI gun acquired on Revelle cruise KIWI02 (August 1997). 3.5 kHz data acquired on Revelle cruise KIWI02. SeaBeam bathymetry acquired on Revelle cruise KIWI02. Hydrosweep bathymetry acquired on the Thompson (September 1999).

Objectives: The objectives of Site H2O-3 if selected as the primary observatory site are to

1.Drill a reentry hole into basement for a permanent broadband borehole seismograph at the H2O area;

2. Provide a borehole at the H2O area for other long-term borehole measurements; and

3.Provide a "reference site" with in situ igneous samples in normal, fast-spreading (140 mm/yr full rate), 45- to 50-Ma ocean crust to constrain geochemical and hydrothermal models of crustal evolution.

Drilling Program: Jet-in test. If this becomes the primary observatory site, set a reentry cone with 20 in casing to ~25 mbsf, RCB core from 25 to 325 mbsf, log with the triple-combo and FMS/sonic tool strings, WST for normal-incidence VSP if time permits, open hole and set 16-in casing ~10 m into basement, open hole and set 10-3/4-in casing TD, and log hole with the BHC sonic tool.

Logging and Downhole: Triple-combo, FMS/sonic, WST for normal-incidence VSP, and BHC sonic for cement bond log

Nature of Rock Anticipated: Fractured pillow basalt

See Figure 12 for the seismic line and Figure 6 for the trackline. Site: H2O-4

Priority: 4
Position: 27°53.298´N, 142°00.456´W
Water Depth: 4980 + 40 m
Sediment Thickness: 50-75 m
Target Drilling Depth: 350 mbsf
Approved Maximum Penetration: Unlimited
Seismic Coverage: SCS with a GI gun acquired on Revelle cruise KIWI02 (August 1997). 3.5 kHz data acquired on Revelle cruise KIWI02. SeaBeam bathymetry acquired on Revelle cruise KIWI02. Hydrosweep bathymetry acquired on the Thompson (September 1999).

Objectives: The objectives of Site H2O-4 if selected as the primary observatory site are to

1.Drill a reentry hole into basement for a permanent broadband borehole seismograph at the H2O area;

2. Provide a borehole at the H2O area for other long-term borehole measurements; and

3.Provide a "reference site" with in situ igneous samples in normal, fast-spreading (140 mm/yr full rate), 45- to 50-Ma ocean crust to constrain geochemical and hydrothermal models of crustal evolution.

Drilling Program: Jet-in test. If this becomes the primary observatory site, set a reentry cone with 20 in casing to ~25 mbsf, RCB core from 25 to 325 mbsf, log with the triple-combo and FMS/sonic tool strings, WST for normal-incidence VSP if time permits, open hole and set 16-in casing ~10 m into basement, open hole and set 10-3/4-in casing TD, and log hole with the BHC sonic tool.

Logging and Downhole: Triple-combo, FMS/sonic, WST for normal-incidence VSP, and BHC sonic for cement bond log

Nature of Rock Anticipated: Fractured pillow basalt

See Figure 10 for the seismic line and Figure 6 for the trackline.

Co-Chief
Junzo Kasahara
Earthquake Research Institute
University of Tokyo
1-1-1 Yayoi, Bunkyo-ku
Tokyo 113-0032
Japan
Internet: kasa2@eri.u-tokyo.ac.jp
Work: (81) 3-3812-2111, ext 5713
Fax: (81) 3-3812-6979

Co-Chief
Ralph A. Stephen
Department of Geology and Geophysics
Woods Hole Oceanographic Institution
MS 24
360 Woods Hole Road
Woods Hole, MA 02543-1542
USA
Internet: rstephen@whoi.edu
Work: (508) 289-2583
Fax: (508) 457-2150

Staff Scientist
Gary D. Acton
Ocean Drilling Program
Texas A&M University
1000 Discovery Drive
College Station, TX 77845
USA
Internet: acton@odpemail.tamu.edu
Work: (979) 845-2520
Fax: (979) 845-0876

Logging Staff Scientist
Yue-Feng Sun
Lamont-Doherty Earth Observatory
Columbia University
Borehole Research Group
Palisades, NY 10964
USA
Internet: sunyf@ldeo.columbia.edu
Work: (914) 365-8504
Fax: (914) 365-3182

Schlumberger Engineer
Mr. Steven Kittredge
911 Center Point Rd.
Carrollton, GA 30117
Internet: kittredge1@webster.oilfield.slb.com
Work: (281) 480-2000
Fax: (281) 480-9550

Operations Manager
Thomas L. Pettigrew
Ocean Drilling Program
Texas A&M University
1000 Discovery Drive
College Station, TX 77845-9547
USA
Internet: pettigrew@odpemail.tamu.edu
Work: (979) 845-2329
Fax: (979) 845-2308

Laboratory Officer
William G. Mills
Ocean Drilling Program
Texas A&M University
1000 Discovery Drive
College Station, TX 77845-9547
USA
Internet: mills@odpemail.tamu.edu
Work: (979) 845-2478
Fax: (979) 845-0876

Marine Lab Specialist: Yeoperson
Lisa K. Crowder
Ocean Drilling Program
Texas A&M University
1000 Discovery Drive
College Station, TX 77845
USA
Internet: crowder@odpemail.tamu.edu
Work: (979) 845-7716
Fax: (979) 845-0876

Marine Lab Specialist: Chemistry
Timothy Bronk
Ocean Drilling Program
Texas A&M University
1000 Discovery Drive
College Station, TX 77845-9547
USA
Internet: bronk@odpemail.tamu.edu
Work: (979) 845-9186
Fax: (979) 845-0876

Marine Lab Specialist: Chemistry
Anne Pimmel
Ocean Drilling Program
Texas A&M University
1000 Discovery Drive
College Station, TX 77845-9547
USA
Internet: pimmel@odpemail.tamu.edu
Work: (979) 845-3602
Fax: (979) 845-0876

Marine Lab Specialist: Curator
Kim A. Bracchi
Ocean Drilling Program
Texas A&M University
1000 Discovery Dr.
College Station, TX 77845
USA
Internet: bracchi@odpemail.tamu.edu
Work: (979)
Fax: (979) 845-0876

Marine Lab Specialist: Downhole Tools, Marine Lab Specialist: Thin Sections
Edgar Dillard
Ocean Drilling Program
Texas A&M University
1000 Discovery Drive
College Station, TX 77845-9547
USA
Internet: dillard@odpemail.tamu.edu
Work: (979) 458-1874
Fax: (979) 845-0876

Marine Lab Specialist: Paleomagnetics
Mads Radsted
Ocean Drilling Program
Texas A&M University
1000 Discovery Drive
College Station, TX 77845
USA
Internet: radsted@odpemail.tamu.edu
Work: (979) 845-3602
Fax: (979) 845-0876

Marine Lab Specialist: Photographer
Leah Shannon Center
Ocean Drilling Program
Texas A&M University
1000 Discovery Drive
College Station, TX 77845
USA
Internet: center@odpemail.tamu.edu
Work: (979) 845-2480
Fax: (979) 845-0876

Marine Lab Specialist: Underway Geophysics
Johanna M. Suhonen
Ocean Drilling Program
Texas A&M University
1000 Discovery Drive
College Station, TX 77845-9547
USA
Internet: suhonen@odpemail.tamu.edu
Work: (979) 845-9186
Fax: (979) 845-0876

Marine Electronics Specialist
Jan Jurie Kotze
Ocean Drilling Program
Texas A&M University
1000 Discovery Drive
College Station, TX 77845
USA
Internet: kotzejj@netactive.co.za
Work: (979) 845-3602
Fax: (979) 845-0876

Marine Electronics Specialist
Pieter Pretorius
Ocean Drilling Program
Texas A&M University
1000 Discovery Drive
College Station, TX 77845-9547
USA
Internet: pretorius@odpemail.tamu.edu
Work: (979) 845-3602
Fax: (979) 845-0876

Marine Computer Specialist
Margaret Hastedt
Ocean Drilling Program
Texas A&M University
1000 Discovery Dr.
College Station, TX 77845
USA
Internet: hastedt@odpemail.tamu.edu
Work: (979) 862-2315
Fax: (979) 458-1617

Marine Computer Specialist
Erik Moortgat
Ocean Drilling Program
Texas A&M University
1000 Discovery Drive
College Station, TX 77845-9547
USA
Internet: moortgat@odpemail.tamu.edu
Work: (979) 845-7716
Fax: (979) 845-0876

ODP/TAMU Programmer
Dwight Hornbacher
Ocean Drilling Program
Texas A&M University
1000 Discovery Drive
College Station, TX 77845-9547
USA
Internet: hornbacher@odpemail.tamu.edu
Work: (979) 845-1927
Fax: (979) 845-4857