Approximately 115,000-km² was surveyed with a multibeam seafloor mapping sonar system in the southeastern Hawaiian Islands during a collaborative research program between scientists from Japan and U.S. institutions that was funded by the Japan Marine Science and Technology Center (JAMSTEC). The primary focus of the cruises was to carry out manned and robotic submersible diving programs on the deep underwater flanks and rift zones of several Hawaiian Islands, the giant submarine landslide deposits along the Hawaiian Ridge, and the expansive lava flows located on the Hawaiian Arch. Details of the mapping program are provided here to accompany the digital data on the CD-ROM that is included with this monograph. In addition, other authors of manuscripts in this monograph have contributed their extended datasets, which can also be found on the archive.

The two cruises to Hawaii sponsored by the Japan Marine Science and Technology Center (JAMSTEC) in 1998 and 1999 included significant seafloor mapping [Naka et al., 2000], because only a few deepwater bathymetric surveys around the island of Hawaii had adequate resolution. High quality bathymetric data were essential for program objectives including basic submersible vehicle operations, dive and sample location, and geologic mapping.

Because identical SeaBeam 2112 sonar mapping systems are mounted on duplicate hulls of the sister ships Kairei and Yokosuka, merging their data is relatively simple and seamless. The SeaBeam system was run nearly every night for 12-14 hours during all cruise legs. Several full days were dedicated to SeaBeam surveying during the 1998 site survey cruise and on submersible or remotely operated vehicle (ROV) maintenance days.

Products from the seafloor mapping include standard contour maps, shaded relief bathymetry, beam amplitude, and acoustic backscatter imagery. Bathymetry data portrays seafloor depth, while the backscatter data provides textural information that distinguishes bare rock, sedimented areas, small blocks, and structural lineations. Acoustic backscatter is analogous to sidescan imagery acquired with towed deepwater systems such as GLORIA [Laughton, 1981], SeaMARC II [Blackinton et al., 1983], and HAWAII MR1 [Rognstad, 1992].

The only large areas of multibeam coverage prior to the JAMSTEC surveys were west, south, and east of the island of Hawaii. U.S. governmental agencies collected these data using early SeaBeam systems with a narrower swath width [Chadwick et al., 1993a,b, 1994a,b; Clague et al., 1994; Smith, 1994; Moore and Chadwick, 1995]. The data, at reduced resolution to match the surrounding data, are included in a summary map and digital database of the southeastern Hawaiian Islands that is upgraded as additional data become available [Duennebier et al., 1994]. A Krupp Atlas Hydrosweep multibeam system was used to partially map the Nuuanu debris avalanche deposit off northeastern Oahu in 1998 during a deep seismic reflection survey [Moore et al., 1998]. Another Hydrosweep survey covers the Hilo Ridge on the northeastern flank of Hawaii island [Holcomb et al., 2000]. High-resolution bathymetry and acoustic backscatter survey data were acquired in 1998, using a Kongsberg Simrad EM 300 multibeam system [Dartnell and Gardner, 1999; MBARI, 2000], in shallow to intermediate water depths (from tens of meters to ~3000 m) for select areas from Niihau to Hawaii [Gardner and Hughes-Clarke, 1998; Torresan and Gardner, 2000; Clague et al. 2000].

SeaBeam 2112 is a multibeam survey system built by L-3 Communications Sea Beam Instruments, Inc. for producing wide-swath contour maps and acoustic backscatter images of the seafloor. Two main subsystems compose the hardware a 12 kHz transmitter and a receiver. The sonar beams, with a narrow 2° beam angle fore/aft, are projected as a swath and travel through the water column to the sea floor and are reflected off the bottom.

An array of hydrophones mounted across the bottom of the ship receives the reflected sonar signals. This receiver array detects and processes the returning echoes through multiple stabilized narrow athwartship beams (2° x 2°) in a fan shape. The swath width varies from 150° to 90°, decreasing with increasing water depth. The system electronics process the signals, and based on the travel time of the received signals and signal intensity, calculates the bottom depth and other characteristics for echoes received across the swath. The bathymetry data represents a maximum of 149 data points per sonar ping, while the acoustic backscatter data contains up to 2000 pixels per ping. Swath location is based on navigation from the Global Positioning System satellites, using a differential GPS system, and ship motion input from an onboard vertical reference unit.

The horizontal resolution of the bathymetry data depends on depth and ship speed. The accuracy of the depth measurement is specified as 0.5% of the depth or better. One important parameter for accuracy of depth and position of the bathymetric survey is the sound velocity profile. Data quality also depends greatly on the sea state. Favorable sea conditions during the typical reduced trade wind period of August and September, during which time the cruises were scheduled, allowed for surveying at speeds from 10 to 16 knots, though at times ship speed was reduced on some northeast transects headed into the seas. The typical swath width for this system around the Hawaiian Ridge (3000-5000 m water depth) is 10 km, or 2-3 times the depth.

Post-processing includes editing of the cross track and navigation data (deletion of bad data, correction of position, etc.), making grid files, and various maps. The software used for post-processing includes MB-System [Caress and Chayes, 1996] and the GMT-System [Wessel and Smith, 1995]. Bathymetry processing for all survey lines was performed onboard using the MB-System interactive program mbedit. Amplitude and acoustic backscatter data processing were carried out in batch mode shoreside after the cruise using other MB-System programs and the recommended processing sequence outlined in the MB-System manual and summarized on the CD-ROM. After all processing is completed, the remaining points are gridded or mosaicked and various maps are produced. The grid cell interval is 150 m for the bathymetric grids and 75 m for backscatter grids.

4.1 North Arch lava flows

In 1999, the R/V Yokosuka mapped ~15,000 km² of the North Arch lava flows for the first time synoptically with a multibeam system (Fig. 1). Approximately two-thirds of the flows were surveyed, based on previous wide-swath GLORIA sidescan sonar surveys covering the entire region [Clague et al., 1990]. The high reflectivity measured with the acoustic backscatter component of the SeaBeam 2112 revealed the low-relief lava flows much better than the bathymetry. However, the bathymetric component was key in identifying the detail of numerous lava vents distributed throughout the flow field [Clague et al., this volume].

4.2 Offshore Oahu and Molokai

Roughly 50,000 km² of seafloor was surveyed off the northern coasts of Oahu and Molokai islands, covering the entire Nuuanu and Wailau landslide deposits (Figs. 1, 2). The main survey area extended to 230 km from the Oahu shore, with exploratory lines out to 300 km on top of the northern Hawaiian Arch (Fig. 1). The distal limit of the slides appears to be 230 km, which matches the interpretation from the GLORIA sidescan sonar surveys [Moore et al., 1989].

The improved resolution over previous survey data allows detailed mapping of the block distribution, orientation, and structure of the landslide. Several attempts have been made to delineate the boundary between the two slide deposits, determine the relative timing of the events, and reconstruct the pre-slide volcanoes from the overlapping slide deposits mapped in this study [Moore and Clague, Satake et al., and Yokose; all this volume]. Fifty to sixty large blocks lie within the boundaries of the Nuuanu and Wailau slide deposits. These blocks are 5-20 km long, 2-20 km wide, and 300-1500 m in relief above the surrounding seabed. Numerous smaller blocks are located within the major block facies while others are dispersed farther afield.

The volcanic platform of Koolau volcano near the northern tip of Oahu, undisturbed by the Nuuanu landslide, was surveyed west to nearly 158°30'W. Dredge and dive samples confirm that submarine lava sequences of mostly pillow lava and some sheet flows compose the outcrop in this area.

4.3 Insular flanks of Hawaii and Maui

The 1998 Kairei and 1999 Yokosuka cruises mapped ~49,000 km² on all sides of the island of Hawaii (except some areas to the north and northwest), from nearshore to abyssal depths (Fig. 1). The surveys included exploratory lines out to 260 km on the crest of the southeastern portion of the Hawaiian Arch. Papers in chapters 1 and 2 of this volume present results from around the island of Hawaii.

The mobile south flank of Kilauea (the Hilina slump) was thoroughly mapped by the addition of survey lines between the initial tracks to increase the data quality by producing a greater percentage of overlapping swath data on the southeast flank of the island. The mostly flat region southeast of the island has now been mapped south to 18°10'N and east to 154°W (Fig. 1), extending earlier multibeam surveys [Chadwick et al., 1993a,b; Smith, 1994]. Only a few more blocks or small seamounts were located and mapped on the abyssal plain southeast of Hawaii island in more detail than presented in the GLORIA images [Groome et al., 1997].

The Puna Ridge (submarine continuation of the Kilauea east rift zone) and Hilo Ridge (offshore extension of either a Kohala or a Mauna Kea east rift zone) were mapped in their entirety. The eastern submarine flanks of Mauna Kea and Kohala volcanoes were surveyed north to nearly 20°30'N covering the distal portion of the Hana Ridge (Haleakala east rift zone) extending from Maui (Fig. 1). A newly identified landslide, the Laupahoehoe slump, was mapped, and the Pololu slump better defined [Smith et al., this volume]. Additionally, ~4100 km² of the Alika and Ka Lae debris avalanche chutes and the South Kona slump off the Kona (west) coast were re-mapped (Fig. 1) in order to gain the acoustic backscatter component that was absent in previous multibeam surveys of the slide complex [Chadwick et al., 1994a,b; Smith, 1994]. The northern portion of the South Hawaii fault zone (far south of Ka Lae, or South Point) was surveyed, but its southeastern extent could not be completed because of transit time constraints. Finally, some improvements were made to bathymetric coverage of the submerged Mahukona volcano (west of Kohala) during Hawaii to Oahu transits (Fig. 1).

The SeaBeam data and images produced from it are available on the CD-ROM included with this monograph. An HTML web style interface is included on the CD-ROM that guides the user to the products. Other authors from this volume have contributed extended datasets related to their papers and these are found using the same index. Simply open the index.htm file in the top directory of the CD-ROM with a web-browsing program.

Plot files of the SeaBeam data are included for those who do not wish to manipulate the data. Metadata files describing parameters of the geospatial data are also located on the CD-ROM.

SeaBeam data products are presented in different formats for importing into several common software packages. For GMT-System and MB-System users, binary netCDF grid files are available. For Earth Systems Research Institute (ESRI) ArcInfo and ArcView Geographic Information System (GIS) software users, *.e00 export files are provided that can be imported as grids using the import command in ArcInfo or the import71 utility in ArcView. Image files are furnished for both bathymetry and backscatter, which can be opened in many image processing software packages.

Acknowledgments. The authors and all onboard scientists wish to thank the Japan Marine Science and Technology Center for sponsoring this work. We are also indebted to Captains O. Yukawa of Kairei and H. Tanaka of Yokosuka, their crews, and the technicians who assisted with SeaBeam data collection and processing. The Hawaii Undersea Research Laboratory and the Geological Survey of Japan provided salary, travel (also JAMSTEC), and computer support for Smith and Satake to attend the cruises, post-process the data shoreside, and present the results at meetings. Reviews by editors M.O. Garcia, E. Takahashi, and P.W. Lipman improved the manuscript. SOEST contribution #5814.

Blackinton, J.G., D.M. Hussong, and J.G. Kosalos, First results from a combination sides-scan sonar and sea floor mapping system (SeaMARC II), in Proc. Offshore Techn. Conf., pp. 307-314, Dallas, TX, 1983.

Caress, D.W., and D.N. Chayes, Improved processing of Hydrosweep DS multibeam data on the R/V Maurice Ewing, Mar. Geophys. Res., 18, 631-650, 1996.

Chadwick, W.W., Jr., J.G. Moore, M.O. Garcia, and C.G. Fox, Bathymetry of southern Mauna Loa Volcano, Hawaii, U.S. Geol. Surv. Misc. Field Studies Map MF-2233, 1993a.

Chadwick, W.W., Jr., J.G. Moore, and C.G. Fox, Bathymetry of the southwest flank of Mauna Loa Volcano, Hawaii, U.S. Geol. Surv. Misc. Field Studies Map MF-2255, 1994a.

Chadwick, W.W., Jr., J.G. Moore, and C.G. Fox, Bathymetry of the west-central slope of the island of Hawaii, U.S. Geol. Survey Miscellaneous Field Studies Map MF-2269, 1994b.

Chadwick, W.W., Jr., J.R. Smith, Jr., J.G. Moore, D.A. Clague, M.O. Garcia, and C.G. Fox, Bathymetry of south flank of Kilauea Volcano, Hawaii, U.S. Geol. Surv. Misc. Field Studies Map MF-2231, 1993b.

Clague, D.A., R.T. Holcomb, J.M. Sinton, R.S. Detrick, and M.E. Torresan, Pliocene and Pleistocene alkalic flood basalts on the seafloor north of the Hawaiian Islands, Earth Planet. Sci. Let., 98, 175-191, 1990.

Clague, D.A., K.A. Hon, J.L. Anderson, W.W. Chadwick, Jr., and C.G. Fox, Bathymetry of Puna Ridge, Kilauea Volcano, Hawaii, U.S. Geol. Surv. Misc. Field Studies Map MF-2237, 1994.

Clague, D.A., J.G. Moore, and J.R. Reynolds, Formation of submarine flat-topped volcanic cones in Hawaii, Bull. Volcanol., 62, 214-233, 2000.

Clague, D.A., K. Uto, and A.S. Davis, Eruption style and flow emplacement in the submarine North Arch Volcanic Field, Hawaii, this volume.

Dartnell, P., and J.V. Gardner, Sea-floor images and data from multibeam surveys in San Francisco Bay, Southern California, Hawaii, the Gulf of Mexico, and Lake Tahoe, California-Nevada, Digital Data Series DDS-55, U.S. Geological Survey, 1999.

Duennebier, T., T. Reed, and H. Staff, Northwestern Hawaiian Islands: merged bathymetry and topography, in Hawaii Seafloor Atlas, Sheet #2, Hawaii Institute of Geophysics and Planetology, Honolulu, 1994.

Gardner, J.V., and J. Hughes-Clarke, Cruise report: RV ocean alert cruise A1-98-HV: mapping Hawaii insular slopes (January 30 through February 23, 1998, Honolulu to Honolulu, Hawai`i), U.S. Geol. Surv. Open-File Rep. 98-212, 26 p, 1998.

Groome, M.G., C.E. Gutmacher, and A.J. Stevenson, Atlas of GLORIA sidescan-sonar imagery of the Exclusive Economic Zone of the United States: EEZ-View, U.S. Geol. Surv. Open-File Rep. 97-540, 1997.

Holcomb, R.T., B.K. Nelson, P.W. Reiners, and N.-L. Sawyer, Overlapping volcanoes: the origin of Hilo Ridge, Hawaii, Geology, 28, 547-550, 2000.

Laughton, A.S., The first decade of GLORIA, J. Geophys. Res. 86 (B12), 11,511-534, 1981.

MBARI, MBARI Multibeam Survey, Version 1, Digital Data Series No. 2, Monterey Bay Aquarium Research Institute, Monterey, 2000.

Moore, G.F., J.K. Morgan, S. Leslie, B. Taylor, and C. Berndt, Morphology and structure of the Nu`uanu debris avalanche, north of O`ahu, Hawai`i, Eos Trans. AGU,, 79, F1008, 1998.

Moore, J.G., and D.A. Clague, Mapping of the Nuuanu landslides in Hawaii, this volume.

Moore, J.G., D.A. Clague, R.T. Holcomb, P.W. Lipman, W.R. Normark, and M.E. Torresan, Prodigious submarine landslides on the Hawaiian Ridge, J. Geophys. Res., 94, 17,465-17,484, 1989.

Moore, J.G., and W.W.J. Chadwick, Offshore geology of Mauna Loa and adjacent areas, Hawaii, in Am. Geophys. Union Monogr. 92, edited by J.M. Rhodes, and J.P. Lockwood, pp. 21-44, American Geophysical Union, Washington, DC, 1995.

Naka, J., and Scientific Team, Tectono-magmatic processes investigated at deep-water flanks of Hawaiian volcanoes, Eos Trans. AGU, 81, 221, 226-227, 2000.

Rognstad, M., HAWAII MR1: A new underwater mapping tool, in Proc. Internatl. Conf. on Signal Processing and Techn., pp. 900-905, 1992.

Satake, K., J.R. Smith, and K. Shinozaki, Three-dimensional reconstruction and tsunami model of the Nuuanu and Wailau giant landslides, Hawaii, this volume.

Smith, J.R., Island of Hawaii and Loihi submarine volcano, high resolution multibeam bathymetry around the island of Hawaii, in Hawaii Seafloor Atlas, Sheet #6, Hawaii Institute of Geophysics and Planetology, Honolulu, 1994.

Smith, J.R., K. Satake, J.K. Morgan, and P.W. Lipman, Submarine landslides and volcanic features on Kohala and Mauna Kea volcanoes and the Hana Ridge, Hawaii, this volume.

Torresan, M.E., and J.V. Gardner, Acoustic mapping of the regional seafloor geology in and around Hawaiian ocean dredged-material disposal sites, U.S. Geol. Surv. Open-File Rep. 00-124, 63 p., 8 map sheets, 2000.

Wessel, P., and W.H.F. Smith, New version of the Generic Mapping Tools released, Eos Trans. AGU, 76, 329, 1995.

Yokose, H., Landslides on the windward flanks of Oahu and Molokai, Hawaii: SHINKAI 6500 submersible investigation, this volume.

___________

K. Satake, Active Fault Research Center, AIST-GSJ, Tsukuba, Ibaraki 305-8567, Japan (kenji.satake@aist.go.jp).

J. R. Smith, Hawaii Undersea Research Lab, University of Hawaii, 1000 Pope Rd., MSB 303, Honolulu, HI 96822 (jrsmith@soest.hawaii.edu).

K. Suyehiro, Deep Sea Research Department, JAMSTEC, 2-15 Natsushima-cho, Yokosuka, 237-0061 Japan. (suyehiro@jamstec.go.jp).

FIGURE CAPTIONS

Figure 1. Main Hawaii Islands (USGS topography) with SeaBeam 2112 shaded relief bathymetry showing coverage during the JAMSTEC surveys with main offshore features mapped in this study labeled. Illumination from the east. Box shows location of Figure 2.

Figure 2. One application of the JAMSTEC SeaBeam 2112 multibeam data available on the CD-ROM. (A) SeaBeam bathymetry merged with SOEST compilation that includes USGS topographic and various bathymetric datasets. Continuous light gray shaded relief bathymetry and topography with illumination from the north, contours every 200 m, bold every 1000 m. (B) SeaBeam backscatter, with darker gray tones as stronger reflectors. Boundaries of Nuuanu and Wailau landslide deposits from Moore and Clague and Satake et al. [both this volume]. For additional examples of multibeam data applications and research using it, see Clague et al., Moore and Clague, Satake et al., and Smith et al. [all this volume].