Eezs of Tonga, Fiji, Tuvalu, Solomon Islands, Vanuatu and Papua New Guinea

Home , North Fiji Basin

SOPAC Technical Report 108

September 1990

SWATH-MAPPING TARGET AREAS IN THE EEZS OF TONGA, FIJI, TUVALU, SOLOMON ISLANDS, VANUATU AND PAPUA NEW GUINEA

Bernard Pelletier ORSTOM B.P. A5 Noumea Cedex, New Caledonia

Prepared for: South Pacific Applied Geoscience Commission (SOPAC) Offshore Programme [3]

CONTENTS

Page

INTRODUCTION ...... 5 IDENTIFYING THE AREAS ALREADY MAPPED ...... 6

TARGET AREAS IN THE EEZ OF FIJI ...... 6 TARGET AREAS IN THE EEZ OF PAPUA NEW GUINEA ...... 11 TARGET AREAS IN THE EEZ OF SOLOMON ISLANDS ...... 13 TARGET AREAS IN THE EEZ OF TONGA ...... 17 TARGET AREAS IN THE EEZ OF TUVALU ...... 20 TARGET AREAS IN THE EEZ OF VANUATU ...... 20

SOME INFORMATION ON NEW SWATH MAPPING SYSTEMS ...... 23

REFERENCES ...... 25

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LIST OF FIGURES

Figure Page

1 Map showing the navigation of swath mapping surveys in the EEZs of SOPAC countries ...... 7

2 EEZ of Fiji showing already mapped area, and proposed areas for future swath map surveys ...... 8

3 EEZ of Papua New Guinea showing already mapped areas, and proposed areas for future swath surveys ...... 12 4 EEZ of Solomon Islands showing the already mapped areas, and the proposed areas for future surveys ...... 14

5 EEZ of Tonga showing the already mapped areas, and the proposed areas for future surveys ...... 18

6 EEZ of Tuvalu showing the already mapped areas, and the proposed areas for future surveys ...... 21

7 EEZ of Vanuatu showing the already mapped areas, and the proposed areas for future surveys ...... 22

LIST OF TABLES

Table 1 Swath mapping target areas in the EEZs of some SOPAC member countries ...... 26

2 Recommended swath-mapping systems for each selected area ...... 28

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INTRODUCTION

For the CCOP/SOPAC 17th Session (October 1988) held in Suva, Fiji, Kroenke (1988) prepared a report which emphasised the value of swath-mapping for the identification of potential resources in the Exclusive Economic Zones (EEZs) of SOPAC countries. The report reviewed the main seafloor mapping systems (deep and shallow water, multi-beam echosounders and bathymetric side-scan sonars), indicated the most appropriate system considering the specific objective of the survey, and finally proposed swath-mapping targets in each SOPAC member country.

The primary objective of the present report is to identify swath-mapping target areas in the EEZs of some SOPAC member countries in order to plan the second SOPAC swath-mapping cruise for 1990-1991. The first was the GLORIA cruise in August 1989 (Tiffin and others, 1990). This work comes under the SOPAC Offshore Programme and is mainly focused on waters from 500 to 4000-5000m deep.

Not all the SOPAC member countries’ waters are reviewed here. This report deals only with the EEZs of Fiji, Papua New Guinea, Solomon Islands, Tonga, Tuvalu and Vanuatu. With the exception of Tuvalu, all of these are countries associated with back-arc basins with resource potential. Back-arc basins are particularly amenable to good results from swath-mapping techniques. Tuvalu, although not part of a volcanic arc, has several large banks in its southern EEZ for which little information exists, and currently has both an active fisheries programme to investigate seamounts, and a boundary delineation programme to determine its legal EEZ. Both these programmes will greatly benefit from swath mapping.

The Cook Islands and Kiribati were not included here because although their EEZs are large, they are remote from the island arcs and long costly transits are required to get to these areas. They will be targets for later cruises. Western Samoa and Guam, also not included, have small EEZs. In Guam, the US Geological Survey plans to survey the EEZ with GLORIA, probably in 1992. These latter two countries thus have prospects for good maps already.

The target areas proposed in this report have been chosen taking into account the known bathymetry, geological and geophysical data and previous swath mapping surveys and are arranged in alphabetical, not priority, order. The characteristics of each area (location, size, depth, objective and recommended mapping system) are summarised on Figures 2 to 7 and in Tables 1 and 2 (see pages 26 and 28). Only a brief description of each area is given in the text.

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IDENTIFYING THE AREAS ALREADY MAPPED

The first step in identifying future swath mapping target areas is to know the location of areas already mapped. Figure 1 is a compilation of tracklines from various cruises that used swath mapping systems (Seabeam, SeaMARC II and GLORIA) in the EEZs of SOPAC countries. The map has been compiled with the assistance of the Data Management section of the SOPAC Technical Secretariat (Techsec) (Yann Morel and Andre Dauzat). Figure 1 also shows the boundaries of the EEZs of SOPAC countries which can be requested at any scale from SOPAC.

The map shows five features:

1. A number of cruises using swath mapping systems have been conducted in the Southwest Pacific since 1984 by Germany (RV Sonne: Seabeam), France (RV Jean Charcot : Seabeam), Japan (RV Kaiyo: Seabeam), Hawaii, USA (RV Moana Wave: SeaMARC II), Scripps, USA (RV Thomas Washington: Seabeam), England (RV Charles Darwin: GLORIA), Australia (HMAS Cook: Seabeam), and SOPAC (HMAS COOK: GLORIA and Seabeam).

2. Most of the areas of full coverage are located in back-arc basins along the active spreading centres or active troughs (Lau Basin, North-Fiji Basin, Vanuatu back-arc Troughs, Woodlark Basin, Manus Basin) although parts of the Tonga and New Hebrides trenches are also covered. Arc areas have received almost no attention.

3. Most of the areas covered are in the EEZs of Tonga, Fiji, Vanuatu and Papua New Guinea.

4. Little swath mapping has been done in the EEZ of Solomon Islands and nothing in the EEZ of Tuvalu.

5. During this compilation, it became apparent that some cruises have not been able to be precisely located due to the lack of good navigational information in SOPAC's database. Consequently, it is recommended that navigation data from the EEZs of SOPAC member countries be sent to Techsec as soon as possible after each cruise.

TARGET AREAS IN THE EEZ OF FIJI (Figure 2)

The EEZ of Fiji is largely composed of active marginal basins in which active spreading centres, extensional zones and fracture zones exist. Most of the previous swath mapping cruises have

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been devoted to these active features (Lau Basin, Peggy Ridge, Fiji Fracture Zone and the various tectonic elements of the North Fiji Basin). However, the EEZ of Fiji also comprises the Fiji Platform, the Lau Ridge (a remnant arc), the northern part of the South Fiji Basin (an inactive marginal basin) and, north of the paleo Vitiaz Lineament, a part of the Pacific Plate where seamounts are present. Although large areas have been already mapped by Seabeam, SeaMARC II and GLORIA, numerous future target areas can be identified due to the complexity of the geology of the North Fiji Basin, resulting from the interaction of the Pacific and Indo-Australian plates, and its location between the opposing Tonga and New Hebrides subduction zones. Occurrences of polymetallic massive sulfides associated with the N-S trending spreading ridge have been proved in the central part of the North Fiji basin. Eight areas can be selected in the EEZ of Fiji for future swath mapping surveys.

Area FJ 1

Little is known about this area, corresponding to the Koro Sea Basin between Viti Levu and the Lau Group, which is probably quite complex due to the supposed counterclockwise rotation of the Fiji Platform during the opening of the North Fiji Basin. The Hunter Fracture Zone, which may be an old subduction zone and is a sub-active feature, ends in the Koro Sea Basin. The main interest in this area is possibly fishing potential, due to its central position with respect to all the Fijian islands, but this area is given a low priority in comparison with the others. The recommended mapping systems are GLORIA or SeaMARC R.

Area FJ 2

This is located just north of the Fiji Platform and is associated with the Fiji Fracture Zone, mapped during the recent SOPAC cruise. An area between the GLORIA tracks and the Vanua Levu Platform, probably part of the Fiji Platform, remains uncharted. This area is interesting for two reasons: fishery potential and completion of the map of the Fiji Fracture Zone. The recommended tools are the SIS 09 or SeaMARC II.

Area FJ 3

This is located in the eastern part of the North Fiji Basin along a seismically active tectonic feature composed of ridges and troughs, This feature connects the Fiji Fracture Zone (176'E) and

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the N-S trending North Fiji Basin spreading centre (21'S) which at this latitude is offset by about 80 km by a fracture zone. Part of this feature, west of Viti Levu, has already been mapped by Seabeam and its interpretation is controversial (extensional zone related to spreading or to strike slip motion). The area is interesting for its hydrothermal mineralisations associated with extension. Because of its large size, the recommended systems are the SeaMARC R or the GLORIA.

Area FJ4

This restricted area is situated around 176'E-17'S, just south of the Fiji Fracture Zone and north of ridges and troughs previously mapped west of Viti Levu. The main goal of this survey is to understand the relationship between the two sets of structures. From an applied point of new, the area has potential for active extensional zones that may be associated with polymetallic sulfides, and for locating seamounts for fishing industries.

Area FJ 5

This is located north of the end of the Fiji Fracture Zone around Balmoral Reef, which is still a poorly understood tectonic feature. Data obtained during the recent GLORIA SOPAC cruise indicate that the left lateral Fiji Fracture Zone is not, as previously supposed, connected with the eastern branch of the North Fiji Basin central triple junction. This requires a connection southward with an extensional zone west of Viti Levu or northward with a compressional zone along Balmoral reef. There may also be extensional features in this area.

Area FJ 6

This area corresponds to the eastern part of the North Fiji Basin, north of the Fiji Platform and east of an area already mapped by Seabeam during the Sonne cruise. Survey of this area is vital to establish the relationship between the North Fiji and Lau basins. An E-W spreading ridge has been already proposed here. Data from the Sonne cruise in the west and from GLORIA cruise in the south indicate the presence of troughs trending NW-SW and N-S respectively. SeaMARC R or GLORIA are well suited for this type of investigation.

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Area FJ 7

Located in the northern part of the North Fiji basin, this area corresponds to the so-called South Pandora Ridge which has been partly mapped with SeaMARC II. This structure is interpreted as a recent and still active spreading ridge associated with seamounts. The objective of the proposed survey is to complete mapping of this structure which may be associated with hydrothermal mineralisations. This survey is considered to be a high priority since the South Pandora ridge is an important active tectonic element of the North Fiji basin. Best-suited techniques are the SeaMARC II, R, SIS 09 or SIMRAD.

Area FJ 8

This is located north of the palaeo Vitiaz trench on a major topographic high composed of the Morton, Louisa, Penguin, Turpie and Alexa banks that are believed to have formed from mid-plate volcanism. Detailed mapping of these banks is proposed because of their potential for several resources (cobalt-rich crusts, Corrallium and fisheries). SIS 09 or SeaMARC ll are the recommended tools.

TARGET AREAS IN THE EEZ OF PAPUA NEW GUINEA (Figure 3)

Previous swath mapping in the EEZ of Papua New Guinea has been devoted to study of the two active oceanic basins: the western part of the Woodlark Basin (Seabeam) and the Manus Basin (SeaMARC ll). Five areas are proposed for future cruises.

Area PNG 1

Located in the central part of the Woodlark basin, this is the same area then as SI 8 (see above).

Area PNG 2

This area is between New Ireland and Bougainville Islands and includes the Queen Ema Basin (which may have potential for hydrocarbon resources), the platform west of Bougainville, the

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western dope of the Feni-Buka Ridge and the southeastern faulted margin of New Ireland. The latter marks the end of the NW-SE trending, left-lateral, strike-slip Weitin Fault which crosscuts southeastern New Ireland and marks the boundary of the active Manus Basin. Swath mapping of this area would establish the tectonic framework, assist the hydrocarbon programme and provide data for geohazards assessment. SeaMARC R or SIS 09 are well suited techniques for this type of investigation.

Area PNG 3

This area extends from northeast of Feni Island to west of Tabar Island and includes the Tabar-Feni Fault zone. Swath mapping of this important tectonic feature would precisely establish its location, orientation and geometry, and thus assist hydrocarbon assessment of the New Ireland Basin. SeaMARC ll, R or SIS 09 are the recommended tools.

Area PNG 4

This corresponds to the western part of the Bismarck Arc from the western end of the New Britain to the Schouten Islands. The objective of the swath map survey is to find new volcanoes related to this arc. It would also be interesting for fishery and geohazard assessment.

Area PNG 5

This area is in the northern part of the Manus Basin, along a seismically active tectonic feature extending from the northern end of the Willaumez Transform westward to the Schouten Islands. This zone could be the site of spreading processes and transform motion that may be associated with hydrothermal mineralisations. SeaMARC R, SIS 09 or SeaMARC ll are recommended techniques to be employed.

TARGET AREAS IN THE EEZ OF SOLOMON ISLANDS (Figure 4)

The geology of the EEZ of the Solomon Islands is complex because the area includes a lot of structures of various ages and type. Despite the size of this EEZ and the presence of scientifically interesting features, there have been few swath mapping cruises in Solomon Island waters. However

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a part of the northern New Hebrides hack-arc troughs has been investigated by Seabeam and GLORIA, and the eastern part of the active Woodlark Basin, southwest of New Georgia Group, has been mapped by SeaMARC II. Eight areas are proposed for future swath mapping surveys.

Area SI I

Located in the easternmost part of the EEZ, this corresponds to the Hazel Holme Fracture Zone, an E-W structure which crosscuts the northeastern part of the North Fiji Basin and joins the South Pandora Ridge in the east to the New Hebrides Arc in the west. The intersection between this zone and the New Hebrides Arc marks also the southern end of the Jean Charcot hack-arc troughs. The Hazel Holme Fracture Zone is seismically active and new marine data indicate that it is a wide, complex, and recently-created extensional zone composed of a succession of horsts and grabens. Volcanism appears to be assodated with it. This structure is an important active tectonic element of the North Fiji Basin and may have potential for hydrothermal mineralisation and metalliferous muds.

Area SI 2

This area is focused on the recently discovered Tikopia Trough (65 km long, 8 km wide and 1500 m deep) elongated WNW-ESE immediately east of the volcanic island of Tikopia. The trough has a flat bottom and volcanoes probably exist along its northern and southern flanks. This trough may have potential for metalliferous muds.

Area SI 3

This lies within the North Fiji basin along the remnant Vitiaz Trench, where several islands and banks are known (Pandora and Charlotte banks, Fataka and Anuta islands, Strathmore Shoal). During a recent cruise using conventional echo sounding between Charlotte Bank and Fataka Islands, four NE-SW tracks revealed the presence of numerous uncharted, large seamounts. A swath mapping survey would locate and map new volcanoes which may he of interest for fisheries. SeaMARC R or GLORIA are well-suited tools for this survey.

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Area SI 4

This lies on the northernmost part of the North Fiji Basin from Vanikoro to Santa Cruz and Duff Islands. The area is seismically active and geologically represents the northern extension of the Jean Charcot back-arc troughs known south of Vanikoro Islands. The results of previous surveys using conventional echo sounding and seismic relection indicate the presence of normal faulting, tilted blocks, troughs and volcanoes. However, the size and geometry of these structures are unknown. The rate of back-arc extension is supposed to be high in this area, which could be the site of spreading processes. Such structures may have importance for mineral resources since hydrothermal mineralisations have been proved elsewhere in similar environments. Swath mapping would also map numbers of new volcanoes that could be interesting for fishery resources. Mapping of seamounts and insular slopes around Vanikoro Santa Cruz and Duff Islands would be also fruitful for the location of potential areas for deep water Corrallium. Survey of this area are considered to be a high priority for the Solomon Islands. The recommended swath mapping system are the SeaMARC R, SIS 09, SeaMARC II or Simrad.

Area SI 5

This is located between the Cape Johnson and San Cristobal trenches. The sea floor and structure of this area, which marks the. transition between the North Fiji Basin and the main Solomon Islands, is completely unknown. Reconnaissance swath mapping survey using SeaMARC R or GLORIA is needed for the interpretation of regional geology and the tectonic framework of this large area of the Solomon Islands EEZ.

Area SI 6

This lies east of Guadalcanal and Florida Island and southeast of Santa Isabel, along the Nudha Ridge and the western part of the Indispensable Basin. Thrust faulting is supposed to occur in this region which is considered to be one of the favourable targets for petroleum exploration in Solomon Islands. The first objective of this survey is thus to assist the hydrocarbon programme, by mapping the surface expressions of active faults, and to establish the structural and regional tectonic framework. Swath mapping would be also useful for geohazard assessment and for identification of potential sites for precious coral. SeaMARC II or SIS 09 are the recommended tools. SeaMARC S and SIS 120 need a much longer survey.

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Area SI 7

This corresponds to the southeastern part of the New Georgia Basin and includes the Iron Bottom Basin (one of the most promising hydrocarbon areas in the Solomons) and the western slopes of Santa Isabel and San Jorge. Interests in this area and the equipment to be employed are the same as those for SI 6.

Area SI 8

This extends over the central part of the active Woodlark Basin and includes the spreading axis and several transform faults. As it has been proved in other areas with similar geological environments (in the EEZs of Tonga, Fiji and Papua New Guinea), this zone may have good potential for hydrothermal mineralisations and should be investigated. First reconnaissance requires the employment of SeaMARC R, SIS 09, SIMRAD or GLORIA.

TARGET AREAS IN THE EEZ OF TONGA (Figure 5)

From east to west, the Tonga area comprises the Tonga Trench where the Pacific plate subducts westward; the Tonga Ridge supporting the main islands of Tonga and in which hydrocarbon resources are possible; the active Tofua volcanic arc; and the active Lau back-arc basin with several spreading ridges. A large part of the Lau Basin has been investigated by Seabeam and GLORIA. Polymetallic sulfides have been proven in the Lau Basin by photos, submersible diving and sampling. Four areas are identified for future swath mapping surveys (Figure 2).

Area TG 1

This area of the Tonga Ridge extends over 600 km from Vava'u (18'S) to the southwest of Pelorus Reef (24'S). The width of the area is about 50-60 km. Water depths range from 0 to 1000m and large parts are more than 500 m. The primary objective is to assist the hydrocarbon program by mapping the traces of active faults. The size and water depths of this area mean that a full swath mapping survey would be very time-consuming. However, it would be useful to survey a restricted area (70 km x 40 km) between Tongatapu - 'Eua and 22'S, selected because of the extensive existing multi-channel seismic coverage and because the area is considered to have the most promising hydrocarbon potential in the EEZ of Tonga.

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The mapping system should have good resolution and be as fast as possible. The recommended system is the SIMRAD. SeaMARC S or SIS 120 is also suitable but would need a longer survey time. Another possibility is the SIS 09 or SeaMARC II because the survey time can be reduced, but in this case the bathymetric swath width is much less than the image swath width so that there is not full bathymetric coverage.

Area TG 2

This area is located along the easternmost edge of the Lau Basin and along the active Tofua Arc from Curacao Reef in the north (15'S) to Pelorus Reef in the south (23'S) (Figure 2). The bathymetry of this area is poorly known. The survey objective is to identify new seamounts for fishing industries, and spreading ridges or troughs which may be associated with hydrothermal mineralisations and metalliferous muds. The size of the area and objectives of the survey require the employment of the SeaMARC R or the GLORIA system (see Table 2).

Area TG 3

This area corresponds to the southernmost part of the Lau Basin, which is almost unknown. The objective of this survey is to find the location of spreading ridges and seamounts which may be associated with polymetallic massive sulfides. Because this survey is a reconnaissance, the SeaMARC R, SIS 09 or GLORIA are recommended.

Area TG 4

This area lies at the northernmost part of the Lau Basin and includes Niuafo'ou Island, Rochambeau Bank and Zephyr Shoal. Although the Lau Basin is generally well covered, this part remains uncharted. Niuafo'ou Island is an active volcano which erupts MORB type lavas. An inactive Pliocene island arc may exist between Rochambeau Bank and Futuna Island.

The area is located just west and north of the last SOPAC GLORIA cruise, the preliminary results of which suggest the presence of a NE-SW spreading ridge from Peggy Ridge toward Zephyr Shoal. The primary objective of this survey is to identify spreading ridges, troughs or seamounts which may be associated with hydrothermal mineralisation. When combined with information

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from previous cruises, this survey will also provide full coverage of the northern Lau Basin and thus a good understanding of its tectonic and geological history.

TARGET AREAS IN THE EEZ OF TUVALU (Figure 6)

The sea floor of the EEZ of Tuvalu is very poorly known. Figure 1 shows that the only swath mapping in Tuvalu waters has been one track passing through the eastern part. A preliminary study based on Seasat satellite data detected three uncharted seamounts within the EEZ of Tuvalu. Because the islands, seamounts and banks of Tuvalu, which are believed to have formed from mid- plate or hot-spot volcanism, represent the most promising potential for mineral and fishery resources for this country, swath mapping of these areas is considered to have a high priority. However, before such an investigation, a more detailed study of the EEZ using satellite data is strongly recommended. Improvement in the processing of the altimetric data now allows detection of smaller seamounts and estimation of their size, shape and depth. Such a study has been recently made with success by ORSTOM in the EEZ of French Polynesia. Nevertheless, two areas located in the northern Melanesian borderland are proposed for swath mapping surveys.

Area TU 1

This area in the southern part of the EEZ of Tuvalu extends from Tuscarora Bank to Niulakita Island. These bathymetric highs are believed to have formed from hot spot volcanism. This may have potential for fishery, cobalt-enriched manganese crust, phosphate and Corralium. SIS 09 and SeaMARC II are well suited for a reconnaissance survey.

Area TU 2

This area is located just south of TU1 over Hera and Bayonnaise banks. The objectives and the techniques to be employed are the same as the area TU1.

TARGET AREAS IN THE EEZ OF VANUATU (Figure 7)

From west to cast, the Vanuatu area is composed of the New Hebrides Trench, the arc including the Aoba Basin in its central part, the back-arc area including in the north and in the

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south extensional troughs, and the western part of the North Fiji Basin. The portion of the trench between Efate and Santo has been mapped by Seabeam, and the length of the back-arc has been almost fully covered by Seabeam and GLORIA. In addition, a small part of the northeastern Aoba Basin has been investigated. Two areas are proposed for new swath mapping surveys.

Area VA 1

This corresponds to the southern end of the Coriolis Troughs just south of Aneityum. At this latitude the troughs are disposed ‘en echelon’ and appear to be developed across the arc platform. This area is interesting for possible metalliferous muds and hydrothermal mineralisation associated with extensional tectonics and arc volcanism. Swath mapping would also detect new submarine seamounts that may have potential for fishery resources. SIS 09, SIMRAD or SeaMARC II are the recommended tools.

Area VA 2

This is located in the central part of the Vanuatu EEZ and corresponds to the east Santo and Malekula basins which have been identified as the area of most promising hydrocarbon potential in Vanuatu. The primary objective of this survey is thus to assist the hydrocarbon programme. Swath mapping would also provide data on slope instability and active faulting. SeaMARC II is the recommended tool.

SOME INFORMATION ON NEW SWATH MAPPING SYSTEMS

Kroenke (1988) reviewed the different swath mapping systems and described those receiving the most attention for deep water (GLORIA, SeaMARC ll and Seabeam) and shallow water surveys (SeaMARC S). Since then, several new swath mapping systems have been or are being developed: SeaMARC R, SIS 09, SIS 120 and SIMRAD EM12.

The SeaMARC R is a 12 khz, long-range, high-resolution sea floor mapping system, which produces simultaneous bathymetric contours and side-scan sonar images across a swath varying from 1 to 40 km wide depending on the water depth and desired mapping accuracy (1, 2,, 5, 10, 20 and 40 km). The bathymetric swath width is 3.4 times the water depth. The survey speed is about 7

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knots. Only one of these was built in fact, for the University of Tokyo Ocean Resources Institute, and is called the Izanagi system.

The SIS 09 is a newer system operating at 9 - 10 kHz. It produces simultaneous bathymetric contours and side scan sonar images of the bottom in water from 100 to 10,000 m deep. The image swath width ranges from 1 to 20 km (1, 2, 5, 10, 20 km). The bathymetric swath width is 3.4 times the water depth. Survey speed is about 7 knots. SIS 09 and SeaMARC R are in fact later versions of SeaMARC II with improved features of range, resolution and focusing and with the ability to cover a given area more rapidly. However only the image swath width increases from SeaMARC II to SeaMARC R, the bathymetric swath width remaining the same.

The SIS 120 (120 kHz) is a new version of the SeaMARC S, upgraded for deeper waters. It produces bathymetric contours and side scan sonar images of the bottom in water from 3 to 3500 m deep. The swath width is 3.4 times the depth of the fish, which is towed 2.5 to 500 m below the surface. The survey speed ranges from 1 or 2 knots to 7 knots depending on the tow depth. Thus in relatively deep waters, the survey speed is very slow. This is a very important point for estimating the survey time using SeaMARC S or SIS 120.

The SIMRAD EM12 is a hull mounted, multibeam, bathymetric system that will be installed on the new French RV L'Atalante and will simultaneously produce swath bathymetry and imagery. The swath width is 3.4 times the altitude (above the bottom) of the fish which is towed 2.5 to 500 m below the surface. The system can be operated in essentially all water depths at a survey speed of 10 knots. This system will he particularly useful in both deep waters (the swath width being greater than that of SeaMARC II but not as wide as that for SeaMARC R or SIS 09 for depths greater than 3-4 km; the survey time is also shorter), and in relatively shallow waters (the survey being more rapid and the swath width larger than those of SeaMARC S or SIS 120 for depths between 300 and 1000 m). The system will undergo trials in 1990.

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REFERENCES

KROENKE, L.W. 1988: A strategy for seabed acoustic characterisation and swath-mapping in the CCOP/SOPAC region. CCOP/SOPAC Miscellaneous Report 41: 49 pages, appendices.

TIFFIN, D.L.; CLARKE, J.E.H.; JARVIS, P.; JOHNSON, D.; HILL, P.; HUGGETT, Q.; PARSON, L.; PRICE, R. and Scientific Party, 1989: CCOP/SOPAC GLORIA Survey, Port Vila-Apia-Port Via on HMAS Cook, 1 August - 1 September 1989. SOPAC Cruise Report 130: 45 pages.

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