LIMITED CCOP /SOPAC Tech. Sec. PROJECT Report No. 7 13 February 1977 Original: English

UNITED NATIONS

Economic and Social Commission for and the Pacific COMMITEE FOR CO-ORDINATION OF JOINT PROSPECTING FOR MINERAL RESOURCES IN SOUTH PACIFIC OFFSHORE AREAS

CRUISE REPORT: KORO AND BLIGH WATER,

(CRUISE MRD 77-1)

19-31 January 1977

by

R. T .R. Winqfie1d(1) , P.R. Roberts(2) and

C.W. Landmesser(3)

Under Mineral Resources Division (Offshore) Fiji and for UNDP Project RAS/72/l22: South Pacific Offshore Prospecting Prepared as a joint contribution with the Technical Secretariat of CCOP/SOPAC to PROJECT CCSP-1/FJ.3: Re-evaluation of seismic and other data available on relinquished petroleum concessions west of the Yasawa Group; PROJECT CCSP-l/FJ.4: Sea-bed sampling off the north coast of ; and PROJECT CCSP-l/FJ.12: Marine geological and geophysical investigation of the southern Koro Sea (extended northward).

1. Marine Geologist, MRD (0), Fiji 2. Geophysicist and electronic engineer on technical aid loan to MRD (O) from I.G.S. (UK). 3. UNDP Consultant on Marine Geology and Geophysics. MINERAL RESOURCES DIVISION (OFFSHORE)

FIJI

CRUISE REPORT 77-1

JANUARY 1977

JOINT CRUISE WITH CCOP/SOPAC ON HMFS KIRO

CRUISE REPORT: KORO SEA AND BLIGH WATER, FIJI

(CRUISE MRD 77-1)

19-31 JANUARY 1977

by

R.T.R. Wingfield (1), P.R. Roberts (2), and

C.W. Landmesser'3)

1. Marine Geologist, MRD (0), Fiji 2. Geophysicist and electronic engineer on technical aid loan to MRD (O) from I.G.S. (UK). 3. UNDP Consultant on Marine Geology and Geophysics.

Contents Page

Introduction and Background 1 Facilities and Equipment 3 Installation on HMFS KIRO 4 Survey Procedures 5 Preliminary Results 7 Lomaiviti Group Areas 7 Bligh Water 7 References 9

Appendix I Cruise MRD 77-1: Cruise Narrative Appendix II Cruise MRD 77-1: Seismic Traverses Appendix III Cruise MRD 77-1: Sampling Station Log Appendix IV Cruise MRD 77-1: Technical Report by P.R. Roberts

Joint MRD (O) Fiji and CCOP/SOPAC Project KORO SEA AND BLIGH WATER, FIJI 19-311 JANUARY 1977: CRUISE REPORT MRD 77-1

Introduction and Background:

Cruise MRD 77-1 was undertaken by the Government of Fiji under the auspices of the Committee for Co-ordination of Joint Prospecting in South Pacific Offshore Areas (CCOP/SOPAC) from 19-31 January 1977 by mer.1bers of the Minera1 Resources Division of the Ministry of Lands and Mineral Resources, Fiji. The survey is one of an ongoing series designed to study the 200 n.m. economic zone surrounding Fiji and comes under projects CCSP-l/FJ.3, 4 and 12. (See Proceedings of the Fifth Session of CCOP/SOPAC, Rarotonga, 1976).

A reconnaissance cruise south end west of Viti Levu was carried out in August 1976 and is described in CCOP/SOPAC Tech. Sec. Project Report No.5 (In-m (0) Fiji Cruise 76-1). Cruise MRD 77-1 was originally intended to study the tectonic setting of the oceanic & area northwest of the Yasawa Islands under project CCSP-l/FJ.3: Re-evaluation of seismic and other data available on relinquished petroleum concessions west of the Yasawa Group, with special emphasis on the search for a possible seismic zone through this which might be the locus of recent shallow focus earthquake activity along an east-west line intersecting . This primary objective was subsequently frustrated by adverse weather conditions and equipment failure. As a result, the cruise plan was revised to sample surface deposits in the sedimentary basin of Blight Water, where water depths range from 200 to 1000 m. This study is a contribution to Project CCSP-l/FJ.4: Seabed sampling off the north coast of Viti Levu. Additionally, bottom samples were taken through the Vatu-i-Ro. channel, a 700m. Deep, 3.5 km. wide passage between reefs forming the south-east entrance to Bligh water, and among the islands of the Lomaiviti Group to the east of Viti Levu in the northwest Koro Sea. Seismic reflection profiles were obtained in the latter area during the early part of the cruise, contributing to an investigation of the northern extension of the area covered under Project CCSP-I/FJ.12: Marine geological and geophysical investigation of the southern Koro Gea between Viti Levu, Kadavu and Moala Islands.

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The two main islands of Fiji, Viti Levu and Vanua Levu, are extended respectively north-westward and westward, by broad shelves of less than 200 m. depth (Fig.1). These shelves are encumbered by islets, (notably the Yasasa Islands, Round island, and Yandua Island), cays, coral heads and elongate reefs. Such broad shelves of relatively shallow depth are unknown elsewhere in parts of the Pacific that are bounded by the marginal deep- sea trenches. Marine geological and geophysical exploration by MRD (O) Fiji over the, next decade will focus on these shelves, since mineral resources proved there would lie in water depths presently feasible for exploitation.

The geology of islands surrounding Bligh Hater consists of a volcanic and vo1canoclastic sequence from Eocene to Recent in age with important marine carbonate intervals (Rodda., 1975). The structure and stratigraphy of the shelf areas and of Bligh Hater is largely conjectural, though extensive seismic data obtained by Southern Pacific Petroleum Company is available at MRD. A Summary description and analysis of petroleum company data has been prepared by Coulson (1974), which appears in CCOP/SOPAC Proceedings of the Third Session, Apia. Work among the Lomaiviti Group by the International Petroleum Company is still held in confidence with MRD, but is briefly described in the same paper. Bottom samples obtained during cruise MRD 77-1 will be examined in relation to this seismic data and a report tlil1 be subsequently published when the information is out of closed file.

Cruise MRD 7.7-1 was organized by Dr. R.T.R. Wingfield under the direction of Ur. R. Richmond, Director of Mineral Development, MRD, Fiji and National Representative of Fiji to CCOP/SOPAC· The seismic profiling system was installed an operated by Mr. P.R. Roberts on loan to Fiji under technical aid furnished by the Government of the united Kingdom through the cooperation of Hr. J .E. Wright, Assistant Director of Institute of Geological Sciences (U.K.), Continental Shelf and Marine Geophysics Division. Ur. C.1·f. Landmesser, UNDP Consultant on Marine Geology and Geophysics, assisted with the set-up of the bottom-sampling equipment, and provided instruction on sampling methods during the first part of the cruise. Other personnel from, Fiji were:

Mr. Patresio Fuata, Technical Officer Mr. Eroni Tupua, Technical Assistant Mr. Vl1iame Bale, Technical Assistant

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HMFS KIRO, a sister ship to HMFS KULA used during cruise 76-1, was provided for the cruise by the Commander Royal Fiji Military Forces under the command of Lieutenant Commander David Elliot, and, during his absence due to illness, under Lieutenant Commander Sekovi Cama. MRD (0) and CCOP/ SOPAC are profoundly grateful for the provision of the vessel by the RFN who additionally undertook to provide bunkers for the operations.

Facilities and Equipment

To obtain continuous seismic reflection profiles during the cruise, an EG&G sparker system (on loan to CCOP/SOPAC from the Australian Bureau of Mineral Resources) was installed on board the vessel. This system was comprised of three model 232 power supply units, three model 233 capacitor banks, two model 231 triggered capacitor banks, a three-electrode spark array, and a 230/115 volt distribution board. The sparker system was operated at a total transmit energy level of 5000 joules, at a 1 per 4 second firing rate.

Additionally, an EG&G Uniboom (MRD (0) Fiji) was carried on board as a spare seismic energy source.

Receiving and recording, equipment, (owned by Fiji Mineral Resources Division) consisted of a custom built, 40 element Seismic Engineering company eel and control panel, two Hewlett Packhard/Sanborne model 8875A differential amplifiers, two model 3100 Kronhite filters, and two Gifft 19 inch, wet paper recorders, one a model 4000, the other a model 4000T. The active section of the hydrophone array contained a depth sensor and two hydrophone groups- a "short" group for shallow water use with the EG&G, "Uniboom" seismic source, and a “long" group for use with the sparker. The eel tow cable was fitted with vinyl fairings made by Fiji Mineral Resources Division. The control panel contained a readout for the depth sensor and a pre-amplifier for the eel signal.

Monitoring and test equipment included an Akai AA-52l0 stereo amplifier with headphones and loudspeaker, a Tektronix model 323 portable oscilloscope (CCOP/SOPAC), a Phillips model PM-3200 oscilloscope (Fiji Mineral Resources Division), and two Triplett multimeters (CCOP /SOPAC). Adequate spares were available only for the Gifft recorders, although there was a good selection of general purpose electronic components made available by CCOP/SOPAC.

Two BKB diesel alternators (Fiji Mineral Resources Division), one an 18.75 KVA, 230 volt, 60 Hertz, single phase machine, the other a 10 KVA, -4- 115 volt, 60 Hertz, single, phase machine, were installed to provide necessary AC power. A 3 KVA 240 VAC Lister generator (CCOP/SOPAC) was carried as a spare AC power supply.

Both the 10 KVA and the 3 KVA diesel generators were found to be defective during installation and the 115 VAC supply for all equipment in the electronics hut was taken from the ship’s 115 VAC supply, stepped up to 230 VAC. The MRD 10 KVA generator was repaired before sailing by the Government Engineers and was carried as a spare. The 230 VAC power sup- ply from the ERD 18.75 KVA generator was led to the power banks in the hold, in isolation from the electronics hut, and was separately earthed. Ear thing of the two systems was by heavy gauge redundant sparker cable led to the ship's main plate.

Battery powered intercom sets were installed from a master in the electronics hut with "slaves" in the ship's bridge and in the hold.

A Hydro Products model HR-60 4 h.p. petrol driven winch (CCOP/ SOPAC), with approximately 1200 m. of 3/16'' wire rope, was installed for bottom sampling by Shipek grab sampler. Free-fall gravity cores (CCOP/ SOPAC) were used for further sampling surface sediments. An Edgerton deep sea camera system (CCOP/ SOPAC), comprised of a Benthos model 371 utility camera, model 381 utility flash, and bottom contact switch, was installed for testing during the cruise.

Installation on HMFS KIRO

Installation of equipment on board the vessel were carried out from 11-18 January 1977. The lay-out was basically similar to that used on board HMFS KULA for cruise MRD 76-1 (see cruise report, CCOP /SOPAC project report No.5). The location of the electronics hut was altered to a position in the centre of the afterdeck, in the former position of the main cable drums of the ship' s, mine-sweeping gear. At the request of the RFN all installation was effected without bolting to the deck. The sparker trigger banks, power supply units, and capacitor banks were fitted below decks in the after hold; the hatch was covered by wooden board with a 10 inch diameter flexible exhaust - trucking for the extractor system. Additional ventilation in the electronics hut and hold, not previously carried, was provided by the use of two 11-inch electric fans. Installation was seriously hampered by prolonged heavy rain related to tropical storm centers located near Fiji. Permanently rigged tarpaulins were erected over hut and hold.

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The 3-element sparkarray was toward on the port quarter through the ship's fair lead, whilst the hydrophone array was towed from a 3" x 3" wooden boom extending outboard to starboard. The length of hydrophone tow cables and the ship's speed were adjusted to give optimum records, achieved with a hydrophone tow depth of approximately 15 feet.

Survey Procedures

Due to unfavorable weather conditions and equipment failure, only 20 hours operation of the sparker system was achieved during the cruise (see Appendix I, Cruise Log). These yielded approximately 135 nautical miles of seismic reflection data, mostly in the north-west Koro Sea among the islands of the Lomaiviti Group with short additional traverses in Bligh Water and west of Viti Levu (see fig. 1). It was originally intended to run continuous seismic profiling on a 24 hour/day basis but this was frustrated by unfavorable weather conditions, associated with tropical storms Marion and June, and later by equipment failure to some extent consequent to these weather conditions.

All three EG&G model 232 power supply units on loan from the Australian Bureau of Mineral Resources failed in sequence due to insulation breakdown to earth on the high voltage (4000VDC) windings. The cause of these failures is attributed to the temperature and humidity within the ship’s hold (see Appendix IV, Technical Report by P.R. Roberts). It is evident that the faults are internal to the power supply transformers, since they are isolated from system overloads by fuses on one side and a diode bridge on the other. A clear lesson from these failures is that climatic conditions in the hot, humid atmosphere of the Fiji hurricane season necessitate airconditioned operation of pouer supply units. It is strongly recommended that air conditioning be installed aboard the prospective offshore vessel. It may be noted that mm cruise 76-1, carried out with the same equipment at the end of the winter season when ambient temperatures were some 10◦F cooler and humidity levels were lower, was fully successful.

Before the failure of the power supply units, the sparker system functioned normally and adjustment of ship’s speed, hydrophone tow depth, and filter and amplifier settings was achieved to obtain optimum results. This provided fine resolution over 0.1 see sub-bottom depth and the coarse recording of prominent reflectors to 0.5 see sub-bottom depth (1200 m. assuming average sonic velocity in sediment of 2400 m. sec.-1).

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During the operational period of the seismic system, from 19-20 January find part of 24 January, bottom sampling equipment was tested and MRD personnel were instructed in use of the Shipek grab sampler and free fall core samplers. Two free fall gravity cores were taken in Bligh Water, after a preliminary sparker traverse over the site had been completed. Additionally the Hydra Products winch was used at night while anchored in Mba Passage, to sample with the Shipek grab and to experiment with the Benthos camera system. Considerable trouble was initially experienced with condensation in the carburetors of the Hydra Products winch, a further indication of the extreme humidity prevailing.

After failure of the seismic system, the vessel entered Bligh Water through Round Island Passage and undertook bottom sampling operations from 0600-1800 daily (see Appendix I, Cruise Lag). 39 sites on a 4 nautical mile interval grid were successfully sampled to provide reconnaissance average. This included 35 Shipek grab samples and 5 free fall gravity cores. Problems were encountered with the Shipek grab, as wire became kinked on the release of strain after the grab hit the bottom, despite the insertion of a swivel shackle loaned by the UFN. 4 free fall cores were lost during sampling attempts, presumably either due to' extremely soft Surface sediments allowing penetration of the trigger weight, or hard seabed preventing sufficient care penetration necessary far triggering. A number of attempts, none of were made successful, were made to evolve a light which- lowered corer, before the end of cruise operation.

Water depth at sampling stations were assessed first from the charted depth, which was consistently found to be greater than depths measured; secondly by HMFS KIRO,s echo-sounder, which provided the only depth measurement at free fall caring sites; and lastly by wire measurement from the 11inoh during Shipek samplings. The winch wire was marked by colored wire at 50 m. intervals. All water depths measured by winch wire in t1atersdeeper than 100 meters were found to' be less than both the charted and echo-sounder depths. This problem is to' be assessed with the Fiji Hydrographer.

Navigation was maintained by the PFN using magnetic compass bearings from the ship's binnacle, and range/bearing readouts farm the ship's radar. Fixes were taken at. 15 minute intervals along each traverse, and while stationed at each sampling site. HRD (0) Fiji has adapted the Degree Rectangle System far numbering cruise traverses and sampling stations, in order to' further ca-ordinate and integrate data from onshore and offshore areas.

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Each rectangle is numbered by the degree co-ordinates of its southwest corner (i.e. rectangle 18/178 has southwest corner 18˚S 178˚ E. This system is standard now for all MRD (0) operations.

Preliminary Results Lomaiviti Group Area

Seismic reflection profiles in the Lomaiviti area, east of Viti Levu, reveal a series of basins positioned between steep slopes and ridges which rise to the surrounding islands. The slopes are comprised of acoustically opaque basement, probably Iithified volcanogenic deposits, of the same volcanic series that are found on the surrounding islands. The basin margins appear fault controlled in most cases, as west of Koro Is., and evidence suggests a block faulted regime. Basins are floored by thin, generally flat-lying sediments and topography within the basins is predominantly smooth. It is evident on several traverses (see. Appendix III, Seismic Traverses), that the basin sediments consist of a younger, horizontally disposed sequence with maximum thickness of approximately 0.25 see (500 m. assuming- sonic velocity of 2000 m. sec. -1). A prominent unconformity separates these younger sediments from an older and thicker series of mildly deformed deposits, extending to at least 0.5 sec. (circa 1000 m.) sub bottom depth. The basins vary from 900 to 2700 meters, in depth, and the limited amount of recent sedimentation suggests these are relatively young basins that are isolated from terrestrial sediment supply by surrounding barrier reefs.

Bottom samples taken ill these basins were dominantly grey-green, glauconitic mud, generally of clay grade, overlain by a thin (0.04 to 0.15 m.) surface layer of brown, weathered sandy or silky mud with bioclasts. The latter deposits are probably derived from recent erosion and reworking- of the exposed Tertiary or early Quaternary sedimentary sequence. Location of sampling stations and description of samples recovered are presented in Appendix III, Sampling Station Log.

Bligh Water

The sedimentary basin of Bligh Water is revealed by oil company seismic data (see Fig. 2, Amoco Line 42) as being similar to the smaller basins described among the Lomaiviti Group. The lesser depth of Bligh water may result from greater sediment infill occasioned by a more continuous terrestrial supply during lower Pleistocene sea levels when surrounding shelves were

-8- exposed. Surface sediments are horizontally bedded and attain thicknesses up to 1.0 sec. sub-bottom depth (see Fig. 2). These are underlain by slightly deformed sediments, which are separated from the overlying deposits by a prominent reflecting horizon. A lack of data p1'ecludes attempts to match this sequence with that found in the Lomaiviti basins at this stage. The Bligh Water basin is divided by a positive east- west ridge, appearing at shallow sub-bottom depth (miles 20-24, Amoco line 42) and as occasional outcrops (west end. line 18/l78/T-4) of deformed deposits, possibly volcanoclastic rocks which underlie the more recent horizontally disposed sediments already described.

Samples recovered from the central part of the Bligh Water basin were dominant1y Green-grey, glauconitic mud. (? soft clay stone), with a thin weathered surface layer containing biostatic material, similar to the surface sediments in the Lomaiviti basins. Howe ever, along the southern margin of the basin, in a zone extending from the reef channels to approximately 6 km. North of the reefs fringing northern Viti Levu, surface deposits of sand are dominant, both as sandy mud’s or muddy sands and as interbred of sand and mud. These sandy sediments were found in water depths as great as 400 meters, and are indicative of a marginal facieses change within the basin. The few samples taken in the lagoons revealed clean sands and sandy mud’s ponds behind barrier reefs. Only one sample 17/178/3, was taken on the steep basin margin, which proved coral rock. Location of sampling stations and description of samples recovered are presented in Appendix III, Sampling Station LOG.

These findings, when considered in relation to available seismic reflection data, indicate that Bligh Water is a partially infi1led basin with thick mudstones grading landward into muddy sands adjacent to the enclosing reefs. Further evidence from seismic profiles (Fig. 2) suggests that isolated coral reef formations and/or faulted volcanogenic basement rocks may be buried within the basin sediments. Such lateral facieses changes and structural features could very well provide suitable traps for accumulation of hydrocarbons.

To the south-east of Bligh Water, bottom samples recovered from the Vatu-I- Ra channel were dominantly sand, grading from fine to granule grain sizes. The occurrence of coarse sediments in this channel is highly suggestive of accelerated bottom currents flowing through this constricted area. Similar conditions are likely to occur in other narrow channels, which are Common in the l1aters surrounding Fiji.

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Traverse 18/176-1, the only seismic reflection line run west of Viti Levu, shows a rough slope which is comprised of acoustically opaque basement with little or no sediment cover. This finding' is in accordance with recent work on the western Fiji Plateau by Lamont-Doherty Geological Observatory where appreciable sediment cover is absent (pers. comm. Professor Heezen).

References:

Rodda, P: 1975 Fiji. In Fairbridge, R.W. (Ed.). The Encyclopedia of world regional geology, Part 1, Dowden, Hutchinson and Ross, Stroudsburg, Pa. pp. 278-82.

CCOP/SOPAC - Proceedings of the Third Session, Apia, western Samoa, 2-10 September 1974.

CCOP/SOPAC - Proceedings of the Fourth Session, Honiara, Solomon Islands, 8-16 September 1975.

CCOP/SOPAC - Proceedings of the Fifth Session, Rarotonga, Cook Islands, 2-8 November 1976 (in press).

(1 of 3) APPENDIX I

CRUISE MRD 77-1: CRUISE NARRATIVE

9 January, Sunday IGS Electronics Engineer P. Roberts arrived Fiji. 10-11 January, Mon/Tues Bench testing of sparker system. 12-18 January HMFS KIRO alongside Navy Wharf. Installation of MRD & CCOP/SOPAC equipment, using MRD crane Operations hampered by prolonged heavy rain. 17-19 January Hurricane warnings and strong northerly winds on fringes of TRS Marion delayed sailing. Lt. Commander Elliot sick replaced by Lt. Commander Cama. 19 January, Wednesday Winds: NW Force 5-6. 0910 Departed Suva. 1000 C1eaxed reef entrance to Suva and headed east for calmer waters. 1100 Ship's radar break down. 1330 Deployed speaker gear and commenced testing. 1438 Traverse 18/178/T-l off Ovalau. 1630 Traverse 18/178/T-2 off Makogai. 1800 Continued as 18/179/'1'-1 off Wakaya. 1915 Traverse 18/179/'1'-2 between Wakaya and Mbatika. 2000 First power bank failed. Heavy smoke. 2100 Traverse 18/179/T-3 between Wakaya and Koro. 2338 Traverse l8/179/T-4 between Wakaya and Koro. 20 January, Thursday Winds: NW Force 3-4. 0300 Traverse 18/179/T-S West of Koro. 0700 Continued as 18/178/T-3 to Makogai Passage. 0745 Raised gear and proceeded through Vatu-i-Ra Passage to Bligh Water. - 1315 Traverse 18/178/T-4 North of Charybdis Reef. 1434-1500 Took free fall gravity cores at station 18/178/1. 1500 Underway to Mba Passage. 1715 Anchored. 1815 Received hurricane warnings for tropical storm "June" heading for Lautoka.

Appendix I (2 of 3) 21 January, Friday winds:' S var/light to N mod inc; fresh, heavy rain. 0045 Underway from Mba Passage to Lautoka. 0855 Secured alongside at Lautoka. 0900-1700 Continuous warnings of approaching tropica1 storm "June". Secured all gear and battened down. 1845-0145 (Sat) MRD: party stood down survey and returned to Suva. 21 January, Friday - 24 January, Monday 1800-1~00 Survey stood down due to proximity tropical revolving storm "June" by RFN.

24 January, Monday Very hot; light airs . 1440 MRD personnel and Lt. Commander Elliot returned 1540 Departed Lautoka. 1540-1730 Reconnected and deployed Sparker gear on passage to Navula Channel. 2015 started Traverse 18/176/1. 2nd power bank Failed Switched banks. 2215 Third power bank failed. 2215-2400 Checking transformers. 25 January, Tuesday Winds: Var. Force 1-2 to ENE Force 4-5. 0001-1000 Heading for Round Island passage NW of Yasawas. Check seismic insulation breakdown of all power Bank’ transformers. 1200-1900 Entered Bligh Water tested. Shipek winch. Anchored Yandua Passage. 26 January, Wednesday Winds: E Force 1-2 to ESE Force 4. 0645-1800 Sampling operations NE Bligh Water. Shipek fouled reef S of Yandua and required welding. Anchored off Vanua levu.

7-7 January, Thursday Winds: E Force 1 to E Force 4, torrential Showers. 0645-1800 Sampling operations western Bligh Water, Pascoe Reefs to. W of Charybdis Reef. Anchored Nuku- rauvula Passage, Viti levu.

Appendix I (3 of 3)

28 January, Friday Winds: S Force 0-1 to ESE Force 4-5. 0630-1745 Sampling operations S. Bligh Water - Mba Passage. Secured Ellington Wharf for night to take on water.

29 Janaury, Saturday Winds: Light SE to ESE Force 2; showers. 0700-1745 Sampling operations SE Bligh Water and Vatu-i- Ra Channel. Alongside Ievuka on Ovalau for night.

30 January, Sunday Winds: Light E to E Force 4; thunderstorms. 0800-1745 Sampling operations among Lomaiviti Group, NW Koro Sea. Returned Ievuka for evening to facilitate RFN rendezvous in morning.

31 January, Monday Lt. airs; rain. 0200 Sailed Iewka. 0300 Main engines defect. 0900 Entered Suva. 1000-1700 Demobilized all MRD/OOOP gear.

(1 of 3) APPENDIX II

CRUISE MRD 77-1: SESIMIC TRAVERSES

18/178/T-1 SSW-NNE&N. 5KJ. Fixes 1-7. Moderately smooth bottom 900-1000m. E. of Ovalau Young surface sediments with slight dips some 0.2- NW Koro Sea 0.25 see (1 way) thick, overlie with angular disconformities sediments with steeper dip seen to 0.5 see (l-way).

18/l78/T-2 NW-SE 5&6. 5KJ. Fixes l-7. Basin 900-1050 m, then rough rising to 750 m. peaks. W. of Wakaya The two sequences seen on line T-1 are truncated about NW Koro Sea Fix 4 by a rise of Complex basement which outcrops From 4.5 forming rounded peaks with thin sediment Pools between. 18/179/T-1 Continuation Line T-2 above, Fixes 7-11. 6.5KJ. Rough 750-1050 m. to 8.3 then smooth basin to EOL Sloping down 1050 m. to 1200 m. W&Ws of Wakaya Basement (aa) Continues to 8.3 then slopes down with NW Koro Sea flat bedded sediments to SE with upper sequence 0.1 sec thick on prominent surface above further flat bedded strata seen to 0.6 see pen.

18/179/T-2 E from EOL T-l. Fixes 1-5. 5KJ. Basin ca 1200 m. to 2 .3. Then ridge rising to 620 m. sloping off in steps to EOL at 1350m.

Through Wakaya/ Thick sediment as end T-1 truncated against basement Mbatika channel ridge at 2.3. On E side of basement ridge, basement NW Koro sea is overlain by E. dipping beds thickening to 0.25 sec (1 way TT) ,themselves overlain by flat-bedded seds to 0.1 see thick at EOL.

Appendix II (2 of 3)

1 8/179/T-3 N from EOL T-2. Fixes 1-7. Moderately rough bottom 1350-2400 m. E of Wakaya & Generally an indifferent record due to water depth and Makongai sea state. Rolling topography apparently formed by NW Koro Sea hard basement without reflectors overlain by sparsely developed patches of surface sediment to 0.1 sec (1 way TT) thick, the latter forming ridges isolated by erosion. l8/l79/T-4 NW-SE. Fixes 1-10. Slight slope 2400-2550 m. to 7.0. Then blocks between 2450 and 2650 m. deep. Fran E of Makongai Near start of line thin sediment group of line '1'-3 is to 5 of Koro overlain by gently undulating younger sediments. NW Koro Sea these are seen without penetration to 0.2 sec (1 WTT) over most of the line. Block faulted inliers of the older sediments occur from 7-EOL. l8/179/T-5 SE-NW then W. Fixes 1-6.5. Basin bottom at SOL at SN&W of Koro 2700 m. is stepped up by gigantic fault scalps, 'c' NW Koro Sea visible into bottom to 0.25 sec (1 W'l'T); to 2600 m. at 0.45, to 1950 m. from 1.0 to 1.3, to 1500 m. at 1.8, and to a ridge at 2.3 least depth 1150 m. '1t1e faults are 1Qo1 angle, apparent dip 5, the steps being formed by horizontal strata with prominent reflectors at 0.1 sec 1 WTT intervals. The ridge falls rapidly from 1175 to 2300 m. from 2.35 to 4.0 into a basin floored by flat lying sediments to EOL. Forming a basin from 2300-2400 m. floored by flat sediments seen to 0.15 sec (1 WTT). l8/l78/T-3 Continuation W&Ws. Fizzes 6.5-11. Rough topography W from Koro to rising from basin bottom at 2400 m. up a slope with Makongai Channel peaks to 300 m. high, to least depth at EOL of 600 m. NW Koro Sea in channel. Bottom mostly of high ridges capped with peaks of gently inclined sediments isolated by erosion.

Appendix II (3 of 3)

18/178/T-4 E-W. 5 KJ. Fixes 1-5. Even bottom about 650 m. Bligh Water N of Flat bedded young sediments to 0.25 sec (1 Way) overlie Olarybdis Reef rough topography of basement rising to seabed out- crop to west. Basement of mildly deformed, faulted, well bedded strata.

18/176/T-1 SE-NW. 5KJ. Fixes 1-9. Rough bottom descending 1050 to 2400 m. Outside Mamanutha Rough topography seemingly erosional since sub-bottom Islands reflectors are terminated by bott~. Probably a hard rock batter- whole line without recent sediment cover.

(1 of 11) APPENDIX IV

HRD CRUISE 77-1: TECHNICAL REPORT by P.R. Robert

Introduction During this survey complete failure of all high voltage transformation utilized in the EG&G Sparker/Boomer seismic system (on loan to CCOP/SOPAC from BER) was experienced and subsequent inspection of all the units in the laboratory revealed nothing untoward that could have caused such failure. It is considered that the adverse conditions, both in terms of humidity and temperature, in which these units were stored prior to and during the survey period caused the failure.

This report sets out to give a detailed account of mobilization, operation, subsequent checks and prevailing climatic conditions during the period and to indicate what future action is required to ensure successful operation.

1nitial Inspection and Mobilization Following my arrival in Suva preparation for mobilization of the equipment aboard HMFS KIRO commenced on 11 January, the work commitment being such that only visual inspection of all the equipment was possible.

The Sparker/Boomer system, which had been stored in partial air conditioning was examined and apart from some minor corrosion and dirt deposits all units were found to be in good order. The interconnecting loads also proved to be in sound mechanical order, and electrical continuity and insulation checks proved satisfactory.

Mobilization commenced on 12 January, with the Sparker/Boomer system being transferred from the CCOP /SOPAC project office to the hold on the after deck of the vessel on 13 January. By Sunday 16 January, power supplies had been connected - after some difficulty - and dirt deposits were wiped from the accessible parts of the units. The Three Candle Spark array was connected and put into the water and the system given pre-operational checks, each unit being connected in turn into each possible combination of connections to ensure that all units to be used were in good order. By late afternoon the complete system was considered to be in sound working order.

At the same time a small extractor fan with hose was fitted into the hold hatch cover, but since no electrical supplies were available it could not be used. Also its small size would have done little to reduce the extremely high temperatures being' experienced in the hold, those being much Appendix IV (2 of 11) higher than outside since the held was exposed to the sun and no ventilation was being applied.

Because of poor weather forecasts sailing was postponed until Wednesday 19 January; thus for 7 days the equipment had been stored ill the held in conditions that could only be described as extremely peer. Rain and high temperatures were experienced for most of this period with humidity being in excess of 95.% at times.

Deployment and Running: (First, Failure)

After sailing en 19 January, the equipment was deployed and set into operation, no. difficulties were experienced and the system was seen giving reasonable results.

The system had been connected for 5000 J Working, i.e. using two Capacitor banks, the trigger and power supply unit.

Capacitor Banks S/N 86 S/N 162 Power Supply Unit S/N 9 (New Unit belonging to MRD) Trigger Unit S/N (?)

At 2000 hours, after 3 hours operation, the first Power, Supply Unit failed. I was summoned by Charles Landmesser who informed me of the failure and that smoke was coming from the, after hold - he had net been down to investigate but thought it wiser to inform me.

Upon entering the held I switched off both supply voltages and immed- iately noticed smoke coming from P.S.U. S/N 9. Closer inspection showed that the lid of the unit, which should have been in the open position, had vibrated down into such a position that it partially blocked the top of the unit, yet failed to operate the safety cut-out switch which is brought into operation when the lid is closed. Inspection of the inside of the unit revealed the source of trouble to be the main transformer and I concluded that overheating of this device had caused the failure and that the overheating was a direct result ef the accidental partial closing of the covering lid.

The main points emerging from this event were: (l) had the lid of the unit been properly secured overheating may net have occurred; since it did and because the lid was only partially closed it gives rise to (2) the ambient temperature in the held was much higher than outside, mainly because

Appendix IV (3 of 11) of the lack of ventilation. Local temperature within the units was excessive and critical. I believe that in lower operational temperatures the partial closing ,of the cover would not have resulted in transformer failure.

From (1 ) and (2 ) it was obvious that future operation of the system must not be attempted without the 1id being securely fastened and a fan directed across the open unit in an attempt to reduce local temperatures.

The second power Supply unit was fitted and the system manually operated several times to ensure correct operation. It is worth noting that in all aspects the system behaved normally including operation of the high voltage trip circuit. The system was put back on line and operated without further difficulty until 1415 hours on 20 January.

It is most pertinent to make comment upon the fire hazard experienced in this particular incident. During mobilization it was noted that a C02 fire extinguisher was available at the foot of the ladder into the hold but no consideration was given to the possibility of entering the hold in smoke conditions. This particular incident highlighted this point, and following discussions with Dr. Wingfield and the Captain, breathing apparatus and an extra CO2 extinguisher was made available at the entrance to the hold and full instructions as to their use given. Again it must be noted that conditions in the hold could 'have been improved, had there been adequate ventilation.

Events Leading To Failure of Remaining Units The survey was suspended on the night of 20 January in anticipation of a forecasted hurricane. Friday (21 January) saw us tied up at Lautoka with all cables to the after hold disconnected and hatches secured; the equipment was thus stored until 1600 hours on Monday 24 January. Again during the weekend rain and high temperatures were recorded

After reconnecting the system and departing Lautoka, the sparker system was deployed and cycled by hand to ensure correct operation. Once again the system operated in the normal manner giving no reason for concern whatsoever. The recorder to was started and after the second pulse the power supply unit failed. Note that as in previous operation the energy was at 5000 Joules with a trigger rate of 4 seconds; also that all units being used were as previously connected when successful operation was experienced. Appendix IV (4 of 11) Inspection of the Power Supply Unit revealed that the input fuse had blown. In order to locate quickly the cause of the problem the Power Supply Unit was isolated from the remainder of the system, a second fuse added and relay Kl operated by hand. The unit immediately failed blowing the second fuse. Since a most arduous day had been experienced, I decided to leave a more detailed inspection until the next day and proceeded to connect up the third Power Supply Unit.

Prior to putting the Sparker on line again, the system was operated by hand many times and also left to stand in order. to observe correct operation of the High and Lou Voltage trip circuitry. This particular check gives an indication as to the condition of the storage capacitors in the system. A reasonably long delay existed between High Voltage and Low Voltage trip and, as far as I could tell, the capacitors were in good order. At this stage, being completely satisfied that the system was operating correctly and was behaving in a manner consistent with past experience, operation was resumed and continued for 3 hours before the third failure occurred.

Checks on the Power Supply Unit again revealed blown fuses. The mains transformer within the unit was completely isolated and Checks with an AVO meter and merger showed that the secondary side of the transformer had gone earthy i.e. 200 OHMS to earth. The second transformer gave similar results. Further tests the following day confirmed, that both transformers had failed in a similar manner and that the system 1'TaS beyond. repair.

Inspection of Units in Laboratory Because of the failure of the Power Supply Units, it was impossible to test under operational conditions. Subsequent checks made on the units consisted mainly of physical examination and where possible insulation and continuity checks using an AVO meter and Meager. The fo110l·ring are results of the test performed on components of the system:

Power Supply Units S/N 8 Each of these units have defective S/N 9 transformers and are in need of repair. S/T 86

Appendix IV (5 of 11) Trigger Units S/N 107 Not used except under test conditions. This unit bad a previous fault in that a capacitor has been leaking. It had been' taken out of circuit and made safe. S/N (?) Used (belongs MRD). With reference to the above checks, both unit proved to be in sound working order. No faults could be found. In fact the trigger unit which was used during the survey (HRD (0) Fiji) is practically brand new. Capacitor Bank Ser, No. 162 - in use Both of these units proved to be in good Ser. No. 86 - in use order with low voltage tests on isolated capacitors proving satisfactory. Ser. To. 89 Used during initial tests only, since exterior Suggested slightly worse condition than other two units. Two minor problems found on this unit: a) A dry solder joint was found on the main H.T. coil connection. There was no evidence of overheating, and this could not possibly have Caused the problems experienced with the Power Supply Units. (b) A wire connecting an in-parallel capacitor completely come adrift with both ends out of the crimp tags. It would appear ~hat the lead had not been crimped correctly. Some slight arcing had occurred to the case of the capacitor probably whilst falling off. However, this was not conducive with the catastrophic failure experienced, even if it had been ill use. In view of these two faults and prior to any cleaning, the unit was completely dis- mantled and checked, each capacitor being tested up to 500 V. The unit could not be faulted under these conditions.

Appendix IV (6 of 11) It must be noted that although each capacitor has been given low voltage tests they are not proved to be in good order. It is possible for such a unit to fail under operational voltages yet give reasonable results from such low voltage tests. Although it is possible, I do not think it probable since L~ experience is such that complete failure occurs.

Conclusions Failure of the transformers was most probably caused by overheating and this could be achieved in one of two ways:

(a) An external short circuit causing a steady high current to be drawn through the transformer and through the high wattage vitreous resistors in the H. T. line. These two factors would have the effect of raising the local ambient temperature until failure occurred.

(b) Deterioration of the transformer itself, attributable to climatic and operational conditions causing breakdown in the insulation of the transformer windings. Higher currents would be drawn and this would raise the temperature of the unit until breakdown occurred.

From (a), (i) the most probable area for failure is the capacitors and these usually fail in a catastrophic manner. All checks carried out on the capacitors have proved, satisfactory but it must be reme111bered that since high voltage checks are not possible the results gained nay be inconclusive. However, I would add that high voltage trip checks referred to earlier indicated that the capacitor bank was holding its charge in an acceptable ,tanner giving no signs of failure or current drain. (ii) Other possibilities of failure could be faulty leads or inline components; extensive checks on those points have proved satisfactory and no attributable fault found. (iii) The capacitor bank which had two minor problems was not used but even if it had been it could not possibly have caused the problem because there were only signs of minor arcing; the failure wou1d have had to be such that a steady current was being drawn and for that, tracking from an electrode to earth would have shown quite clearly and would have been indicated by the high voltage trip circuit not being activated, since the charge would not be allowed to accumulate on the capacitors.

Thus practical checks have proved negative and no faults found that could have caused failure of three transformers.

Appendix IV (7 of 11) From (b), (i) the failure of the first transformer was initially contributed to the partial closing of the lid of the unit. In retrospect it would appear that failure would have occurred in a similar manner to the other twos and that the incident only aggravated the situation an(l to some extent was misleading.

(ii) Although the Sparker/Boomer system has been stored for some time in partial air conditioning, the air-conditioner unit is too small for the volume of room (and it is currently being improved) and Dr. Kroenke (fomer UNDP Marine Geologist) had indicated in a previous memo that humidity levels are quite high.

(iii) Whilst the equipment was stored aboard HMFS KIRO two definite periods of extreme adverse weather conditions existed, und even underway the temperature in the hold was much higher than outside. The lack of proper ventilation and the higher temperatures would cause higher local temperatures to be generated within the units themselves; although a fan was directed across the top of the unit, little was being achieved in reducing the ambient temperature.

In the absence of a serious fault condition existing, I must draw the conclusion that failure resulted from the adverse conditions in which the system was stored and operated and that serious thought must be given to its future operational environment.

Proper and adequate ventilation is essential for both equipment operation and long term storage and whilst a continuous air conditioned environment would be the ideal answer, I do not believe it to be essential; what must be avoided are the extreme conditions experienced on the HMFS KIRO, with particular reference to long periods of storage in the conditions outlined.

General Status Report on Equipment

Following my arrival at Fiji on 9 January preparation for mobilization of the seismic equipment commenced on 11 January. It was not possible to give all items complete operational checks and in some instances checks were limited to visual inspection and continuity readings. The following is a breakdown of work completed.

Appendix IV (8 of 11) (A) Seismic Recording System

Comprising (i) 2 Gifft recorders (ii) 2 Krohn-Hite-Filters (iii) 2 H.P. Diff Amps (iv) 1 Monitor amplifier (v) 1 Hydrophone Streamer and pre-amplifier unit

Items (i), (ii), and (iii): Each of these units were individually tested using a signal generator and oscilloscope then assembled as a system, with all interconnecting leads being tested, a signal fed in at the input of the first amplifier through the filter unit into the recorder. All checks were satisfactory.

These units had been stored in an air conditioned environment and were in good condition.

Spares existed for only the Gifft recorders and corresponded with previously compiled list (CCOP/SOPAC Project Report No.5, by Mr. Hill).

Item (iv): Hot being an essential part of the system this item was not tested. However it was subsequently connected into t he system and worked satisfactorily.

Item (v): The pre-amplifier 'assembly had just arrived from the manufacturer follol1ing repair (a fault Pad. existed in the depth detecting circuitry), and Has connected to the hydrophone. By tapping the hydrophone, operation was observed for a few minutes and failure occurred. The pre-amplifier was dismantled and tests revealed a poor electrical contact on the printed circuit board (power supply section), probably caused during repair. The fault was rectified and subsequent test proved satisfactory. Handbooks for all of the units were available and in reasonable condition.

(B) Seismic Energy Systems (EG&G Sparker/Boomer) Comprising (i) 2 Trigger Units (ii) 2 Power Supply Units (iii) 3 Capacitor Banks (2000 Joule) (iv) 1 3-Candle Spark array ( v) 1 Uniboom sled and transducer

Appendix IV (9 of 11) Item (i): Of these ~10 units, one was virtua11y new (MRD (0) Fiji). The other (Ser no. 107) was found to have an outstanding faulty capacitor which had been disconnected and made safe. Both units were inspected and found to have slight dirt deposits, this being removed whilst aboard HNFS KIRO.

Item (ii): Visually inspected, some dirt deposits found and as in (i) cleaned whilst aboard the vessel.

Item (iii): Units given external visual inspection; only two ,units in reasonable condition, the third having a somewhat rusted exterior.

General: Apart from a spare unsericeab1e Trigger unit, spares for this system are non-existent. References should be made to the manufacturer’s manual and the recommended spares level ordered.

All leads (black) tested for continuity and insulation and found to be satisfactory. A spare grey lead, although seemingly, in good order, was condemned on the previous cruise and was not used. It has been marked as unserviceable.

Item (iv): The array was found to be in good condition with 14 spare candles. Item (v): Unused; as yet in perfect condition. Handbooks checked: It must be noted that in two respects the diagram for Power Supply Units differs from the actual unit, in that the input fuses and the high wattage resistors in the H.T. line are not indicated. This may lead to some confusion at a later date and the manufacturers should be contacted and correct diagrams obtained.

(C) Generators A t this time two HRD generators were available (i) 240 Volt Single phase (18 KVA) (ii) 115 Volt Single phase (10 KVA)

Both generators were started up, the electrical outputs checked off load and found to be in order.

A third generator (CCOP/SOPAC) was being made available (240 Volt Single phase 3 KVA) but had not been removed from its packing case.

Appendix IV (10 of 11)

Mobilization commenced on 12 January and most items of equipment had been placecl into position and made ready for operation.

Earthling arrangement were good; separate leads had been connected from the Hut, which served as a Electronics Laboratory, and the sparker equipment in the after hold and made off onto the ship's earth plate.

AC Power Supplies The generators was connected and started, and electrical checks indicated a low voltage condition from the 115 VAC unit. Eventually the fault was traced to the coupling between the engine and generator. The machine was removed from the vessel and repaired ashore.

The third generator belonging to CCOP/SOPAC was started and checks on this revealed a low voltage condition. Components within the voltage control circuitry were checked but no fault could be found. Since the actual circuit did not compare with the manufacturer’s manual, some difficulty was experienced and the unit had to be stripped in order to establish the circuit lay-out. Normally a variable resistor is fitted into the field windings enabling adjustment of output voltage and current, this being shown in the circuit diagram. In fact a fixed resistor has been used making adjustment impossible. The manufacturers should be consulted on this problem and if necessary the unit returned for repair/adjustment.

Eventually in order to establish mains supply for the testing of the instrumentation, permission was given to use the ship's AC power supply. This proved satisfactory and rather than having two deck generators running at one time, the ship's AC supply was used throughout the survey, without difficulty.

Apart from the power supply problems no other difficulties were experienced and by Sunday afternoon (16 January) all equipment had been installed, tested and made ready for operation.

Operation

Apart from the complete failure of the sparker system (please refer pp 1-7, Appendix IV), no other equipment breakdowns were experienced.

Appendix IV (11 of 11)

Demobilization was commenced and completed on Monday, 31 January. Each item of electronic equipment was tested and apart from the sparker system, returned to the shelf in a functional condition.

No attention has been given to the generators but from experience gained during the failure, both units require a major overhaul with attention being paid to the electrical assembly and exhaust systems. If the units are not going to be used, then the engines should either be inhibited or started up and run for a few hours each week.