Multichannel seismic survey sonobuoy refraction survey and ...

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(1) Navigation Equipment: Magnavox Integrated System MX-702A and MX-II05. Edo Western doppler sonar (2) Bathymetric Equipment: Raytheon Line Scan Recorders with 3.5kHz and 12kHz transducers (3) Gravity Equipment: La Coste & Romberg S-53 sea gravity meter La Coste & Romberg G-426 land gravity meter for land ties at Pago Pago, Nuku'alofa and Suva (4) Magnetic Equipment: Geometrics proton magnetometer G801g (5) Single-channel Seismic Equipment: Raytheon Line Scan R"corder 100-metres long Teledyne streamer 95 or 148 cu.inch airgun (6) Multichannel Equipment: Globe Universal Sciences Model HDDR 4200 amplifer and HDDR 2000 Tape recorder Two Raytheon Line Scan Recorders and SIE dry write camera 2400 meters long Seismic Engineering streamer 5 airguns with total capacity of 1313 cu.inch. (7) Seismic Refraction Equipment: Fairfield Select Inc. amplifiers and Hewlet-Packard 3968A tape recorder Two Raytheon Line Scan Recorders SQS 418 Navy sonobuoys (52 Nos deployed) (8) Dredging and Coring: Chain dredge and 3 metre long gravity corer consisting of plastic liner and 800lbs lead block as weight. 3
4 PRELIMINARY RESULTS During the survey 2357km of multichannel seismic data were recorded. Concurrently, single-channel seismic, gravity and magnetic data were also recorded. In addition, 2176km of single-channel seismic data together with gravity and magnetic data were recorded; 719km north of Tongatapu between Pago Pago and Nuku’alofa; and 1457 south of Tongatapu while in transit to various dredge-sites. The multichannel seismic track lines and the locations of sonobuoy deployment from sonobuoy Nos. 5-49 are shown in Figure 1. The multichannel line Nos. 10 and 11 tie with the DSDP well site 203. Also, more than 750m of single-channel seismic, gravity and magnetic data were recorded in transit from the last dredge-site D9 about 30km SW of 'Eua to Suva with the objective of gathering more data in studying the Lau basin and ridge. The three probable reefal buildups identified from the CCOP/SOPAC Line N-O were also observed on the single-channel seismic record of E-W Line No. 11. One of the reefal buildups, most likely the one in the centre, was also observed on the single-channel seismic record of N -5 Line No. 14. These establish the presence of probable reefal buildups in that area. No other obvious reefal buildups were observed on any other single-channel seismic records. In most of the lines, especially on Line Nos. 3-8, the sedimentary beds appear to thicken from east to west from about 0.5 to 1.5 sec. to over 3.0 sec. (about 5600m). Angular unconformities are observed at about 0.2-0.5 sees. and the sedimentary beds below the unconformity apparently dip westwards; the dips are found to be very gentle. Many normal faults, some of which are active up to recent times are observed on the single-channel seismic sections. Magnetic anomalies are observed over the Pleistocene-recent volcanic trend and where the probable shallow basement is believed to exists. Some of the sonobuoy graphic records were analyzed on board using the digitizing table and a desktop computer. Preliminary results of a few sonobuoy refraction profiles are included as Appendix 8. Locations for dredging and coring were chosen by the participating scientists in consultations with the Co-Chief Scientists, by studying the Polaroid photographs (pasted together to form a continuous strip for each line) of the single-channel seismic data. Though several attempts to core were made on 6 or 7 sites chosen from the single-channel seismic data, none successfully penetrated more than a few cm due to the hard seabed surface encountered.
Page 1 and 2: CCOP/ SOPAC- TRIPARTITE CRUISE REPO
Page 3: PERSONNEL PARTICIPATING David Schol
Page 7 and 8: Gauss, G.A., 1979: Tonga offshore s
Page 9: APPENDIX A NARRATIVE 1800hrs GMT 26
Page 13 and 14: Group 4: Limestone foraminifera. Ex
Page 15: Dredge Site 0-7 Amount recovered wa

Multichannel seismic survey sonobuoy refraction survey and ...

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