TAN1712-1803 voyage report for ocean bottom seismograph recovery in support of seismic surveys (ORCSS 2 and 3): 3D survey offshore East Coast North Island

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Kellett, R.L.; Bassett, D.; Arai, R.; Obana, K.; Stucker, V.K.; Henrys, S.A.; Davidson, S.R.; Hart, R.J.; Kodaira, S.; Maekawa, T.; Michailos, K.; Mori, S.; O'Brien, G.A.; Saijo, T.; Terada, I.; Tsukuda, K.; Bangs, N.L.; Bell, R. 2019 TAN1712-1803 voyage report for ocean bottom seismograph recovery in support of seismic surveys (ORCSS 2 and 3): 3D survey offshore East Coast North Island. Lower Hutt, N.Z.: GNS Science. GNS Science report 2018/36. 31 p. + appendices; doi: 10.21420/A8MV-S722

Abstract:

Deployment and recovery of Ocean Bottom Seismometers (OBSs) occurred on three separate cruises of the RV Tangaroa between September 2017 and April 2018 (ORCSS 1 to 3), as part of a multi-national seismic experiment on the Hikurangi subduction margin off the east coast of the North Island. Two cruises (ORCSS 2 TAN1712 and ORCSS 3 TAN1803) were dedicated to the NZ3D experiment where 100 OBSs were positioned on a dense grid offshore Gisborne. TAN1712 deployed the instruments between December 17th and December 19th, 2017, in a rectangular area of 6 km by 48 km centred on the IODP Leg 372/375 Hikurangi Margin drill holes. Cruise TAN1803 recovered the instruments between March 28th and April 6th, 2018. During the three month deployment, the instruments recorded active airgun shots from the RV Marcus Langseth that was conducting a 3D streamer survey across the NZ3D area (Voyage MGL1801). A subset of the instruments, with longer battery lives, recorded earthquakes for the period following the completion of the active source experiment. A total of 97 instruments were recovered on TAN1803 with one additional instrument recovered by a recreational fisherman and returned to GNS. In addition to the OBS deployment, a number of additional tasks were completed. Seawater samples were collected on a transect across the entrance to Hawke Bay during TAN1712 for a collaborator at Hawke’s Bay Regional Council. Cruise TAN1803 commenced with the delivery of O-rings to the scientific drilling vessel RV JOIDES Resolution. These O-rings were crucial for the successful installation of borehole observatories. In total the ORCSS 2 and 3 voyages were very successful with a 98% success rate in instrument deployment and recovery achieved in significantly less time than budgeted. (auth)