Seismogenesis at Hikurangi Integrated Research Experiment (SHIRE) Report of RV Tangaroa cruise TAN1710, 23 Oct-20 Nov 2017

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Barker, D.H.N.; Van Avendonk, H.; Fujie, G. 2019 Seismogenesis at Hikurangi Integrated Research Experiment (SHIRE) Report of RV Tangaroa cruise TAN1710, 23 Oct-20 Nov 2017. Lower Hutt, N.Z.: GNS Science. GNS Science report 2019/01. 22 p. + 3 appendices; doi: 10.21420/ H28Y-5N43

 

Abstract:
In October and November 2017, The R/V Tangaroa was engaged in a large onshore-offshore seismic experiment on the Hikurangi margin of North Island, New Zealand, with a team of scientists from New Zealand, the United States, and Japan. This data acquisition campaign was part of the SHIRE project (“Seismogenesis at Hikurangi Integrated Research Experiment”). The goals of this Earth science project were: 1) to obtain constraints on the deep structure of the Hikurangi margin, with an emphasis on Raukumara peninsula in the north, and 2) to record seismicity over several months. During the marine seismic experiment, we used the acoustic source and streamer of the US academic research vessel R/V Marcus Langseth (cruise MGL1708) to gather marine seismic reflection and refraction data. Another group of scientists deployed seismographs on the Raukumara peninsula to record the acoustic source of the Langseth, as well as local earthquakes. The R/V Tangaroa took part in the SHIRE project to deploy and recover a fleet of 100 short-period ocean-bottom seismometers (OBSs) from the Japan Agency for Marine-Earth Science and Technology (JAMSTEC). Cruise TAN1710 of the New Zealand vessel R/V Tangaroa started with mobilization on October 23, 2017, in Wellington. The objective of TAN1710 was to deploy and recover OBSs at 114 sites along four major lines. SHIRE Line 1 is oriented NW–SE between the Bay of Plenty and the northern Hikurangi Trough. Land seismometers on the Raukumara peninsula section of this transect recorded the Langseth source as well. SHIRE Line 2 is a margin-crossing transect on the southern Hikurangi margin, while Line 3 and Line 4 are two margin-parallel lines on the continental shelf and on the Hikurangi Plateau, respectively. The science team on board the R/V Tangaroa first dropped 93 instruments on the four transects by October 29. After the R/V Marcus Langseth started surveying these geophysical transects on November 1, 21 of the instruments from Line1 and Line 3 were repositioned on SHIRE Line 4. The last OBS was recovered on November 15. Thanks to the dedicated work of all science teams, especially the JAMSTEC group and the officers and crew of the R/V Tangaroa, all OBS instruments were retrieved with excellent data. The R/V Tangaroa returned to Wellington on November 19, and equipment was demobilized on November 20. TAN1710 was the first of three voyages undertaking OBS operations in cooperation with seismic work by RV Marcus G Langseth and was also referred to as ORCSS1 (Ocean bottom seismograph deployment and ReCovery in support of Seismic Surveys). Two other RV Tangaroa voyages undertook OBS deployment (TAN1712) and recovery (TAN1803) activities in conjunction with the NZ3D seismic survey offshore Gisborne (ORCSS2 and ORCSS3, respectively). (auth)