New Zealand 3D full waveform inversion (NZ3D-FWI) 2017-2018 field acquisition report

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Bell R, Gray M, Morgan J, Warner M, Fagereng A, McNeill L, Jacobs K, Henrys SA, Fry B, Watkins S, Lacey H, Black JA, Lane V, Daly D, Lindsay D, Bangs N, Arai R, Kodaira S, NZ3D-FWI team. 2019. New Zealand 3D full waveform inversion (NZ3D-FWI) 2017-2018 field acquisition report. Lower Hutt (NZ): GNS Science. 79 p. (GNS Science report; 2019/71). doi:10.21420/ZZ8R-QR04.

This report documents the acquisition and archiving of a major 3D active-source and passive seismic imaging experiment, NZ3D-FWI. The NZ3D-FWI project aims to image the Hikurangi subduction zone (upper and lower plates and plate boundary fault) along the north Hikurangi margin where shallow slow slip events occur. The primary aim of the project is to collect data optimally to produce high-resolution velocity models using Full-waveform inversion (FWI). The deployment, servicing and collection of the NZ3D-FWI onshore instruments between December 2017 and October 2018 was conducted by Imperial College London, GNS Science, Cardiff University, University of Southampton and Victoria University of Wellington. A 15 x 60 km volume of 3D seismic reflection data was collected offshore of Gisborne by the R/V Marcus Langseth, funded by the National Science Foundation (NSF, USA), the Natural Environment Research Council (NERC, UK) and GNS Science. 99 ocean bottom seismographs were deployed in the 3D seismic reflection volume footprint by JAMSTEC and GNS Science. The onshore NZ3D-FWI deployment included 49 CMG-6TD broadband seismometers from NERC SEIS-UK, which were deployed from December 2017 to October 2018 and detected airgun shots from the 3D seismic reflection survey and local and teleseismic earthquakes over the nine-month period. 119 short-period DATA-CUBE3 instruments loaned from the German Instrument Pool Potsdam (GIPP), and 25 short-period GSX3 instruments from the Earthquake Research Institute (ERI), Tokyo, were deployed between December 2017 and February 2018. These recorded airgun sources and seismicity over a two-month period. The deployment involved a broader array (the Gisborne array), which covered an area of 15 x 30 km with an instrument spacing of ∼2 km. These instruments will primarily be used to construct a high-resolution onshore-offshore velocity model in conjunction with the data collected by the offshore instruments. A denser array of instruments (the Waimata Valley array) with spacing of ∼500 m is aimed at understanding mud volcano processes using active and passive source methods. (auth)