DOI: 10.5281/zenodo.6758018
title: Low-fold seismic reflection data acquired across the Northern Hikurangi subduction margin and incoming Hikurangi Plateau, New Zealand

description: Two-dimensional seismic reflection data were acquired on two surveys of the Northern Hikurangi subduction margin, New Zealand in 2011 and 2015. The survey data were collected to support research of tectonic structure, slow slip processes, stratigraphic architecture, and thermal state of the subduction margin and incoming plate, as well as to support ocean-floor drilling associated with IODP Expeditions 372 and 375. The surveys include (1) R/V <em>Tangaroa</em> NIWA voyage TAN1114 undertaken in 2011 by the National Institute of Water and Atmospheric Research (NIWA) and GNS Science, as part of the <em>OS2020 Northern Hikurangi Margin Geohazards</em> survey; and (2) R/V <em>Rodger Revelle</em> cruise RR1508 undertaken in 2015 by Oregon State University as part of the <em>Subduction Thrust Investigation of New Zealand using Geothermics and Seismics (STINGS)</em> project (see Figure 1). TAN1114 voyage was funded by the New Zealand Government Oceans 2020 Programme, and core research programme funding by NIWA and GNS Science. Cruise RR1508 was funded by NSF grants OCE-1355878 and OCE-1355870. <strong>R/V <em>Tangaroa</em> TAN1114 Seismic Data</strong> <strong>Data Acquisition:</strong> The seismic system used on R/V <em>Tangaroa</em> during the 2011 National Institute of Water and Atmospheric Research (NIWA) survey TAN1114 included a source comprising two Sodera 45/105 GI guns operated in true GI mode. The guns were deployed 35 m behind the vessel RV <em>Tangaroa</em> at 5 m water depth. Lines TAN1114-01 to -13, and part of line 14 were acquired with a shot interval of 10.8 seconds (~25 m sailing at 4.5 knots), providing a nominal coverage of 12-fold data. Part of line TAN1114-14 and lines 15-23 were acquired with a shot interval of 21.6 seconds (~50 m sailing at 4.5 knots), providing a nominal 6-fold coverage. Data were recorded on a Geometrics GeoEel 48-channel seismic streamer with 6 X 100 m active sections, and a group interval of 12.5 m. The streamer was deployed at a depth of 7.5 m, apart from line TAN1114-01 where it was towed at 5 m depth. Depth control was maintained with a CSMX depth control system including three DigiCourse 5011 compass birds. The record length was 8 s and the sample rate 2 ms. Differential GPS was used for positioning. Table 1 summarises TAN1114 recording parameters and Table 2 lists TAN1114 lines acquired and processed. TAN1114 line coordinates are detailed in Table 3. <strong>Data Processing:</strong> A total of 29 seismic lines were processed providing 1350 km of multichannel seismic reflection data. The lines were processed to post-stack time-migrated SEGY sections, using GNS Science GLOBE CLARITAS. With allowance for overlap of line segments the data were grouped into 51167 shot-point locations. Raw data were written to disk as IBM standard SEG-Y files. IBM Claritas Extended SEG-Y data were written to disk after geometry was added, after stack, and after migration. Shots were CDP sorted from disk during the stacking process to avoid creating large and unnecessary separate CDP sorted files. Post-stack migration (finite difference migration) has been applied to the stacked sections to produce a dip-true image, this results in clearer resolution of structural features such as faults and folds, and of detailed sedimentary features such as on-lapping and truncated reflections. Sea-floor multiple reflections disturb structural imaging especially in water depths less than 500 m. All seismic data are written to disk as processed sections in SEG-Y format. Line TAN1114-A is a composite splice including parts of lines TAN1114-4A, -6A and 7A. Details of the TAN1114 processing parameters are given in Table 4 and SEG-Y trace headers in Table 5. <strong>R/V <em>Rodger Revelle</em> RR1508 Seismic Data</strong> <strong>Data Acquisition:</strong> The 2015 R/V <em>Rodger Revelle</em> survey RR1508 used a seismic system operated by Scripps Institute of Oceanography. Of two sub-regions surveyed during this cruise, only data from the northern Hikurangi margin are presented here. The seismic system used was similar to that on <em>Tangaroa</em> TAN1114, including a source comprising two Sodera 45/105 GI guns operated in true GI mode. The guns were deployed at a depth of 3.5 m and the shot spacing was 25 m. Data were recorded on a Geometrics GeoEel 48-channel seismic streamer with 6 X 100 m active sections, and a group interval of 12.5 m. The streamer was deployed at a depth of 3.5 m. During acquisition of the HKS01 lines, only the nearest 40 data channels were recorded. The record length was 8 s and the sample rate 1 ms. Differential GPS was used for positioning. Table 6 summarises RR1508 recording parameters and Table 7 lists RR1508 lines acquired and processed. <strong>Data Processing: </strong>A total of 13 HKS01 seismic lines were processed to post-stack time-migrated SEGY sections, using GNS Science GLOBE CLARITAS. Data processing included application of geometry, sorting, trace editing, normal moveout correction, stack, filtering and finite difference migration. All seismic data are written to disk as processed sections in SEG-Y format. Details of the RR1508 processing parameters are given in Table 8 and SEG-Y trace headers in Table 9. <strong>List of files</strong> Figure 1. TAN1114 and RR1508 seismic line locations on the northern Hikurangi margin. Table 1. Summary of TAN1114 recording parameters. Table 2. Summary of TAN1114 lines acquired and processed. Table 3. Summary of TAN1114 line coordinates. Table 4. Summary of TAN1114 seismic processing sequence. Table 5. Summary of TAN1114 SEG-Y trace headers. Table 6. Summary of RR1508 recording parameters. Table 7. Summary of RR1508 lines acquired and processed. Table 8. Summary of RR1508 seismic processing sequence. Table 9. Summary of RR1508 SEG-Y trace headers. Processed SEGY seismic data TAN1114-01.sgy TAN1114-02.sgy TAN1114-03.sgy TAN1114-04.sgy TAN1114-04A.sgy TAN1114-05.sgy TAN1114-06.sgy TAN1114-06A.sgy TAN1114-07.sgy TAN1114-07A.sgy TAN1114-08.sgy TAN1114-09.sgy TAN1114-10.sgy TAN1114-10B.sgy TAN1114-11.sgy TAN1114-12.sgy TAN1114-12T.sgy TAN1114-13.sgy TAN1114-14.sgy TAN1114-15.sgy TAN1114-16.sgy TAN1114-17.sgy TAN1114-18.sgy TAN1114-19.sgy TAN1114-20.sgy TAN1114-21.sgy TAN1114-22.sgy TAN1114-23.sgy TAN1114-A.sgy RR1508-HKS01_01.sgy RR1508-HKS01_02.sgy RR1508-HKS01_02A.sgy RR1508-HKS01_03.sgy RR1508-HKS01_04.sgy RR1508-HKS01_05.sgy RR1508-HKS01_05A.sgy RR1508-HKS01_06.sgy RR1508-HKS01_07.sgy RR1508-HKS01_08.sgy RR1508-HKS01_09.sgy RR1508-HKS01_09A.sgy RR1508-HKS01_10.sgy