Marine‐controlled source electromagnetic study of methane seeps and gas hydrates at Opouawe Bank, Hikurangi Margin, New Zealand

• DOI: 10.1002/2016jb013702
• Publication Date: 2017-04-17T19:47:21Z
• Authors: Katrin Schwalenberg; Dennis Rippe; Stephanie Koch; Carsten Scholl
• Keywords: Seafloor Spreading; Clathrate hydrate; Petroleum seep; Cold seep; Outcrop; Seabed

Abstract Marine controlled source electromagnetic (CSEM) data have been collected to investigate methane seep sites and associated gas hydrate deposits at Opouawe Bank on the southern tip of Hikurangi Margin, New Zealand. The bank is located in about 1000 m water depth within stability field. are characterized by active venting typical fauna accompanied with patchy carbonate outcrops seafloor. Below seeps, migration pathways reach from below bottom‐simulating reflector (at around 380 sediment depth) toward seafloor, indicating free transport into shallow CSEM acquired a seafloor‐towed, electric multi‐dipole system measuring inline component three profiles analyzed using 1‐D 2‐D inversion techniques. High‐resolution 3‐D multichannel seismic same area. electrical resistivity models show several zones highly anomalous resistivities (>50 Ωm) which correlate high amplitude reflections top narrow vertical conduits, coexistence hydrates zone. Away seeps normal background between ~1 2 Ωm. Archie's law has applied estimate gas/gas saturations seeps. At intermediate depths 50 200 40 80% may be dominating pore filling constituent. 10 dominates as plumes suggest.