IODP Expedition 338: NanTroSEIZE Stage 3: NanTroSEIZE plate boundary deep riser 2

[摘要] The Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE) is designed toinvestigate fault mechanics and seismogenesis along a subduction megathrust,with objectives that include characterizing fault slip, strain accumulation,fault and wall rock composition, fault architecture, and state variablesthroughout an active plate boundary system. Integrated Ocean Drilling Program(IODP) Expedition 338 was planned to extend and case riser Hole C0002F from856 to 3600 meters below the seafloor (m b.s.f.). Riser operations extendedthe hole to 2005.5 m b.s.f., collecting logging-while-drilling (LWD) andmeasurement-while-drilling, mud gas, and cuttings data. Results reveal twolithologic units within the inner wedge of the accretionary prismthat areseparated by a prominent fault zone at ~ 1640 m b.s.f. Due to damageto the riser during unfavorable winds and strong currents, riser operationswere suspended, and Hole C0002F left for re-entry during future riserdrilling operations.

Contingency riserless operations included coring at the forearc basin site(C0002) and at two slope basin sites (C0021 and C0022), and LWD at one inputsite (C0012) and at three slope basin sites (C0018, C0021 and C0022). Coresand logs from these sites comprehensively characterize the alteration stageof the oceanic basement input to the subduction zone, the early stage ofKumano Basin evolution, gas hydrates in the forearc basin, and recentactivity of the shallow megasplay fault zone system and associated submarinelandslides.

[学科分类] 地质学