Expedition 338 summary

Abstract

The Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE) is a multidisciplinary scientific project designed to investigate fault mechanics and seismogenesis along subduction megathrusts through reflection and refraction seismic imaging, direct sampling, in situ measurements, and long-term monitoring in conjunction with laboratory and numerical modeling studies. The fundamental scientific objectives of NanTroSEIZE include characterizing the nature of fault slip and strain accumulation, fault and wall rock composition, fault architecture, and state variables throughout an active plate boundary system. As part of the NanTroSEIZE program, operations during Integrated Ocean Drilling Program (IODP) Expedition 338 were planned to extend and case riser Hole C0002F, begun during IODP Expedition 326 in 2010, from 856 to 3600 meters below seafloor (mbsf). Riser operations extended the hole to 2005.5 mbsf, collecting a full suite of logging-while-drilling (LWD) and measurement-while-drilling, mud gas, and cuttings data. However, because of damage to the riser during unfavorable wind and strong current conditions, riser operations were cancelled. Hole C0002F was suspended at 2005.5 mbsf and left for reentry during future riser drilling operations, which will deepen the hole to penetrate the megasplay fault at 5000 mbsf.Contingency riserless operations included coring at Site C0002 (200-505, 902-940, and 1100.5-1120 mbsf), LWD at IODP Sites C0012 (0-710 mbsf) and C0018 (0-350 mbsf), and LWD and coring at IODP Sites C0021 (0-294 mbsf) and C0022 (0-420 mbsf). These sites and drilling intervals represent key targets not sampled during previous NanTroSEIZE expeditions but relevant to comprehensively characterize the alteration stage of the oceanic basement input to the subduction zone, the early stage of Kumano Basin evolution, gas hydrates in the forearc basin, recent activity of the shallow megasplay fault zone system, and submarine landslides.

Data report: clay mineral assemblages and illite/smectite diagenesis in cuttings from Hole C0002P, IODP Expedition 348, Nankai Trough accretionary prism

“…F3). During Expedition 338 (Strasser et al, 2014a), that same boundary in Hole C0002F was placed at 1740 mbsf (Fig. F3).…”

“…F1) numerous times over the past four decades Kagami, Karig, Coulbourn, et al, 1986;Shipboard Scientific Party, 1991;Shipboard Scientific Party, 2001;Moore et al, 2005). The Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE) is the latest of those efforts Screaton et al, 2009;Underwood et al, 2010;Expedition 333 Scientists, 2012;Strasser et al, 2014a; see the "Expedition 348 summary" chapter [Tobin et al, 2015a]). Integrated Ocean Drilling Program (IODP) Site C0002 is located on the NanTroSEIZE transect near the seaward edge of the Kumano Basin (Fig.…”

“…That configuration of two cutting tools resulted in thorough mixing of cuttings over a vertical interval of at least 43.8 m (Strasser et al, 2014a). Hole C0002N was drilled without the reamer bit, so the vertical extent of mixing was reduced considerably.…”

Data report: clay mineral assemblages in the upper Shikoku Basin, results from IODP Expedition 333, Sites C0011 and C0012

“…The Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE) comprises several sampling expeditions that crossed the subduction system offshore southwest Japan Screaton et al, 2009;Tobin et al, 2009Tobin et al, , 2015Underwood et al, 2010;Strasser et al, 2014; see the "Expedition 333 summary" chapter [Expedition 333 Scientists, 2012a]). Integrated Ocean Drilling Program (IODP) Expeditions 322 and 333 concentrated on coring the inputs of sediment to the subduction zone (see Underwood et al, 2010; also see the "Expedition 333 summary" chapter [Expedition 333 Scientists, 2012a]).…”

Data report: Pleistocene planktonic foraminifers from the Kumano forearc basin, IODP Expedition 338 Holes C0002K and C0002L

“…However, because of damage to the riser system under severe weather conditions during the expedition, riser operations were canceled. Contingency riserless coring at Site C0002 was conducted to sample the upper part of the forearc basin sediment (see the "Expedition 338 summary" chapter [Strasser et al, 2014a]). …”