NanTroSEIZE: The IODP Nankai Trough Seismogenic Zone Experiment

Shear strength of sediments approaching subduction in the Nankai Trough, Japan as constraints on forearc mechanics

“…Scientific drilling has focused on this region by targeting the rupture area of the 1944 earthquake, as inferred by tsunami and seismic waveform inversions [Tanioka and Satake, 2001;Kikuchi et al, 2003]. During the first stage of the multiexpedition Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE), several drill sites penetrated two major fault zones at shallow depths (< $1 km): the frontal thrust region and a major out-of-sequence thrust fault (megasplay) as well as a site landward in the Kumano basin designed to ultimately reach the seismogenic zone [Tobin and Kinoshita, 2006;Kinoshita et al, 2009]. These sites are located offshore the Kii Peninsula, known as the Kumano transect.…”

Scientific Drilling

“…NanTroSEIZE is a multiexpedition, multistage IODP drilling program focused overall on understanding the mechanics of seismogenesis and rupture propagation along subduction plate boundary faults (Tobin and Kinoshita, 2006). This program includes a coordinated effort to characterize (through integrating core/log with seismic images), sample (core/cuttings), and instrument (borehole observatory) the plate boundary fault system near the updip limit of the locked zone of Tonankai great earthquakes at 5-7 km below seafloor (Figs.…”

NanTroSEIZE Stage 1 Expeditions 314, 315, and 316: First Drilling Proram of the Nankai Trough Seismogenic Zone Experiment

“…The fundamental goal of NanTroSEIZE science plan (Tobin and Kinoshita, 2006b) is to access, sample, and then instrument the faults in aseismic and seismogenic regions of the megathrust system. This involves drilling of key elements of the active plate boundary system at several locations off the Kii Peninsula, from the shallow onset of the plate interface to depths where earthquake slip and locking takes place (Figs.…”

“…2; Moore et al, 2009). A series of sites targeted the thrust sheet, fault zone, and footwall of the lower of these branches, which was judged to be the most active and most significant of the seismically imaged splays (Tobin and Kinoshita, 2006b;Moore et al, 2009). …”

“…Integrated Ocean Drilling Program (IODP) Expeditions 314, 315, and 316 were carried out as a unified program of drilling collectively known as Stage 1 of the Nankai Trough Seismogenic Zone Experiment, or NanTroSEIZE, the first multi-stage complex drilling project in IODP and the most ambitious effort in scientific ocean drilling to date (Tobin and Kinoshita, 2006b;Kinoshita et al, 2006). The first of four planned operational stages, the Stage 1 expeditions were conducted aboard the new riser-capable drilling vessel Chikyu from September 2007 to February 2008, and were Chikyu's inaugural IODP expeditions.…”