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

Tobin, H. J.; Kinoshita, Masataka; Ashi, Juichiro; Lallemant, S.; Kimura, Gaku; Screaton, E.; Thu, M.K.; Masago, Hideki; Curewitz, D.

doi:10.2204/iodp.sd.8.01.2009

Cited by 4 publications

(2 citation statements)

References 27 publications

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“…To determine the appropriate friction law and the value of effective normal stress for actual subduction zones, more rock laboratory experiments and in-situ observations such as those by the deep ocean-floor drilling vessel "Chikyu" (e.g., Tobin et al, 2009) are needed. In the following sections, we discuss our simulation results on the basis of the slowness law.…”

Section: Discussionmentioning

confidence: 99%

Migration process of very low-frequency events based on a chain-reaction model and its application to the detection of preseismic slip for megathrust earthquakes

et al. 2012

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In order to reproduce slow earthquakes with short duration such as very low frequency events (VLFs) migrating along the trench direction as swarms, we apply a 3-D subduction plate boundary model based on the slowness law of rate-and state-dependent friction, introducing close-set numerous small asperities (rate-weakening regions) at a depth of 30 km under high pore pressure condition, in addition to a large asperity. Our simulation indicates that swarms of slip events occur repeatedly at the small asperities, and these events are similar to the observed slow earthquake group, especially to VLF, on the basis of the relation between characteristic duration and seismic moment. No slip events occur there without the small asperities, which mean that the close-set numerous small asperities may be one of the necessary conditions for generating the short-duration slow earthquakes such as VLFs. In the preseismic stage of the megathrust earthquakes that occur at the large asperity, the swarms of VLFs have higher migration speeds and higher moment release rate as well as shorter recurrence interval. Thus, monitoring the migration of slow earthquakes may be useful in imaging the preseismic slip of megathrust earthquakes.

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Section: Discussionmentioning

confidence: 99%

Migration process of very low-frequency events based on a chain-reaction model and its application to the detection of preseismic slip for megathrust earthquakes

et al. 2012

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“…In order to understand the state and properties of the Nankai Trough seismogenic zone, a series of ocean scientific drillings has been conducted since 2007 as part of the Integrated Ocean Drilling Program (IODP) Nankai Trough Seismogenic Zone Experiments (NanTroSEIZE) (Fig. 1; Tobin and Kinoshita 2006;Kinoshita et al 2009;Expedition 326 Scientists 2011;Henry et al 2012;Kopf et al 2011;Saffer et al 2010;Saito et al 2010;Screaton et al 2009;Strasser et al 2014;Tobin et al 2009;Tobin et al 2014;Kinoshita et al 2014;Kopf et al 2016). The ultimate goal of NanTroSEIZE is to core, log, and monitor the locked region of the plate boundary megathrust approximately 5 km below the seafloor at Site C0002.…”

Section: Tectonic Setting and Previous Researchmentioning

confidence: 99%

Geometrical dependence on the stress and slip tendency acting on the subduction megathrust of the Nankai seismogenic zone off Kumano

Kinoshita

Shiraishi

Demetriou

et al. 2019

Prog Earth Planet Sci

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We assess the dependence of megathrust geometry near the updip edge of the Nankai seismogenic zone according to the slip tendency of the megathrust based on a reprocessed 3D PSDM seismic volume image and International Ocean Discovery Program (IODP) NanTroSEIZE drilling data off the coast of the Kii Peninsula, central Japan. The plate boundary fault surface is manually picked from the 3D seismic volume and is divided into three groups: low dip (10°-15°) trending NW to N in the NE region, intermediate dip (~25°) trending north in the western region, and high dip (30°-40°) trending NW in the SE corner. We then calculate the overburden (S v ) by converting the modeled 3D velocity to bulk density. Here, S v ranges from 100 MPa near the SW edge to 160 MPa on the NE corner. In order to derive horizontal principal stresses (S H and S h ) and the pore fluid pressure (P p ), we assign the ratio of horizontal-to-vertical principal stresses, r (= S H /S v ), and the ratio of pore fluid pressure-to-vertical stress, λ (= P p /S v ) based on IODP drilling data. The directions of S H and the slip on the fault are set parallel to the plate convergence vector (N55W). Assuming a triaxial condition (S H > S h = S v ), the slip tendency (Ts) can be calculated from the dip angle and dip azimuth of the fault surface, r, and λ. We found that Ts is sensitive to the variation in fault geometry. For r = 1.2 and λ = 0.7 (normalized pore pressure ratio λ* = 0.25), Ts is low (~0.1) in the low-angle dip region and higher (> 0.2) in the high-angle dip region. This suggests that the high-angle fault is optimally oriented under this condition. Low Ts in the low-angle dip region would correspond to a weaker region due to a low frictional strength, assuming that the fault surface should slip simultaneously. Using the high pore pressure ratio (λ*~0.85) beneath the fault zone, the fault beneath IODP Site C0002 is very close to failure if r > 1.2.

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Major Scientific Achievements of the Integrated Ocean Drilling Program

Becker

2014

Earth and Life Processes Discovered From Subseafloor Environments - A Decade of Science Achieved by the Integrated Ocean Drilli

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

Cited by 4 publications

References 27 publications

Migration process of very low-frequency events based on a chain-reaction model and its application to the detection of preseismic slip for megathrust earthquakes

Migration process of very low-frequency events based on a chain-reaction model and its application to the detection of preseismic slip for megathrust earthquakes

Geometrical dependence on the stress and slip tendency acting on the subduction megathrust of the Nankai seismogenic zone off Kumano

Major Scientific Achievements of the Integrated Ocean Drilling Program

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