In Situ Stress and Pore Pressure in the Deep Interior of the Nankai Accretionary Prism, Integrated Ocean Drilling Program Site C0002

Kitajima, H.; Saffer, D. M.; Sone, H.; Tobin, H. J.; Hirose, Takehiro

doi:10.1002/2017gl075127

Cited by 22 publications

(55 citation statements)

References 39 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…S hmin and S Hmax gradually increase from 33.2 and 49.4 MPa at 975 mbsf to 57.1 and 139.6 MPa at 3,005 mbsf under hydrostatic conditions, respectively. Comparing with previous in situ stress estimation (Chang & Song, ; Kitajima et al, ), we find that their results fall between our estimated values of S hmin and S Hmax , confirming that our method provides realistic constraints on S hmin and S Hmax .…”

Section: Discussionsupporting

confidence: 86%

“…Black dashed line is overburden stress S v (Tobin et al, 2015). S Hmax and S hmin estimated in previous studies are also shown (Chang & Song, 2016;Kitajima et al, 2017). us to determine the strength and stress around the target research fields when materials for mechanical tests are limited. In addition, our estimation provides more realistic strength profile within the accretionary prism by accounting for porosity dependences, in contrast to the simple strength profile based on the Coulomb criteria with constant values of the unconfined compressive strength and coefficient of internal friction.…”

Section: Discussionmentioning

confidence: 88%

“…The minimum value of S hmin and the maximum value of S Hmax gradually increase from 33.2 and 49.4 MPa at 975 mbsf to 57.1 and 139.6 MPa at 3,005 mbsf, respectively (Figure ). We compare our results with in situ stress estimation at Site C0002 based on the borehole breakout analysis (Chang & Song, ) and empirical relations between compressional wave velocity, porosity, and stress states (Kitajima et al, ). Their estimated in situ stresses with an assumption that the stress state is in either normal or strike‐slip regime fall between our estimated S hmin and S Hmax values.…”

Section: Estimation Of In Situ Strengthmentioning

confidence: 98%

See 2 more Smart Citations

Strength Profile of the Inner Nankai Accretionary Prism at IODP Site C0002

Kitamura

Kitajima

Sone

et al. 2019

Geophysical Research Letters

Self Cite

View full text Add to dashboard Cite

The strength of accretionary prisms is important for understanding their formation and the generation of earthquakes along the underlying plate boundary faults. We establish a continuous depth profile of rock strength and possible ranges of the minimum and maximum horizontal stresses (Shmin and SHmax) based on indentation tests on cuttings samples at the Integrated Ocean Drilling Program (IODP) Site C0002 in the Nankai accretionary prism. The rock strength (i.e., differential stress) increases with depth from 5.1 and 11.0 MPa at 975 meters below the seafloor (mbsf) to 22.8 and 59.6 MPa at 3005 mbsf in normal and reverse faulting regimes, respectively. The minimum value of Shmin and the maximum value of SHmax range from 33.2 and 49.4 MPa at 975 mbsf to 57.1 and 139.6 MPa at 3005 mbsf, respectively. Our estimated strength, in combination with Coulomb wedge model, may improve understanding of the evolution of accretionary prisms.

show abstract

Section: Discussionsupporting

confidence: 86%

Section: Discussionmentioning

confidence: 88%

Section: Estimation Of In Situ Strengthmentioning

confidence: 98%

See 1 more Smart Citation

Strength Profile of the Inner Nankai Accretionary Prism at IODP Site C0002

Kitamura

Kitajima

Sone

et al. 2019

Geophysical Research Letters

Self Cite

View full text Add to dashboard Cite

show abstract

“…Previous researches suggested that drilling energy corresponds to an approximation of in situ compressive rock strength if the background energy could be minimized (Karasawa et al 2002;Hoberock and Bratcher 1996). However, comparison between EST and triaxial strength or other strength estimation from logging P-wave velocity (Kitajima et al 2017) for site C0002 in the Nankai trough indicated that the values of EST may be overestimated (Hamada et al 2018). Therefore, EST is considered only as an "equivalent strength," which can reflect the relative in-situ rock strength (triaxial shear strength) over a wide depth scale.…”

Section: Evaluation Of Estmentioning

confidence: 99%

In-situ mechanical weakness of subducting sediments beneath a plate boundary décollement in the Nankai Trough

Hamada

Hirose

Ijiri

et al. 2018

Prog Earth Planet Sci

Self Cite

View full text Add to dashboard Cite

The study investigates the in-situ strength of sediments across a plate boundary décollement using drilling parameters recorded when a 1180-m-deep borehole was established during International Ocean Discovery Program (IODP) Expedition 370, Temperature-Limit of the Deep Biosphere off Muroto (T-Limit). Information of the in-situ strength of the shallow portion in/around a plate boundary fault zone is critical for understanding the development of accretionary prisms and of the décollement itself. Studies using seismic reflection surveys and scientific ocean drillings have recently revealed the existence of high pore pressure zones around frontal accretionary prisms, which may reduce the effective strength of the sediments. A direct measurement of in-situ strength by experiments, however, has not been executed due to the difficulty in estimating in-situ stress conditions. In this study, we derived a depth profile for the in-situ strength of a frontal accretionary prism across a décollement from drilling parameters using the recently established equivalent strength (EST) method. At site C0023, the toe of the accretionary prism area off Cape Muroto, Japan, the EST gradually increases with depth but undergoes a sudden change at~800 mbsf, corresponding to the top of the subducting sediment. At this depth, directly below the décollement zone, the EST decreases from~10 to 2 MPa, with a change in the baseline. This mechanically weak zone in the subducting sediments extends over 250 m (~800-1050 mbsf), corresponding to the zone where the fluid influx was discovered, and high-fluid pressure was suggested by previous seismic imaging observations. Although the origin of the fluids or absolute values of the strength remain unclear, our investigations support previous studies suggesting that elevated pore pressure beneath the décollement weakens the subducting sediments.

show abstract

“…Chang et al (2010) estimated stress magnitudes from borehole breakout analyses and rock mechanics and showed that the horizontal stress becomes larger than the vertical stress at 1000-1400 mbsf. Meanwhile, Kitajima et al (2017) estimated stress magnitudes from the empirical relationship between P-wave velocity and porosity levels and found that the horizontal stress gets larger than vertical stress at 1000-1400 mbsf. Hamada et al (2018) estimated the strength of rock using drilling parameters and found strength increases at around 2800 mbsf, which may also correspond to the depth where the estimated in situ porosity shows a stepwise decrease.…”

Section: Geological Interpretationsmentioning

confidence: 99%

Simultaneous estimation of in situ porosity and thermal structure from core sample measurements and resistivity log data at Nankai accretionary prism

Yabe

Fukuchi

Hamada

et al. 2019

Earth Planets Space

View full text Add to dashboard Cite

The shallow accretionary prism of the Nankai Trough is a location where both large interplate earthquakes and slow earthquakes occur. Since the physical properties of sedimentary materials are important topics for understanding the structure of the prism, numerous ocean drilling expeditions have been conducted in that region to obtain logging data and core samples. Although the physical properties of the obtained samples are normally measured onboard immediately after coring, estimations of in situ physical properties are difficult because of differences in laboratory and in situ physical conditions. Herein, we propose a new method for estimating in situ porosity from downhole electrical resistivity log data that evaluates in situ porosity and thermal structure simultaneously using correlations between the porosity and resistivity, and between the porosity and thermal conductivity that were established based on laboratory measurements. When constructing physical property correlations, X-ray computed tomography data play an important role in estimating the porosity of samples from which resistivity or thermal conductivity were measured. To validate our method, we compared the estimation with density log data collected at Site C0002 and found that the estimated in situ porosity shows good agreement with the in situ porosity converted from density log data. A comparison with porosity measured onboard for core and cutting samples showed that they are consistent with each other. With this new method, continuous distributions of in situ porosity and thermal structure can be estimated simultaneously based on resistivity log data and heat flow, which are basic quantities acquired during ocean drilling science expeditions. which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.

show abstract

In Situ Stress and Pore Pressure in the Deep Interior of the Nankai Accretionary Prism, Integrated Ocean Drilling Program Site C0002

Cited by 22 publications

References 39 publications

Strength Profile of the Inner Nankai Accretionary Prism at IODP Site C0002

Strength Profile of the Inner Nankai Accretionary Prism at IODP Site C0002

In-situ mechanical weakness of subducting sediments beneath a plate boundary décollement in the Nankai Trough

Simultaneous estimation of in situ porosity and thermal structure from core sample measurements and resistivity log data at Nankai accretionary prism

Contact Info

Product

Resources

About