3D fault-zone architecture across the brittle–plastic transition along the Median Tectonic Line, SW Japan: Fault-rock characterization

Katori, Takuma; Shigematsu, Norio; Kameda, J.; Miyakawa, Ayumu; Matsumura, Risa

doi:10.1016/j.jsg.2021.104446

Cited by 9 publications

(5 citation statements)

References 90 publications

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“…Thermal modeling indicates that a shear heating model compatible with the observed results requires a high values of frictional strength and very high slip rates to be maintained for ~0.1 million years (Figures 8 and 11). High differential stresses estimated from mylonite samples from the brittle-ductile transition zone (Katori et al, 2021;Okudaira & Shigematsu, 2012) are consistent with the required high frictional strength. However, several recent studies propose movement on the MTL and other major faults are associated with a low frictional coefficient of less than ~0.2 (Holdsworth, 2004;Imber et al, 2008;Jefferies, Holdsworth, Wibberley, et al, 2006;Wibberley & Shimamoto, 2003.…”

Section: Possible Origins Of Thermal Anomaly Iii: Shear Heatingsupporting

confidence: 71%

“…This study assumes the MTL is vertical and uses the horizontal distance. Previous studies that have examined the present fault dip in the Iitaka district have reported a northerly dip of 60° (Katori et al, 2021; Shigematsu et al, 2012). The assumed dip of the MTL fault zone will influence the perpendicular distance between the sampling points and the central fault plane.…”

Section: Resultsmentioning

confidence: 87%

Section: Resultsmentioning

confidence: 98%

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Recognition of broad thermal anomaly around the median tectonic line in central Kii peninsula, southwest Japan: Possible heat sources

Yamaoka

Wallis

2022

Island Arc

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Application of Raman spectroscopy of carbonaceous material thermometry to samples of metasedimentary rock from the low‐grade Sanbagawa belt in the central Kii peninsula reveals a progressive decrease in temperature from ~390 °C close to the northern boundary, a major continental shear zone—the median tectonic line (MTL)—to ~270 °C and ~7 km to the south and roughly constant temperature distribution thereafter. Within the Sanbagawa belt, the thermal structure is not significantly modified by slip‐on fault boundaries between different geological units or folding. Meso‐ and microstructural observations combined with strain analysis using detrital grains in meta‐mudstone indicate a similar deformation history throughout the area and no correlation between ductile strain and temperature gradients. These observations suggest the observed thermal structure was developed after the main stages of ductile deformation of the Sanbagawa belt were complete and are not due to localized preferential exhumation along with the MTL. The observations also require a heat source along with the MTL. Order of magnitude estimates suggest the influx of warm fluid along the MTL are viable causes of the observed thermal anomaly. Although shear heating would be another possible explanation, thermal calculations require anomalous fast slip rates along the MTL and much greater frictional strength than generally considered reasonable. For these reasons, fluid infiltration is our preferred model.

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Section: Possible Origins Of Thermal Anomaly Iii: Shear Heatingsupporting

confidence: 71%

Section: Resultsmentioning

confidence: 87%

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Recognition of broad thermal anomaly around the median tectonic line in central Kii peninsula, southwest Japan: Possible heat sources

Yamaoka

Wallis

2022

Island Arc

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“…The MTL divides the low-P/high-T Ryoke metamorphic terrain in the north from the high-P/low-T Sanbagawa terrain in the south and is the longest onshore fault in the Japan arc (Wallis and Okudaira 2016). The rocks around the observatory ITA are variably affected by the faultings along the MTL (Shigematsu et al 2012(Shigematsu et al , 2017Mori et al 2015;Katori et al 2021).…”

Section: Geological Settings and Data With Previous Interpretationsmentioning

confidence: 99%

Quantitative logging data clustering with hidden Markov model to assist log unit classification

Yabe

Hamada

Fukuchi

et al. 2022

Earth Planets Space

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Revealing subsurface structures is a fundamental task in geophysical and geological studies. Logging data are usually acquired through drilling projects, which constrain the subsurface structure, and together with the description of drill core samples, are used to distinguish geological units. Clustering is useful for interpreting logging data and making log unit classification and is usually performed by manual inspection of the data. However, the validity of clustering results with such subjective criteria may be questionable. This study proposed the application of a statistical clustering method, the hidden Markov model, to conduct unsupervised clustering of logging data. As logging data are aligned along the drilled hole, they and the geological structure hidden behind such sequential datasets can be regarded as observables and hidden states in the hidden Markov model. When log unit classification is manually conducted, depth dependency of logging data is usually focused. Therefore, we included depth information as observables to explicitly represent depth dependency of logging data. The model was applied to the following geological settings: the accretionary prism at the Nankai Trough, the onshore fault zone at the Kii Peninsula (southwest Japan), and the forearc basin at the Japan Trench. The optimum number of clusters were searched using a quantitative index. The clustering results using the hidden Markov model were consistent with previously reported classifications or lithological descriptions; however, our method allowed a more detailed division of logging data, which is useful to interpret geological structures, such as a fault or a fault zone. Therefore, the use of the hidden Markov model enabled us to clarify assumptions quantitatively and conduct clustering consistently for the entire depth range, even for different geological sites. The proposed method is expected to have wider applicability and extensibility for other types of data, including geochemical and structural geological data. Graphical Abstract

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“…According to their finding, the undeformed shale gradually transits to the strongly deformed shale from level A to level D. To conclude, most of the research was performed to serve the sample collection, and few efforts have been made to predict the planar distribution of different TDSs based on the distribution and intensity of geological structures. Based on structural observation and modeling, Katori et al (2021) constructed the rock deformation distribution patterns on the sides of the Median Tectonic Line (the largest onshore fault of Japan); their research showed that the rock deformation transit with the pattern of "strongly cataclasite, weakly cataclasite, ultramylonite, mylonite, protomylonite" and the tectonite of the same type were distributed in belts parallel to the main structural line.…”

Section: Introductionmentioning

confidence: 99%

Distribution Prediction of Shale Deformation Structures in Tectonically Complex Area Based on Relationship Between Geological Structures and Shale Deformation

Cheng

Jiang

et al. 2022

Front. Earth Sci.

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The alteration of shale structures and properties induced by tectonic activities is an important factor restricting the efficient utilization of shale gas resources. Predicting the distributions of shale deformation structures is of significance for the potential evaluation and favorable area optimization of shale resources in tectonically complex areas. Taking the Wufeng–Longmaxi shale of the southern Sichuan Basin as the research object, deformation observations of shale outcrops and shale core samples were conducted to reveal the distribution patterns of shale deformation structures in fault and fold structures. On this basis, the distribution rules of shale deformation structures in the unexposed areas were predicted by considering the structural framework of the study area. Our research indicated that faults can cause structural deformation in a limited area and that the influences of reverse faults were relatively more significant. Shale near the fault planes of reverse faults usually showed intense folding deformations, with well-developed bedding-parallel and crumpled cleavages. Strong deformation structures (crumpled, mylonitized, scaly, fractured-crumpled, and flaky structure) were distributed. Structural deformations in shale near normal faults were mainly characterized by the increase of tectonic fractures, and shale usually showed cataclastic structure. In the areas affected by strike-slip faults, bedding-perpendicular fractures and the fractures high-angle oblique to bedding planes were well developed. Folds can cause shale to deform in a larger area than faults. Shale in core zones usually displayed strong deformation structures. In the core–limb transitional areas of folds, shale mainly developed bedding-parallel and bedding-perpendicular fractures, and shale usually displayed platy and cataclastic structure. The observed structural deformations in fold limbs were generally weak, and shale usually showed primary structure and weak brittle deformation structures. According to the structural framework of the study area, it is predicted that strong deformation structures are mainly distributed in the core zones of anticlines (especially the tight and closed ones) and near the fault planes of large-scale reverse faults, while medium-intensity brittle deformation structures (platy and cataclastic structure) are distributed in core–limb transitional areas of anticlines and near the normal and strike-slip faults. In the limbs of anticlines and the areas controlled by synclines (mostly wide and gentle), shale mainly shows primary structure and weak brittle deformation structures.

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3D fault-zone architecture across the brittle–plastic transition along the Median Tectonic Line, SW Japan: Fault-rock characterization

Cited by 9 publications

References 90 publications

Recognition of broad thermal anomaly around the median tectonic line in central Kii peninsula, southwest Japan: Possible heat sources

Recognition of broad thermal anomaly around the median tectonic line in central Kii peninsula, southwest Japan: Possible heat sources

Quantitative logging data clustering with hidden Markov model to assist log unit classification

Distribution Prediction of Shale Deformation Structures in Tectonically Complex Area Based on Relationship Between Geological Structures and Shale Deformation

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