Tectonic Basin Formation in and Around Lake Biwa, Central Japan

Takemura, Keiji; Haraguchi, Tsuyoshi; Kusumoto, Shigekazu; Itoh, Yasuto

doi:10.5772/56667

Cited by 4 publications

(5 citation statements)

References 9 publications

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“…Comparing the thickness of accumulated sediments from about 1.5 Ma to the present day 2 , 33 with the locations of the benthic vents detected between 2009 and 2012 shows that the vents are located along the area of shallow sedimentation, corresponding roughly to the location of the former mountain range (Fig. 3 ).…”

Section: Geologic History Of Lake Biwamentioning

confidence: 97%

“…Thus, we conclude that neither groundwater inflows or bottom shear stresses were responsible for the sudden recent turbidity observed in the Tantan surveys. Rather, we believe that the evidence suggests that benthic vents are the cause, and when seeking possible mechanisms of their formation in Lake Biwa, the lake’s geologic history and formation 2 , 32 becomes crucial.…”

Section: Alternative Origins and Locations Of Ventsmentioning

confidence: 98%

“…The present area of Lake Biwa is believed to have been mountainous terrain a few million years ago, but then subsided at about 0.74 mm year −1 . This occurred because it lies on the northwest section of a crustal block that was affected by a change in direction of compression, first from south to north then from east to west, owing to complex plate tectonic interactions in the central island 2 .…”

Section: Geologic History Of Lake Biwamentioning

confidence: 99%

“…Lake Biwa, the oldest and largest tectonic lake in Japan, formed almost 4.2 million years ago in an area 100 km south of its present location. Plate tectonic activity is believed to have moved the lake to the present location about 0.4–1.5 million years ago 1 , 2 . The lake volume is 27.5 km 3 , or about 34% of Japan’s surface fresh water 3 .…”

Section: Introductionmentioning

confidence: 99%

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Increasing benthic vent formation: a threat to Japan’s ancient lake

Kumagai

Robarts²,

Aota

2021

Sci Rep

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An autonomous underwater vehicle (AUV) was deployed in Lake Biwa from 2000 to 2012. In December 2009, ebullition of turbid water was first found in the deepest area (> 90 m) of the North Basin. Follow-up investigations in April and December 2010 and January 2012 confirmed the existence of benthic vents similar to the vents observed in other deep lakes. Importantly, vent numbers per unit travel distance in Lake Biwa dramatically increased from only two vents (0.37 vents km−1) in December 2009 to 54 vents (5.28 vents km−1) in January 2012, which could be related to recent tectonic activity in Japan, e.g., the M9.1 Tohoku earthquake in March 2011 and slow earthquakes along the Nankai Trough from 2006 to 2018. Continuous back-up investigations from 2014 to 2019 revealed additional benthic vents in the same area. The sudden increase in benthic vent activity (liquid and gaseous ebullitions) have significant potential to alter lake biogeochemistry and, ultimately, degrade Japan’s major drinking water source and may be a harbinger of major crustal change in the near future.

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Section: Geologic History Of Lake Biwamentioning

confidence: 97%

Section: Alternative Origins and Locations Of Ventsmentioning

confidence: 98%

Section: Geologic History Of Lake Biwamentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Increasing benthic vent formation: a threat to Japan’s ancient lake

Kumagai

Robarts²,

Aota

2021

Sci Rep

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“…The BSFZ is constituted of the NNE-SSW-trending west-dipping faults separated by clear small gaps or steps (e.g., the Zeze, Hiei, Katata, Hira, Katsuno, Kamidera, Aibano, and Chinai faults; Fig. 11a), and is reported to have a reverse fault sense of east side subsidence (Takemura et al 2013).…”

Section: Interpretationsmentioning

confidence: 99%

Ambient Noise Tomography for a High-resolution 3D S-Wave Velocity Model of the Kinki Region, Southwestern Japan, using Dense Seismic Array Data

Nthaba

Ikeda

Nimiya

et al. 2021

Preprint

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Research interest in the Kinki region, southwestern Japan, has been aroused by the frequent occurrence of microearthquake activity that do not always coincide with documented active fault locations. Previous studies in the Kinki region focused mainly on deep, large-scale structures and could not e ciently resolve ne-scale (~10 km) shallow crustal structures. Hence, characterization of the upper crustal structure of this region at an improved spatial resolution is required. From the cross-correlation of the vertical components of the ambient seismic noise data recorded by a densely-distributed seismic array, we estimated Rayleigh wave phase velocities using a frequency domain method. Then, we applied a direct surface wave tomographic method for the measured phase velocity dispersion data to obtain the 3D S-wave velocity model of the Kinki region. The estimated velocity model reveals a NE-SW trending low-velocity structure coinciding with the Niigata-Kobe Tectonic Zone (NKTZ) and the active Biwako-seigan Fault Zone (BSFZ). Also, we identi ed ne-scale lowvelocity structures coinciding with known active faults on the eastern side of the NKTZ, as well as sets of lowvelocity structures across the Tanba region, that may be attributable to the weathering effects or activity of unidenti ed concealed fault zones. Furthermore, sedimentary basins manifest as low-velocity zones extending to depths ranging from ~1.5 to 2 km, correlating with those reported in previous studies. Our results therefore contribute towards fundamental understanding of earthquake faulting as well as tectonic boundary and will be useful for hazard assessment and disaster mitigation. Data And MethodsWe utilized the vertical component of continuously recorded seismic waveforms by permanent and temporary stations from April 1 to September 30 during the year 2019. The permanent stations included 78 Hi-net stations,

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Ambient noise tomography for a high-resolution 3D S-wave velocity model of the Kinki Region, Southwestern Japan, using dense seismic array data

Nthaba

Ikeda

Nimiya

et al. 2022

Earth Planets Space

View full text Add to dashboard Cite

Research interest in the Kinki region, southwestern Japan, has been aroused by the frequent occurrence of microearthquake activity that do not always coincide with documented active fault locations. Previous studies in the Kinki region focused mainly on deep, large-scale structures and could not efficiently resolve fine-scale (~ 10 km) shallow crustal structures. Hence, characterization of the upper crustal structure of this region at an improved spatial resolution is required. From the cross-correlation of the vertical components of the ambient seismic noise data recorded by a densely distributed seismic array, we estimated Rayleigh wave phase velocities using a frequency domain method. Then, we applied a direct surface wave tomographic method for the measured phase velocity dispersion data to obtain a 3D S-wave velocity model of the Kinki region. The estimated velocity model reveals a NE–SW trending low-velocity structure coinciding with the Niigata–Kobe Tectonic Zone (NKTZ) and the active Biwako-seigan Fault Zone (BSFZ). Also, we identified fine-scale low-velocity structures coinciding with known active faults on the eastern side of the NKTZ, as well as sets of low-velocity structures across the Tanba region. Furthermore, sedimentary basins manifest as low-velocity zones extending to depths ranging from ~ 1.5 to 2 km, correlating with those reported in previous studies. Our results therefore contribute towards fundamental understanding of earthquake faulting as well as tectonic boundary and will be useful for hazard assessment and disaster mitigation. Graphical abstract

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Tectonic Basin Formation in and Around Lake Biwa, Central Japan

Cited by 4 publications

References 9 publications

Increasing benthic vent formation: a threat to Japan’s ancient lake

Increasing benthic vent formation: a threat to Japan’s ancient lake

Ambient Noise Tomography for a High-resolution 3D S-Wave Velocity Model of the Kinki Region, Southwestern Japan, using Dense Seismic Array Data

Ambient noise tomography for a high-resolution 3D S-wave velocity model of the Kinki Region, Southwestern Japan, using dense seismic array data

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