Oceanic crust in the Japan Basin of the Japan Sea by the 1990 Japan‐USSR Expedition

Hirata, Naoshi; Karp, Baruch; Yamaguchi, Takashi; Kanazawa, Toshihiko; Suyehiro, Kiyoshi; Kasahara, Junzo; Shiobara, Hajime; Shinohara, Masanao; Kinoshita, Hajimu

doi:10.1029/92gl02094

Cited by 68 publications

(53 citation statements)

References 4 publications

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“…The distribution of the moho depth is almost flat in the eastern but slightly deeper in the western Japan Basin (Yoshii, 1972;Hirata et al, 1992a). This fact indicates that the chemical or mineralogical com- position of the basement layer of the crust in the Japan Basin is fairly homogeneous.…”

Section: Introductionmentioning

confidence: 61%

“…From the results of the seismic refraction experiments carried out so far by Japanese, American, and Russian scientific parties, the crustal structure of the Japan Basin is very similar to that of a typical oceanic basin with a thickness of basaltic basement 6-6.5 km (Murauchi, 1972;Ludwig et al, 1975;Karp and Lelikov, 1990;Hirata et al, 1992a;Yamaguchi, 1993). The crust in the Japan Basin basically consists of three oceanic layers: the sedimentary layer with a P-wave velocity of 1.7-3.3 km/s with a thickness ca.…”

Section: Introductionmentioning

confidence: 99%

“…In this study, we reexamined magnetic lineations of the Japan Basin using geomagnetic total field data, and single channel seismic reflection data to determine acoustic basement depth of relief. Seismic refraction studies of recent USSR-Japan joint surveys (Hirata et al, 1992a;Yamaguchi, 1993) are also referred to. Magnetic research on the Japan Sea has been carried out as early as in 1967 by Yasui et al (1967).…”

Section: Introductionmentioning

confidence: 99%

“…The Japan Basin in the northern part of the Japan Sea has a thin oceanic crust seismically similar to a typical oceanic crust in the Western Pacific region and shows weak but definite magnetic lineation patterns (Hirata et al, 1992a;Isezaki and Shevaldin, in press). The presence of various geomorphological heterogeneities of the Japan Sea makes it difficult to understand its tectonic history.…”

Section: Introductionmentioning

confidence: 99%

“…DELP (Dynamics and Evolution of the Lithosphere Program) 1985 cruise (Japanese DELP Research Group, 1987), USSR-Japan joint study (e.g. Karp and Lelikov,1990;Hirata et al,1992a), and ODP (Ocean Drilling Program) (e.g. Tamaki et al,1992) have accumulated a series of new informations and constraints on ages of Japan Sea formation and its present geophysical environments.…”

Section: Introductionmentioning

confidence: 99%

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A Supplement to Magnetic Anomaly of the Japan Basin.

Nakasa¹,

Kinoshita²

1994

J. geomagn. geoelec

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Magnetic and seismic reflection data of the Japan Basin with a good quality of ships positioning were selected to make a magnetic anomaly and reflective basement contour maps. The magnetic contour map reveals a number of magnetic anomaly lineations. We identified one additional lineation group trending N70°-75°E in the western side of the two another lineations trending N30°-35°E, N65°E formerly identified by other researches. The trends of these anomalies are qualified to be real ones by use of modified semblance analyses. Age identification of these magnetic anomaly lineations is achieved by introducing a basement magnetization model based on the Cenozoic magnetic reversal time-scale referring to the age constraints of other works. Albeit the Japan Basin has a smooth topography of 3,000-3,700 m water depth, the reflective basement map shows fairly rugged topography. The reflective basement topography has no correlation to the magnetic anomaly patterns of the present study area. Therefore we adopt an assumption of a flat magnetic basement model referring to recent seismic refraction studies of this area. Using variable half spreading rates, layer thickness, intensity of natural remanent plus induced magnetization, and skewness parameters, a possible range of ages of the formation of these magnetic anomalies is determined. Among a number of possibilities, we assign the age of these anomalies to 13-24 Ma. The older age 22-24 Ma and a half spreading rate 8.0 cm/yr are the best fit to the eastern area. The central area shows an age 22-24 Ma and a slower half spreading rate 7.5 cm/yr. The youngest age 13-15 Ma, and faster half spreading rate 10.0 cm/yr fit to the western anomaly group. We conclude that the formation of the Japan Basin proceeded toward west changing its spreading direction.

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Section: Introductionmentioning

confidence: 61%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A Supplement to Magnetic Anomaly of the Japan Basin.

Nakasa¹,

Kinoshita²

1994

J. geomagn. geoelec

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Seismic constraints of the formation process on the back‐arc basin in the southeastern Japan Sea

Sato

Kodaira

et al. 2014

JGR Solid Earth

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To clarify the formation process of the back-arc basin in the Japan Sea, which is located next to the northwestern Pacific, a seismic survey using ocean bottom seismographs and an air gun array was undertaken in areas from the northern Yamato Basin to the coast of the northeastern Japan Island Arc off Awa-shima Island. The crust beneath the northern Yamato Basin off Awa-shima Island is approximately 16 km thick. The upper and lower crusts are, respectively, about 5 km thick with a steep velocity gradient and about 10 km thick with a gentle velocity gradient. In the basin, there are very few units with P wave velocity of 5.4-6.0 km/s, corresponding to the continental upper crust. The crustal structure of the northern Yamato Basin has characteristics of thicker oceanic crust. The high-velocity lowermost crust in the northern Yamato Basin with 7.2-7.4 km/s might show melt formed by a slightly high mantle temperature during the opening of the basin. However, the crust beneath the areas from the Sado Ridge to the coast, which is approximately 25-26 km thick, is slightly thinner than that of the continental crust and island arc crust. The crustal structure beneath this area is inferred to be a rifted continental and/or a rifted island arc crust.

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Accurate measurements of residual topography from the oceanic realm

2014

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In the oceans, our understanding of plate subsidence as a function of age permits residual depth anomalies to be identified and mapped. These anomalies may reflect dynamic topography and could be an important means for constraining convective circulation of the sublithospheric mantle. Here we analyze a global database of seismic reflection and wide‐angle profiles from heavily sedimented oceanic crust, which abuts continental lithosphere. At 449 locations, we calculated water‐loaded subsidence, compared it with a reference age‐depth relationship, and determined residual depth. We then combined these spot measurements of residual depth with observations from mid‐oceanic ridges and from selected ship track bathymetry to construct a global map of residual depth. Our results suggest that the amplitude of residual depth varies by up to ±1 km with wavelengths of order 103 km. We compare our residual depths with free‐air gravity and seismic tomographic anomalies. Our results show that residual depths correlate with long‐wavelength gravity anomalies. In contrast, correlations between residual depths and vertically averaged shear velocity anomalies within the upper and/or the lower mantle are weaker. The largest discrepancies occur at short (∼1000 km) wavelengths. These combined observations suggest that residual depth anomalies could be generate by density variations within a thin (∼102 km) low‐viscosity layer beneath the lithosphere. Our global compilation should play a significant role in helping to refine predictive geodynamical models.

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Oceanic crust in the Japan Basin of the Japan Sea by the 1990 Japan‐USSR Expedition

Cited by 68 publications

References 4 publications

A Supplement to Magnetic Anomaly of the Japan Basin.

A Supplement to Magnetic Anomaly of the Japan Basin.

Seismic constraints of the formation process on the back‐arc basin in the southeastern Japan Sea

Accurate measurements of residual topography from the oceanic realm

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