TY - JOUR
T1 - P-wave velocity structure of the margin of the southeastern Tsushima Basin in the Japan Sea using ocean bottom seismometers and airguns
AU - Sato, Takeshi
AU - Sato, Toshinori
AU - Shinohara, Masanao
AU - Hino, Ryota
AU - Nishino, Minoru
AU - Kanazawa, Toshihiko
N1 - Funding Information:
The authors thank the captain, officers, crew and scientific members of the R/V Tansei-maru in ORI, Univ. of Tokyo. We wish to thank C. Igarashi in ORI, Univ. of Tokyo for his support during the airgun operation and K. Hoshi in Chiba Univ. for her support during the expedition. We thank Dr. N. Isezaki in Chiba Univ. for fruitful discussions on the results of this paper. We gratefully acknowledge anonymous reviewers for critical comments and suggestions. We thank JNOC for permission to publish this work. The figures and maps in this paper were made using the GMT graphic package ( Wessel and Smith, 1998 ). This research is partly supported by the Grant-in-Aid for Scientific Research, number 12640401, from the Ministry of Education, Science, Culture and Sports of Japan.
PY - 2006/1/20
Y1 - 2006/1/20
N2 - The Tsushima Basin is located in the southwestern Japan Sea, which is a back-arc basin in the northwestern Pacific. Although some geophysical surveys had been conducted to investigate the formation process of the Tsushima Basin, it remains unclear. In 2000, to clarify the formation process of the Tsushima Basin, the seismic velocity structure survey with ocean bottom seismometers and airguns was carried out at the southeastern Tsushima Basin and its margin, which are presumed to be the transition zone of the crustal structure of the southwestern Japan Island Arc. The crustal thickness under the southeastern Tsushima Basin is about 17 km including a 5 km thick sedimentary layer, and 20 km including a 1.5 km thick sedimentary layer under its margin. The whole crustal thickness and thickness of the upper part of the crust increase towards the southwestern Japan Island Arc. On the other hand, thickness of the lower part of the crust seems more uniform than that of the upper part. The crust in the southeastern Tsushima Basin has about 6 km/s layer with the large velocity gradient. Shallow structures of the continental bank show that the accumulation of the sediments started from lower Miocene in the southeastern Tsushima Basin. The crustal structure in southeastern Tsushima Basin is not the oceanic crust, which is formed ocean floor spreading or affected by mantle plume, but the rifted/extended island arc crust because magnitudes of the whole crustal and the upper part of the crustal thickening are larger than that of the lower part of the crustal thickening towards the southwestern Japan Island Arc. In the margin of the southeastern Tsushima Basin, high velocity material does not exist in the lowermost crust. For that reason, the margin is inferred to be a non-volcanic rifted margin. The asymmetric structure in the both margins of the southeastern and Korean Peninsula of the Tsushima Basin indicates that the formation process of the Tsushima Basin may be simple shear style rather than pure shear style.
AB - The Tsushima Basin is located in the southwestern Japan Sea, which is a back-arc basin in the northwestern Pacific. Although some geophysical surveys had been conducted to investigate the formation process of the Tsushima Basin, it remains unclear. In 2000, to clarify the formation process of the Tsushima Basin, the seismic velocity structure survey with ocean bottom seismometers and airguns was carried out at the southeastern Tsushima Basin and its margin, which are presumed to be the transition zone of the crustal structure of the southwestern Japan Island Arc. The crustal thickness under the southeastern Tsushima Basin is about 17 km including a 5 km thick sedimentary layer, and 20 km including a 1.5 km thick sedimentary layer under its margin. The whole crustal thickness and thickness of the upper part of the crust increase towards the southwestern Japan Island Arc. On the other hand, thickness of the lower part of the crust seems more uniform than that of the upper part. The crust in the southeastern Tsushima Basin has about 6 km/s layer with the large velocity gradient. Shallow structures of the continental bank show that the accumulation of the sediments started from lower Miocene in the southeastern Tsushima Basin. The crustal structure in southeastern Tsushima Basin is not the oceanic crust, which is formed ocean floor spreading or affected by mantle plume, but the rifted/extended island arc crust because magnitudes of the whole crustal and the upper part of the crustal thickening are larger than that of the lower part of the crustal thickening towards the southwestern Japan Island Arc. In the margin of the southeastern Tsushima Basin, high velocity material does not exist in the lowermost crust. For that reason, the margin is inferred to be a non-volcanic rifted margin. The asymmetric structure in the both margins of the southeastern and Korean Peninsula of the Tsushima Basin indicates that the formation process of the Tsushima Basin may be simple shear style rather than pure shear style.
KW - Formation process
KW - Japan Sea
KW - Ocean bottom seismometers
KW - P-wave velocity structure
KW - The southeastern Tsushima Basin
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U2 - 10.1016/j.tecto.2005.09.001
DO - 10.1016/j.tecto.2005.09.001
M3 - Article
AN - SCOPUS:30344467800
SN - 0040-1951
VL - 412
SP - 159
EP - 171
JO - Tectonophysics
JF - Tectonophysics
IS - 3-4
ER -