Marine geophysical study of the Solomon Arc convergent zone
Grant-in-Aid for international Scientific Research
|Allocation Type||Single-year Grants|
|Research Institution||The University of Tokyo|
SUYEHIRO Kiyoshi University of Tokyo, Ocean Research Institute, 海洋研究所, 助教授 (20133928)
末廣 潔 東京大学, 海洋研究所, 助教授
COFFIN Millard University of Texas at Austin, Institute for Geophysics, 研究員
SHIPLEY Thomas University of Texas Austin, Institute for Geophysics, 上級研究員
MANN Paul University of Texas at Austin, Institute for Geophysics, 研究員
SHINOHARA Masanao Chiba University, Department of Earth Sciences, 理学部, 助教授 (90242172)
TAIRA Asahiko University of Tokyo, Ocean Research Institute, 海洋研究所, 教授 (50112272)
COFFIN Milar U. of Texas at Austin, Inst. for Geophysics, 研究員
|Project Period (FY)
1993 – 1994
Completed(Fiscal Year 1994)
|Budget Amount *help
¥9,000,000 (Direct Cost : ¥9,000,000)
Fiscal Year 1994 : ¥3,000,000 (Direct Cost : ¥3,000,000)
Fiscal Year 1993 : ¥6,000,000 (Direct Cost : ¥6,000,000)
|Keywords||Solomon Arc / OBS / subduction / seismicity / San Cristobal Trench / プレート沈み込み / ソロモン島弧 / デジタル海底地震計 / 反射法探査 / オントンジャワ海台|
The Solomon island arc area is a complex plate convergence zone. On the northern side is the North Solomon Trench at which the Pacific plate is being consumed. Another trench on the southern side is the San Cristobal Trench, where the Indo-Australian plate and the Solomon Sea plate seem to be subducting beneath the Solomon arc. The San Cristobal Trench becomes less conspicuous west of Guadalcanal.
A plate subduction zone is usually best described by the seismic data, that is by the determination of hypocenters that define the geometry of the subducting slab. However, in a complex region like the Solomon area, the worldwide seismic network dataset is unable to resolve the complexity unless one assumes the tectonics operating in the region. Only less than 10 events are determined each year west of Guadalcanal.
The only way to obtain high spatial resolution in hypocenter determination is to conduct an on-site seismic observation with very high sensitivity. We have improved our digital ocean bottom seismograph (OBS) in 1993 and made a temporary microseismicity observation west of Guadalcanal using 5 OBS's for the period of Aug.28 through Sep.7 in 1994.Our preliminary results indicate (1) about 200 times higher seismic detectability compared to the International Seismological Center determinations, (2) subduction of the Indo-Australian plate to about 50 km with a surprisingly large dip angle of about 50 degrees, (3) almost no seismicity in the small basin between the double arc, (4) 60 to 90 km deep events probably associated with the Pacific plate subduction.
We are planning an arc transect to obtain the whole crustal structure of the arc system, which will help to link the above findings with the structure and tectonics.
Research Output (11results)