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IUGG XXIV General Assembly July 2-13, 2007 Perugia, Italy<br />

(S) - <strong>IASPEI</strong> - International Association of Seismology and Physics of the Earth's<br />

Interior<br />

JSS011 Oral Presentation 2102<br />

Three-dimensional share wave speed structure beneath the South Pacific<br />

superswell<br />

Dr. Takehi Isse<br />

JAMSTEC IFREE <strong>IASPEI</strong><br />

Daisuke Suetsugu, Hajime Shiobara, Hiroko Sugioka, Kazunori Yoshizawa,<br />

Toshihiko Kanazawa, Yoshio Fukao, Guilhem Barruol<br />

We determined three-dimensional shear wave speed model beneath the South Pacific superswell down<br />

to a depth of 200 km by analyzing broadband data from ocean bottom seismograph and island stations<br />

temporary deployed in the French Polynesia region. The temporal data covers period from 2003 to 2005<br />

for the BBOBS stations deployed on the seafloor and from 2001 to 2005 for the island stations deployed<br />

during the PLUME project. This enables us to study the upper mantle structure beneath the Superswell<br />

with an unprecedented high resolution. We measured the dispersions of fundamental mode of Rayleigh<br />

waves at periods between 40 and 140 seconds by using a two-station method. Resolution analyses<br />

indicate that these temporary stations may locally improve the lateral resolution to about 400 km. We<br />

observe superficial slow anomalies associated to the spreading ridges such as the Lau Basin and two<br />

kinds of hotspot signatures: We found pronounced and continuous slow anomalies down to at least 200<br />

km depth near the Society, McDonald, Marquesas, and Pitcairn hotspots whereas the slow anomalies<br />

beneath the Samoa, Rarotonga and Arago hotspots are only present at depths shallower than 80 km.<br />

Keywords: surface wave tomography, bbobs, superswell

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