Japan Geoscience Union Meeting 2015

Presentation information

International Session (Oral)

Symbol S (Solid Earth Sciences) » S-IT Science of the Earth's Interior & Techtonophysics

[S-IT03] Structure and dynamics of Earth and Planetary deep interiors

Tue. May 26, 2015 9:00 AM - 10:45 AM 106 (1F)

Convener:*Takashi Yoshino(Institute for Study of the Earth's Interior, Okayama University), Satoru Tanaka(Department of Deep Earth Structure and Dynamics Research Japan Agency for Marine-Earth Science and Technology), Dapeng Zhao(Department of Geophysics, Tohoku University), Masanori Kameyama(Geodynamics Research Center, Ehime University), John Hernlund(Earth-Life Science Institute, Tokyo Institute of Technology), Chair:Masanori Kameyama(Geodynamics Research Center, Ehime University), John Hernlund(Earth-Life Science Institute, Tokyo Institute of Technology)

10:00 AM - 10:15 AM

[SIT03-19] New constraints on S-wave velocity structure near the western edge of the Pacific LLSVP

*Satoru TANAKA1, Hitoshi KAWAKATSU2 (1.JAMSTEC, 2.ERI, Univ. Tokyo)

Keywords:LLSVP, Pacific, S-wave velocity structure, lower mantle

S-wave velocity structure near the edge of the Pacific Large-Low Shear Velocity Province (LLSVP) has been examined by many researchers (e.g., He et al., 2006; He and Wen, 2009; Takeuchi et al., 2008; Idehara et al., 2013). They have mainly used the differential travel times of ScS-S observed by global or local broadband networks (e.g., IRIS GSN, F-net, CNDSN and so on). Here we add the new data of ScS-S and S-SKS travel time data obtained by NECESSArray and a temporal broadband ocean bottom seismograph network in the Philippine Sea by the Stagnant Slab Project (SSP-BBOBS) (Shiobara et al., 2005).
ScS-S anomalies observed by NECESSArray in conjunction with those by F-net, which covers the region beneath the eastern Micronesia, are roughly explained by the existing 3D S-wave models. However, S-SKS anomalies, which are affected by S-waves propagated near the base of the mantle beneath the western Micronesia and the north of New Britain Island, suddenly changes from positive in the eastern area to almost zero or slightly negative in the western, whereas all the models predict large positive anomalies without significant changes. To confirm this S-SKS observation, we further examined ScS-S anomalies observed by the SSP-BBOBS. Some data indicate nearly zero in the corresponding area although the data are scattered and still sparsely distributed. Since a low velocity anomaly beneath the New Guinea Island are confirmed by Takeuchi et al. (2008) and Idehara et al. (2013), our observation suggests that the Pacific LLSVP is separated beneath the north of New Britain Islands. The models of 3D mantle structure are possibly insufficient near the western edge of the Pacific LLSVP.

Acknowledgements. The authors are grateful to the participants of NECESSArray and SP-BBOBS projects and the staffs of IRIS and F-net for providing valuable data.