Azusa Shito
Japan Agency for Marine-Earth Science and Technology
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Featured researches published by Azusa Shito.
Geophysical Research Letters | 2001
Azusa Shito; Takuo Shibutani
Seismic structure of the upper mantle transition zone beneath the Philippine Sea region is studied using waveform modeling. Models AZ41 and AZ40 were derived to represent the structure beneath the north central part and northwestern regions, respectively. AZ41 has high-velocity anomalies from 510 km to 660 km 3% faster than a global model ak135, a depression of the ‘660’ discontinuity to 690 km, and a small (+2%) discontinuity at 510 km. Model AZ40 is the same as AZ41 except there is no depression of the ‘660’. On the other hand, the waveforms which sampled the southern region can be explained with the global model ak135. These results support the interpretation that subducted Pacific lithosphere is stagnant above the ‘660’ in the northern part, whereas in the southern part it penetrates into the lower mantle. In accord with earlier suggestions, the different configuration of the subducted slab suggested above could be due to the migration of the trench.
Journal of Geophysical Research | 2015
Azusa Shito; Daisuke Suetsugu; Takashi Furumura
Po/So waves are characterized by their high-frequency content and long-duration travel over great distances (up to 3000 km) through the oceanic lithosphere. Po/So waves are developed by the multiple forward scattering of P- and S-waves due to small-scale stochastic random heterogeneities. To study the nature of these heterogeneities, Po/So waves are analyzed in the Philippine Sea Plate, which consists of three regions with different lithospheric ages. In the Philippine Sea Plate, Po/So waves propagate in the youngest region (15 Ma) and propagate more effectively in older regions. We investigate the mechanism of this propagation efficiency using numerical Finite Difference Method simulations of 2-D seismic wave propagation. The results of this study demonstrate that the increase in propagation efficiency of Po/So waves depends on the age of the oceanic lithosphere, and this relationship can be qualitatively explained by thickening of the oceanic lithosphere including small-scale heterogeneities and a reduction in the intrinsic attenuation. These small-scale heterogeneities may form continuously in oceanic lithosphere from the time of its formation at a spreading ridge, via the solidification of melts distributed in the asthenosphere.
Physics of the Earth and Planetary Interiors | 2010
Daisuke Suetsugu; Toru Inoue; Masayuki Obayashi; Akira Yamada; Hajime Shiobara; Hiroko Sugioka; Aki Ito; Toshihiko Kanazawa; Hitoshi Kawakatsu; Azusa Shito; Yoshio Fukao
Earth and Planetary Science Letters | 2009
Takehi Isse; Hajime Shiobara; Yoshihiko Tamura; Daisuke Suetsugu; Kazunori Yoshizawa; Hiroko Sugioka; Aki Ito; Toshihiko Kanazawa; Masanao Shinohara; Kimihiro Mochizuki; Eichiro Araki; Kazuo Nakahigashi; Hitoshi Kawakatsu; Azusa Shito; Yoshio Fukao; Osamu Ishizuka; James B. Gill
Physics of the Earth and Planetary Interiors | 2003
Azusa Shito; Takuo Shibutan
Geophysical Research Letters | 2013
Azusa Shito; Daisuke Suetsugu; Takashi Furumura; Hiroko Sugioka; Aki Ito
Physics of the Earth and Planetary Interiors | 2003
Azusa Shito; Takuo Shibutan
Physics of the Earth and Planetary Interiors | 2010
Takehi Isse; Hajime Shiobara; Jean-Paul Montagner; Hiroko Sugioka; Aki Ito; Azusa Shito; Toshihiko Kanazawa; Kazunori Yoshizawa
Archive | 2007
Azusa Shito; Hajime Shiobara; Hiroko Sugioka; Akinori Ito; Hitoshi Kawakatsu; Christoph Adam; Toshihiko Kanazawa
Japan Geoscience Union | 2017
Masashi Ogiso; Mitsuyuki Hoshiba; Azusa Shito; Satoshi Matsumoto