| Budget Amount *help |
¥4,030,000 (Direct Cost: ¥3,100,000、Indirect Cost: ¥930,000)
Fiscal Year 2013: ¥650,000 (Direct Cost: ¥500,000、Indirect Cost: ¥150,000)
Fiscal Year 2012: ¥1,690,000 (Direct Cost: ¥1,300,000、Indirect Cost: ¥390,000)
Fiscal Year 2011: ¥1,690,000 (Direct Cost: ¥1,300,000、Indirect Cost: ¥390,000)
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| Outline of Final Research Achievements |
The aim of this project was to investigate the detail structure of slow seismic velocity anomaly at the base of the mantle and to estimate the form of the mantle upwelling flow. The amplitude of direct S waves for earthquakes in Western Pacific recorded at U.S. are anomalously small. The results of waveform forward modelling show that a previously proposed cylindrical ultra low velocity zone placed at the base of the mantle can be one of the cause of the anomalous S wave amplitudes. The result also shows that due to a finite frequency effect, it is often difficult to distinguish whether the distortion of S waveforms is caused by a large low shear velocity province or an ultra velocity zone at the base of the mantle. The result infers that what is seen as a large low shear velocity province in tomographic models could be in reality a cluster of plumes, whose images are blurred due to technical limitations in handing the finite frequency effect of S waves.
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