TY - JOUR
T1 - Seismological evidence for compositional variations at the base of the mantle transition zone under Japan Islands
AU - Yamada, Akira
AU - Zhao, Dapeng
AU - Inoue, Toru
AU - Suetsugu, Daisuke
AU - Obayashi, Masayuki
N1 - Funding Information:
We thank F. Niu for providing us with his data of the topography of the 660 km discontinuity. This study was supported by the Global-COE Programs for Deep Earth Mineralogy at Ehime University and for Earth and Planetary Dynamics at Tohoku University. Figures were made by using GMT ( Wessel and Smith, 1998 ). We appreciate the editorial effort by Prof. M. Santosh and Prof. S. Maruyama and helpful review comments and suggestions from two anonymous reviewers.
PY - 2009/12
Y1 - 2009/12
N2 - Temperature and water content anomalies just above the 660-km discontinuity under the Japan Islands are estimated from seismological observations. Two sets of seismological observations of P-wave velocity perturbations and depth variations of the 660-km discontinuity are used, which are (1) long-wavelength (~ 500 km) variations from seismic tomography based on a grid parameterization and waveform analysis of ScS reverberations and (2) moderate-wavelength (~ 150 km) variations from seismic tomography with a block parameterization and receiver-function analysis. To estimate temperature and water content anomalies, partial derivatives of velocity and depth variations with respect to temperature and water content determined by mineral physics studies are used. Under Southwest Japan, low temperature and high water-content anomalies are obtained from both sets of seismological observations, which have already been found by a previous study. Under Northeast Japan, however, there are discrepancies between the results estimated from the two data sets, possibly due to the different resolution scales. This discrepancy is dismissed when examining distributions of the temperature and water content anomalies. These anomalies can be grouped into two geographical locations, one group under Southwest Japan, the other under Northeast Japan. The two groups are clearly separated and exhibit common features in both sets of the seismological observations. The grouping is interpreted by a compositional difference between the subducting Pacific slab under Southwest Japan and a normal mantle under Northeast Japan.
AB - Temperature and water content anomalies just above the 660-km discontinuity under the Japan Islands are estimated from seismological observations. Two sets of seismological observations of P-wave velocity perturbations and depth variations of the 660-km discontinuity are used, which are (1) long-wavelength (~ 500 km) variations from seismic tomography based on a grid parameterization and waveform analysis of ScS reverberations and (2) moderate-wavelength (~ 150 km) variations from seismic tomography with a block parameterization and receiver-function analysis. To estimate temperature and water content anomalies, partial derivatives of velocity and depth variations with respect to temperature and water content determined by mineral physics studies are used. Under Southwest Japan, low temperature and high water-content anomalies are obtained from both sets of seismological observations, which have already been found by a previous study. Under Northeast Japan, however, there are discrepancies between the results estimated from the two data sets, possibly due to the different resolution scales. This discrepancy is dismissed when examining distributions of the temperature and water content anomalies. These anomalies can be grouped into two geographical locations, one group under Southwest Japan, the other under Northeast Japan. The two groups are clearly separated and exhibit common features in both sets of the seismological observations. The grouping is interpreted by a compositional difference between the subducting Pacific slab under Southwest Japan and a normal mantle under Northeast Japan.
KW - Mantle transition zone
KW - Seismic observations
KW - Subducting slab
KW - Temperature anomaly
KW - Water content
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U2 - 10.1016/j.gr.2009.04.009
DO - 10.1016/j.gr.2009.04.009
M3 - Article
AN - SCOPUS:69749097311
VL - 16
SP - 482
EP - 490
JO - Gondwana Research
JF - Gondwana Research
SN - 1342-937X
IS - 3-4
ER -