TY - JOUR
T1 - Detection of metastable olivine wedge in the western Pacific slab and its geodynamic implications
AU - Jiang, Guoming
AU - Zhao, Dapeng
AU - Zhang, Guibin
N1 - Funding Information:
We thank the Data Management Centers of the China National Seismic Network and the Japanese High-Sensitivity Seismic Network (Hi-net) for providing the high-quality waveform data used in this study. We are grateful to the Editor (V. F. Cormier) and other two anonymous reviewers for their helpful comments and suggestions. This work was co-supported by the National Science Foundation of China (Grant No. 40904021), Beijing Higher Education Young Elite Teacher Project, the Fundamental Research Fund of Key Laboratory of Geo-detection (China University of Geosciences, Beijing), Ministry of Education and the Fundamental Research Funds for the Central Universities in China. Most figures are made using the GMT software ( Wessel and Smith, 1998 ).
Publisher Copyright:
© 2014 Elsevier B.V.
PY - 2015/1/1
Y1 - 2015/1/1
N2 - Seismic tomography and numerical simulations show that the western Pacific slab bends horizontally when it reaches the boundary between the upper mantle and lower mantle beneath northeast Asia. It is expected that a metastable olivine wedge (MOW) exists in the cold core of the slab because of a delayed phase transition from olivine to its high-pressure polymorphs. However, it is still debated whether the MOW actually exists or not, and even if it exists, its physical properties, such as seismic velocity and density, are still unclear. In this work we use high-quality arrival-time data of 17 deep earthquakes occurring within the Pacific slab under northeast Asia to study the detailed structure of the slab. The deep earthquakes are relocated precisely by applying a modified double-difference location method to arrival-time data recorded at both Chinese and Japanese stations. Based on the precise hypocentral locations, a forward modeling method and differential travel-time residuals data are used to estimate seismic velocity within the deep source zone, which can decrease or remove the influence of ambient velocity heterogeneities. Our results show that the MOW does exist within the Pacific slab under northeast Asia, and the MOW has a mean velocity anomaly of 7-9% lower than the iasp91 Earth model. The existence of MOW in the slab has important geodynamic implications. It can reduce the speed of slab subduction and affect the generation of deep earthquakes.
AB - Seismic tomography and numerical simulations show that the western Pacific slab bends horizontally when it reaches the boundary between the upper mantle and lower mantle beneath northeast Asia. It is expected that a metastable olivine wedge (MOW) exists in the cold core of the slab because of a delayed phase transition from olivine to its high-pressure polymorphs. However, it is still debated whether the MOW actually exists or not, and even if it exists, its physical properties, such as seismic velocity and density, are still unclear. In this work we use high-quality arrival-time data of 17 deep earthquakes occurring within the Pacific slab under northeast Asia to study the detailed structure of the slab. The deep earthquakes are relocated precisely by applying a modified double-difference location method to arrival-time data recorded at both Chinese and Japanese stations. Based on the precise hypocentral locations, a forward modeling method and differential travel-time residuals data are used to estimate seismic velocity within the deep source zone, which can decrease or remove the influence of ambient velocity heterogeneities. Our results show that the MOW does exist within the Pacific slab under northeast Asia, and the MOW has a mean velocity anomaly of 7-9% lower than the iasp91 Earth model. The existence of MOW in the slab has important geodynamic implications. It can reduce the speed of slab subduction and affect the generation of deep earthquakes.
KW - Deep earthquakes
KW - Differential residual
KW - Focal mechanism
KW - Metastable olivine wedge
KW - Western pacific slab
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U2 - 10.1016/j.pepi.2014.10.008
DO - 10.1016/j.pepi.2014.10.008
M3 - Article
AN - SCOPUS:84911992806
VL - 238
SP - 1
EP - 7
JO - Physics of the Earth and Planetary Interiors
JF - Physics of the Earth and Planetary Interiors
SN - 0031-9201
ER -