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Spatial variations of the 660-km discontinuity in the western Pacific subduction zones observed from CEArray triplication data |
Baoshan Wang1, Fenglin Niu2 |
1 Institute of Geophysics, China Earthquake Administration, Beijing 100081, China
2 Department of Earth Science, Rice University, Houston, TX 77005, USA |
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Abstract We examined the spatial variation of velocity structures around the 660-km discontinuity at the western Pacific subduction zones by waveform modeling of triplication data. Data from two deep earthquakes beneath Izu-Bonin and Northeast China are used. Both events were well recorded by a dense broadband seismic network in China (CEArray). The two events are located at approximately the same distance to the CEArray, yet significant differences are observed in their records: (1) the direct arrivals traveling above the 660-km discontinuity (AB branch) are seen in a different distance extent: ~29° for the NE China event, ~23° for Izu-Bonin event; (2) the direct (AB) and the refracted waves at the 660-km (CD branch) cross over at 19.5° and 17° for the NE China and the Izu-Bonin event, respectively. The best fitting model for the NE China event has a broad 660-km discontinuity and a constant high velocity layer upon it; while the Izu-Bonin model differs from the standard IASP91 model only with a high velocity layer above the 660-km discontinuity. Variations in velocity models can be roughly explained by subduction geometry.
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Received: 20 September 2010
Published: 10 February 2011
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Fund:National Natural Science Foundation of China under grant 40874095 and NSF under grant EAR-063566 |
Corresponding Authors:
Baoshan Wang
E-mail: wangbs@cea-igp.ac.cn
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