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
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
摘要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.
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.
基金资助:National Natural Science Foundation of China under grant 40874095 and NSF under grant EAR-063566
通讯作者:
Baoshan Wang
E-mail: wangbs@cea-igp.ac.cn
引用本文:
Baoshan Wang, Fenglin Niu. Spatial variations of the 660-km discontinuity in the western Pacific subduction zones observed from CEArray triplication data[J]. 《地震学报》英文版, 2011, 24(1): 77-85.
Baoshan Wang, Fenglin Niu. Spatial variations of the 660-km discontinuity in the western Pacific subduction zones observed from CEArray triplication data. Earthquake Science, 2011, 24(1): 77-85.