Multiple discontinuities near 660 km beneath Tonga area
Multiple discontinuities near 660 km beneath Tonga area
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DOI：
10.1029/2006gl027262
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发表时间：
2006-10
影响因子：
5.2
通讯作者：
S. Zang;Yuanze Zhou;J. Ning;R. Wei
中科院分区：
文献类型：
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作者：
S. Zang;Yuanze Zhou;J. Ning;R. Wei
我们利用太平洋西北地震台网(PNSN)记录的深部地震研究了汤加俯冲带下的不连续面。利用转换相SDP发现了汤加俯冲带下约660公里处的多个不连续面。还确定了转换后的相位与直接P波的振幅比(Ac/Ap)。Ac/Ap值大的强健转换相最多出现在660-690 km深度范围内，峰值出现在680 km处，其次出现在700-745 km深度范围内，峰值出现在740 km深度范围内。俯冲板对这两个不连续面有明显的压制作用。根据实验和数值研究，一种可能的解释是，第一种不连续是由γ尖晶石向钙钛矿和镁钛矿的转变形成的，第二种不连续是由钛铁矿向钙钛矿的转变形成的。
We study the discontinuities beneath Tonga subduction zone using the deep earthquakes recorded by the Pacific Northwest Seismic Network (PNSN). The multiple discontinuities around 660 km beneath Tonga subduction zone are found using converted phase SdP. The amplitude ratios of the converted phase with the direct P wave (Ac/Ap) are also determined. The largest number of robust converted phases with large Ac/Ap comes from the depth range of 660–690 km, its peak is at 680 km; the second one appears in the depth range of 700–745 km, its peak is at 740 km. The two discontinuities are obviously depressed by the subduction slab. According to experimental and numerical studies, a possible explanation of the observation is that the first discontinuity is formed by the transition of γ‐spinel to perovskite and magnesiowüstite and the second is formed by the transition of ilmenite to perovskite.