Seismological Study of 920km-mantle Discontinuity and the Mantle Transition Zone

920km地幔不连续面和地幔过渡带地震学研究

• 批准号: 07640550
• 负责人: KAWAKATSU Hitoshi
• 金额: $ 1.47万
• 依托单位: University of Tokyo
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 1995
• 资助国家: 日本
• 起止时间: 1995 至 1996
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-07640550/
• 关键词: mantle transition zone; 920km discontinuity; J-array; structure of earth's interior

We have shown that certain features seismologically observable do exist in the mid-mantle beneath several subduction zones in the western ocean hemisphere.By stacking hundreds of short-period seismograms observed in Japan ("J-array"), we have suggested that there is a seismic discontinuity at a depth of-920km beneath Tonga, Japan, and Indonesia subduction zones. Further study for Indonesia subduction zone, however, revealed a large depth variation of the discontinuty and thus we now cell it a "mid-mantle discontinuity". The depth variation of the mid-mantle discontinuity beneath the Indonesia arc, where the discontinuity deepens from 940 km at the eastern end to 1080 km at the western end, appears to be well correlated with the location of the high-velocity anomalies (HVA) in recent tomographic models. However, the mid-mantle discontinuity cannot be simply coincided with the bottom of the high-velocity anomalies as was suggested in our earlier paper as one possible explanation, because … More a velocity increase at the discontinuity is observed from the waveform analysis.We utilized near receiver P-to-S conversion waves (so-called receiver function) to study the effect of the presence of a slab on the mantle transition zone discontinuities. Broadband waveforms of deep events occurred in Tonga observed at three stations in the northwestern ocean hemisphere, HIA,MDJ,MAJO,are stacked to produce receiver functions beneath those stations. Beneath the station in the northeast China (MDJ) where the subducted Pacific plate appears to stagnate along the '660-km' discontinuity, the discontinuity response function has more complicated features than those of other stations. The inversion result indcates no depression of the '660-km' discontinuity at the tip of the subducting slab beneath MDJ ; instead a multiple-discontinuity structure down to a depth of 780 km (at 670km, 740km and 780km) is observed. We interpret these features as the first in situ evidence for the garnet*ilemenite*perovskite phase transformation, as well as for gamma-spinel*perovskite+ Mg- wustite transformation. Less

我们已经证明，在西大洋半球的几个俯冲带之下的中地幔中确实存在某些地震学上可观测到的特征，通过叠加在日本观测到的数百个短周期地震记录（“J-阵列”），我们提出在汤加、日本和印度尼西亚俯冲带之下-920km处存在地震间断。然而，对印尼俯冲带的进一步研究表明，该间断面的深度变化很大，因此我们称之为“中地幔间断面”。印度尼西亚弧下的中地幔不连续的深度变化，其中不连续加深940公里的东端到1080公里的西端，似乎是很好的相关性与最近的层析模型中的高速异常（HVA）的位置。然而，中地幔不连续不能简单地与高速异常的底部重合，正如我们在早期的文章中作为一种可能的解释所建议的那样，因为 ...更多信息 利用近场接收P-S转换波（接收函数）研究了板片的存在对地幔过渡带不连续面的影响。将位于西北大洋半球的HIA、MDJ、MAJO三个台站观测到的汤加深部地震宽带波形叠加，得到这些台站下方的接收函数。在中国东北地区（MDJ），俯冲的太平洋板块沿“660-km”间断沿着停滞，其间断响应函数较其它台站更为复杂。反演结果表明，MDJ俯冲板片端部的“660-km”不连续面没有凹陷，而是在780 km深处（670 km、740 km和780 km处）观察到了多个不连续面结构。我们将这些特征解释为石榴石 * 钛铁矿 * 钙钛矿相变以及γ-尖晶石 * 钙钛矿+ Mg-浮氏体转变的第一个原位证据。少

项目成果

Niv and Kawakatsu: "Depth variation of the mid-mantle seismic discontinuity" Geophysical Research Letters. 24. 429-432 (1997)

Niv 和 Kawakatsu：“中地幔地震不连续性的深度变化”地球物理研究快报。

Niv and Kawakatsu: "Complex structure of the mantle discontinuities at the tip of subducting slab beneath the northeast china" Journal of Physics of Earth. 44. 701-711 (1996)

Niv 和 Kawakatsu：“中国东北地区俯冲板片顶端地幔不连续性的复杂结构”，《地球物理学杂志》。

Niu, F., and H.Kawakatsu: "Complex structure of the mantle discontinuities at the tip of the subducting slab beneath the northeast China : a preliminary investigation of broadband receiver functions" J.Phys.Earth. 44. 701-711 (1996)

Niu, F. 和 H.Kawakatsu：“中国东北地区俯冲板片顶端地幔不连续性的复杂结构：宽带接收器功能的初步研究”J.Phys.Earth。

Niu and Kawakatsu: "Direct evidence for the undulation of the 660-km discontinuity beneath Tonga:Comparison of Japan and California array data" Geophysical Research Letters. 22. 531-534 (1995)

Niu 和 Kawakatsu：“汤加下方 660 公里不连续性波动的直接证据：日本和加利福尼亚阵列数据的比较”地球物理研究快报。

Niv and Kawakatsu: "Complex structure of the mantle discontinuities at the tip of the subducting slab beneath the northeast china" Journal of Physics of the Earth. 44. 701-711 (1996)

Niv 和 Kawakatsu：“中国东北地区俯冲板片顶端地幔不连续性的复杂结构”，《地球物理学杂志》。