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Receiver function imaging of high-resolution seismic discontinuity structure in the crust and the mantle beneath the Japan Islands

日本列岛地壳和地幔高分辨率地震不连续结构的接收函数成像

基本信息

批准号：
14340131
负责人：
HIRAHARA Kazuro
金额：
$ 7.87万
依托单位：
Nagoya University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2004
项目状态：
已结题

项目摘要

We migrate the receiver functions(RFs) observed at high-density short and broad-band seismic stations (J-array, Hi-net and F-net) to investigate the seismic velocity discontinuity structure in the crust and the upper mantle beneath the Japan Islands.For the crust and the uppermost mantle structure, we use short-period RFs. In the Chugoku and Kinki region in southwest Japan where the stations are closely installed, we can recognize positive RF amplitudes corresponding to P-S converted phases at the velocity discontinuity between the upper and lower crust and the Moho discontinuity. The positive RF amplitudes corresponding to the oceanic Moho above the subducting Philippine Sea(PHS) plate are clearly traced down to a depth of 100 km. Comparison of the RFs with deep seismicity shows that the earthquakes in the oceanic crust and in the slab occur down to a depth of 40-60km and the PHS has the deeper aseismic portion.In the northeast Japan, we can successfully catch the slab layering struct … More ure. Namely, we can clearly image the top of the subducting Pacific slab, the oceanic Moho and surprisingly the bottom of the slab. And the RFs suggest the existence of seismic discontinuity structure corresponding to the lower seismic zone in the double seismic zone. These new findings impose strong constraints on the thermal structure and the material composition in and around the subducting slab.For the deep discontinuity structure in the upper mantle, we use the data from broadband seismic stations. The 410 km discontinuity seems to be fiat except for the inside of the slab, where the 410 is elevated locally by 30 km. The 660 is gradually inclined toward the west, which depression is caused by the cold stagnant slab. In addition, examination of frequency dependence of RF amplitudes corresponding to 410 and 660 km shows that RFs in the Japan Islands has different frequency appearance comparing to those in the Korea, suggesting that there exists different amount of water in the upper mantle beneath the Japan Islands and the Korea. Less

本文对高密度短波和宽带地震台站（J-array、Hi-net和F-net）观测到的接收函数（rf）进行了迁移，研究了日本列岛地壳和上地幔的地震速度不连续结构。对于地壳和上地幔结构，我们使用短周期rf。在台站密集分布的日本西南部Chugoku和Kinki地区，我们可以在上下地壳速度不连续和莫霍不连续处识别到P-S转换相对应的正RF振幅。在俯冲的菲律宾海（PHS）板块上方，与大洋莫霍相对应的正射频振幅可以清楚地追溯到100公里的深度。与深部地震活动性的对比表明，洋壳和陆板地震发生深度为40 ~ 60km，小灵通地震部分较深。在日本东北部，我们可以成功地捕捉到板状分层结构。也就是说，我们可以清楚地描绘出俯冲的太平洋板块的顶部，大洋莫霍，以及令人惊讶的板块底部。在双地震带中存在与下地震带相对应的地震不连续结构。这些新发现对俯冲板块内部和周围的热结构和物质组成提出了强有力的限制。对于上地幔深部不连续构造，我们使用宽带地震台站的数据。410公里的不连续性似乎是固定的，除了板的内部，410在局部升高了30公里。660逐渐向西倾斜，这是由冷滞板造成的洼地。此外，对410 km和660 km对应的RF振幅的频率相关性分析表明，日本列岛的RF与韩国的RF具有不同的频率表现，这表明日本列岛和韩国的上地幔存在不同的水量。少