Seismic exploration of the deep structure beneath the westsern Pacific

西太平洋深层构造地震勘探

• 批准号: 05402015
• 负责人: FUKAO Yoshio
• 金额: $ 14.66万
• 依托单位: The University of Tokyo
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for General Scientific Research (A)
• 财政年份: 1993
• 资助国家: 日本
• 起止时间: 1993 至 1995
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-05402015/
• 关键词: broadband seismometer; tomography; mantle; core-mantle; westsern Pacific; グローバル地震学; マントル構造; 海洋プレート; ポセイドン計画; 地震波速度; 地球構造; 背弧海盆

Seismic exploration of the deep structure beneath the western PacificThis project aimed at revealing the structure of the deep mantle beneath the western Pacific, the largest subduction zone over the globe.To achieve this goal, we planned(1)to install a broadband station at kamehckoe(kamchatka), (2)to version up the Ponape station, Micronesia, and(3)tomake a tomographic study to obtain a seismic image of the mantle beneath the wastern Pacific.Following is a brief report on the results of our research project.(1)Installation of a broadband station at KamehckoeIn 1993 we made various preparation for the installation of a seismic station, including the acquiement and set up of the equipments, negotiation with Russian researchers, and the construction of a vault by them. In 1994 we set up the broadband instruments inside the vault and the operation started for the two components of the instruments.In 1995 the seismometer of the remaining component started in operation. Now all the three co … More mponent seismometers are operated in normal condition.(2)Version up of the observation system at PonapeIn 1993 the installation of a broadband station was completed at Ponape by a different fund.In 1994 the observation system was up-dated thanks to the replacent of telephone lines with optical cables throughout the island.In 1995 the data transmission system was improved.On the whole, we were able to obtain the data with a good quality throughout the project period.(3)Seismic tomographic study of the Earth's interiorWhole mantle P wave tomography(1993) : We made a whole mantle P wave tomography by increasing the data as 5 times as large as those used in Fukao et al.(1992)and obtained a sharper image of the stagnant slabs in the mantle transition zone.We also measured the travel time differences between P and PP waves by a waveform correlation method on broadband seismograms.Travel time differences were found to be consistent with the tomographic model where the resolution in the model is good.measurement of group velocities of surface waves(1994) : We used the newly obtained broadband data at Ponape and Titi-jima to measure the group velocities of Rayleigh waves.We found that in terms of group velocity the oldest ocean floor(160 Ma)between Mariana and Ponape is fastest and the youngest ocean floor between Mariana and Titi-jima is slowest among the sea floors of the Pacific Ocean.PcP travel time tomography for the core/mantle boundary(1995) : We obtained a laterally heterogeneous structure in the vicinity of the core/mantle boundary(CMB) by a tomographic inversion of P and PcP travel time data. We focused on extracting the significant features of the CMB rather than presenting a new model.We found the low-velocity anomalies beneath southeastern Asia and the high-velocity anomaly under the Arctic region. Less

西太平洋深层结构地震勘探该项目旨在揭示西太平洋下深层地幔的结构，这是全球最大的俯冲带。为了实现这一目标，我们计划(1)在kamehckoe安装一个宽带站（堪察加半岛），（2）对密克罗尼西亚的波纳佩站进行版本更新，以及（3）进行层析成像研究，以获得废太平洋下地幔的地震图像。以下是简要报告我们的研究项目的结果。 (1)在Kamehckoe安装宽带站1993年我们为安装地震台做了各种准备工作，包括设备的购置和安装、与俄罗斯研究人员的谈判以及1994年，我们在拱顶内安装了宽带仪器，仪器的两个部分开始运行。1995年，其余部分的地震仪开始运行。现在所有三个组成的地震仪都在正常状态下运行。（2）波纳佩观测系统的升级1993年，由另一个基金在波纳佩完成了宽带站的安装。1994年观测系统升级了由于全岛电话线已更换为光缆。1995年数据传输系统得到改进。总体而言，我们能够在整个项目中获得质量良好的数据(3)地球内部地震层析研究全地幔P波层析成像(1993)：我们将数据增加到Fukao等人(1992)所用数据的5倍，进行了全地幔P波层析成像，得到了地幔过渡带中静止板片的更清晰图像。我们还通过宽带波形相关方法测量了 P 波和 PP 波之间的行时差异地震图。发现走时差与层析模型一致，模型中的分辨率良好。表面波群速度的测量（1994）：我们使用新获得的波纳佩岛和蒂蒂岛宽带数据来测量表面波群速度。瑞利波的群速度。我们发现就群速度而言，马里亚纳和波纳佩之间最古老的洋底（160 Ma）最快，而马里亚纳和蒂蒂岛之间最年轻的洋底是太平洋海底中最慢的。PcP 核/地幔边界走时层析成像（1995）：我们通过 P 和PcP 旅行时间数据我们专注于提取 CMB 的显着特征，而不是提出新模型。我们发现了东南亚下方的低速异常和高速异常。北极地区以下。

项目成果

大林政行、 桜井太郎、 深尾良夫: "走時インバーションによるマントル3次元構造" 地学雑誌. 104,7. 934-940 (1995)

Masayuki Obayashi、Taro Sakurai、Yoshio Fukao：“通过旅行时间反演的地幔三维结构”地质杂志 104,7（1995）。

Geller,R.J.and N.Takeuchi: "A new method for computing highly accurate DSM synthetic seismograms" Geophys.J.Int.123. 449-470 (1995)

Geller,R.J. 和 N.Takeuchi：“一种计算高精度 DSM 合成地震图的新方法”Geophys.J.Int.123。

Sugioka, H., Y.Fukao and S.Sakai: "Anomalously Early First Arrivals to the J-array from Teleseimic Events" J.Phys.Earth. 44. 687-699 (1996)

Sugioka, H.、Y.Fukao 和 S.Sakai：“遥震事件异常提前首次到达 J 阵列”J.Phys.Earth。

Fukao, Y.: "Single-force representation of eartquakes due to landslides or the collapse of caverns" GeoPhys.J.Int.122. 243-248 (1995)

Fukao, Y.：“山体滑坡或洞穴塌陷引起的地震的单力表示”GeoPhys.J.Int.122。

Minoru Takeo: "THE 1993 KUSHIRO-OKI,JAPAN,EARTHQUAKE:A HIGH STRESS-DROP EVENT IN A SUBDUCTIONG SLAB" Geophysical Research Letters. 20. 2607-2610 (1993)

Minoru Takeo：“1993 年日本钏路冲地震：俯冲板中的高应力下降事件”地球物理研究快报。