Elucidating the water content in the oceanic mantle using the ocean bottom seismometers

使用海底地震仪阐明大洋地幔中的水含量

• 批准号: 20J22082
• 负责人: KIM Hye Jeong
• 金额: $ 1.79万
• 依托单位: The University of Tokyo
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for JSPS Fellows
• 财政年份: 2020
• 资助国家: 日本
• 起止时间: 2020-04-24 至 2023-03-31
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-20J22082/
• 关键词: 沈み込み帯; レシーバー関数; 海底地震観測; 堆積層; 地震波速度構造; スラブ; レシーバー関数

Our research aims to elucidate the hydrated regions under the Pacific plate of various ages and the subduction beneath Japan by locating low-velocity zones with in situ observations. However, the ocean bottom seismometer (OBS) records were difficult to use to gain a reliable analysis. The highly complex record due to the structure (water and slow velocity sediment) was a challenge. This research aims to exactly understand the challenges and further present methods that can overcome the difficulties.In the second year of FY2021, our work that discusses the effects of slow seafloor sediment and suggests a way to overcome the influence using the data in off Tohoku region has been published in an international journal. The work shows the low-velocity zone of the subduction zone extends beneath the shallow depths than previously reported. To discuss the variability along the trench, we collected additional OBS arrays in the off Aomori and off Ibaraki regions to extend the imaging region. The data has been pre-processed using active source records for determining component azimuths of the OBSs.In addition, a method to constrain seafloor sediment structures using passive records is developed. Research progress during FY2020 and 2021 helped us to realize that identifying sediment phases in the OBS records is important to do a structural analysis of deeper depths of 100 km. During this year, we attempted to use body waves to constrain sediment structures in high resolution and succeeded. The result of this work is planned to be presented at conferences in FY2022.

我们的研究旨在通过定位带有原位观察结果的低速区，阐明各个年龄和日本下方的俯冲板下的水合区域。但是，很难使用海洋底部地震计（OBS）记录来获得可靠的分析。由于结构（水和缓慢的速度沉积物）引起的高度复杂的记录是一个挑战。这项研究旨在准确理解可以克服困难的挑战，并进一步提出的方法。在2021财年的第二年中，我们的工作讨论了缓慢的海底沉积物的影响，并提出了一种在国际杂志上发表了使用Toohoku地区的数据来克服影响的方法。该工作显示俯冲带的低速区延伸到浅深度以前的延伸。为了讨论沿沟渠的变异性，我们收集了AOMORI和IBARAKI区域中的其他OBS阵列以扩展成像区域。使用主动源记录对数据进行了预处理，以确定OBS的组件方位角。此外，开发了一种使用被动记录来限制海底沉积物结构的方法。在2020财年和2021财年期间的研究进展有助于我们意识到，在OBS记录中识别沉积物阶段对于对100公里深度的结构分析很重要。在这一年中，我们试图使用身体波来限制高分辨率并取得成功的沉积物结构。这项工作的结果计划在2022财年的会议上提出。

项目成果

Receiver Function Imaging of the Amphibious NE Japan Subduction Zone: Effects of Low-Velocity Sediment Layers

日本东北部俯冲带两栖接收函数成像：低速沉积层的影响

• 发表时间: 2021
• 作者: HyeJeong Kim;Hitoshi Kawakatsu;Takeshi Akuhara;Masanao Shinohara;Hajime Shiobara;Hiroko Sugioka;Ryota Takagi
• 通讯作者: Ryota Takagi