Development of free-fall pop-up type ocean bottom strong motion meter for study of asperites

开发用于星石研究的自由落体弹出式海底强运动仪

• 批准号: 16540380
• 负责人: SHINOHARA Masanao
• 金额: $ 1.6万
• 依托单位: The University of Tokyo
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 2004
• 资助国家: 日本
• 起止时间: 2004 至 2005
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-16540380/
• 关键词: Ocean bottom seismometer; Accelerometer; Strong motion observation

To understand characteristics of large earthquakes which occur in a subduction zone, it is necessary to study an asperity where large earthquakes occur repeatedly. Because observation near an asperity is needed for studies of asperities, ocean bottom seismometer (OBS) is essential to observe seismic waves from earthquakes in subduction area. Since a conventional OBS is designed for high-sensitivity observation, OBS records of large earthquake which occurred near OBS are often saturated. To record large amplitude seismic waves, a servo-type accelerometer is suitable. However it was difficult for OBS to use an accelerometer due to large electric power consumption. Recently a servo-type accelerometer with a large dynamic range and low-power consumption is being developed. In addition, a pressure vessel of OBS can contain much more batteries by using a large size titanium sphere. For the long-term sea floor observation of aftershock of the 2004 Sumatra-Andaman Earthquake, we installed a small three-component accelerometer to a conventional long-term OBS and obtained both high-sensitivity seismogram and low-sensitivity (strong motion) accelerograms on the sea floor. The OBS with the accelerometer was deployed on February 24, 2005 in a southern part of the source region of the 2004 Sumatra-Andaman Earthquake, and recovered on August 3. The accelerograms were obtained from the deployment to April 13 when the CF memory became full. Although there are some small troubles for the recording, we could obtain low-sensitivity accelerograms on sea floor with a good S/N ratio. The largest aftershock (2005/3/28 Mw=8.5) whose epicentral distance is about 470km was recorded and the records of this aftershock is not saturated. We continue to improve the system including re-selection of a sensor for better quality data

为了了解发生在俯冲带中的大地震的特征，有必要研究大地震重复发生的凹凸体。海底地震仪（OBS）是研究海底凹凸体的重要手段，它是海底凹凸体附近地震波观测的基础。由于传统的OBS是为高灵敏度观测而设计的，所以在OBS附近发生的大地震的OBS记录往往是饱和的。为了记录大振幅的地震波，伺服型加速度计是合适的。然而，由于大的电力消耗，OBS难以使用加速度计。最近，一个伺服型加速度计具有大的动态范围和低功耗正在开发中。另外，通过使用大尺寸的钛球，OBS的压力容器可以容纳更多的电池。为了对2004年苏门答腊-安达曼地震的余震进行长期海底观测，我们在常规的长期OBS上安装了一个小型三分量加速度计，获得了高灵敏度的地震记录和低灵敏度（强震）的海底加速度记录。带有加速度计的OBS于2005年2月24日部署在2004年苏门答腊-安达曼地震震源区的南部，并于8月3日恢复。从部署到4月13日CF存储器满时获得了加速度图。虽然记录过程中存在一些小的问题，但我们可以获得信噪比较好的低灵敏度海底加速度记录。2005年3月28日记录到最大余震（Mw=8.5），震中距约470 km，余震记录不饱和。我们继续改进系统，包括重新选择传感器以获得更高质量的数据

项目成果

Low-sensitivity acceleration seismic records obtained on sea floor in the source region of the 2004 Sumatra-Andaman Earthquake

2004年苏门答腊-安达曼地震震源区海底获得的低灵敏度加速地震记录

• 发表时间: 2006
• 期刊: Chikyu monthly Gogai (in press)
• 作者: Masanao Shinohara;Toshihiko Kanazawa;Tomoaki Yamada;Yoshiko Yamanaka
• 通讯作者: Yoshiko Yamanaka

2004年スマトラ・アンダマン地震震源域における海底観測による加速度計地震記録

2004 年苏门答腊-安达曼地震震中海底观测的加速度计地震记录

• 发表时间: 2006
• 期刊: 月刊地球 号外
• 作者: 篠原雅尚;金澤敏彦;山田知朗;山中佳子
• 通讯作者: 山中佳子