Buoy Platform Development for Observation of Tsunami and Crustal deformation
Buoy Platform Development for Observation of Tsunami and Crustal deformation
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海啸和地壳变形观测浮标平台开发
DOI：
10.1007/1345_2015_114
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发表时间：
2016
期刊：
影响因子：
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通讯作者：
and Y. Kaneda
中科院分区：
文献类型：
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作者：
Takahashi N.;Y. Ishihara;T. Fukuda;H. Ochi;J. Tahara;T. Mori;M. Deguchi;M. Kido;Y. Ohta;R. Hino;K. Mutoh;G. Hashimoto;O. Motohashi;and Y. Kaneda
我们与日本海洋地球科学技术机构、东北大学和日本宇宙航空研究开发机构合作，建造了一个浮标系统，用于实时观测海啸和地壳变形。我们的系统最重要的特点是抵抗日本周围大地震破裂带的强海流（例如，黑潮最大速度> 5节），以及实时传输数据的能力。我们的系统有四个单元：（1）一个浮标站，其GPS/声学站作为中心基地，（2）一个位于海面以下1，000米处的有线终端站（WES），其作为分段基地，（3）一个压力海底单元（PSU），其包括一个压力传感器，以及（4）六个GPS/声学转发器，用于测量地壳变形。用于探测海啸的压力数据和地壳形变的垂直分量通过线端和浮标站发送到陆地站，正常模式下间隔1 h，海啸模式下间隔15 s。浮标和六个转发器之间测量的数据也每隔一周发送到陆地站。铱卫星用于将所有数据传输到地面站。压力观测的动态范围为+scin-8米，精细分辨率为2毫米，地壳形变测量的精度小于1米。我们对系统进行了为期5个月的观察，并进行了海上试验。由于电池的重量，观察期的长度会影响整个系统。我们重新安排了整个系统的几何形状，使其具有更重的重量和浮标上的大量电池，考虑到长期观察，并决定松弛比为1.6。此外，重要的是要长时间观察，以尽量减少电力消耗。我们使用双脉冲的PSU和WES之间的声学数据传输。两个脉冲之间的时间差表示观察到的压力值。对于PSU，我们根据2011年东北地震产生的海啸数据设计了海啸模式，这些数据由有线网络系统数据和离线底部压力数据记录。结果证实，即使第一海啸信号包括强震信号，也可以检测到海啸。在这种情况下，海啸是在第一次地震到达后10-20秒检测到的。在海上试验中，我们成功测试了我们设计的海啸模式。利用浮标系统在强海流区进行了为期5个月的压力和地壳形变实时观测。但是，目前有一些问题需要解决。对于声波数据传输，WES处声波信号检测的1 ms阶跃差、多个相位的错误检测是需要解决的问题。我们将考虑分配映射的传输数据的时间差的双脉冲，并采取措施的PSU和WES。此外，我们还考虑了未来降低松弛率的策略。从WES到浮标站的数据传输，我们经历了钢丝绳的电气不健康，这是由于渔业活动的损坏和浮标旋转带来的扭矩。我们考虑了减少旋转的对策。
We constructed a buoy system for real-time observations of tsunamis and crustal deformation in collaboration with the Japan Agency for Marine-Earth Science and Technology, Tohoku University, and the Japan Aerospace Exploration Agency. The most important characteristics of our system are resistance to the strong sea currents in the large-earthquake rupture zone around Japan (e.g., the Kuroshio maximum speed > 5 knots), and the capability to transmit data in real-time. Our system has four units: (1) a buoy station with a GPS/Acoustic station serving as a central base, (2) a wire-end station (WES) 1,000 m below the sea surface that serves as a staging base, (3) a pressure seafloor unit (PSU) comprising a pressure sensor, and (4) six GPS/Acoustic transponders to measure crustal deformation. The pressure data used to detect tsunamis and the vertical component of crustal deformation are sent to the land station via the wire-end and buoy stations at intervals of 1 h in normal mode and 15 s in tsunami mode. The data measured between the buoy and six transponders are also sent to the land station at 1-week intervals. The Iridium satellite is used for data transmission of all data to land station. The dynamic range for pressure observations is + ∕− 8 m with a fine resolution of 2 mm, and the accuracy of the crustal deformation measurements is less than 1 m. We tuned the system for an observation period of 5 months and carried out a sea trial. The length of the observation period influences the total system due to the weight of the battery. We rearranged the geometry of the total system to new one with heavier weight and a lot of batteries on the buoy considering long period observation and decided upon a slack ratio of 1.6. In addition, it is important for a long observation period to minimize electrical consumption. We used double pulses for acoustic data transmission between the PSU and WES. The time difference between two pulses indicates the observed pressure value. For the PSU, we designed a tsunami mode on the basis of data from the tsunami generated by the 2011 earthquake off Tohoku, which were recorded by cabled network system data and offline bottom pressure data. The results confirmed that a tsunami can be detected even if the first tsunami signals include strong-motion signals. In this case, the tsunami was detected 10–20 s after the first seismic arrival. During sea trials, we successfully tested the tsunami mode we designed. We succeeded real-time observation of pressure and crustal deformation using buoy system in strong sea current speed area for 5 months. However, there are some issues to be resolved at this moment. For acoustic data transmission, 1 ms step difference of the detection of acoustic signals at the WES, wrong detection of the multiple phases are issues to be resolved. We will consider assigned mapping of transmitted data to the time difference of the double pulses and take measures on the PSU and WES. In addition, we consider strategy to reduce slack ratio in the future. For data transmission from the WES to the buoy station, we experienced electrical unhealthy of the wire rope due to damages by the fisheries activities and the torsion brought by rotation of the buoy. We consider the countermeasure to reduce the rotation.