MRI: Offshore Earthquake Monitoring at Subduction Zones Using Autonomous Underwater Vehicles and High-Speed Optical Telemetry For Data Retrieval

MRI：使用自主水下航行器和高速光学遥测数据检索在俯冲带进行近海地震监测

• 批准号: 1532035
• 负责人: John Collins
• 金额: $ 92.32万
• 依托单位: Woods Hole Oceanographic Institution
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-08-15 至 2021-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1532035&HistoricalAwards=false
• 关键词: MRI; Offshore; Earthquake; Monitoring; Subduction

The earth's subduction zones, where one tectonic plate overrides another, are the sites of the planet's largest and most dangerous earthquakes. Recent examples are the 2004 magnitude 9.1 Sumatra and the 2010 magnitude 9 Tohoku, Japan earthquakes. In addition to massive destruction brought about by ground shaking, both of these earthquakes generated devastating tsunamis. These events are a reminder that fault motion in our planet's largest earthquakes happens offshore under the continental shelf, a region that is challenging to monitor. The scarcity of seismic instrumentation in the source regions of these great earthquakes has limited the seismological community's ability to answer fundamental scientific questions and to evaluate hazards in real-time. Sustained offshore monitoring of subduction zones would not only lead to improved understanding of these faults but also potentially allow the identification of increased short-term risk. Extensive foreshock sequences located far offshore preceded both the 2010 Tohoku event and the recent 2014 magnitude 9 Pisagua Chile earthquake. These sequences demonstrated that there are detectable time periods on the scale of weeks when subduction zones are more likely to produce a large rupture. To fully understand this basic fault behavior and possibly utilize an understanding of it to reduce risk, rapid access to high quality seismic data from offshore directly above the great earthquakes is needed. The seismological community routinely deploys seismographs offshore, but data access requires ship-based instrument recovery, a lengthy and expensive task that may not be possible or desirable during a potential foreshock sequence. Seismology is a fast moving science: earthquakes are detected within seconds, magnitude estimates are tweeted within minutes, fault planes are determined within hours, and research articles are often submitted within weeks of a major earthquake. The full potential of offshore seismic data can only be realized if these data are rapidly ingested into data centers. Recent advances at Woods Hole Oceanographic Institution in optical telemetry and marine robotics, coupled with the availability of commercial off-the-shelf low-power seismic sensors, data loggers and atomic clocks offer the capability for multi-year deployments of arrays of ocean-bottom seismographs (OBS) that are capable of delivering high-frequency, accurately-timed seismic data to shore with data latencies of hours to days without OBS recovery. This project will develop such a system by integrating a WHOI-designed optical modem capable of telemetry rates of 20 Mbits/second with an OBS and with a long-range (up to 286 nautical miles) REMUS Autonomous Underwater Vehicle (AUV). These proven rates allow telemetry of a week of high-rate (100 Hz) seismic data on 4 channels (ground motion and pressure) in minutes (or a year of data in less than 2 hours). Moreover, accurate timing is critical for earthquake location but OBS lack the benefit of GPS timing. The optical link will also allow measurement of the offset of the OBS clock relative to a GPS-synchronized time signal carried by the AUV to a precision of ~1 microsecond. These technologies will make possible multi-year deployments of OBS arrays with on-demand data offload and clock-check without the need for annual recovery/re-deployment cruises, saving hundreds of thousands of dollars per experiment. This capability will be particularly suitable for the dense near-shore arrays needed to monitor subduction zones.

地球的俯冲带（一个构造板）覆盖了另一个构造区，是地球最大，最危险的地震的地点。最近的例子是2004年9.1苏门答腊和2010年的9级，日本地震。除了震撼地面造成的巨大破坏外，这两种地震都造成了毁灭性海啸。这些事件提醒人们，我们地球上最大的地震中的断层运动发生在大陆架下的海上，该地区具有挑战性。这些大地震源区域中地震仪器的稀缺性限制了地震界回答基本科学问题并实时评估危害的能力。对俯冲带的持续海上监测不仅会改善对这些断层的理解，而且还可以识别出增加的短期风险。位于遥远近海的广泛预测序列之前是2010年的Tohoku事件和最近的2014年9级Pisagua智利地震。这些序列表明，在俯冲带更有可能产生较大破裂的几周尺度上存在可检测的时间。为了充分理解这种基本的断层行为，并可能利用对IT的理解来降低风险，需要快速访问高质量的地震数据，直接从大地震上方上方的海上数据获得。 地震社区通常会在海上部署地震仪，但是数据访问需要基于船舶的仪器恢复，这是一项漫长而昂贵的任务，在潜在的预换序列中可能是不可能或不可取的。地震学是一门快速移动的科学：在几秒钟内检测到地震，在几分钟内发布了幅度估计，在几小时内确定断层平面，并且研究文章通常在大地震发生后几周内提交。 只有在这些数据迅速摄入数据中心时，才能实现离岸地震数据的全部潜力。伍兹孔海洋学在光学遥测和海洋机器人技术中的最新进展，再加上商业现成的低功能地震传感器，数据记录仪和原子钟的可用性，可为高度数据划分的数据提供多年的多年阵列，这些数据能够提供高度的数据，这些数据能够提供高度的数据，以确保精确的数据供应。 OBS恢复。该项目将通过集成WHOI设计的光学调制解调器，能够与OBS和远距离（高达286海里）Remus Automons水下车（AUV）相结合。这些经过验证的速率允许在4个通道（地面运动和压力）（或在不到2小时内的一年的数据）内对一周的高速（100 Hz）地震数据进行遥测。此外，准确的时机对于地震位置至关重要，但OBS缺乏GPS计时的好处。光学链路还将允许测量ABS时钟的偏移相对于AUV携带的GPS同步时间信号的偏移，精度为〜1微秒。这些技术将通过按需数据卸载和时钟检查可以使OBS阵列的多年部署无需年度恢复/重新部署巡航，从而节省了每项实验数十万美元。该功能特别适合监视俯冲带所需的近近岸阵列。