An Acoustic Array At Axial Seamount for Geodesy and Autonomous Vehicle Support

用于大地测量和自动驾驶车辆支持的轴向海山声学阵列

• 批准号: 2130060
• 负责人: William Wilcock
• 金额: $ 86.71万
• 依托单位: University of Washington
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-12-15 至 2026-11-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2130060&HistoricalAwards=false
• 关键词: Acoustic; Array; Axial; Seamount; Geodesy

Studies of all kinds of volcanoes are important to understand how volcanoes work and improve the ability to forecast eruptions. Axial Seamount is a submarine volcano that lies 300 miles off the coast of Oregon that has been studied for nearly four decades. The volcano rises about 3000 ft above the surrounding seafloor and its summit is characterized by a 5-mile by 2-mile caldera that is 300 ft deep. The volcano erupted in 1998, 2011 and 2015, with the last eruption captured by a cabled observatory that is part of the Ocean Observatories Initiative. The observatory includes a seismic network that detects earthquakes and seafloor pressure sensors that show that the caldera floor rises slowly between eruptions as magma moves into the volcano and sinks rapidly during eruptions when magma is released. Some of the up and down movement of the seafloor occurs by slip on faults that underlie the caldera and some occurs because the volcano inflates and deflates like a balloon. Which mechanism is most important and whether this changes with time as the volcano nears an eruption is unknown. This project will install a 10-year 4-station network of acoustic transponders that will monitor the time for sound waves to travel between stations to measure changes in the horizontal distance between stations. One station will be connected to the cabled observatory so that measurements will be obtained in real time. These measurements will constrain the relative roles of fault motions and magma chamber inflation and deflation. The acoustic network will also support experiments to learn how to control submarine robots with acoustic commands and compare a calibrated pressure sensor built by a commercial company with two academic calibrated pressure instruments that are already on the observatory. The project will train a graduate student and at least one undergraduate intern from an underrepresented group. In the future, the techniques developed for this project can be applied in other settings such as subduction zones and unstable submarine slopes. Efforts to advance our understanding of volcanoes and eruption forecasting are best served by studying volcanism in a wide variety of settings. Indeed, mid-ocean ridge volcanoes may represent some of the most tractable systems to understand because they have shallow magmatic systems, relatively uniform petrology, and known crustal thickness. Axial Seamount is one of the most extensively studied sites on the global network of mid-ocean ridges. Three eruptions have been observed in 1998, 2011 and 2015, with the most recent recorded by the seismic network and bottom pressure and tilt instruments on the Ocean Observatories Initiative (OOI) Regional Cabled Array (RCA). There is a near continuous 20-year record from calibrated seafloor pressure sensors recording cycles of inflation and rapid syn-eruptive deflation that are consistent with the hypothesis that the eruptions are inflation predictable. However, the vertical geodetic observations cannot fully discriminate between broadly distributed inflation and uplift of the caldera that is accommodated by movement on the buried outward-dipping faults that underlie the east and west walls of the Axial caldera. This project will install a 10-year 4-station acoustic network at Axial Seamount that will range between each pair of transponders and include a pressure gauge, temperature sensor and velocimeter on each transponder. One station will be connected to the OOI-RCA enabling real time data acquisition and control of the transponder array. Understanding the dynamics of calderas and the role of ring faults in accommodating strain and modulating eruptions is an important topic in volcano research. The horizontal strain measurements enabled by the acoustic network will, in conjunction with ongoing vertical geodesy from seafloor pressure observations and repeat AUV mapping, determine the relative roles of magma chamber inflation and deflation and motion on the buried outward dipping faults that lie beneath the east and west caldera walls. These observations will be used to determine whether the outward dipping faults are locked early in the reinflation cycle when earthquake rates are low or whether they slip aseismically. The seismic catalog can then be used to infer whether the level of coupling varies during the eruptive cycle. The horizontal ranging will also contribute data to support more detailed models of magma chamber inflation than have been obtained to date and will constrain the width of dikes that propagate across the acoustic baselines. A secondary objective is to provide an acoustic network that can support efforts to demonstrate and optimize remote communication and navigation of AUVs, an essential step toward the deployment of remotely operated AUVs that can capture future eruptions.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

对各种火山的研究对于了解火山如何工作和提高预测喷发的能力非常重要。 轴海山是一座海底火山，位于距离俄勒冈州海岸300英里的地方，人们已经对它进行了近四十年的研究。 这座火山高出周围的海底约3000英尺，其山顶的特点是一个5英里乘2英里的破火山口，深300英尺。 该火山于1998年，2011年和2015年爆发，最后一次喷发由海洋观测站计划的一部分有线观测站捕获。 该观测站包括一个检测地震的地震网络和海底压力传感器，这些传感器显示，当岩浆进入火山时，火山口底部在喷发之间缓慢上升，而在岩浆释放时，火山口底部在喷发期间迅速下沉。 海底的一些上下运动是由于火山口下面的断层滑动造成的，而另一些则是由于火山像气球一样膨胀和收缩造成的。哪种机制是最重要的，以及当火山接近喷发时，这种机制是否会随着时间的推移而变化，都是未知的。该项目将安装一个为期10年的4站声波转发器网络，监测声波在各站之间传播的时间，以测量各站之间水平距离的变化。 将有一个观测站与有线观测台相连，以便能够获得真实的测量结果。 这些测量将限制断层运动和岩浆房膨胀和收缩的相对作用。 声学网络还将支持实验，以学习如何通过声学命令控制潜艇机器人，并将商业公司制造的校准压力传感器与天文台上已经存在的两个学术校准压力仪器进行比较。该项目将从代表性不足的群体中培训一名研究生和至少一名本科实习生。今后，为该项目开发的技术可应用于其他环境，如俯冲带和不稳定的海底斜坡。 努力提高我们对火山和喷发预测的理解，最好是通过研究各种环境中的火山活动。 事实上，大洋中脊火山可能代表了一些最容易理解的系统，因为它们有浅的岩浆系统，相对统一的岩石学，以及已知的地壳厚度。 轴海山是全球洋中脊网络上研究最广泛的地点之一。 1998年、2011年和2015年观测到三次喷发，最近一次是由海洋观测站倡议（OOI）区域电缆阵列（RCA）上的地震网络和海底压力和倾斜仪器记录的。有一个近连续20年的记录，从校准的海底压力传感器记录通货膨胀和快速同步喷发通缩周期，这是符合假设的喷发是通货膨胀可预测的。 然而，垂直大地测量观测不能完全区分广泛分布的膨胀和隆起的破火山口，这是由运动所容纳的埋在下面的向外倾斜的断层的东部和西部的墙壁轴破火山口。 该项目将在轴海山安装一个为期10年的4站声学网络，该网络将覆盖每对转发器之间的范围，并在每个转发器上安装一个压力计、温度传感器和速度计。 一个站将连接到OOI-RCA，从而能够进行真实的实时数据采集和转发器阵列的控制。了解破火山口的动力学和环形断层在调节应变和调节喷发中的作用是火山研究中的一个重要课题。 声学网络实现的水平应变测量将与正在进行的海底压力观测垂直大地测量和重复AUV测绘相结合，确定岩浆房膨胀和收缩以及位于东西破火山口壁下方的埋藏向外倾斜断层的运动的相对作用。 这些观测结果将用于确定向外倾斜的断层是否在地震率较低时在再膨胀周期的早期锁定，或者它们是否在地震中滑动。 地震目录，然后可以用来推断耦合水平是否在喷发周期的变化。 水平测距还将提供数据，以支持比迄今为止获得的更详细的岩浆房膨胀模型，并将限制跨越声学基线传播的堤坝的宽度。第二个目标是提供一个声学网络，以支持演示和优化AUV的远程通信和导航，这是部署远程操作AUV的重要一步，可以捕捉未来的爆发。该奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的知识价值和更广泛的影响审查标准进行评估的支持。