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的工作原理和提高预测喷发的能力非常重要。 轴海山是一座海底火山，位于距俄勒冈州海岸 300 英里的地方，人们对它的研究已经进行了近四十年。 该火山高出周围海底约 3000 英尺，其山顶有一个 5 英里 x 2 英里长、深 300 英尺的破火山口。 该火山曾于 1998 年、2011 年和 2015 年喷发，最后一次喷发由海洋观测计划一部分的有线观测站捕捉到。 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，而在火山喷发期间，当岩浆释放时，火山口底部迅速下沉。 海底的一些上下运动是由于火山口下方的断层滑动而发生的，另一些则是因为火山像气球一样膨胀和收缩而发生的。哪种机制最重要，以及当火山接近喷发时这种机制是否会随着时间而变化尚不清楚。该项目将安装一个为期10年的4站声学应答器网络，该网络将监测声波在站之间传播的时间，以测量站之间水平距离的变化。 一个站将连接到有线天文台，以便实时获得测量结果。 这些测量结果将限制断层运动和岩浆室膨胀和紧缩的相对作用。 该声学网络还将支持实验，以学习如何使用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有的两个学术校准压力仪器进行比较。该项目将培训一名研究生和至少一名来自代表性不足群体的本科生实习生。将来，该项目开发的技术可以应用于其他环境，例如俯冲带和不稳定的海底斜坡。 研究各种环境下的火山活动可以最好地促进我们对火山和喷发预测的了解。 事实上，洋中脊火山可能代表了一些最容易理解的系统，因为它们具有浅层岩浆系统、相对均匀的岩石学和已知的地壳厚度。 轴向海山是全球洋中脊网络中研究最广泛的地点之一。 1998 年、2011 年和 2015 年观测到了三次喷发，最近一次由海洋观测倡议 (OOI) 区域电缆阵列 (RCA) 的地震网络和底部压力和倾斜仪器记录。经过校准的海底压力传感器记录了通货膨胀和快速同步喷发通货紧缩的周期，该记录近乎连续 20 年，这与喷发是可预测通货膨胀的假设是一致的。 然而，垂直大地测量不能完全区分广泛分布的火山口膨胀和隆起，这是由轴状火山口东壁和西壁下方埋藏的向外倾斜断层的运动所适应的。 该项目将在 Axial Seamount 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，并在每个转发器上包括压力表、温度传感器和速度计。 一个站将连接到 OOI-RCA，实现转发器阵列的实时数据采集和控制。了解破火山口的动力学以及环形断层在调节应变和调节喷发中的作用是火山研究的一个重要课题。 声学网络实现的水平应变测量将结合海底压力观测和重复 AUV 测绘正在进行的垂直大地测量，确定岩浆室膨胀和收缩以及运动对位于东部和南部下方的埋藏外倾断层的相对作用。西火山口墙壁。 这些观测结果将用于确定外倾断层是否在地震发生率较低时在再膨胀周期的早期被锁定，或者是否发生抗震滑动。 然后可以使用地震目录来推断耦合水平在喷发周期期间是否发生变化。 水平测距还将提供数据来支持比迄今为止获得的更详细的岩浆室膨胀模型，并将限制穿过声学基线传播的岩墙的宽度。第二个目标是提供一个声学网络，可以支持演示和优化 AUV 远程通信和导航的工作，这是部署能够捕捉未来火山喷发的远程操作 AUV 的重要一步。该奖项反映了 NSF 的法定使命，并被视为值得通过使用基金会的智力优点和更广泛的影响审查标准进行评估来支持。