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并提高预测喷发的能力很重要。 Axial Seamount是一座海底火山，距离俄勒冈州海岸300英里，已经研究了近四十年。 该火山在周围的海底上升约3000英尺，其山顶的特征是5英里的2英里火山口，深300英尺。 该火山于1998年，2011年和2015年爆发，最后一次爆发被有线天文台捕获，该天文台是海洋天文台倡议的一部分。 天文台包括一个地震网络，该地震网络检测地震和海底压力传感器，该地震传感器表明，随着岩浆驶入火山，火山爆发时，火山口地板在爆发之间缓慢上升，并在释放岩浆时迅速下沉。 海底的某些上下移动是由于火山口的基础的断层而发生的，有些是因为火山像气球一样膨胀和放气。哪种机制是最重要的，随着火山接近喷发的时间，这是否随着时间而变化。该项目将安装一个10年的声音传输的4个建筑网络，该网络将监视声波在电台之间传播的时间，以测量电台之间水平距离的变化。 一个站将连接到电缆天文台，以便实时获得测量。 这些测量结果将限制断层运动和岩浆腔通胀和放气的相对作用。 声学网络还将支持实验，以学习如何使用声学命令来控制海底机器人，并比较商业公司构建的校准压力传感器和两个已经在天文台上的学术校准压力仪器。该项目将培训一名研究生和至少一名本科生的本科实习生。将来，为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潜艇斜坡。 通过在各种环境中研究火山主义，可以为提高我们对火山和喷发预测的理解做出的努力。 实际上，中海山脊火山可能代表了一些最可理解的系统，因为它们具有较浅的岩浆系统，相对均匀的岩石学和已知的地壳厚度。 轴向海山是全球中山脊全球网络上最广泛研究的地点之一。 在1998年，2011年和2015年观察到了三次爆发，地震网络和底压和倾斜仪器在海洋天文台倡议（OOI）区域有线电视阵列（RCA）记录。从校准的海底压力传感器记录通货膨胀和快速综合爆发的循环中，有几乎连续的20年记录，这与爆发是通货膨胀的假设一致的。 然而，垂直的大地测量观察结果不能完全区分广泛分布的通货膨胀和升高的火山口，这是由于埋在外向的倾斜断层上的移动所容纳的，这是轴向火山口的东壁和西墙。 该项目将在轴向海山上安装一个为期10年的4层声网络，该网络将在每对发音器之间进行范围，并在每个应答器上包括一个压力表，温度传感器和速度计。 一个站将连接到OOI-RCA，从而实现了对应答器阵列的实时数据采集和控制。了解火山口的动态以及环形断层在适应应变和调节喷发中的作用是火山研究中的一个重要主题。 声学网络实现的水平应变测量将与海底压力观测值的持续垂直地理位置结合在一起，并重复AUV映射，确定岩浆腔室膨胀以及位于东部和西卡尔德拉（East West Caldera）壁下方的外向浸入断层上的岩浆腔膨胀以及运动的相对作用。 这些观察结果将用于确定当地震率低时，在重置周期的早期，向外浸入断层是否被锁定。 然后，可以使用地震目录来推断耦合水平在喷发循环中是否有所不同。 与迄今为止获得的水平范围还将贡献数据，以支持更多的岩浆腔膨胀模型，并将限制在声学基准中传播的堤防的宽度。次要目标是提供一个声学网络，可以支持展示和优化AUVS的远程沟通和导航的努力，这是迈向远程操作的AUVS部署的重要一步，该步骤可以捕获未来的爆发。该奖项反映了NSF的法定任务，并通过使用该基金会的知识优点和广泛影响来评估NSF的法定任务，并被认为是值得的支持。