A Rotating Tiltmeter for Marine Geodesy: Development and Testing at Axial Seamount on the Ocean Observatories Initiative Cabled Array

用于海洋大地测量的旋转倾斜仪：海洋观测站倡议电缆阵列上轴向海山的开发和测试

• 批准号: 1634103
• 负责人: William Wilcock
• 金额: $ 46.58万
• 依托单位: University of Washington
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-09-15 至 2022-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1634103&HistoricalAwards=false
• 关键词: Rotating; Tiltmeter; Marine; Geodesy; Development

Measurements of ground deformation due to the motion of the Earth's tectonic plates are important for scientific research aimed at understanding volcanoes and earthquakes. Tiltmeters are instruments that measure changes in the tilt or slope of the ground that can occur for example, when a volcano inflates prior to an eruption or when the stresses that cause earthquakes lift up one part of the earth relative to another. A challenge with designing tiltmeters is that the measurements tend to drift with time due to instability in the sensors ¡V this limits their ability to measure tilt signals that are changing slowly. This project will develop a new type of tiltmeter that will correct for instrument drift by calibrating the sensor against the Earth's gravitational force, which can be considered constant at any point on the Earth. The tiltmeter will be deployed on a real-time cabled seafloor observatory at Axial Seamount, an active volcano in the Northeast Pacific Ocean. This is a site of significant scientific interest; the volcano has erupted three times in 20 years. It is also a site where tilt is being measured by other methods which allows validation of the new instrument. The data collected by this instrument will be made available to the public and other scientists. In the future, the tiltmeter may contribute to studies that seek to understand the geological processes that lead to great subduction zone earthquakes or that cause hazardous volcanic eruptions. The project will train a graduate student and provide field opportunities for undergraduates to help deploy the instrument at sea.Geodetic measurements of seafloor deformation are essential to understand geodynamic processes at oceanic plate boundaries but are quite challenging. The project will employ a novel approach to creating a short-baseline tiltmeter. The tiltmeter is based on a high-resolution three-component quartz crystal accelerometer. If the accelerometer is deployed on a stable platform that is coupled to the seafloor, changes in tilt of the horizontal channels of the accelerometer will lead to changes in the measured accelerations with time but so will the drift of the sensors. The approach to correcting the horizontal channels for sensor drift is to conduct a periodic calibration by rotating (or "flipping") each horizontal channel into the vertical for a short interval to measure the acceleration of gravity, g. Since g is to a high degree of accuracy invariant at any location, changes in the measurement of g between successive rotations can be attributed to sensor drift. This measurement of drift can then be used to correct each horizontal accelerometer channel to obtain a time series of true tilt changes between calibrations. The resulting tiltmeter will have unique characteristics ¡V a high-dynamic range (it cannot go off scale), high precision (~ a few nrads) and good long-term stability after calibration (10 micro rads). At least a year of data will be collected at the Ocean Observatories Initiative cabled observatory on Axial Seamount.

由于地球构造板的运动而导致的地面变形的测量对于旨在了解火山和地震的科学研究很重要。倾斜度是测量可能发生的地面倾斜或斜率变化的工具，例如，当火山在喷发前膨胀或导致地震的应力抬起地球的一部分时，相对于另一个地球的一部分。设计倾斜度的挑战是，由于传感器中的不稳定，测量值往往会随着时间的流逝而漂移，这限制了它们测量缓慢变化的倾斜信号的能力。该项目将开发一种新型的倾斜表，该项目将通过校准传感器针对地球的重力来校正仪器漂移，在地球上的任何位置都可以将其视为恒定。倾斜度表将部署在东北太平洋的一座活火山Axial Seamount的实时有线的海底观察员中。这是一个具有巨大科学兴趣的地点；该火山在20年内爆发了三次。它也是通过其他方法测量倾斜的站点，该方法允许验证新仪器。该工具收集的数据将提供给公众和其他科学家。将来，倾斜表可能会导致试图了解导致俯冲带或引起危险火山喷发的地质过程的研究。该项目将培训一名研究生，并为大学生提供帮助在海上部署该乐器的现场机会。对海底变形的地理测量对于了解海洋板块边界的地球动力学过程至关重要，但面临挑战。该项目将采用一种新颖的方法来创建短基线倾斜表。倾斜表基于高分辨率的三成分石英晶体加速度计。如果将加速度计部署在耦合到海底的稳定平台上，则加速度计的水平通道的倾斜变化将导致随着时间的推移变化，但传感器的漂移也会随着时间而变化。校正传感器漂移水平通道的方法是通过旋转（或“翻转”）每个水平通道进入垂直方向进行周期性校准，以使其短时间间隔以测量重力的加速度，g。由于G在任何位置都处于高度准确性，因此测量的变化可以使用漂移的测量来校正每个水平加速度计通道，以获得校准之间真正倾斜度变化的时间序列。所得的倾斜度表将具有独特的特征。v的高动力范围（不能脱离规模），高精度（〜几个NRAD）和校准后良好的长期稳定性（10 micro rads）。在海洋天文台倡议上，将至少收集一年的数据。