Development of an integrated Borehole Geodetic and Seismic Sensor: Project Completion

集成钻孔大地测量和地震传感器的开发：项目完成

• 批准号: 1955127
• 负责人: Mark Zumberge
• 金额: $ 14.95万
• 依托单位: University of California-San Diego Scripps Inst of Oceanography
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-03-01 至 2022-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1955127&HistoricalAwards=false
• 关键词: Development; integrated; Borehole; Geodetic; Seismic

Seismometers measure the shaking of the ground caused by earthquakes, ranging in intensity from tiny tremors undetectable by humans to large damaging earthquakes that pose a hazard to structures and people. It is the very small shaking from nearby sources, or the ultra-low frequency vibration following large events that cause the Earth to ring like a bell for many days afterward, that are difficult to capture. We are constantly trying to improve seismometers to be able to record this wide range of signals. Studying them can provide much information about what is inside the Earth. Seismic waves are the "light" that lets us see inside the Earth and seismometers are the "eyes" that let us create images of the internal Earth structure. In addition to shaking, earthquakes and related phenomena cause slow, gradual deformation of Earth's crust. To detect these deformations, extremely precise sensors are needed. Two types of deformation are often searched for: a very slight change in the position of the ground with respect to local vertical, called "tilt," and elongation or compression of the ground, called "strain." These are not unrelated, but the types of signals caused by tectonic activity are normally extremely small – measured by parts per billion in both tilt and strain. This Division of Erath Science Instrumentation and Facilities Program award supports development of a highly sensitive optical detection method and instrument to measure the motion of masses suspended by pendulums or a spring in a housing cemented into the bottom of a borehole. Optical fibers send laser light down to the sensor housing and return the light after it has been reflected from mirrors attached to the masses. By analyzing this light with electronics and a small computer located outside the borehole, the researchers can detect motions of the masses comparable to the diameter of individual atoms, and therefore detect both small seismic shaking and deformation of the ground caused by earthquake-related activity. As the investigators learn more about earthquake processes, the better are the chances of one day making precise forecasts of where and when they might occur.Support from this award will allow for fabrication and installation of a borehole system that utilizes optical-fiber interferometry to provide in one borehole: (a) a broadband vertical seismometer/gravimeter, (b) a broadband two-component horizontal seismometer/tiltmeter, and (c) a low-noise vertical long baseline strainmeter. The combined system will be able to measure vertical and horizontal ground velocities, gravity, tilt, and strain with sensitivities that compare favorably with any existing system over time scales from 10 Hz to many days; the downhole components are entirely passive, giving a long instrument lifetime and resistance to high downhole temperatures. The instrument is to be installed in an existing borehole at Pinon Flat Observatory for testing and comparison with the seismic and strain systems already operated there. The combined instrument promises an alternative to multi-instrument observations from independent seismometers, GPS receivers, gravimeters, tiltmeters and strain meters. The seismic observations are anticipated to meet the current requirements of Global Seismographic Network stations and geodetic measurements would offer lower noise observations than GPS at periods shorter than weeks. Target applications could include studies of the dynamics of crustal deformation including slow slip events, continuous and episodic slip, and other Earth movements that are known to occur but which do not generate damaging earthquakes. A deployed instrument could help to understand the effects of magmatic and subsurface fluid dynamics (e.g., hydrocarbon extraction and CO2 sequestration) on crustal deformation.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.

地震仪测量地震引起的地面的震动，从人类无法检测到的微小震颤到对结构和人构成危害的大型破坏性地震。这是附近来源的摇动，或者是在大事件发生大事件后的超低频率振动，导致地球像铃一样响起了很多天，很难捕获。我们一直在努力改善地震仪，以便能够记录这种广泛的信号。研究它们可以提供有关地球内部的大量信息。地震波是使我们看到地球内部的“光”，地震仪是“眼睛”，使我们可以创建内部地球结构的图像。除了摇动外，地震和相关现象会导致地壳的缓慢变形。为了检测这些变形，需要非常精确的传感器。经常搜索两种类型的变形：相对于局部垂直行业的地面位置有很小的变化，称为“倾斜”，地面的伸长或压缩，称为“应变”。这些不是无关的，但是由构造活动引起的信号类型通常非常小 - 倾斜和应变的零件均以每十亿分的零件来衡量。 Erath Science仪器和设施计划奖的这一划分支持了一种高度敏感的光学检测方法和工具，以测量摆在摆悬浮的质量的运动，或者在井井有条到井眼底部的住房中悬挂的质量。光纤将激光光向下发送到传感器壳体，并在从附着在质量上的镜子中反射出光线后将其返回。通过用电子设备和位于钻孔外的小型计算机分析这一光，研究人员可以检测到与单个原子直径相当的质量的运动，因此可以检测到与地震相关活性引起的小地震震动和地面变形。 As the investigators learn more about earthquake processes, the better are the chances of one day making precise forests of where and when they might occur.Support from this award will allow for fabrication and installation of a borehole system that utilizes optical-fiber interference to provide in one borehole: (a) a broadband vertical seismometer/gravimeter, (b) a broadband two-component horizo​​ntal seismometer/tiltmeter, and (c)低噪声垂直长基线应变计。组合系统将能够以灵敏度的垂直和水平地面速度，重力，倾斜和应变来测量与任何现有系统随时间尺度从10 Hz到许多天的敏感性相比；井下组件完全是被动的，具有较长的仪器寿命和对高井下温度的抵抗力。该仪器将安装在Pinon Flat天文台现有的钻孔中，以与已经运行的地震和应变系统进行测试和比较。该组合仪器有望从独立地震仪，GPS接收器，粒度计，倾斜度和应变仪的多个仪器观察中进行替代。预计地震观察结果将满足全球地震学网站的当前需求，而大地测量结果将比几周短的GP提供较低的噪声观察结果。目标应用可能包括对地壳变形的动力学的研究，包括慢滑动事件，连续和情节滑移以及其他已知发生但不会产生破坏性地震的地球运动。部署的仪器可以帮助理解岩浆和地下流体动力学（例如，碳氢化合物提取和二氧化碳隔离）对地壳变形的影响。该奖项反映了NSF的法定任务，并被认为是值得通过基金会的知识绩效和更广泛影响的审查审查的审查标准来通过评估来通过评估来支持的。