Ultra-low frequency electromagnetic monitoring of earthquakes within the Earthscope Plate Boundary Observatory

Earthscope板块边界观测站内地震的超低频电磁监测

• 批准号: 0346236
• 负责人: Simon Klemperer
• 金额: --
• 依托单位: Stanford University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-05-15 至 2011-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0346236&HistoricalAwards=false
• 关键词: Ultra; low; frequency; electromagnetic; monitoring

On an annualized basis, earthquakes in California kill several people and cause several billions of dollars of property damage every year. There is a natural societal interest in understanding whether earthquakes are predictable; and if they are predictable, developing ways to obtain even a few minutes of warning. We are attempting to address this societal need by studying electromagnetic emissions as one of the most promising potential pre-seismic transients. Our network of monitoring stations complements commercial "earthquake prediction" services operating magnetic monitoring stations in California by providing an independent source of data for the public. Part of the mission of the National Science Foundation's Plate Boundary Observatory (PBO) is to learn whether earthquakes are predictable. We are building a network of three ultra-low frequency electromagnetic (ULF-EM) recording sites in northern California in order to understand earthquake physics and to detect pre-seismic transients if they exist. Our electromagnetic sensors include ultra-sensitive magnets to detect tiny changes in Earth's magnetic field, and low-noise electric cables to detect tiny electric currents inside the Earth. Our ULF-EM sensors are collocated with existing PBO sites, so that any anomalies observed on our electromagnetic sensors can be cross-checked against more-conventional earthquake detection instruments: strain meters and seismographs. All our data is transmitted to a public data archive on a continuous basis, 24 hours a day. We monitor our instruments on a daily basis to confirm that they are recording valid data, and we run the data through a set of standardized programs to search for possible anomalies. It is possible that we will recognize a major change in signal levels or character before an earthquake, but it is more likely that after a major earthquake we will have a valuable dataset that we can use to test hypotheses about the way earthquakes initiate, and to help us understand future earthquake cycles.We are recording ULF-EM data because ultra-low frequency (0.01-10 Hz) magnetic field anomalies prior to and following large earthquakes (magnitude greater than 6.5) have been reported from a number of different regions of the world. If real, these signals contain important information about the physics of earthquakes, particularly fluid motion in and around the fault before during and after seismic activity. We are collocating our magnetic sensors with PBO strain-meters and seismometers in order to allow signals from earthquakes to be separated from artifacts related to sensor tilt. We are recording with identical, spatially separated recorders in order to exclude other potential sources of magnetic signals (including man-made signals). Continuous recording of the magnetic and electric field before, during and after, and spatially close to, a significant earthquake, is required to demonstrate the reality or absence of ULF-EM signals. We are locating our ULF-EM recording sites along the San Andreas and other major faults in San Francisco Bay Area, because these faults have a large potential for a major earthquake in the next decade.

每年一次，加利福尼亚州的地震杀死了数十亿人，每年造成数十亿美元的财产损失。了解地震是否可预测存在自然的社会兴趣。如果它们是可以预测的，则开发出获得几分钟警告的方法。我们试图通过研究电磁排放作为最有前途的潜在瞬态瞬态之一来解决这一社会需求。我们的监测站网络通过为公众提供独立的数据来源，补充了加利福尼亚州的商业“地震预测”服务。国家科学基金会板块边界观测站（PBO）的一部分是了解地震是否可预测。我们正在加州北部建立一个由三个超低频率电磁（ULF-EM）记录位点组成的网络，以了解地震物理学并在存在前瞬态瞬态。我们的电磁传感器包括超敏感的磁铁，以检测地球磁场的微小变化，以及低噪声电缆，以检测地球内部的微小电流。 我们的ULF-EM传感器与现有的PBO位点相互关联，因此在我们的电磁传感器上观察到的任何异常，都可以针对更规定的地震检测仪器进行交叉检查：应变计和地震仪。 我们所有的数据每天24小时连续传输到公共数据存档。 我们每天监视我们的仪器，以确认它们正在记录有效的数据，并通过一组标准化程序来运行数据，以搜索可能的异常情况。 我们可能会在地震发生前认识到信号水平或性格的重大变化，但是在大地震发生后，我们将拥有一个有价值的数据集，我们可以用来测试有关地震开始方式的假设，以帮助我们了解未来的地震循环。 6.5）已从世界上许多不同地区报告。如果真实，这些信号包含有关地震物理学的重要信息，尤其是在地震活动中和之后断层内和周围的流体运动。我们正在将磁性传感器与PBO应变 - 仪和地震仪隔开，以允许将地震中的信号与与传感器倾斜有关的伪影分开。 我们正在使用相同的空间分离记录器记录，以排除其他潜在的磁信号来源（包括人造信号）。需要对磁场和电场进行连续记录，并在空间上，在空间上接近一场明显的地震，以证明现实或没有ULF-EM信号。我们正在安德烈亚斯（San Andreas）和旧金山湾区的其他主要断层沿线定位ULF-EM录音地点，因为这些断层在未来十年内具有巨大的大地震潜力。