Noise Observatory for Imaging the Subsurface Beneath Yellowstone (NOISY)

用于黄石地下成像的噪声观测站 (NOISY)

• 批准号: 1050669
• 负责人: Jesse Lawrence
• 金额: $ 35.34万
• 依托单位: Stanford University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-08-15 至 2015-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1050669&HistoricalAwards=false
• 关键词: Noise; Observatory; Imaging; Subsurface; Beneath

Technical Abstract:We are investigating how to generate stable time-lapsed tomography images of the Yellowstone region from the ambient seismic field. We deploy and re-deploy broadband seismometers each summer (June-September) around Yellowstone to capture time-lapsed snapshots of the ambient noise field. The Yellowstone region is uniquely active with time varying seismicity, aseismic deformation, heat flow and geyser activity, making it an ideal location to image time varying properties of the subsurface.By averaging many correlations of hour-long durations of ambient noise measured at each pair of broadband seismic stations, we generate noise correlation functions (NCFs). These NCFs are empirical representations of the Green?s function between two (or more) stations. By repetitively resampling the ambient seismic field, we generate independent measurements of the inter-station Green's function for separate time periods. When the subsurface properties (such as seismic velocity or attenuation) vary with time, the NCFs change as well.The major effort of this study is aimed at improving the signal-to-noise ratio of both the NCFs and time derivative of the NCFs. We remove the temporal effect of a time-varying ambient noise source field by generating synthetic NCFs corresponding to the source field estimated for the entire network. The transfer function between the synthetic NCFs generated with observed and uniform source-fields convolved with the observed NCF yields a source-field-corrected NCF. We evaluate time varying phase and amplitude of this corrected NCF for consistent patterns useful for four-dimensional tomography.Nontechnical Abstract:Determining the time-varying properties of a major volcano such as Yellowstone is essential to understanding how magma chambers inflate and deflate. This study is providing better understanding of how the North American continental crust is evolving in real time. We are testing fast algorithms to analyze the potential of real-time estimation of time-varying subsurface properties, which may eventually contribute to real-time hazard assessment. We are also testing how inexpensive accelerometers connected to internet-connected computers in homes and schools can contribute to greater understanding of 4D imaging of volcanoes. The new seismic data generated through this project are providing new insights into 4D continental processes and generating new understanding of one of Earth?s most visited geotourist locations.

技术摘要：我们正在研究如何从周围的地震场产生稳定的黄石地区的时间推移层析成像图像。 我们每年夏天（6月至9月）在黄石公园周围部署和重新部署宽带地震仪，以捕获环境噪声场的时间推移快照。 黄石地区具有独特的时变地震活动性、地震形变、热流和间歇泉活动性，是研究地下时变特性的理想场所，通过对每对宽频带地震台站测量的环境噪声的多个小时持续时间的相关性进行平均，生成噪声相关函数（NCF）。 这些NCF的经验表示的绿色？在两个（或多个）站之间运行。 通过重复地重新观测周围的地震场，我们产生了独立的测量站间的绿色的功能为单独的时间段。 当地下属性（如地震速度或衰减）随时间变化时，NCF也会发生变化，本文的主要工作是提高NCF的信噪比和NCF的时间导数。 我们通过生成与整个网络估计的源场相对应的合成NCF来消除时变环境噪声源场的时间效应。 由观测源场和均匀源场生成的合成NCF之间的传递函数与观测NCF卷积，得到源场校正的NCF。 我们评估随时间变化的相位和振幅的一致模式有用的四维tomography.Nontechnical摘要：确定一个主要的火山，如黄石火山的时变特性，这是必不可少的了解岩浆房膨胀和收缩。 这项研究使人们更好地了解北美大陆地壳在真实的时间内是如何演变的。 我们正在测试快速算法来分析时变地下特性的实时估计的潜力，这最终可能有助于实时危险评估。 我们还在测试如何将廉价的加速度计连接到家庭和学校的互联网连接计算机上，以帮助更好地了解火山的4D成像。 通过这个项目产生的新的地震数据提供了对4D大陆过程的新见解，并产生了对地球？最受欢迎的地理旅游景点。