Recognizing Signatures of Slow Slip in Plate Boundary Observatory Borehole Pore Pressure Data

识别板块边界观测钻孔孔隙压力数据中的慢滑移特征

• 批准号: 1829492
• 负责人: Patrick Fulton
• 金额: $ 8.08万
• 依托单位: Texas A&M University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-09-01 至 2019-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1829492&HistoricalAwards=false
• 关键词: Recognizing; Signatures; Slow; Slip; Plate

Within the past 15-20 years, large unusual earthquakes that slip over the course of days to weeks, rather than seconds, have been discovered to repeatedly occur along subduction zone faults. Although these slow slip earthquakes do not create seismic shaking, recognizing their occurrence is important because they can influence the potential of regular earthquakes and tsunamis. These slow slip earthquakes are sometimes associated with extremely quiet seismic rumblings, but are otherwise identified through continuous Global-Positioning-System monitoring that reveals small motions occurring at dedicated stations. The aim of this study is to evaluate a potential complementary method for identifying these events through the use of groundwater pressure data. As a fault slips, it squishes and relaxes the water saturated rocks below the ground like a sponge. With sensitive instruments within wells / boreholes, the resulting water pressure changes can sometimes be observed. This project seeks to improve the ability and speed at which slow slip earthquakes are detected by incorporating the analysis of groundwater pressure data from existing monitoring facilities along the Cascadia subduction zone within the United States Pacific Northwest. The project will study and robustly identify water pressure changes associated with fault slip and will support graduate students to conduct research as part of the project. The results will be disseminated through published papers and public presentations.This project will detect and analyze suspected signatures of subduction zone slow slip hidden within continuous pore pressure records from Earthscope's Plate Boundary Observatory borehole array. The science is motivated by an aim to improve our understanding of the temporal and spatial distribution of slow slip within subduction zones. Hydrogeologic signatures of fault slip behavior can provide an additional constraint on large-scale slow slip beyond seismic tremor detections or transients in continuous positioning measurements. Suspected pore pressure signatures of fault slip, however, must be differentiated from unrelated local hydrogeologic disturbances and meteorological effects. This study addresses these issues by analyzing existing borehole pore pressure data during known large-scale slow slip events and uses signal processing and statistical techniques with a variety of data types to improve the robust identification and discrimination of suspected signals. The results are expected to improve our understanding of the hydrogeologic response to fault slip, help further assess the timing and extent of large-scale slow slip events, and potentially provide a real-time statistically-based slow slip detection algorithm independent of continuous positioning data or seismologic observations.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.

在过去的15 - 20年中，已经发现，在俯冲带断层沿线反复发生，几天到几周而不是几秒钟的大型不寻常的地震被发现反复发生。尽管这些缓慢的地震不会引起地震震动，但认识到它们的发生很重要，因为它们可以影响常规地震和海啸的潜力。这些缓慢的地震有时会与极其安静的地震隆隆声有关，但通过连续的全球位置系统监测来识别出来，从而揭示了在专用站点发生的小动作。这项研究的目的是评估通过使用地下水压力数据来识别这些事件的潜在补充方法。当断层滑倒时，它像海绵一样挤压并放松水饱和的岩石。使用井 /钻孔中的敏感仪器，有时可以观察到所得的水压变化。该项目旨在通过纳入美国太平洋西北太平洋西北部卡斯卡迪亚俯冲带的现有监测设施的地下水压力数据来分析地下水压力数据，以提高检测到缓慢地震的能力和速度。该项目将研究并坚定地识别与故障滑移相关的水压变化，并将支持研究生作为项目的一部分进行研究。结果将通过已发表的论文和公开演讲来传播。该项目将检测并分析隐藏在Earthscope的板块边界孔口钻孔井阵列中的俯冲带慢滑层的可疑签名。该科学的目的是提高我们对俯冲带内缓慢滑移的时间和空间分布的理解。断层滑移行为的水文地质特征可以为超出地震震颤检测或连续定位测量中的瞬态而对大规模慢滑动提供额外的限制。然而，可疑的断层滑动孔压缩必须与无关的局部水文障碍和气象效应区分开。这项研究通过在已知的大规模慢滑动事件中分析现有的钻孔孔隙压力数据来解决这些问题，并使用具有多种数据类型的信号处理和统计技术来改善可疑信号的鲁棒识别和歧视。预计结果将提高我们对缺陷滑倒的水文地质响应的理解，有助于进一步评估大规模缓慢的事件的时机和程度，并可能提供基于统计的基于统计的慢速滑移检测算法的实时时间，而与持续的定位数据或SEOMSOLOGIC观察无关。NSF的法定任务和审查均通过评估良好的依据，并且在范围内得到了良好的影响。