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

在过去的15-20年里，人们发现沿着俯冲带断层反复发生的不寻常的大地震，会在几天到几周的时间内滑动，而不是几秒钟。尽管这些慢滑地震不会造成地震震动，但认识到它们的发生是很重要的，因为它们可以影响常规地震和海啸的可能性。这些慢滑地震有时与极其安静的地震隆隆声有关，但除此之外，还可以通过全球定位系统的连续监测来识别，这些监测揭示了专用台站发生的微小运动。这项研究的目的是评估一种潜在的补充方法，通过使用地下水压力数据来确定这些事件。当断层滑动时，它会挤压和松弛地下饱和的岩石，就像海绵一样。利用井/井中的灵敏仪器，有时可以观察到由此产生的水压变化。该项目力求通过纳入对美国太平洋西北部卡斯卡迪亚俯冲带沿线现有监测设施的地下水压力数据的分析，提高检测慢滑地震的能力和速度。该项目将研究并有力地确定与断层滑动相关的水压力变化，并将支持研究生进行研究，作为该项目的一部分。结果将通过已发表的论文和公开演示进行传播。该项目将检测和分析隐藏在来自Earthcope的板块边界观测站钻孔阵列的连续孔压记录中的俯冲带慢滑的可疑特征。这门科学的目的是提高我们对俯冲带内慢滑的时间和空间分布的理解。断层滑动行为的水文地质特征可以为连续定位测量中超越地震震动检测或瞬变的大规模慢滑提供额外的约束。然而，断层滑动的可疑孔隙压力特征必须与无关的局部水文地质干扰和气象影响区分开来。这项研究通过分析已知大规模慢滑事件期间的现有钻孔孔压数据来解决这些问题，并使用各种数据类型的信号处理和统计技术来提高对可疑信号的稳健识别和区分。这些结果有望提高我们对断层滑动的水文地质响应的理解，有助于进一步评估大规模慢滑事件的时间和范围，并有可能提供独立于连续定位数据或地震观测的实时基于统计学的慢滑检测算法。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

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.