EAR-PF: Spectral morphology and source characteristics of low-frequency earthquakes near Parkfield, CA

阿曼达·托马斯博士获得了美国国家科学基金会地球科学博士后奖学金，将在斯坦福大学开展一项研究和教育计划。她的研究工作将主要集中在更好地约束最近在加利福尼亚州帕克菲尔德发现的低频地震（LFEs）的震源特性。LFEs是深断层滑动的地震表现，相对于浅层地震，通常会耗尽高频能量。该项目的目标是确定每个低频地震族的震源机制解，分离LFE源光谱，量化角频率等频谱参数，探索Parkfield常规地震和低频地震频谱形态的空间变异性。地震预报和地面运动预报可以估计大地震发生的可能性、震动强度及其对某一地区的潜在影响。这些工具在很大程度上依赖于诸如震级、复发间隔和破裂区域等参数。虽然深滑动可能会影响这些因素，但它的影响被排除在破裂预测之外，因为它既没有很好地表征，也没有很好地理解。将从慢滑现象的研究中收集到的结果整合到地震预报和地面运动模拟中，可能会改进这些模型。拟议的教育计划包括两个部分：指导一个关于地震震源的研究生研讨会，以及在加州教授一门关于地质灾害的入门级实地课程。研究生研讨会的目标是通过讨论该领域的经典和最新文献，发展对震源的全面了解。本科实地课程将使学生接触地球科学，并提高对地质灾害的认识，如岩崩、地震和火山爆发。学生将使用简单的数据收集和分析技术，再加上集体讨论和解释，以确定加州的构造演化是如何产生这些威胁的，并量化它们的潜在影响。

Dr. Amanda Thomas has been granted an NSF Earth Sciences postdoctoral fellowship to carry out a research and education plan at Stanford University. Her research efforts will primarily focus on better constraining source properties of recently discovered low-frequency earthquakes (LFEs) in Parkfield, CA. LFEs are the seismic manifestation of deep fault slip and are typically depleted in high-frequency energy relative to shallow earthquakes. The goals of this project are to determine focal mechanism solutions for each low-frequency earthquake family, to isolate LFE source spectra and quantify spectral parameters such as corner frequency, and to explore the spatial variability of spectral morphology of both regular and low-frequency earthquakes in Parkfield. Earthquake forecasts and ground motion predictions estimate the probability of a large earthquake, the intensity of shaking, and its potential impact on a region of interest. These tools rely heavily on parameters such as magnitude, recurrence interval, and rupture area. While deep slip could potentially influence each of these, its effect is excluded from rupture forecasts because it is neither well characterized nor well understood. Incorporating the results gleaned from studies of slow-slip phenomena into earthquake forecasts and ground motion simulations may improve such models. The proposed education plan involves two components: directing a graduate seminar on seismic sources and teaching an entry level field course on geologic hazards in California. The goal of the graduate seminar will be to develop a comprehensive understanding of the earthquake source through discussion of classic and recent literature in the field. The undergraduate field course will expose students to earth science and promote awareness of geologic hazards, such as rock falls, earthquakes, and volcanoes. Students will use simple data collection and analysis techniques coupled with collective discussion and interpretation to determine how the tectonic evolution of California gave rise to such threats and to quantify their potential impact.