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

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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.