Infrasonic Hotspot Mapping and Atmospheric Probing with the USArray

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The seismometers of the USArray not only directly measure ground motion, they also indirectly provide valuable information about other phenomena that affect ground motion. For example, it is known that infrasound, low-frequency sound below ~20 Hz, can be detected by seismometers through acoustic-to-seismic conversion. Infrasound events are usually located with globally spaced infrasound arrays. It has been recently shown that the density of USArray seismic stations permits one to locate sources with much greater accuracy and with altitude resolution, despite probable variations in site conditions. This project will expand upon previous work on the detection and location of more than one hundred high-quality infrasonic events that were registered by the USArray during 2008. The goal of this project is to identify the occurrence, location, and frequency of events that produced USArray-registered infrasonic signals over a time span of six years, resulting in a unique continental-scale infrasonic events research database. The second component of the project is to illuminate the infrasonic travel time branches for several of these events, which may provide both remarkable insights into infrasonic propagation as well as a test of the state-of-the-art atmospheric velocity models. Finally, we will analyze detection trends and test an existing atmospheric propagation hypothesis based on the previous 2008 results.