A repeating secondary source of infrasound from the Wells, Nevada, earthquake sequence

Arrowsmith, Stephen J and Burlacu, Relu and Whitaker, Rod and Randall, George
Geophysical Research Letters, 36(11), 2009

The Wells, Nevada, earthquake of February 21, 2008, generated a complex seismo‐acoustic wavefield. Epicentral infrasound was recorded at 5 seismo‐acoustic arrays in Nevada, Utah, and Wyoming. In addition to epicentral infrasound, the earthquake triggered a secondary source of infrasound at the BGU array in Utah, which was also triggered by subsequent aftershocks. By applying simple constraints on the propagation of seismic and infrasound waves, we show that the secondary source is an isolated peak (‘Floating Island’) that appears to efficiently generate infrasound through the interaction with seismic surface waves. This hypothesized source location is broadly consistent with crosswind directions extracted from the Ground‐to‐Space (G2S) atmospheric model (for the appropriate time and source/receiver locations), although modeling the propagation of infrasound predicts this source location to be within the so‐called ‘zone‐of‐silence’. In contrast to epicentral infrasound, secondary infrasound associated with the Wells, Nevada, earthquake sequence appears to be local to each array (i.e., not observed at multiple arrays). Secondary infrasonic arrivals observed at BGU are much higher in amplitude than epicentral arrivals, highlighting the importance of being able to clearly identify and separate epicentral and secondary arrivals for infrasonic event discrimination.