Mapping the sources of proximal earthquake infrasound

Abstract:

We recorded a M_WR3.6 earthquake in Idaho (USA) on 7 April 2020 with a network of six three-element infrasound arrays and co-located broadband seismometers situated within 25 km of the epicenter. Infrasound array processing is used to identify the arrival of seismic-to-atmospheric coupled phases and as much as 90 s of infrasound coda. Apparent velocities ranging from seismic speeds to sub-horizontal atmospheric sound speeds are attributed to a superposition of incident wave types. We find that the arriving infrasound originates from a broad back azimuth range that deviates from epicentral back azimuth and indicates the ubiquity of secondary radiators. Secondary radiators, which often coincide with regions of elevated topography, are located using a distance ranging technique derived from earthquake initiation time. The analysis of infrasound sources from proximal earthquakes provides an opportunity to map ground shaking distributions.