Resolving complex wavefields from earthquake infrasound using a dense array

"Secondary infrasound" produced by shaking of topographic features during earthquakes contains potentially useful information on ground motion; however, the presence of many interfering waves from different radiators complicates source analyses that lead to ground motion estimates. To address this problem, we explore the capabilities of a 20-element infrasound array to resolve acoustic wavefield components with greater detail than would be possible with typical infrasound arrays with fewer elements. We consider various array-processing methods for this problem including methods capable of resolving multiple sources (e.g., CLEAN). Our recordings include small local events (aftershocks of the M6.5 Central Idaho earthquake--M2.5-3.5, <40 km distance) with purely tropospheric propagation, and a regional event (Tonopah, NV--M6.5, 700 km distance) involving stratospheric or thermospheric returns; we analyze infrasound from these earthquakes and use them as case studies for our array methods. Many routine applications of infrasound face the challenge of distinguishing wave sources of interest from superposed waves from many sources, and geophysical instrumentation suitable for "large-N" recording is increasingly available. Consequently, we expect our methods and findings to be broadly applicable beyond our specific problem of earthquake infrasound.