Infrasound as a Depth Discriminant

There is a need for routine measurements of infrasound from earthquakes, in conjunction with modeling, to better constrain our understanding of the generation of infrasound from earthquakes, in particular the effect of source depth. Here, we first outline a systematic search for infrasound from earthquakes from a range of magnitudes. Based on our observations, earthquakes with Mw>~5 appear to be reliable sources of infrasound, independent of depth, with the detection of infrasound at regional distances largely driven by path and receiver effects. We identified clear infrasound detections from large earthquakes as deep as 123 km. In contrast, earthquakes with Mw<~4 are poor infrasound sources and are unlikely to be detected regionally. In particular, we note that there has yet to be a conclusive detection from an earthquake with Mw<3.0. Our results imply that magnitude, rather than depth, appears to be the dominant factor influencing the generation of infrasound from earthquakes. To understand these observations further, we have developed a coupled seismoacoustic modeling technique comprising a three-dimensional (3D) finite difference algorithm, Rayleigh integral, and time domain parabolic equation. By gluing these techniques together, we are modeling the generation and propagation of infrasound from earthquakes. The effect of depth on these simulations, with comparison to our observational dataset, is discussed. 2011 Monitoring Research Review: Ground-Based Nuclear Explosion Monitoring Technologies