Repeating Infrasound From an Earthquake Doublet in Alaska

Abstract

Earthquake infrasound contains information concerning the underground media and the earthquake source. We identify three types of repeating infrasound: local, secondary, and epicentral infrasound from two successive Mw6.2 earthquakes (separated by <2 h and <10 km) in Alaska. The path effects are the same for the two sets of repeating infrasound, letting us focus on the coupling mechanism. We calculate the relative power spectral density change between the two events using acoustic and seismic records from array I53 and individual USArray stations. In the 0.9–2.1 Hz band, we find that seismic energy is converted efficiently into acoustic energy. In addition, we identify similar spatial distributions of the seismic and diffracted infrasonic energies, which indicate the influence of different earthquake focal mechanisms on the infrasound observations. This study sheds light on the generation mechanism of earthquake infrasound and demonstrates the potential for monitoring infrasound to constrain earthquake source properties.