[1] Infrasonic signals have been observed from 31 earthquakes by arrays of microphones operated by the Los Alamos National Laboratory between 1983 and 2003. The properties of the signals are presented. Signal amplitudes corrected for propagation and distance show a relation with seismic magnitude. The variance in the relation is understood primarily in terms of the uncertainties or errors in the ground motion, deduced from an independent data set, and the stratospheric winds, which strongly influence signal propagation. Signal durations can extend over many minutes. A relation is found between signal duration and magnitude. To understand this, we propose a model in which regions distant from the epicenter are excited by seismic surface waves. The surface motion of these regions, in turn, produces signals which precede or follow the signals from the epicenter. Analysis failed to detect signals from 56 earthquakes during the observation period. Predicted signal-to-noise ratios for these earthquakes indicated that the signals would have been too weak for detection.
[1] Over the last several years, a large number of ground-based infrasound arrays have been established for explosion monitoring as part of the International Monitoring System of the Comprehensive Nuclear Test Ban Treaty Organization. Results from these arrays have become valuable in understanding long-range infrasound propagation in the atmosphere and complement earlier data. Two types of signals are often observed for a given source: those refracted at stratospheric heights and at thermospheric heights. In this contribution we compare several characteristics of these two signal types including observed pressure amplitude, average travel velocity, bearing, and signal duration. For this study we use archival data from atmospheric nuclear explosions, high explosive chemical explosions on the surface, earthquakes with previously detected stratospheric signals, and earthquakes for which stratospheric signals were not detected. We show that the combination of stratospheric and thermospheric signals may provide independent estimates of wind propagation conditions and source characteristics. The observations of both signal types may increase the confidence level of an infrasound signal detection.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.