Following several months of modest precursory activity, southern Chile’s Calbuco volcano erupted in two major explosive phases beginning on 22 April 2015. The event led to the evacuation of more than 6,500 residents and affected aviation, agriculture, and infrastructure nearby. It also generated powerful seismic and infrasonic waves that were recorded at local, regional, and remote seismoacoustic stations, including five belonging to the International Monitoring System (IMS) infrasound network, at distances between 1,525 and 5,122 kilometers away. Now Matoza et al. are using the Calbuco data set to determine whether the global IMS infrasound network, which was designed to detect nuclear tests in Earth’s atmosphere, can also be used to monitor volcanic activity, despite the prevalence of wind and other interfering background infrasound signals.
By applying a recently developed source location and ray tracing method to the IMS infrasound data to correct for stratospheric crosswinds, the team successfully isolated both of Calbuco’s eruption signals and compared them to a suite of other observations (this video shows an audible representation of infrasound signals). The results reveal a chronology that is consistent with regionally and locally recorded data and a source location within 172 kilometers of the eruption site. The researchers attribute this discrepancy to inaccuracies in atmospheric specifications, such as stratospheric wind speeds, and note that data from existing seismic networks can be used to improve the infrasound network’s capabilities in the future.
These findings highlight the potential for the IMS network to not only monitor the nuclear explosions for which it was designed but also detect—and even perform detailed studies of—volcanic eruptions occurring thousands of kilometers away. (Journal of Geophysical Research: Solid Earth, https://doi.org/10.1002/2017JB015182, 2018)
—Terri Cook, Freelance Writer