Local, Regional, and Remote Seismo-acoustic Observations of the April 2015 VEI 4 Eruption of Calbuco Volcano, Chile

The two major explosive phases of the 22-23 April 2015 eruption of Calbuco volcano, Chile, produced powerful seismicity and infrasound. The eruption was recorded on seismo-acoustic stations out to 1,540km and on five stations (IS02, IS08, IS09, IS27, and IS49) of the International Monitoring System (IMS) infrasound network at distances from 1,525 to 5,122km. The remote IMS infrasound stations provide an accurate explosion chronology consistent with the regional and local seismo-acoustic data and with previous studies of lightning and plume observations. We use the IMS network to detect and locate the eruption signals using a brute-force, grid-search, cross-bearings approach. After incorporating azimuth deviation corrections from stratospheric crosswinds using 3-D ray tracing, the estimated source location is 172km from true. This case study highlights the significant capability of the IMS infrasound network to provide automated detection, characterization, and timing estimates of global explosive volcanic activity. Augmenting the IMS with regional seismo-acoustic networks will dramatically enhance volcanic signal detection, reduce latency, and improve discrimination capability.