Seismic and Infrasonic Monitoring

Seismology and infrasound are important and effective tools for monitoring volcanoes and forecasting eruptions. In the past two decades there have been over 25 successful forecasts. Well-monitored volcanoes have six or more local seismic stations within 15 km and several regional stations (>15 km) which are able to detect volcanic earthquakes of M∼0 under the volcano. Ongoing data analyses provide the basis for determining the eruptive state of the volcano. Infrasonic monitoring complements seismic monitoring in that it provides direct and unambiguous records of surface activity that are largely “uncontaminated” by internal volcano sources. Eruptions are well detected by arrays of infrasound sensors that may be deployed local to a volcano or at regional and global distances. Most volcano acoustic studies focus on infrasound in the band 0.1-20 Hz, as this is the band of most intense volcanic sounds and these long wavelengths propagate with very little attenuation.