Volcano Seismicity at Long-dormant Stratovolcanoes Open

Date: May 11, 2016 6min 10s Intermediate Spanish

Generalized model of volcano-tectonic unrest prior to eruption

Earthquakes near and beneath volcanoes alert may indicate that magma and volcanic gases are on the move. This animation represents generalized patterns of seismic and geological activity at some, but not all, long dormant stratovolcanoes worldwide during the months to hours leading up to an eruption. The volcano-tectonic earthquake pattern is common at long-dormant volcanoes but uncommon at frequently active volcanoes. 

Animation, based on work by Randall White and Wendy McCausland, results from a collaboration between USGS's Volcano Disaster Assistance Program and IRIS. The purpose of the animation is to facilitate teaching international students about volcano monitoring. This animation is based on the work of Randall White and Wendy McCausland (Volcano-tectonic earthquakes: A new tool for estimating intrusive volumes and forecasting eruptions; 2016, Journal of Volcanology and Geothermal Research 309 (2016) 139155)

CLOSED CAPTIONING: .srt file is included with the downloiad. Use appropriate media player to utilize captioning.


  • Different seismic signatures will reflect varying geologic processes.
  • Deep low-frequency earthquakes and/or tremor occur as magma that formed in the lower crust rises into conduits.
  • An aseismic zone separates the deep and shallow earthquakes.
  • High-frequency volcano-tectonic, or VT earthquakes occur at shallow levels in the upper crust.
  • Shallow low-frequency and Hybrid earthquakes occur just below the summit.

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