The long-held assumption that volcanic earthquakes are always induced by the impact of moving magma on cool rocks is overturned by two research papers published in Nature this week. Fracturing and faulting within high-temperature eruptible magma itself can also generate seismic events, according to the reports.
Yan Lavallée of Lugwig-Maximilians University and colleagues in Germany and the UK have found that volcanic dome lavas are seismogenic — that is, they can cause earthquakes. Further, as the lavas cross from the ductile to brittle regime, the character of the seismicity changes until complete brittle failure occurs at high strain rates. Lavallée and colleagues’ findings are based on rheological experiments on volcanic dome lavas.
Hugh Tuffen and colleagues of University College London have detected acoustic emissions that are indicative of seismogenic rupture in experiments where they deformed high-temperature silica-rich magmas under simulated volcanic conditions.
The authors of both papers suggest that monitoring magma seismicity could be used to improve forecasting for some volcanic eruptions.
- Seismogenic lavas and explosive eruption forecasting (Letter p507, doi: 10.1038/nature06980)
- Evidence for seismogenic fracture of silicic magma (Letter p511, doi: 10.1038/nature06989)
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