Deep “long-period” earthquakes: early indications of volcano activation
Studying the seismicity of a volcanic area is one of the main methods for studying and monitoring volcanic activity. Indeed, the upwelling of magma from deep magma reservoirs and the pressure changes will cause small earthquakes in the volcanic "plumbing" that can be detected on the surface.
Long-period” volcanic earthquakes are the most directly linked to magma movements and pressure variations in the volcano-magmatic system.
In particular, “long-period” volcanic earthquakes observed at great depths (several tens of km) represent signs of activation of the deep parts of magmatic systems and are thus among the first precursors of a future eruption.
In an article published in the journal Nature Geoscience, a French-Russian team presents a study of deep “long-period” volcanic earthquakes recorded beneath the Klyuchevskoy volcano on Russia’s Kamchatka peninsula. The results of this study show that the deep magmatic reservoir, located at the boundary between the upper mantle and the earth’s crust (Moho), systematically reactivates a few weeks or months before the surface reservoirs. They therefore suggest that these deep LP earthquakes represent robust precursors to the early activation of a volcanic system.
Finally, this study also enabled us to estimate magmatic pressure transfer velocities within volcanic conduits, showing that transport through a porous medium is a plausible mechanism for magma transfer into the deep parts of the crust.
Réf : N. M. Shapiro, D. V. Droznin, S. Ya. Droznina, S. L. Senyukov, A. A. Gusev & E. I. Gordeev, 2017, Deep and shallow long-period volcanic seismicity linked by fluid-pressur transfer. Nature Geosciences. doi:10.1038/ngeo2952
