04.05.2016: For quite some time already, a causative link between earthquakes and volcanic activity is suggested. How exactly this interaction may be explained is, however, poorly understood. A new mechanisms is now proposed by a team of scientists from the University of Hiroshima and the GFZ: earthquakes can induce the magma stored in volcanoes to “slosh”.

The most recent example of an interaction between earthquakes and volcanoes is the eruption of the volcano Aso in Japan that followed an earthquake with a magnitude of 7 on 16 April 2016. The effect of earthquake on nearby volcanoes is varied: some volcanoes are activated, showing increased seismicity or degassing, others deflate or show no response at all. This diverse picture is reflected in statistical studies that have so far only found a weak causative link between earthquakes and volcanoes.

Mechanisms so far proposed to explain triggering of volcanoes include dislodging of small bubbles in magmas or the liquefaction of crystal networks in the magma reservoirs. These mechanisms can, however, not explain why different volcanoes show diverse reactions.

The reaction of magma resembles that of coffee in a mug

Prof. Atsuko Namiki, from Hiroshima University, and her co-authors Dr. Eleonora Rivalta, Dr. Heiko Woith, and Dr. Thomas R. Walter from the GFZ, now propose a new mechanism for the reaction of volcanos: the sloshing of a bubbly magma in magma-reservoirs.

Sloshing is the resonant sway motion induced in fluid containers subject to movement, such as the sloshing of coffee in a moved mug. Damage of petroleum tanks caused by sloshing after earthquakes is a well-known phenomenon. The scientists propose that the shaking from earthquake waves may have a similar effect on magma in open summit conduits and in magma chambers of volcanoes.

Experiments in the so-called "Bubble lab" at the GFZ explain for the phenomenon that strong, distant earthquakes, rich in low frequencies, have the largest effect: they resonate magma conduits and reservoirs whose width is more than 0.5 meters. It is also shown that the density of the lava and the shape of the magma-chambers have an effect on the response reaction of a volcano.

Prof. Atsuko Namiki received a DAAD fellowship to visit GFZ in summer to conduct new experiments together with the GFZ-scientists. (ak)

>>This article in Science Highlights

Namiki, A., Rivalta, E., Woith, H., Walter, T.R., 2016. Sloshing of a bubbly magma reservoir as a mechanism of triggered eruptions. Journal of Volcanology and Geothermal Research, doi:10.1016/j.jvolgeores.2016.03.010