How Volcanoes Produce ‘Drumbeat’ Earthquakes



In 2011, the Kizimen volcano within the Kamchatka peninsula of the Russian Far East started to erupt in an uncommon method. After nearly a century mendacity dormant, the bottom started to shake with a sequence of earthquakes that fashioned a robust, common drumbeat.

Drumbeat earthquakes are uncommon though geologists have often recorded them. Nonetheless, this one was unusual as a result of the beat was regular for days however over time modified to a decrease frequency with a extra highly effective “beat”.

That’s a puzzle. Volcanologists have varied theories to elucidate how volcanoes trigger earthquakes however these don’t account for the drumbeat impact at Kizimen.

Now Parovik Roman on the Vitus Bering Kamchatka State College in Russia and a few colleagues have developed a mannequin that explains this unusual habits and the way totally different beats can emerge from the identical volcano.

Volcanologists have lengthy identified that the motion of magma and excessive strain gases by way of fissures forces the bottom aside with explosive power. This course of creates the quakes that volcanoes are identified for. Nonetheless, it doesn’t clarify the drumbeat impact.

Stick-Slip Mannequin

So Roman and colleagues turned to a primary concept in earthquake science – the stick-slip mannequin, which explains how most typical earthquakes happen. The mannequin consists of a block sitting on a floor being pulled with a step by step rising power. At first, friction prevents the block from shifting however when the power overcomes friction, the block all of a sudden slips. That is equal to the sudden motion of the earth in an earthquake.

Roman and colleagues says one thing comparable can occur inside volcanoes as magma forces its strategy to the floor. On this case, the top of the stream can solidify in order that the strain builds till it provides method, permitting the liquid magma to burst by way of. This sudden shift creates an earthquake.

The method results in a drumbeat impact when the solidification adopted by bursting repeats frequently. On the Kizimen volcano in 2011, this was occurring each 14 seconds in March however by October the frequency had slowed significantly to as soon as each couple of minutes.

What causes the frequency to vary? Roman and colleagues says that the viscosity of magma can change over time. And when the stream turns into thicker and stronger, the speed at which it solidifies adjustments too.

The researchers created a mathematical mannequin that accounts for all these particulars after which in contrast it to the earthquake information generated by the volcano all through 2011.

It seems that the speed of solidification, or freezing, is a very necessary issue within the interval of the drumbeats. “The freezing coefficient of the block had the best affect on the oscillations,” says Roman and colleagues. Magma that freezes extra readily creates a more practical block requiring extra power to beat. This slows down the frequency of the drumbeat however makes it extra highly effective, simply as noticed at Kizimen.

That’s an fascinating end result that provides larger perception into the habits of sure volcanoes and the unusual drumbeat earthquakes they produce.

It additionally suggests a brand new strategy to analyze volcanoes by learning the frequency of the earthquakes they produce and the way that is altering. This new strategy to peer inside volcanoes may assist perceive how situations are altering inside.

That may very well be helpful — volcanologists want all the assistance they’ll get to review their expenses

Ref: Mathematical Mannequin of the Stick-Slip Impact for Describing the “Drumbeat” Seismic Regime Through the Eruption of the Kizimen Volcano in Kamchatka : arxiv.org/abs/2107.00827



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