Observations of Klyuchevskaya Sopka and its neighbors helped Russian scientists find out how deep-seated “volcanic” earthquakes can be used to predict the volcanic eruptions, according to an article published in the journal Nature Geoscience.
It is impossible to predict exactly when the eruption will occur after the activation of the deep-seated focus.It can be roughly said that if the depth of activity of long-period earthquakes is observed, it can be expected that in a few weeks or months, the upper part of the volcanic system will activate with possible eruptions, – explains Nikolai Shapiro from the Institute of Volcanology and Seismology of FEB RAS in Petropavlovsk-Kamchatsky, whose words are quoted by the press service of the Russian Science Foundation.
Under each volcano there is a magma chamber – a reservoir of porous rocks that can absorb large amounts of liquid magma. Before the eruption, this chamber overflows, which leads to its “inflation” and the rise of the altitude in the vicinity of the volcano. By how much the camera has “blown up”, scientists can estimate the volume of magma contained in it and give an estimate of the eruption and the probability of its occurrence.
The process of filling this chamber, as scientists explain, usually proceeds “jerks”, and not at a constant speed. As a result, the pressure inside the magma chamber periodically changes sharply, and these changes give rise to relatively weak and long-period seismic waves moving toward the surface. The man does not feel these tremors, but the instruments of seismologists fix them in many active volcanoes.
Shapiro and his colleagues found that these shocks can be used to predict the volcanic eruptions, observing the seismic activity in the vicinity of the Klyuchevskaya volcano of the nearby Nameless and Flat Tolbachik volcanoes in 2011 and 2012.
These observations revealed several interesting patterns. Eruptions of each of these three volcanoes were usually preceded by two types of long-period oscillations. First, the tremors arose at a depth of 30 kilometers, where a general magma chamber presumably lies feeding the Klyuchevskaya hill and its two “neighbors”. Then similar, but slightly different, oscillations arose directly under the volcanoes themselves, at a relatively shallow depth, a kilometer or less.
As a rule, about a month after the appearance of the oscillations, an eruption began, but their presence was not a guarantee of the rapid awakening of volcanoes – in some cases Klyuchevskaya hill and its brethren “fell asleep” and another catastrophe was canceled. Nevertheless, the increase in seismic activity at great depths, as Shapiro noted by his colleagues, allows anticipating possible volcanic eruptions and preparing for them.
On average, as observations of these fluctuations show, magma rises to the surface relatively slowly – it moves at a speed of 10 meters per second spends about 2-3 months to overcome 30 kilometers of distance between the deep magmatic chamber and the volcanoes of Kamchatka. In the case of the volcano Tolbachik eruption in November 2012, this process took 5 months, which leaves a lot of time to prepare for the eruption and carry out additional measurements.