Mr Dahm, that the volcanism was extinguished in the Eifel, but only in the long time of sleep, say some scientists. So what is new about your study?
confirm This scientific opinion, we hereby. The special feature of our measurements and observations that we see for the first time, seismic evidence for processes that occur directly under the Eifel-of-date. So we have direct evidence for magmatic-induced earthquakes or magmatic processes.
“Magmatism” is not the same volcano eruption…?
A volcano is not only active, if something comes out of this. That is why we speak of the Magmatism. Magmatic processes in the crust of the earth to happen much more than just there, where the volcano is. These processes may be constantly active, and you don’t notice on the surface of something.
In the Eifel mountains, it shakes but always perceptibly, as the new registrations from the usual Eifel-earthquakes differ?
In the Eifel tectonic earthquakes are known, of course, tension tremors, which are also perceived by the population, and vibration have frequencies exceeding ten Hertz. Now we can register a so-called Deep-Low-Frequency (DLF) earthquake, translated: low-frequency deep cooker quake. The deepest earthquakes in the Eastern Eifel region, the deepest ever to be determined in Germany. The DLF earthquakes differ from tectonic earthquakes due to the lower frequencies – approximately one to ten Hertz. They are very gentle earthquake, not felt – on the Richter scale, usually smaller than two. It is associated generally with Magmenbewegung.
The compression of the seismological monitoring network in 2013, these registry at all. May DLF-quake be normal for the East Eifel volcanic field?
This is something that we can not answer: It may be that the DLF earthquakes in 2013 occurred for the first time in a long time. But it could also be that they existed before the seismic network improvement already and we were not able to you simply see. The are now young observations, and we think it is important, again exactly in the old data just to have a look. Maybe you can find something with improved evaluation methods.
What is to the observed events so special?
The DLF earthquakes are concentrated on a small area under the Laacher see and in a row like on a thread, just down from ten to about 43 km depth. The structure resembles a channel. The earthquakes happen in “clusters”, clusters, but not evenly distributed, but in different floors. Each Cluster was reactivated in the same place. The DLF events to come in brief episodes that last for a few minutes. After that, silence again.
And what has this to do Magma with these quakes?
In the standard model for the DLF earthquake of the following occurs in the vicinity of small Fluid – or magma reservoir: The reservoirs are momentarily under-voltage, and if the Rock falls on the edge of the reservoir, a weak earthquake. The rupture in the inner Fluid region of the reservoir, penetrates, this can begin to swing. We think now – and this is our main point – that the progression of the collapse is slowed down greatly, because the edge zone is partially crystallized. This slowdown could explain the low-frequency character of this earthquake. The model could also describe what reactivates the registered DLF-events always in the same place: the Reservoir is always encouraged.