Earthquake swarm examples and a look at the generation mechanism of the Vogtland/Western Bohemia earthquake swarms

Earthquake swarms occur at many locations all over the world. In most cases, they do not occur just once but happen rather repeatedly at a particular location. We compared intraplate earthquake swarm regions, especially the Vogtland/Western Bohemia area, with plate margins, leading to the conclusion of a fluid triggered earthquake swarm mechanism which is independent of the global tectonics. These observations were brought together with theoretical models concerning hydro fracturing with respect to pore pressure changes due to fluid movements in seismically active areas. This concept was applied to a finite element model of the Vogtland/Western Bohemia earthquake swarm region. The results show that it is not possible to get high enough stress accumulations for the generation of earthquake swarms within relatively short timespans by the regional stress field alone. But periodic pore pressure variations and linear temperature changes caused realistic deformations and stress accumulations which coincide with the measured ones of the Vogtland/Western Bohemia earthquake swarm region.