Rain triggers earthquakes at most in karst areas. Picture: Rootmaker, wikipedia.de
Read aloud The tremendous water pressure in water-filled cavities in the rock is the reason why heavy rain can cause earthquakes. That concludes the geologist Steve Miller from the University of Bonn from a mathematical model in which he determined the pressure in a so-called karst system, penetrate into the large amounts of water. The force of water in such a cleft-and-dug system can actually grow so large that it can cause earthquakes in a tectonically unstable system, Miller has shown. Already two years ago, German scientists had presented data, according to which heavy rainfall can cause earthquakes. The researchers from the University of Potsdam referred to measurements at the 1, 771 meter high Hochstaufen in the Chiemgau Alps. After heavy rains, they exposed a series of small earthquakes on the massif, but they were too weak to be directly perceived by humans. According to the researchers, the water entering the karst system changes the pressure conditions in the rock, causing tremors in already unstable systems.

However, this increase in pressure could be about 3, 000 times larger than previously thought, was now the model developed by Miller. The scientist is assuming a pressure increase in the order of one megapascal, which corresponds to a water column of 100 meters. This high pressure could be enough to blow up rocks and cause an earthquake where fractures already exist in the tectonic system, explains Miller. However, such high pressures could only occur in karst areas, where the rock is criss-crossed by cracks and fissures. Miller therefore hypothesizes that only in such limestone massifs is there a correlation between rainfall and earthquake.

Online service of the science magazine "New Scientist" ddp / science.de? Ulrich Dewald

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