A study by scientists at ETH Zurich, published on ScienceDirect on 15 November 2017, provides a powerful new way of looking at the risk of large earthquakes in the Alps, Apennines, Zagros and Himalaya mountain ranges.
Most know that mountain ranges are built by tectonic plates pushing against each other. However, some forget how seismically active these zones are. For example, according to Swiss Re most Swiss home owners don’t have earthquake insurance and some buildings in risk zones are not designed to withstand a powerful shake.
- Despite the exposure to seismic risk, few Swiss homeowners take out earthquake insurance (Le News)
- Earthquakes a serious hazard for parts of Switzerland (Le News)
The ETHZ research, led by Luca Dal Zilio, shines a spotlight on the earthquake potential of mountainous tectonic plate collision zones. In addition, their modeling helps to explain why some mountain ranges shake more violently than others.
Earthquakes occur all the time, but most of them are so small they go unnoticed. The frequency of large ones, like the 7.3 shake in the Zagros region near the Iran-Iraq border three days ago, or the 6.2 one near Norcia in Italy last year, is what really matters.
The team’s modeling shows the frequency of large earthquakes is related to the speed of plate movement. Plate movement is faster in the Zagros and Himalayan regions than in the Alps and Apennines. Zones with faster movement seem to be colder and more brittle, something which, along with faster movement, increases the size of quakes.
According to Dal Zilio, the Zagros quake earlier this week fits their modeling. The Arabian plate is moving relative to Eurasian plate at a rate of about 26 mm a year. “Our findings have shown that, for a convergence rate of 20 – 30 mm a year we could expect a maximum magnitude of earthquakes in a range between 7.3 and 7.8″, he said.
If, as this new research suggests, the speed of plate movement is more important than historical earthquake records for predicting the likelihood of a big Alpine shake, then we need to relook at the risks.
Published study on ScienceDirect – in English