January 19, 2010
The Seismic Gap South Of Istanbul
How prone is Istanbul to earthquake risk?
The chain of earthquakes along the North Anatolian fault shows a gap south of Istanbul. The expected earthquakes in this region represent an extreme danger for the Turkish megacity. A new computer study now shows that the tensions in this part of the fault zone could trigger several earthquakes instead of one individual large quake event. In the latest issue of Nature Geosciences (Vol 3, doi:10.1038/NGEO739) Tobias Hergert of the Karlsruhe Institute for Technology and Oliver Heidbach of the GFZ German Research Centre for Geosciences present the results of the computer simulation, which was developed within the framework of the CEDIM (Centre for Disaster Management and Risk Reduction Technology).project "Megacity Istanbul".
An important factor in judging seismic hazard is the movement rates of the tectonic fault. For their study Hergert and Heidbach divided the area into 640,000 elements, in order to determine, three-dimensionally, the kinetics of the fault system. "The model results show that the movement rates at the main fault are between 10 and 45% smaller than accepted to-date" explains Oliver Heidbach of the GFZ. "In addition the movement rates vary by 40% along the main fault" The authors interpret this variability as an indication that the built-up tension in the Earth's crust can also unload in two or three earthquakes with a smaller magnitude rather than in one enormous quake. This, however, by no means implies an all-clear for Istanbul. The authors explicitly point out in their article that the short distance of the main fault to Istanbul still represents an extreme earthquake risk for the megacity. The fault zone is less than 20 kilometres from the city boundary, disaster precaution before the occurrence of a quake is essential.
On the Net: