The metropolitan area of Istanbul with around 15 million inhabitants is considered to be particularly earthquake-prone. In order to be able to assess the risk correctly, researchers must decipher the processes underground. Now, a team including Marco Bohnhoff from the GFZ German Research Center for Geosciences has made new progress. Below the Marmara Sea, they detected earthquakes that were not directly caused by tectonic stresses but by rising natural gas. Their findings are published in the journal Scientific Reports.