Earthquake risk is a vast issue triggering the urbanization of Istanbul. Plans and laws, conceived as sociotechnical tools that play a key role in this process, combine scientific facts and recommendations for the city. This article discusses the production of scientific facts and their inclusion into planning tools to define earthquake risk in Istanbul. Grounded on the Actor-Network Theory (ANT), our methodology follows the statements of scientists in journal articles, supplemented with semi-directed interviews with geologists and geophysicists. On this basis, the article shows the circulation of statements and scientific facts until they get selected to be included in sociotechnical tools with which the city is performed.