On August 17, 1999, a devastating earthquake occurred in Northwestern Turkey. The magnitude of the earthquake was 7.2, claiming approximately 18,000 lives. Many buildings in eastern Marmara were severely damaged or destroyed, while most industrial sites, transportation and communication lines shared a similar fate. Since the earthquake, a number of scientific studies and projects, both international and national, have been conducted, concluding that another earthquake at the magnitude of at least 7 will hit Istanbul, causing at least 30 thousand deaths and the collapse of over 50 thousand buildings. Even though there is a consensus among scientists that an earthquake will happen again in Istanbul, earth scientists do not have an agreement about the actual location, size, and shape of the faultline, leading to a plethora of different theories and arguments about the expected earthquake. Driving from Science and Technology Studies, this paper aims to unfold the ways in which earth scientists produce scientific knowledge about the fault and discuss it with other scientists. Based on fieldwork, this paper not only aims to understand why there are different earthquake theories but more importantly investigates how these theories constitute and contribute to new governmental policies in the name of being prepared for the expected disaster.