The central US, especially Oklahoma, has become a seismically active region since 2009. Knowing the current stress state of the crust in Oklahoma is essential for understanding this activity increase. My thesis focuses on stress analysis with two main objectives. First, using a stress inversion method to reconstruct the state of stress from focal-mechanisms of 562 events for the 2010 to 2015 period. The other objective is the calculation of the stress change on subsurface faults under the stress state derived from the first part.