Hi Ljaz,

Gravity data from GRACE satelitte is usually used to estimate changes in groundwater quantity of a region based on the mass change. If you want  to use it to identify a fault, you need to relate the them in one way or another.

Good luck!

If the density contrast of two sides of the fault be enough you can distinguish the fault trend by satelitte gravity data. You need to process the gravity data for achiveving to this aim. The satelitte gravity data do not show that a fault is active or inactive. You can use GPS data or  temperature-sensitive sensor and ....  I write a paper that publish erelong. I have been used from satelitte gravity data for fault detection. You can study the applied method in my paper in this address

https://www.researchgate.net/publication/298212510_Iidentification_of_Suitable_Discrete_Wavelet_for_Gravity_Data_Decomposition

I hope to be useful

Conference Paper Identification of Suitable Discrete Wavelet for Gravity Data...

Satellite gravity can be very helpful in many applications but not in your case. If you know the exact location of the fault, then it is quite simple: just plant the sufficient number of low-frequency seismographs along the strike of the fault and its branches and interpret their records to identify the active segments you are looking for. If you know only the approximate location of the fault, then it is rather complex: you need the regional geology data, DEM (topography), high-resolution aeromagnetic (HRAM) data and differential GPS to pinpoint the fault location before you could consider steps in the direction of the simple part described above.