What are three ways in which geologists use seismographic data?

I am not completely sure, but I believe they use it for:

1. Predicting earthquakes(and finding the center of the earthquake).

2. Mapping faults(a crack in the earth's surface, where earthquakes often occur).

3. Detecting changes along faults(seeing if there has been any movement and etc.).

I hope this helps :)

It is used to map faults, detect changes along faults, and to develop a method for predicting earthquakes. Hope this helped!