Evidence for rock deformation and several processes implying the release of considerable energy was well know for at least a century prior to the PT model. For instance, Charles Lyell's Principles of Geology (1875) makes abundant reference to seisms, and attributes them to various deformation processes such as uplift, volcanos and orogenesis.

What plate tectonics does is provide a comprehensive framework for a host of geological information, one of those bits beeing why earthquakes occur where they do (but seafloor spreading also played a crucial role). Proximal causes were already an understood concept as early as the 17th century, as was the association of tremors with orogenic mountain belts, or volcanoes in some areas. As such, quakes were explained on an individual ad hoc basis and attributed to local processes such as folding, thrusting etc., which isn't untrue, just incomplete.

See: Bolt, 2015, "*Earthquakes and Earth structure: a perspective since Hutton and Lyell *" for a more thorough discussion.