Synthesizing geological and geophysical approaches to investigate the deformation of the lithosphere offers the potential for important new insights because of the range of timescales and lengthscales sampled by the different techniques, although successfully spanning this range represents one of the main challenges to be overcome when conducting such work. Nonetheless, significant progress has been made in linking such diverse observations and models. For example, the recognition of transient and mostly aseismic slip in some parts of subduction zones being coupled to field-based analysis of mixed-lithology fault zones has resulted in a new understanding of the mechanisms for generating transient fault slip at velocities intermediate between earthquakes and plate motions [1–5]. Similarly, observations of earthquake faulting in the lower continental crust made both petrologically (preserved as pseudotachylytes) and seismologically has resulted in a new appreciation of the diversity of rheology in the continental crust, and the importance of trace amounts of water in controlling the deformation [6–10]. In February 2020, the Royal Society hosted a Hooke discussion meeting to further explore links between geological and geophysical methods of studying faulting, titled ‘Understanding earthquakes using the geological record’. This introduction highlights some of the common themes of the meeting, relating to the factors that govern fault behaviour, and the feedbacks between faulting and the geological evolution of the Earth’s crust and upper mantle.