Tectonic earthquakes are usually the result of movement along faults in the crust, expressed as release of energy which is then transmitted as seismic waves. How did most of that energy accumulate before its release? build-up of geothermal heat rising from the mantle and core as plastic (ductile) strain in crustal rocks as elastic strain in crustal rocks frictional heating during the fault movements build-up of solar energy transmitted to the crust from wind and water waves (including tsunamis).