The Hidden Energy of Earthquakes

Earthquakes release energy stored in rocks over millennia. Most of this energy doesn't manifest as ground shaking but dissipates as heat and rock fracturing.

How Much Energy Transforms into Shaking?

A team at MIT conducted lab experiments to quantify the energy budget of earthquakes. They found that only 1-10% of a lab earthquake's energy causes physical shaking. The rest of the energy is divided between breaking rocks (1-30%) and heating the area around the epicenter, with temperatures that can melt the material.

The Memory of Rocks

The research also revealed that a region's tectonic history influences the distribution of seismic energy. "The deformation history—essentially what the rock remembers—really influences how destructive an earthquake could be," says Daniel Ortega-Arroyo, lead author of the study. This history affects the material properties in the rock and dictates how it will slip.

Future Implications

Understanding how an earthquake's energy is distributed between shaking, heat, and rock fracturing could help scientists assess a region's vulnerability to future seismic events. If the intensity of the shaking generated by a past earthquake is known, the impact of energy on rocks deep underground can be estimated, and the future seismic risk can be assessed.