Earthquakes are driven by energy stored in rocks over millennia – energy that, once released, we feel primarily as ground shaking. But earthquakes also cause heat waves and cause underground rocks to break and become damaged. And exactly how much energy is expended in each of these three processes is extremely difficult to measure in the field.
Now, with the help of carefully controlled miniature “laboratory earthquakes,” MIT geophysicist Matej Peck and his colleagues have quantified this so-called energy budget. They found that only 1% to 10% of the Lab earthquake’s energy causes physical vibration, while 1% to 30% is spent breaking the rock and forming new surface. In most earthquakes the area around the epicenter heats up, causing a rise in temperature that can actually melt the surrounding material.
The team also found that the fraction of earthquake energy that produces heat, vibration and rock breakage can vary depending on the tectonic activity the area has experienced in the past. “The history of deformation – essentially what the rock remembers – really influences how destructive an earthquake can be,” says lead author Postdoc Daniel Ortega-Arroyo, PhD ’25. paper At work. “That history affects a lot of the physical properties in the rock, and it dictates to some extent how it will slide.”
Lab earthquakes – which involve subjecting samples of specially prepared powdered granite and magnetic particles to continuously increasing pressure in a custom-built apparatus – are a simplified analog of what happens during a natural earthquake. Going forward, if scientists have an idea of how much shaking earthquakes caused in the past, they may be able to estimate the extent to which earthquake energy melted or fractured underground rocks. This can reveal how more or less sensitive the area is to future earthquakes.
