Earthquakes are pushed by vitality saved up in rocks over millennia—vitality that, as soon as launched, we understand primarily within the type of the bottom’s shaking. However a quake additionally generates a flash of warmth and fractures and damages underground rocks. And precisely how a lot vitality goes into every of those three processes is exceedingly tough to measure within the discipline.
Now, with the assistance of fastidiously managed miniature “lab quakes,” MIT geophysicist Matěj Peč and colleagues have quantified this so-called vitality price range. Solely about 1% to 10% of a lab quake’s vitality causes bodily shaking, they discovered, whereas 1% to 30% goes into breaking apart rock and creating new surfaces. The overwhelming majority heats up the realm round a quake’s epicenter, producing a temperature spike that may truly soften surrounding materials.
The group additionally discovered that the fractions of quake vitality producing warmth, shaking, and rock fracturing can shift relying on the tectonic exercise the area has skilled previously. “The deformation historical past—basically what the rock remembers—actually influences how harmful an earthquake could possibly be,” says postdoc Daniel Ortega-Arroyo, PhD ’25, lead writer of a paper on the work. “That historical past impacts loads of the fabric properties within the rock, and it dictates to a point how it will slip.”
The lab quakes—which contain subjecting specifically ready samples of powdered granite and magnetic particles to steadily growing strain in a custom-built equipment—are a simplified analogue of what happens throughout a pure earthquake. Down the street, if scientists have an concept of how a lot shaking a quake generated previously, they may be capable to estimate the diploma to which the quake’s vitality additionally affected rocks deep underground by melting or breaking them aside. This in flip may reveal how a lot roughly weak that area is to future quakes.
