MIT geologists have achieved a breakthrough in understanding how an earthquake releases and partitions its energy by creating “lab quakes,” miniature analogs of natural seismic events. Their work provides the first complete measurement of how earthquake energy is distributed among ground shaking, heat generation, and rock fracturing. Traditional field studies can detect surface shaking, but they cannot easily measure the immense heat or hidden rock damage occurring deep underground. By simulating quakes on a small scale in a controlled laboratory environment, the team has quantified the entire energy budget of these events, offering a new lens through which to view seismic risk.
The researchers designed experiments using small samples of granite, a rock common in the Earth’s seismogenic layer where natural earthquakes originate. They ground granite into powder, mixed it with magnetic particles, and enclosed the mixture between pistons wrapped in a gold jacket. Applying steadily increasing pressure, they induced sudden slips—miniature quakes—while piezoelectric sensors recorded shaking and the magnetic particles tracked temperature changes. After each event, the scientists examined grain structure to assess rock fracturing.
Their results show that the majority of earthquake energy is converted to heat, not motion. On average, about 80 percent of a lab quake’s energy instantly heated the surrounding material, sometimes reaching temperatures of 1,200 °C—hot enough to melt rock for a brief moment. Roughly 10 percent of the energy generated measurable shaking, and less than 1 percent went into breaking the rock and creating new surfaces. In some experiments, fault slip velocities reached 10 meters per second, though the movement lasted only microseconds before rapid cooling.
Another key insight is that a region’s deformation history strongly influences how earthquake energy is partitioned. Rocks that have previously been shifted or stressed behave differently when they fail again. According to graduate student Daniel Ortega-Arroyo, this “memory” of past tectonic motions affects material properties and helps determine how destructive a future quake might be. Understanding how prior stress changes a fault’s response could improve forecasts of seismic hazards.
The implications of these findings are far-reaching. Natural earthquakes are driven by energy stored over millions of years as tectonic plates grind together, but current technology mostly captures the shaking we feel on the surface. By revealing how much earthquake energy is hidden as heat or internal rock damage, MIT’s lab results can guide seismologists in estimating a region’s true seismic risk. For example, if historical records show how much shaking occurred during a past quake, scientists might infer how much additional energy went into melting or fracturing rock below, helping to assess whether the area is more or less vulnerable to future events.
Reported in AGU Advances by Matěj Peč, Ortega-Arroyo, and colleagues from Harvard and Utrecht University, this integrated approach offers one of the most detailed pictures yet of the physics behind quake ruptures. Although the complexity of the Earth cannot be fully reproduced, these controlled experiments provide critical data for refining earthquake models and developing better strategies for natural hazard mitigation, ensuring that the hidden dynamics of earthquake energy are no longer overlooked.
https://phys.org/news/2025-09-geologists-energy-earthquake.html