Earth tremors account for only 10% of an earthquake's energy

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Technological Innovation Website Editorial Team - September 18, 2025

A scanning electron micrograph highlights a region of rock that slipped during a laboratory earthquake. The central "fluid" area represents a portion of the rock that was melted and turned into glass due to intense frictional heating. [Image: Matej Pec/Daniel Ortega-Arroyo]

Laboratory earthquakes

The earthquakes that cause destruction and death represent only a fraction of the total energy released by an earthquake. For example, each earthquake also generates a heat wave, along with a domino-like fracturing of underground rocks.

But measuring exactly how much energy is needed for each of these processes is extremely difficult - if not impossible - to do directly in the field.

Knowing this, Daniel Ortega-Arroyo and colleagues at MIT in the US decided to create small earthquakes in the laboratory, miniature analogues of natural earthquakes, carefully triggered in a controlled environment, full of sensors and measuring devices.

And this allowed them, for the first time, to quantify the complete energy balance of earthquakes, in terms of the fraction of energy that turns into shaking, into fractures, and into heat.

Where does the energy from an earthquake go?

Measurements revealed that only about 10% of the energy from a laboratory earthquake causes physical shaking. An even smaller fraction—less than 1%—is expended on fragmenting rocks and creating new surfaces. Thus, most of an earthquake's energy—on average 80%—is expended heating the region around the epicenter.

In experiments, researchers observed that a laboratory earthquake can produce a temperature spike hot enough to melt surrounding material and briefly turn it into molten rock.

Geologists have also discovered that an earthquake's energy budget depends on the region's deformation history—the degree to which rocks have been displaced and disturbed by previous tectonic movements. The fractions of earthquake energy that produce heat, shaking, and rock fractures can vary depending on the region's past experience.

"The deformation history—essentially what the rock remembers—really influences how destructive an earthquake can be," Daniel said. "This history affects many of the material properties in the rock and determines, to some extent, how it will move."

These findings will help seismologists predict the likelihood and severity of earthquakes in seismic-prone regions. For example, if scientists have an idea of ​​the intensity of the vibration generated by a past earthquake, they can estimate the degree to which the earthquake's energy also affected deep underground rocks, melting or fragmenting them. This, in turn, could reveal how vulnerable or vulnerable the region is to future earthquakes.

Diagram illustrating a rock sample subjected to a laboratory earthquake, which releases energy in three forms: fracturing and comminution (reduction in grain size), frictional heating, and seismic shaking. [Image: Matej Pec/Daniel Ortega-Arroyo]

How to create earthquakes in the laboratory

The team generated miniature earthquakes in the laboratory that simulate the seismic sliding of rocks along a fault zone. These microquakes are a simplified analog of what occurs during a natural earthquake, but they represent a very valid alternative to the inability to see the real thing.

Small samples of granite were used, representative of the rocks of the seismogenic layer, the geological region of the continental crust where earthquakes typically originate. The granite was ground into a fine powder and then mixed with an even finer powder of magnetic particles, which act as a kind of internal temperature gauge—the intensity of a particle's magnetic field changes in response to a temperature fluctuation.

These samples were placed in a device the team built, designed to apply increasing pressures, similar to the pressures experienced by rocks in Earth's seismogenic layer, about 10 to 20 kilometers below the surface. Custom-made piezoelectric sensors, attached to each end of the sample, measured any vibrations that occurred as the pressure increased.

Under certain stresses, some samples slipped, producing a microscale seismic event, similar to an earthquake—a laboratory microquake. By analyzing the magnetic particles in the samples, it was possible to estimate how much each sample was temporarily heated and the amount of vibration each sample experienced. The researchers also examined each sample under a microscope, assessing how the size of the granite grains changed.

Using all these measurements, they were able to estimate the energy budget of each laboratory earthquake—on average, 80 percent of an earthquake's energy is converted to heat, 10 percent generates shaking, and less than 1 percent is converted to rock fractures.

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