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Why do some earthquakes release more energy than others? A research team led by Prof. Dr. Armin Dielforder from the University of Greifswald has managed to demonstrate a clear physical connection between the energy released during earthquakes and the strength of rocks deep in the earth's crust. The results were recently published in the journal Communications Earth & Environment.
Stress builds up along faults as tectonic plates slide past each other. As soon as the load-bearing capacity of faulted rocks is exceeded, the stress is released in the form of an earthquake. Until now, however, it has been difficult to determine how much stress accumulates before an earthquake – and whether stronger rocks actually release larger amounts of energy.
The current study conducted by a team led by Dr. Gian Maria Bocchini from the Ruhr University Bochum and Prof. Dr. Armin Dielforder from the University of Greifswald now shows: the deeper an earthquake occurs, the greater the stress drop and the amount of energy released. As the strength of rocks is higher at greater depths, seismological data can be used to draw conclusions about the relative strength of the Earth's crust.
“Our results provide a physical foundation for the relationship between the release of stress during earthquakes and the strength of the faults,” explains Dr. Gian Maria Bocchini. “They allow us to use seismological measurements to derive how resistant the rock is in certain regions - something that was previously very difficult to determine.”
Analysis of extensive data from Japan
For their analysis, the team examined data from earthquakes in north-east Japan over a period of eleven years following the 2011 Tohoku-Oki earthquake (magnitude 9.0). The region is considered to be seismologically particularly well monitored. The analysis revealed a clear trend: the stress drop increases with the depth of an earthquake.
By comparing the results with numerical models, the researchers were able to demonstrate that stronger faults can withstand greater stress - and consequently release larger amounts of energy when they fail.
Constant solidity over time
“Interestingly, the stress drop values have hardly changed in all the years after the Tohoku-Oki earthquake,” notes Prof. Dr. Armin Dielforder from the University of Greifswald. “The strength of faults appears to remain constant over time, which could contribute to the understanding of aftershock sequences.”
Significance for future earthquake research
The study not only provides an explanation for previously conflicting observations, but also creates a foundation for modelling the mechanical properties of the Earth's crust more accurately in the future. In the long term, the results could help to improve the understanding of the processes of earthquakes and thus also seismic risk assessment.
Further information
Publication: Bocchini, G. M., Dielforder, A., Kemna, K. B., Harrington, R. M., & Cochran, E. S.: Earthquake stress-drop values delineate spatial variations in maximum shear stress in the Japanese forearc lithosphere, in: Communications Earth & Environment, 2025, https://doi.org/10.1038/s43247-025-02877-y
Contact at the University of Greifswald
Prof. Dr. Armin Dielforder
Institute of Geography and Geology
Friedrich-Ludwig-Jahn-Straße 17 A, 17489 Greifswald
Tel.: +49 3834 420 4560
armin.dielforder@uni-greifswald.de
Porträt Prof. Dr. Armin Dielforder
Source: Foto: Gina Heitmann
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