The roughness of tectonic plates may predict earthquake magnitude

The roughness of tectonic plates may predict earthquake magnitude. Researchers at McGill University have established a link between the ruggedness of tectonic plates and the frequency and magnitude of earthquakes. The study confirms the idea that tectonic plates with rough patches are more resistant to slipping and less likely to trigger a major earthquake.

The team examined tectonic plates that have varying degrees of roughness, which could help explain why some earthquakes are stronger than others.

“We already knew that the roughness of a fault was an important factor, but we did not know how rough faults in the subsurface truly are, nor how variable the roughness is for a single fault,” said study first author Professor James Kirkpatrick.

Earthquakes arise when rocks beneath the Earth’s surface break along geological fault lines and slide past each other. The characteristics of an individual fault, such as the smoothness or roughness of is surface, can influence the magnitude of an earthquake. 

However, it is difficult to assess specific fault properties because the systems are located so far beneath the ground.

To investigate the characteristics of fault lines, the Mcgill team used high-resolution seismic reflection data to map and measure the roughness of a plate boundary fault located off the coast of Costa Rica.

The researchers found that some parts of the fault have a rougher surface than others. Previous earthquakes in this particular region have been only moderate. Professor Kirkpatrick believes the history of lower-magnitude events is tied to the rough patches identified along the fault.

“These rough patches are stronger and more resistant to earthquake slip,” said Professor Kirkpatrick. “The historical record of earthquakes is relatively short, so we can’t say with certainty that larger ones have not occurred. Future seismic events in the area, which will be recorded with modern equipment, should help us determine if they show the same limited magnitude.”

Next, the researchers will apply their findings to other subduction zones, where existing data can help them validate their conclusions. 

“This connection between the fault roughness and earthquake magnitude might one day help us understand the size and style of earthquakes most likely to occur at a given fault.”

The study is published in the journal Nature Geosciences. 

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By Chrissy Sexton, Earth.com Staff Writer