Earthquake prediction difficulties - oceanic transform faults

What is it about?

The continuing controversy over the Strait of Messina bridge (https://www.ilfattoquotidiano.it/2024/11/12/ponte-sullo-stretto-rischio-sismico-ingv/7763383/) illustrates the difficulties in predicting major earthquakes even over long timescales. Stress conditions change after large earthquakes, leading other faults potentially to be at risk of failure. This has been studied with some success using so-called Coulomb stress modelling.

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Photo by Çağlar Oskay on Unsplash

Photo by Çağlar Oskay on Unsplash

Why is it important?

In our study of a moderately large (Mw 6.6) earthquake led by Guilherme de Melo, we found the aftershocks occurred almost all to the east of a main shock and not in areas expected from Coulomb stress modelling (Fig. 1). Other researchers have found examples where this occurs, which is suspected to be due to damage to fault rocks during the passage of the most violent seismic waves. Also curious, the aftershocks occurred around one or more areas where the seabed has east-west structures, which we interpreted as "oceanic core complexes". Such complexes are created were large-offset normal faults carry deep rocks to the surface, including gabbros and serpentinites. They imply that the crust and uppermost mantle is lithologically heterogeneous. Could such heterogeneity be responsible for the aftershocks occurring around where they did? The article is open-access: de Melo, GWS, Mitchell, NC, SY Sokolov, The 2020 Mw 6.6 Vernadsky transform earthquake sequence: rupture and Coulomb stress changes surrounding an oceanic core complex, Marine Geophysical Res. (https://doi.org/10.1007/s11001-024-09558-z) Fig. 1: Aftershocks of the 2020 Mw 6.6 earthquake on a Mid-Atlantic Ridge transform fault. Fig. 2: The morphology of the transform valley north wall.

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