Extremely early recurrence of intraplate fault rupture following the Tohoku-Oki earthquake

Shaking up earthquake expectations

31 July 2019

A once-in-a-millennium earthquake unexpectedly struck twice within 6 years.

Intraplate earthquakes occur away from the shifting boundaries between two tectonic plates. They can happen when old faults or weaknesses in the crust rupture under the stress and strain of moving over the curved Earth. They usually occur about once every 1,000 years in any one location.

However, a team that included researchers from Tohoku University’s Graduate School of Medicine found that the March 2011 Tohoku-Oki earthquake was followed by a strong afterslip just 8 days later and another quake less than 6 years later on exactly the same fault. The team modelled strain patterns around the fault, and found that the first afterslip caused extreme deformation of the crust, which rapidly rebuilt the stress leading to the quake in December 2016.

Fast and furious localized deformation following a quake could indicate an increased risk of a repeat event in the near future.

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References

1. Nature Geoscience 11, 777−781 (2018). doi: 10.1038/s41561-018-0201-x