The postearthquake stress state on the Tohoku megathrust as constrained by reanalysis of the JFAST breakout data
Abstract
The Japan Trench Fast Drilling Project (JFAST) endeavored to establish the stress state on theshallow subduction megathrust that slipped during theM9 Tohoku earthquake. Borehole breakout datafrom the drill hole can constrain both the orientation and magnitude of the principal stresses. Here wereanalyze those data to refine our understanding of the stress state on the fault. In particular, we (1) improvethe identification of breakouts, (2) consider a fuller range of stress states consistent with the data, and (3)incorporate new and more robust laboratory constraints on rock strength. The original conclusion that theregion is in a normal faulting regime after the earthquake is strengthened by the new analysis. The combinedanalysis suggests that the earthquake released sufficient elastic strain energy to reset the local stressfield.
Domains
Earth SciencesOrigin | Publisher files allowed on an open archive |
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