The State of Stress on the Fault Before, During, and after a Major Earthquake

Emily E. Brodsky, James J. Mori, Louise Anderson, Frederick M. Chester, Marianne Conin, Eric M. Dunham, Nobu Eguchi, Patrick M. Fulton, Ryota Hino, Takehiro Hirose, Matt J. Ikari, Tsuyoshi Ishikawa, Tamara Jeppson, Yasuyuki Kano, James Kirkpatrick, Shuichi Kodaira, Weiren Lin, Yasuyuki Nakamura, Hannah S. Rabinowitz, Christine RegallaFrancesca Remitti, Christie Rowe, Demian M. Saffer, Saneatsu Saito, James Sample, Yoshinori Sanada, Heather M. Savage, Tianhaozhe Sun, Sean Toczko, Kohtaro Ujiie, Monica Wolfson-Schwehr, Tao Yang

Research output: Contribution to journalReview articlepeer-review

47 Scopus citations


Earthquakes occur by overcoming fault friction; therefore, quantifying fault resistance is central to earthquake physics. Values for both static and dynamic friction are required, and the latter is especially difficult to determine on natural faults. However, large earthquakes provide signals that can determine friction in situ. The Japan Trench Fast Drilling Project (JFAST), an Integrated Ocean Discovery Program expedition, determined stresses by collecting data directly from the fault 1-2 years after the 2011 Mbinfweinf 9.1 Tohoku earthquake. Geological, rheological, and geophysical data record stress before, during, and after the earthquake. Together, the observations imply that the shear strength during the earthquake was substantially below that predicted by the traditional Byerlee's law. Locally the stress drop appears near total, and stress reversal is plausible. Most solutions to the energy balance require off-fault deformation to account for dissipation during rupture. These observations make extreme coseismic weakening the preferred model for fault behavior. Determining the friction during an earthquake is required to understand when and where earthquakes occur. Drilling into the Tohoku fault showed that friction during the earthquake was low. Dynamic friction during the earthquake was lower than static friction. Complete stress drop is possible, and stress reversal is plausible.

Original languageEnglish (US)
Pages (from-to)49-74
Number of pages26
JournalAnnual Review of Earth and Planetary Sciences
StatePublished - May 2020

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science


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