Seismological Stress Drops for Confined Ruptures Are Invariant to Normal Stress

Will Steinhardt*, Sam Dillavou, Mary Agajanian, Shmuel M. Rubinstein, Emily E. Brodsky

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

1 Scopus citations


Seismic moment and rupture length can be combined to infer stress drop, a key parameter for assessing earthquakes. In natural earthquakes, stress drops are largely depth-independent, which is surprising given the expected dependence of frictional stress on normal stresses and hence overburden. We have developed a transparent experimental fault that allows direct observation of thousands of slip events, with ruptures that are fully contained within the fault. Surprisingly, the observed stress drops are largely independent of both the magnitude of normal stress and its heterogeneity, capturing the independence seen in nature. However, we observe larger, normal stress-dependent stress drops when the fault area is reduced, which allows slip events to frequently reach the edge of the interface. We conclude that confined ruptures have normal stress independent stress drops, and thus the depth-independent stress drops of tectonic earthquakes may be a consequence of their confined nature.

Original languageAmerican English
Article numbere2022GL101366
JournalGeophysical Research Letters
Issue number9
StatePublished - 16 May 2023

Bibliographical note

Publisher Copyright:
© 2023. The Authors. Geophysical Research Letters published by Wiley Periodicals LLC on behalf of American Geophysical Union.


  • analog model
  • experiment
  • friction
  • stress drop


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