Researchers Identify a Stopping Phase That Governs How Large Strike-Slip Earthquakes End

by Riko Seibo
Kyoto, Japan (SPX) ) May 01, 2026
Researchers at Kyoto University have identified a distinct seismic signal - a negative phase in near-fault waveforms - that marks the abrupt arrest of large strike-slip earthquakes and carries significant implications for seismic hazard assessment near active fault systems. The findings are published in Science.

The discovery emerged from analysis of strong-motion acceleration records collected close to fault lines. While reviewing the data, the team noticed a negative phase that did not conform to existing interpretations of rupture dynamics. Its consistent appearance near rupture endpoints suggested it might represent a previously overlooked component of the earthquake process.

"This study originated from a broader effort to better understand near-fault seismic recordings and interpret them in terms of the earthquake source process," said first author Jesse Kearse.

The researchers validated their observations with satellite data and used numerical dynamic rupture simulations to model how rupture propagation terminates. The analysis confirmed that the negative phase - termed the stopping phase - is produced when an earthquake rupture comes to a sudden halt at a sharp barrier, rather than decelerating gradually. Abrupt stops generate significantly stronger signals than gradual ones.

The stopping phase produces extended, whiplash-like ground motions that differ from the shaking associated with the main rupture front. These motions pose particular engineering challenges for structures located close to strike-slip faults and near fault segment boundaries, where abrupt rupture arrest is most likely to occur.

The team found evidence of the stopping phase in near-field records from many large earthquakes, suggesting it is a widespread and systematic feature of strike-slip rupture dynamics rather than an anomaly specific to particular events.

The research has practical consequences for how seismic hazard is modeled and communicated in regions crossed by major strike-slip faults. The team intends to extend the work by analyzing a global catalog of near-fault earthquake records to better characterize the conditions that produce abrupt rupture arrest and the strongest stopping-phase signals.

Research Report:Stopping phase reveals abrupt arrest of large strike-slip earthquakes