In a groundbreaking advancement in seismology, researchers at Kyoto University have unveiled a crucial yet previously unrecognized component of earthquake dynamics referred to as the “stopping phase.” This discovery stems from detailed analyses of strong-motion seismic data recorded near fault lines, which revealed an intriguing and consistent negative phase in waveforms that challenged established interpretations of rupture processes during earthquakes. This finding sheds light on the complex mechanics of how large strike-slip earthquakes abruptly halt, offering vital insights into seismic hazard assessments and engineering challenges associated with ground motion near fault ruptures.
The research team, led by Jesse Kearse alongside co-author Yoshihiro Kaneko, embarked on this study driven by a broader objective to decode the nuances embedded within near-fault seismic recordings, aiming to connect these signals to the physical processes governing earthquake sources. Their meticulous scrutiny of waveforms exposed a systematic negative phase that appeared reliably near the terminal points of ruptures. This phenomenon suggested the presence of a distinct seismic phase that had eluded previous earthquake rupture modeling and theory.
To investigate this anomaly, the researchers employed a multifaceted approach that integrated observational data with physics-based numerical simulations. They first analyzed high-resolution strong-motion acceleration records collected in close proximity to strike-slip faults, utilizing advanced corrections to mitigate instrument noise—an essential step to ensure that subtle waveform features were genuine and not artifacts. Complementing these ground-based data, satellite observations furnished independent validation, providing a comprehensive picture of ground displacement patterns during seismic events.
The final and pivotal stage involved dynamic rupture simulations, which allowed the team to model the earthquake source physics and particularly focus on the rupture arrest process. By replicating how seismic ruptures propagate and subsequently cease, the simulations revealed that the observed negative waveform phase corresponds directly to the sudden termination of rupture propagation. This “stopping phase” is generated most potently when a rupture halts abruptly rather than tapering off gradually, a finding that calibrated and enhanced our understanding of earthquake cessation mechanisms.
Importantly, this stopping phase manifests as whiplash-like ground motions that endure over extended durations, distinct from the initial shaking attributed to rupture initiation and propagation. These motions represent a critical, yet previously underappreciated, source of seismic hazard, especially near anticipated rupture endpoints and within fault segment boundaries where abrupt rupture arrest typically occurs. Recognizing the stopping phase obliges the reassessment of seismic hazard models to explicitly incorporate these ground motion signatures, thereby refining predictions of earthquake impact on infrastructure and human safety.
Beyond practical hazard implications, this research marks a significant conceptual leap in earthquake source physics by documenting and characterizing a reproducible and coherent phase linked to rupture cessation. The stopping phase emerges as a fundamental feature in numerous near-field seismic records of large strike-slip earthquakes worldwide, underscoring the universality of this mechanism. These discoveries underscore the intricacy of rupture dynamics, revealing that the process of halting an earthquake rupture is as physically informative and dynamically rich as its initiation and propagation.
The implications for engineering and urban planning are profound. Structures near strike-slip faults have traditionally been designed with an emphasis on the initial and sustained shaking phases. However, the discovery of a robust stopping phase with its distinctive ground motion characteristics challenges engineers to conceive designs resilient against not only the general shaking but also these prolonged, whiplash-like ground accelerations that could impose unique stresses on built environments.
This study also enhances the toolkit available for seismologists studying earthquake rupture processes. As direct observation of real-time rupture arrest remains elusive due to the rapid and complex nature of seismic waves, the stopping phase provides an indirect diagnostic signature, allowing researchers to infer rupture halt characteristics from high-fidelity ground motion recordings. Consequently, this promotes a more nuanced interpretation of earthquake source physics, facilitating improved earthquake simulations and risk models.
Moreover, the research methodology exemplifies the synergy between empirical observation and computational modeling. By harmonizing data from multiple observational platforms with physics-driven simulations, the team could elucidate previously hidden features of earthquake dynamics. This integrative approach sets a precedent for future studies seeking to decode other enigmatic aspects of seismic phenomena, thereby advancing the broader understanding of Earth’s tectonic behavior.
Looking ahead, the Kyoto University researchers plan to extend their analyses globally, examining the worldwide repository of near-fault seismic records to validate and generalize the presence and characteristics of the stopping phase across diverse fault systems and tectonic settings. Such investigations will help refine the models of rupture dynamics, potentially unveiling variations in stopping behavior linked to fault geometry, geological conditions, or earthquake magnitude.
Conclusively, the identification of a seismic stopping phase fundamentally redefines how geoscientists perceive the termination of earthquake ruptures. It reveals that the end of an earthquake is not a passive or gradual process but is marked by a distinct, physically detectable wave signature that carries crucial information about the rupture’s abrupt arrest. This insight opens avenues for improved seismic risk forecasting and the development of mitigation strategies tailored to protect communities from the multifaceted hazards posed by large earthquakes.
The study titled “Stopping phase reveals abrupt arrest of large strike-slip earthquakes” was published on April 23, 2026, in the prestigious journal Science. It stands as a seminal contribution to seismology, offering new paradigms for interpreting near-fault seismic data, understanding earthquake physics, and guiding future seismic hazard reduction efforts worldwide.
Subject of Research: Not applicable
Article Title: Stopping phase reveals abrupt arrest of large strike-slip earthquakes
News Publication Date: 23-Apr-2026
Web References: http://dx.doi.org/10.1126/science.aef3733
References: Kearse, J. and Kaneko, Y. (2026). “Stopping phase reveals abrupt arrest of large strike-slip earthquakes.” Science, DOI: 10.1126/science.aef3733.
Image Credits: Kyoto University / Jesse Kearse
Keywords
Earthquake rupture dynamics, stopping phase, strike-slip faults, ground motion, seismic hazard, dynamic rupture modeling, near-fault seismic data, rupture arrest, seismic waveforms, earthquake source process, seismic hazard modeling, earthquake engineering
