Seismicity Burst Evolution Suggests Systematic Fault Zone Condition Changes in Japan After the 2011 M9 Tohoku‐Oki Earthquake

Abstract Earthquake clusters result from stress perturbations and time‐dependent geophysical processes. Distinct features of these earthquake clusters and their spatiotemporal evolution can provide insights into transient fault zone processes and conditions. Here we apply new statistical methods to systematically identify seismicity bursts in Japan from 2002 to 2025 using the Japan Meteorological Agency Catalog. We identify over 4,000 highly compact seismicity clusters, named seismicity bursts, throughout the main islands of Japan. The identified seismicity bursts have lower b‐values and different stress ratios when compared the whole catalog. We observe a significant, widespread increase in seismicity burst activity along the active volcanic front in the northeastern Honshu arc after the 2011 magnitude (M) 9 Tohoku‐oki earthquake. This increase in seismicity burst activity extends beyond 10 years, reflecting a lasting change. Additionally, the seismicity bursts show a clear decrease in the effective stress drops after the M9 earthquake. These changes most likely result from the static and dynamic stress perturbations of the M9 earthquake, which consequently caused a combination of processes, including the opening of fluid migration pathways and induced transient aseismic slip. These processes may be facilitated by an increase in fault zone damage and subsequent weakening of crustal faults. The identified burst activity indicates that the M9 Tohoku‐oki earthquake induced a sustained change in the crustal fault system across a broad region.