Swarm cessation and aftershock drivers following the pressure release of a four-year-long seismic sequence at the Noto Peninsula

We investigated the interplay of seismic and aseismic processes during the 2024 Mw 7.5 Noto Peninsula earthquake sequence. Comparing pore fluid pressure evolution from prior swarm activity with Coulomb stress perturbations from the 2023 Mw 6.3 sequence, we find that high pore pressure likely played a more significant role in triggering the 2024 mainshock than elastic triggering. Using our template matching catalog for the 2024 sequence and existing slip models, we show that physical drivers vary spatially. To validate our interpretations, we modeled the temporal evolution of background seismicity rates in the 2020–2025 Japan Meteorological Agency catalog. Static stress changes from the mainshock contributed to early seismicity, with strong effects in the southwest. The southwest and central zones exhibit signs of migrating afterslip, while the northeastern seismicity is primarily driven by more localized afterslip. Using evidence of swarm cessation in the central zone, we found that the Noto Peninsula experienced poroelastic rebound effects after pressure release, consistent with a cyclical fault-valving mechanism.