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The Multi-segment Complexity of the 2024 Mw 7.5 Noto Peninsula Earthquake Governs Tsunami Generation

The 1 January 2024, Mw 7.5 Noto Peninsula (Noto‐Hanto) earthquake ruptured in complex ways across an active near-shore fault system, causing strong ground shaking, ionospheric disturbances, and a large tsunami within the Sea of Japan. We unravel the complex rupture dynamics and tsunami generation of the Noto Peninsula earthquake using a 6‐subevent centroid moment tensor (CMT) model that we obtain from a Bayesian inversion of teleseismic and strong motion data. For the inversion, we use a Markov Chain Monte Carlo method with a Metropolis–Hasting accept-reject criterion, where the number of subevents is not prescribed but iteratively updated based on reducing the seismic waveform misfit. We observe a bilateral rupture propagation with two distinct rupture episodes: an initial, onshore rupture toward the southwest followed by a subsequent, partly offshore rupture toward the northeast, which re‐nucleates at the earthquake's hypocenter after a 20 s delay and causes significant seafloor uplift. Such re-nucleation may have been aided by upward fluid migration due to fault valving, allowing high pore-fluid pressure to effectively weaken the fault, offering a physics-based explanation of this effect. This second rupture episode with substantial moment release toward the northeast (40%), that is, offshore, may be necessary not only for improving the fit to seismic waveforms but also for more accurate tsunami generation. Here, we map the subevent model to seafloor deformation to construct a complex multi‐fault uplift model, validated against geodetic observations, that aligns with known fault system geometries and informs tsunami simulations. The model can explain tsunami wave amplitude, timing, and polarity of the leading wave, which are crucial for tsunami early warning. Upon comparison with alternative source models and analysis of 2000 multi‐CMT ensemble solutions, we highlight the importance of incorporating complex source effects for realistic tsunami simulations.

Session: Late-breaking on Recent and Future Large Earthquakes - I

Type: Oral

Room: Key Ballroom 10

Date: 4/15/2025

Presentation Time: 10:30 AM (local time)

Presenting Author: Fabian Kutschera

Student Presenter: Yes

Invited Presentation: 

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