Abstract The 15‐s‐long weak initial rupture of the 2024 MW 7.5 Noto earthquake overlapped with a fluid‐rich region of a preceding earthquake swarm and was accompanied by enhanced high‐frequency seismic radiation. To understand the radiation and related source processes, we investigate rupture behaviors of four nearby M5+ events. We find that the 5 May 2023 MW 5.7 event exhibits similar characteristic radiation, resulting in a relatively low source spectral decay rate. Apparent moment‐rate functions and dynamic rupture simulations, constrained from near‐source waveform data, consistently suggest a northeastward rupture with multiple asperities. Such rupture heterogeneities under a fluid‐rich condition can explain the weak, long seismic radiation but with enhanced high‐frequency signals in the MW 5.7 event and the initial rupture of the 2024 MW 7.5 Noto earthquake. The multi‐asperity model also holds implications for other observations, including the depth dependence of high‐frequency radiation and the low spectral falloff rates observed for low‐frequency earthquakes.
Observations from the Little Bunker
Last updated: November 30, 2025 04:25 AM
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