Interplate slip before, during, and after the 2024 <i>M</i><sub>w</sub> 7 Hyuga-nada earthquake, southwest Japan.

Ozawa, Shinzaburo; Munekane, Hiroshi; Suito, Hisashi; Yarai, Hiroshi · Science · 2025

basic_science · Level V

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Abstract

Using Global Navigation Satellite System data, we investigated the interplate slip before, during, and after the 2024 Hyuga-nada earthquake in Japan. Before the earthquake, a moment magnitude (<i>M</i><sub>w</sub>) 6.0 slow-slip event (SSE) was observed from late 2023 in a downdip extension of the mainshock. The coseismic slip was adjacent to the 1996 Hyuga-nada earthquake source. The afterslip resolved near the hypocenter area and in the downdip extension of the mainshock, reaching <i>M</i><sub>w</sub> 6.7 on 16 September 2024. Leading up to the earthquake, the recurrence interval for SSEs in the preslip area shortened from an average of 2 years, estimated from observations over the past 30 years, to 1 year, consistent with simulations in which the weakening of the Nankai megathrust was attributed to the cause.