Surface-wave relocation and characterization of the October 2023 tsunamigenic seismic unrest near Sofugan volcano, Izu Islands, Japan

Chanel Ashlie Deane; J.D. Pesicek; Stephanie G. Prejean; Paul S. Earle; David R. Shelly; William L. Yeck

doi:10.1029/2024gl113504

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Surface-wave relocation and characterization of the October 2023 tsunamigenic seismic unrest near Sofugan volcano, Izu Islands, Japan

Chanel Ashlie Deane·J.D. Pesicek·Stephanie G. Prejean·Paul S. Earle·David R. Shelly·William L. Yeck

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Abstract

A moderate-magnitude earthquake swarm occurred in the remote Izu Islands region of Japan between October 1 and 8, 2023. The swarm included 151 shallow earthquakes cataloged by the U.S. Geological Survey, which notably included a roughly 2.5-hr episode of 15 successive magnitude (M) < 5.5 earthquakes. Origin times were coincident with regionally recorded tsunami waves, but tsunamigenesis for moderate-magnitude earthquakes is uncommon, indicating that volcanic activity generated the ocean displacements. Leveraging a surface-wave relative relocation approach, we estimate precise epicentroid locations for the remote swarm. Final epicentroids and caldera analogs indicate a three-stage model to explain swarm activity: (a) caldera pressurization due to magma intrusion, (b) depressurization via dike propagation away from the caldera, and (c) eruption corresponding with caldera reactivation either by collapse or additional intrusion.

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Geophysical Research Letters Article

Source-reported bounding extent: 32.958492752206496° to 34.82287677805212° latitude; 139.25840884901504° to 139.99669459503235° longitude. This indicates report coverage, not an exact sampling location. View area on OpenStreetMap.

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Chanel Ashlie Deane, J.D. Pesicek, Stephanie G. Prejean, Paul S. Earle, David R. Shelly, William L. Yeck. 2025-01-30. Surface-wave relocation and characterization of the October 2023 tsunamigenic seismic unrest near Sofugan volcano, Izu Islands, Japan. https://doi.org/10.1029/2024gl113504

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