Seismic Imaging Detects Active Magma Recharge in Kikai Caldera 7300 Years After Holocene's Largest Eruption

Researchers from Kobe University and JAMSTEC deployed systematic seismic surveys across the submerged caldera, firing airgun pulses recorded by ocean-bottom seismometers to distinguish solid crust from partial melt. The resulting velocity model revealed an extensive low-velocity zone whose location and geometry match the pre-7,300 BP reservoir, indicating the system is recharging rather than simply retaining residual magma.

The underwater setting permitted dense spatial sampling unavailable at most subaerial supervolcanoes, yielding the first quantitative image of post-caldera recharge at this scale. This finding aligns with petrologic evidence from the new lava dome and challenges assumptions that such systems remain dormant for tens of millennia after major collapse.

Prior reporting emphasized hazard implications while understating methodological limits: the study provides only a single snapshot of melt fraction and cannot yet constrain recharge rate or total volume. Repeated 4-D seismic campaigns over the next decade would be required to convert this static image into a dynamic forecast.

Next steps include integration with geochemical sampling of the lava dome and numerical modeling of melt ascent thresholds to establish measurable precursors for renewed super-eruption risk.