- JMA updates (Japanese)
- Tokyo VAAC advisories page
Rodan alert! (Reference)
After noting increased seismicity today, Japan Meteorological Agency (JMA) has raised the alert (Japanese) at Aso to Level 2.
Yes, Aso is an active supervolcano but they’re talking about its frequently active Naka-dake crater.
Per browser translation:
…At Mt. Aso, the amplitude of volcanic tremors has been increasing since around 11:50 a.m. today (4th), and the average amplitude of 1 minute on the north-south component of the Nakadake west flank seismometer has been at or above 2.5 micrometers per second for over an hour.
Due to the increased volcanic activity at Mt. Aso, there is a possibility of an eruption affecting an area of approximately 1 km from the Nakadake First Crater…
What we might see, if we’re lucky, is something like this from October 2021 — spectacular but fairly harmless:
Updates:
December 4, 2025, 1333 UTC: I am updating all these posts. Here is the most recent GVP report:
Most Recent Weekly Report: 23 July-29 July 2025
The Japan Meteorological Agency (JMA) reported that unrest at Asosan had decreased. The amplitude of volcanic tremors had increased during 4-7 July but then returned to low levels afterward. During field surveys on 16 and 23 July scientists observed no changes compared to field surveys conducted before the increased tremor amplitude. Sulfur dioxide gas emissions were low in July, averaging 200-500 tons per day. At 1100 on 25 July the Alert Level was lowered to 1 (on a scale of 1-5).
The JMA page linked above shows no further updates.
July 6, 2025, 3:28 a.m., Pacific: So far, no eruption. JMA notes today that the tremor has less amplitude.
Featured image: k.sha, CC BY-SA 2.0
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