October 22, 2025 | 03:28 pm
TEMPO.CO, Jakarta - The Semeru Volcano Observation Post reported increased volcanic activity at East Java's Mount Semeru on Wednesday, October 22, 2025, with 100 eruption earthquakes recorded over the past 24 hours.
The quakes had amplitudes ranging from 11 to 22 millimeters and lasted between 53 and 149 seconds.
In addition to the eruption events, the seismic station at Mount Sawur in Sumber Wuluh Village, Candipuro District, Lumajang Regency, also recorded other types of volcanic tremors, including avalanche, blast, and distant tectonic earthquakes.
Six avalanche quakes were recorded with amplitudes of 2–5 mm and durations of 30–57 seconds. Nine blast quakes were detected with amplitudes of 3–7 mm lasting 30–56 seconds, and one distant tectonic quake measured an amplitude of 17 mm with an S–P time of 15 seconds and a duration of 50 seconds.
The Center for Volcanology and Geological Hazard Mitigation (PVMBG) confirmed that Mount Semeru remains at Alert Level II (Caution).
“The status remains at Level II,” said Liswanto, an officer at the Observation Post.
Under this alert level, PVMBG has advised the public to refrain from any activities in the southeastern sector within 8 kilometers of the Besuk Kobokan channel from the volcano’s summit.
Residents are also urged to avoid areas within 500 meters of riverbanks along Besuk Kobokan, as they may be affected by pyroclastic flows or lahars that can travel up to 13 kilometers from the crater.
In addition, people and visitors are prohibited from conducting any activities within a 2.5-kilometer radius of the crater due to the danger of rock ejections (lapilli).
PVMBG further warned the public to stay alert for potential pyroclastic flows, lava avalanches, and lahar floods along rivers originating from Mount Semeru’s peak, especially Besuk Kobokan, Besuk Bang, Besuk Kembar, and Besuk Sat, as well as smaller tributaries feeding into Besuk Kobokan.
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