"Based on observations of Semeru's seismic activity, one flood tremor was recorded with an amplitude of 10 mm and a duration of 9,132 seconds, or more than 2.5 hours," Mount Semeru Observation Post Officer Yadi Yuliandi said in a statement on Friday.
During the same period, Mount Semeru's seismic activity was still dominated by 55 eruption earthquakes, with amplitudes of 10–22 mm and durations of 47–226 seconds.
"We also recorded seven avalanche earthquakes with amplitudes of 3–6 mm and durations of 49–140 seconds, followed by 16 gust earthquakes with amplitudes of 4–8 mm and durations of 41–85 seconds," Yuliandi added.
Mount Semeru also experienced eight distant tectonic earthquakes with amplitudes of 8–35 mm, S–P times of 12–34 seconds, and durations of 37–102 seconds.
On Friday morning, Mount Semeru erupted twice, at 4:20 a.m. and 6:11 a.m.
The eruptions were not visually observed but were recorded on seismographs with maximum amplitudes of 22 mm and durations of 134–170 seconds.
Yuliandi noted that Mount Semeru’s status remains at Alert. Therefore, the Center for Volcanology and Geological Hazard Mitigation (PVMBG) issued several recommendations, including a prohibition on any activities in the southeastern sector along Besuk Kobokan within eight kilometers of the eruption center.
Beyond that distance, the public is advised to avoid activities within 500 meters of the riverbanks along Besuk Kobokan, due to the potential for lava flows reaching up to 13 kilometers from the summit.
"The public is also advised to refrain from activities within a three-kilometer radius of Mount Semeru’s peak because of the risk of ejected incandescent rocks," he said.
The PVMBG also urged residents to remain alert to the possibility of hot clouds, lava avalanches, and cold lava flows along rivers originating from the summit of Mount Semeru—particularly Besuk Kobokan, Besuk Bang, Besuk Kembar, and Besuk Sat—as well as potential lava flows in smaller rivers that are tributaries of Besuk Kobokan.
Related news: Indonesia's Mount Semeru erupts twice in a day, ash soars 500 meters
Translator: Zumrotun Solichah, Resinta Sulistiyandari
Editor: M Razi Rahman
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