Mount Semeru Remains on Level III Alert as Eruption Quakes Dominate Activity

Volcanic activity at Mount Semeru, located on the border of Lumajang and Malang regencies in East Java, continues to be dominated by eruption earthquakes. Monitoring data indicates a persistently high frequency of these tremors, reaching dozens of events daily.

According to the Mount Semeru Observation Post, 19 eruption earthquakes were recorded during a six-hour period from midnight to 6:00 AM local time on Thursday, 23 July. The recorded quakes had amplitudes ranging from 13 to 22 millimetres. During the same period, the mountain also experienced seven blast earthquakes with amplitudes between 3 and 6 millimetres.

Liswanto, an officer at the observation post, reported that other volcanic activity was also noted. “Mount Semeru experienced one harmonic tremor with an amplitude of 7 mm and one distant tectonic earthquake with an amplitude of 18 mm,” Liswanto stated in a written report received in Lumajang on Thursday.

The dominance of eruption quakes was also evident in the previous day’s data. Throughout Wednesday, 22 July, a total of 77 eruption earthquakes were recorded, making it the most dominant seismic activity. In addition to the eruption quakes, the 24-hour period saw six avalanche earthquakes and 12 blast earthquakes. Two harmonic tremors were also recorded, with amplitudes of 6 to 7 millimetres and durations between 49 and 81 seconds. The high level of seismicity indicates that volcanic processes are ongoing and being intensively monitored.

In the early hours of Thursday, Mount Semeru erupted twice. The first eruption occurred at 00:29 AM local time, followed by a second eruption at 05:48 AM. The Level III (Siaga) alert status remains in effect for the highest mountain on Java Island.