JAKARTA: A rain-triggered mudflow tremor from Mount Semeru in East Java was recorded for nearly four hours following heavy rainfall on Thursday (Feb 26).
Mount Semeru Observation Post officer Sigit Rian Alfian said the prolonged tremor, caused by heavy rain carrying loose volcanic materials such as ash, sand, and rocks down the volcano’s slopes, was detected during early morning monitoring.
"During the observation period on Thursday from 12pm to 6am local time, one lahar flood tremor was recorded with an amplitude of 17mm and a duration of 13,304 seconds, or three hours and 42 minutes,” he said, according to Antara News Agency, on Thursday.
A rain-triggered mudflow, also known as a lahar, can form a fast-moving flow that travels along rivers and valleys, even without a new eruption.
In addition to the mudflow tremor, Sigit said seismic activity over the past six hours recorded 17 eruption quakes, three rockfall quakes, and one emission quake.
"Visual observation showed that the volcano was covered in fog. No crater smoke was observed. The weather was cloudy to rainy, with weak to strong winds blowing toward the north and northeast,” he said.
Mount Semeru, the highest mountain on Java Island, remains under close monitoring by authorities. - Bernama
