TEMPO.CO, Bandung - The Meteorology, Climatology, and Geophysics Agency (BMKG) detected more than 63 earthquakes from unknown sources from January 23 to April 20, 2021, in Samosir Regency, North Sumatra.

The agency recorded that the sequence of seismic activity occurred at mostly small magnitudes with a very shallow depth. The strongest magnitude was recorded at 3.9 which occurred on March 15 at a depth of five kilometers, while the weakest one was recorded at 0.8 at a depth of two kilometers on April 19.

“Residents of Samosir felt the weak tremor on the MMI scale II,” said Daryono, the agency’s Coordinator for Earthquake and Tsunami Mitigation, in a written statement on Wednesday, April 21, 2021.

Based on all data collected, most of the quake sequences were recorded at a magnitude of less than 2.4 with a depth of fewer than 5 kilometers. “It can be concluded that this series of quakes is classified as quake swarm,” he said.

The quake swarm, Daryono explained, is a series of quake activities with a relatively small magnitude and a very high frequency of occurrence. It occurs for a relatively long time in a local area.

However, although with small magnitudes, the seismic activity in Samosir occurred quite intensively. For example, there were 8 quakes on April 4, 6 quakes on April 6, and 11 quakes on April 18.

The seismic activity, he went on, was not clearly felt by residents and was only recorded by the BMKG’s seismograph network. BMKG appealed to people not to panic and worry about the earthquake swarm in the region.

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ANWAR SISWADI (CONTRIBUTOR)