BMKG says mysterious Bandung booms came from unexplained skyquake phenomenon

The mysterious booms that unsettled residents across Greater Bandung have been classified by Indonesia’s meteorological agency as a skyquake, but the explanation remains incomplete. BMKG said its analysis could not establish the main cause of the phenomenon.

The sounds were reported from Friday night into the early hours of Saturday. BMKG Bandung examined seismic and meteorological monitoring data, including earthquake activity, lightning, weather conditions and magnetic anomalies between 11 p.m. and 5 a.m. The weather in Greater Bandung was relatively clear, and instruments detected no local earthquake activity around the Lembang or Cimandiri faults or other active faults.

BMKG official Teguh Suadi said seismic instruments recorded no earthquake waves at all. Similar booms occurred in Bogor in April 2020, while land-based booms can sometimes follow earthquake swarms or repeated small earthquakes. That explanation did not fit the Bandung readings.

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Based on BMKG earthquake data, no seismic activity was detected in the area.

Other data did show unusual activity elsewhere. Satellite imagery from Himawari and magnetic stations in Serang and Sukabumi recorded magnetic disturbances and concentrated thunderstorms around Mount Anak Krakatau during a volcanic eruption. BMKG said the possible connection remains a major scientific puzzle. The eruption occurred near Krakatau, but residents in closer areas including Banten, Jakarta and Bogor did not report hearing the booms. Given the distance, a normal-scale Krakatau eruption would also have to cross intervening areas before reaching the Bandung basin.

BMKG therefore raised an alternative hypothesis from scientific literature: a skyquake could be triggered by methane released from the floor of an ancient lake basin. Greater Bandung stands on the former Bandung Ancient Lake basin. The agency plans to coordinate further study with the Geological Agency and the Center for Volcanology and Geological Hazard Mitigation. It urged residents to remain calm, avoid panic and sort reliable information from hoaxes.

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Volcanic activity appeared at Krakatau, but it was not reported or discussed by residents in Banten, Jakarta or Bogor, which are closer. This boom phenomenon occurred only in Bandung and its surroundings.