Indonesia’s Megathrust Map Shows 14 Zones, but No Earthquake Timetable

Indonesia’s updated earthquake-hazard map identifies 14 megathrust zones, according to CNBC Indonesia and BBC News Indonesia. CNBC reported that the map assigns a maximum potential magnitude of 9.2 to the Aceh–Andaman zone and 9.1 to the Java zone. Those figures describe possible earthquake scenarios, not forecasts of when an earthquake will occur.

Megathrusts are large faults where one tectonic plate moves beneath another. In Indonesia, a major system runs offshore from western Sumatra past southern Java and toward the Lesser Sunda Islands, Gadjah Mada University earthquake researcher Gayatri Indah Marliyani told BBC News Indonesia. For coastal communities, understanding that geography is part of planning for earthquake and tsunami hazards.

CNBC Indonesia reported that Kosuke Heki, a professor at Japan’s Hokkaido University, discussed similarities between Indonesian subduction zones and Japan’s Nankai Trough during a research visit to Indonesia’s National Research and Innovation Agency in December 2025. Heki said long-term satellite and seabed measurements could help researchers track how strain accumulates where plates are locked together. He also discussed slow-slip events—gradual movement along a fault—as a subject for monitoring, while acknowledging that the timing of a major earthquake remains difficult to predict.

According to CNBC, Indonesia’s Meteorology, Climatology and Geophysics Agency has identified the Sunda Strait and Mentawai–Siberut as zones that have gone centuries without a major release of accumulated strain. The agency cautioned that this does not mean an earthquake will happen soon. Gadjah Mada University has likewise reported that current research cannot accurately predict when one will occur.

Preparedness is already being tested in some exposed areas. The World Health Organization said more than 520 participants took part in a megathrust-earthquake response exercise in Padang, West Sumatra, in 2025. Health offices from 19 districts and cities joined other agencies in practising evacuation, medical response and information-sharing. According to WHO, the exercise also identified gaps in how information moved between teams and how their responsibilities were divided.