Megathrust Zone Surrounds Indonesia, Japanese Expert Points Out Potential Site of Major Earthquake
The threat of a major earthquake in Indonesia is once again drawing attention following the release of the 2024 Indonesian Earthquake Source and Hazard Map, which reveals an increase in megathrust zones to 14.
This latest data indicates a higher level of risk compared to the 2017 map, as evidenced by the increasingly dense hazard contour lines in various regions.
This geological condition in Indonesia has also drawn attention from Japanese expert Professor Kosuke Heki from Hokkaido University, who points out similarities between Indonesia and the Nankai Trough. The Nankai Trough is known as one of the most active megathrust zones in the world, with large earthquakes occurring periodically.
“We understand that magnitude 8 earthquakes in Japan occur at intervals of approximately 50 to 100 years. This is our classic view before a major earthquake occurs,” said Heki while serving as a Visiting Researcher at the National Research and Innovation Agency (BRIN) in late December 2025, as quoted on Saturday (May 16, 2026).
According to Heki, although the timing of major earthquakes is difficult to predict, long-term monitoring of crustal deformation is key to disaster mitigation. He emphasized the role of the Global Navigation Satellite System (GNSS) and deep-sea geodetic measurements in monitoring the accumulation of stress in subduction zones.
“We see that there is aseismic coupling that locks almost along the entire trench axis. Even in the very shallow part of the plate boundary, strain continues to accumulate for the next earthquake,” he explained.
Heki also highlighted the phenomenon of slow-slip events, which often occur before major earthquakes. Although they move very slowly, this phenomenon is considered to be a potential early indicator.
“This phenomenon has been observed repeatedly in the Nankai Trough and other regions of Japan. One of these slow-slip events could trigger the next major earthquake,” he said.
He believes that Indonesia has a great opportunity to develop a similar monitoring system, given the large number of active subduction zones from Sumatra, Java, Bali, Lombok to Maluku. With the strengthening of the GNSS network and deep-sea monitoring technology, Indonesia is considered to be able to monitor tectonic stress accumulation more precisely.
“I am currently working on this in Indonesia,” said Heki.
In the latest map, the Aceh-Andaman Megathrust zone is recorded as having the largest earthquake potential with a maximum magnitude of 9.2. Meanwhile, the Java Megathrust has the potential to trigger earthquakes up to magnitude 9.1.
Several other zones such as Mentawai-Siberut, Mentawai-Pagai, and Enggano each have the potential for earthquakes up to magnitude 8.9.
The Meteorology, Climatology, and Geophysics Agency (BMKG) previously also highlighted the existence of two megathrust zones that are still in a seismic gap, namely the Sunda Strait and Mentawai-Siberut. Both regions have not released major energy for hundreds of years, each since the last earthquake in 1757 and 1797.
The BMKG emphasized that the term “waiting time” is not intended as a prediction of when an earthquake will occur.
“What is meant is the accumulation of energy that is still stored because it has not had a major earthquake for a long time. It does not mean that an earthquake will occur in the near future,” the BMKG wrote in its official statement.