M7.7 Earthquake Shakes Flores, NTT; BMKG Reveals Active Fault to Watch
A magnitude 7.7 earthquake that shook Flores, East Nusa Tenggara (NTT) in the early hours of Saturday, 15 August 2026, was triggered by activity on the Flores Back-Arc Thrust. BMKG has revealed that the fault zone still has the potential to produce an even stronger earthquake.
BMKG Director of Earthquakes and Tsunamis, Wijayanto, explained that the quake, which occurred at 04.58 WIB, was a shallow earthquake with a thrust fault mechanism. “This is an earthquake mechanism caused by the Flores back-arc thrust,” said Wijayanto.
According to BMKG updates, the epicentre was located at sea at a depth of 15 kilometres, approximately 30 kilometres northeast of Nagekeo, NTT.
Activity on the Flores back-arc thrust is a concern because it has a history of producing strong earthquakes. BMKG stated that the magnitude of this earthquake is not yet the maximum potential energy that can be released from the zone. “A magnitude 7.7 earthquake behind the Flores arc has the potential for a maximum earthquake of 7.8 to 7.9. Today it has already released 7.7,” said Wijayanto.
Historical records also show that the Flores region has experienced major earthquakes. In 1992, a magnitude 7.5 earthquake struck the area and caused considerable damage. “From existing history, in 1992 it was magnitude 7.5. The damage at that time was also extraordinary. So, it has been more than 30 years and it has happened again. We will continue to monitor aftershock activity,” said Wijayanto.
The strength of the earthquake and its location at sea prompted BMKG to issue a tsunami early warning shortly after the quake occurred. The first warning was issued at 05.00 WIB, about two minutes after the earthquake. In subsequent updates, BMKG recorded changes in sea levels in several areas.
Several observations showed sea level rises, including in Sikka of 0.20 metres, Kewapante Port in Sikka of 0.38 metres, East Flores of 0.25 metres, Labuan Bajo of 0.36 metres, and Maurole in Ende reaching 0.94 metres.
BMKG also placed several areas under tsunami threat status. An alert status with potential heights of 0.5 to 3 metres was in effect for several areas, including northern Manggarai, northern Ngada, Ende, East Flores, and Jeneponto.