BMKG Chief: Aftershocks in Flores expected to decay over 3-4 weeks

The Meteorology, Climatology and Geophysics Agency (BMKG) estimates that aftershock activity following the magnitude 7.7 earthquake in Flores will take around three to four weeks to decay.

“Because this earthquake is quite large, 7.7 magnitude, the decay will require approximately three to four weeks ahead,” said BMKG Chief Teuku Faisal Fathani in Jakarta on Wednesday.

As of Wednesday at 17.00 WIB, he said BMKG had recorded 3,055 aftershocks with the largest magnitude of 6.2 and the smallest of 1.1. Of that number, 88 earthquakes were felt by the public.

“The number of aftershocks as of 5 pm today, 19 August 2026, is 3,055 aftershocks,” Faisal said.

BMKG continues to monitor seismic activity in real time, while providing information to communities in affected areas and evacuation sites.

Faisal said BMKG has four technical implementation units (UPT) on Flores Island, in Labuan Bajo, Ruteng, Maumere and Larantuka, as well as two posts in Ende and Bajawa.

According to him, one of the public’s concerns after the earthquake is the possibility of another large earthquake occurring within days to weeks.

Faisal explained that the Flores back-arc thrust fault requires a long period of up to decades to re-accumulate energy to produce an earthquake with the strength of the current mainshock.

In addition to concerns about a large earthquake, BMKG noted anxiety among people living in coastal areas about the possibility of a tsunami.

Faisal said Indonesia, through BMKG, has the capability to provide tsunami early warnings resulting from earthquakes in less than three minutes in accordance with international protocols.

“The Indonesian Government through BMKG is able to provide tsunami early warnings resulting from this earthquake in less than three minutes in accordance with international protocols,” he said.

According to him, this early warning capability needs to be followed by strengthening standard operating procedures (SOPs) and evacuation signage, including determining vertical evacuation and routes to safer locations.

This preparedness strengthening is carried out together with the National Disaster Management Agency (BNPB), Basarnas and the regional leadership coordination forum (Forkopimda) in affected areas.

Based on BMKG observations, seismic activity has now entered a decay process. Faisal explained that generally the magnitude of aftershocks will decrease after the mainshock.

BMKG also has two Multi-Hazard Early Warning Systems, in Kemayoran, Jakarta, and Denpasar, Bali, whose buildings use seismic base isolation systems.

Faisal said the facility in Denpasar is prepared as a backup system should the centre in Jakarta be affected by an event that disrupts operations, so that early warning services to the public can continue.

The magnitude 7.7 earthquake shook Nagekeo Regency, East Nusa Tenggara, on Saturday (15/8) at 04.58 WIB.

BMKG issued a tsunami early warning before ending it after observations showed no significant rise in sea level.

The Geological Agency of the Ministry of Energy and Mineral Resources previously stated that the earthquake source was associated with the Flores Back-Arc Thrust, which extends along the northern sea of the Nusa Tenggara Islands.