BMKG Records 4,258 Aftershocks in NTT Following M7.7 Earthquake

Indonesia's Meteorology, Climatology, and Geophysics Agency (BMKG) has reported a significant number of aftershocks following a powerful magnitude 7.7 earthquake that struck Flores, East Nusa Tenggara (NTT). As of Friday, August 21, 2026, the agency recorded a total of 4,258 aftershocks. Of these, 118 tremors were directly felt by residents, with 31 registering magnitudes above 5.0.

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Aftershock activity in the first few days is relatively high and has not shown a significant pattern of decay.

BMKG Earthquake and Tsunami Center Director Wijayanto predicts that this sequence of aftershocks will persist for the next three to four weeks. He noted the complexity of the aftershock pattern, stating that daily seismic occurrences initially reached high numbers, fluctuating significantly before showing a slight increase again. Several significant tremors, with magnitudes between 5.0 and 5.8, have been felt, causing secondary damage to already affected buildings and bridges, and triggering landslides in various locations.

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Daily seismic occurrences reached 704 on the first day, rose to 746 on the second day, hovered between 668, 649, and 627 from the third to fifth days, before climbing again to 802 on the sixth day.

Seismic relocation data indicates that the aftershocks are not uniformly distributed but have formed distinct clusters. The main cluster is located north of Nagekeo, along the Flores Back-Arc Thrust, while secondary clusters have emerged west of this primary zone, north of Manggarai Regency. The focus of seismic activity has also shifted over time, initially spread across clusters from east to west, but concentrating more in the western clusters in recent days as eastern activity waned.

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The aftershock sequence has produced several significant tremors with perceived intensities of IV–VI MMI, which were strongly felt by local residents.

The BMKG maintains a 24/7 real-time monitoring system to track all developments. Officials are continuously analyzing event frequency, magnitude, epicenter distribution, and fault movement to deliver accurate and timely information to the public and authorities. The initial magnitude 7.7 earthquake occurred on Saturday, August 15, 2026, with its epicenter located at sea northeast of Mbay in Nagekeo Regency.

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Seismic relocation data indicates that the aftershocks are not distributed evenly, but have instead formed several distinct clusters.