BMKG Records 4,258 Aftershocks in NTT Following M7.7 Earthquake
The BMKG predicted that this series of aftershocks will persist for the next three to four weeks.
The Meteorology, Climatology, and Geophysics Agency (BMKG) reported 4,258 aftershocks in NTT following an M7.7 earthquake in Flores, East Nusa Tenggara (NTT) on Friday, August 21, 2026, at 5:00 a.m. local time. Of these, 118 tremors were felt by residents, with 31 exceeding a magnitude of 5.0. BMKG's Earthquake and Tsunami Center Director, Wijayanto, anticipated the aftershock sequence would continue for three to four weeks.
The initial phase displayed a complex temporal pattern that had not stabilized, with daily seismic occurrences peaking at 802 on the sixth day. Significant tremors, rated IV–VI MMI, were felt by locals on August 19 at 11:17 p.m. (magnitude 5.6) and August 20 at 5:45 a.m. (magnitude 5.8). Further notable shocks occurred on August 20 at 9:47 a.m. (magnitude 5.8), leading to secondary damage and landslides.
Seismic data shows aftershocks are concentrated in several clusters, with the main group surrounding the original magnitude 7.7 quake's epicenter north of Nagekeo, extending along the Flores Back-Arc Thrust. Secondary clusters emerged west of the primary source, near Manggarai Regency. Activity shifted from an initial even distribution to a concentration in the western clusters by the fifth and sixth days after the mainshock.
BMKG maintains 24/7 monitoring to track the ongoing situation, analyzing data on frequency, magnitude, epicenter locations, fault movement, and focal mechanisms for public and official updates.
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