At 1909 HRS UTC+7 of 26 July, a M6.5 tectonic earthquake with epicentre at 121.92°E, 0.73°S and a depth of 10km (located 59 km Northeast of Tojo Una Una) rocked Tojo Una Una Regency. (source: BMKG)
Considering the location of the epicentres of the location and the depth of the hypocentre, the earthquakes that occurred are results of the activity of the local fault. Analysis shows that the earthquakes have a normal fault mechanism according to the Indonesia’s Badan Meteorologi, Klimatologi dan Geofisika (BMKG).
Further, according to BMKG, the shock of this earthquake was felt in Ampana V - VI MMI (Felt by most of people, many people frightened and run outdoors); in Luwuk, Poso, Morowali V MMI (Felt by most of people, many people wake up); Bolmong Selatan, Bolmong Timur, Kotamobagu, Kota Gorontalo, Kabupaten Gorontalo, Buol, Bone Bolango, Pohuwato III-IV MMI (many people felt it in the house during the day). Modeling results show that this earthquake DOES NOT have a TSUNAMI POTENTIAL.
BMKG monitoring results showed that there was seven aftershocks (M4.1) with a maximum magnitude of M4.2 as of 26 July at 2220 HRS UTC+7. BMKG mentioned that there was eight strong earthquakes (more than M6.0) including M6.5 earthquake that occurred in 26 July 2021 since 1923.
According to the ASEAN Disaster Monitoring and Response System (DMRS) and Pacific Disaster Center (PDC Global), based on the preliminary data, earthquakes of this depth and magnitude are expected to result in moderate to severe shaking within 130.0 km (80.78 miles) from the epicenter. It is estimated that 429,193 people, 95,376 households, and $3.96 Billion (USD) of infrastructure (total replacement cost) are concentrated within this radius.
According to BNPB, as of 27 July at 0822 HRS UTC+7, Badan Nasional Penanggulangan Daerah (BPBD) Tojo Una Una Regency reported that the M6.5 earthquake was felt strongly for three seconds in Tojo Una Una Regency. A few areas are experienced power outage after the earthquake in the regency.
BMKG advised people that reside on the coasts of Bolaang and Bunta to stay away from the beach, to stay calm, and not be influenced by issues that cannot be justified. It was also advised to avoid buildings that are cracked or damaged by the earthquake.
According to Pusat Vulkanologi dan Bencana Geologi (PVMBG), Central Sulawesi Province is located in the low to high earthquake disaster prone area including Tojo Una Una Regency.
As of 27 July at 0900 HRS UTC+7, BNPB reported that a few people previously displaced to higher places have already come back to their houses.
The AHA Centre will continue to monitor for further developments and issue necessary updates