Indonesia’s Meteorology, Climatology and Geophysics Agency (BMKG) has confirmed that the 7.7-magnitude earthquake that struck waters south of Mindanao in the Philippines on Monday morning was caused by subduction activity and has the potential to generate a tsunami affecting several parts of eastern Indonesia.
The earthquake occurred at 6:37 a.m. WIB and prompted BMKG to issue a tsunami early warning for coastal areas in North Sulawesi, Gorontalo, Central Sulawesi, North Maluku and East Kalimantan.
BMKG Head Teuku Faisal Fathani said the earthquake was classified as a shallow tectonic event generated by the movement of tectonic plates beneath the seabed.
“By considering the location of the epicentre and the depth of the hypocentre, the earthquake was a shallow earthquake caused by plate subduction activity. The analysis of the source mechanism indicates that the earthquake had a thrust fault mechanism,” Faisal said during a press conference at the BMKG headquarters in Jakarta on Monday, as quoted from Kumparan.
According to BMKG, the earthquake’s epicentre was located northwest of Karatung Island, North Sulawesi, at a depth of 47 kilometres. A separate BMKG report recorded the event at a depth of 105 kilometres, approximately 236 kilometres northwest of Tahuna in the Sangihe Islands.
Tremors Felt Across Eastern Indonesia
The earthquake was felt across several regions in eastern Indonesia, particularly in North Maluku, North Sulawesi and Gorontalo.
“The impact of the earthquake’s shaking (intensity scale) was felt in various regions,” Faisal said.
Areas experiencing intensity level IV on the Modified Mercalli Intensity (MMI) scale included Morotai City and North Halmahera, where shaking was felt by many people indoors and caused doors and windows to creak.
An intensity of III–IV MMI was reported in North Gorontalo Regency, while intensity III shaking was felt in Batang Dua, Ternate, West Halmahera, South Halmahera, East Halmahera, Central Halmahera, Gorontalo, Manado, Minahasa, Bitung, Parigi Moutong, Palu and East Bolaang Mongondow.
Despite the widespread tremors, BMKG reported no immediate damage or casualties.
“To date, there have been no reports of damage caused by the earthquake,” Faisal said.
The National Disaster Management Agency (BNPB) also stated that conditions remained safe and under control based on preliminary assessments from local authorities.
Authorities Urge Vigilance as Tsunami Alerts Remain in Effect
Following tsunami modelling conducted by BMKG, several coastal areas were placed under either “Alert” or “Advisory” status.
The BNPB urged residents in affected coastal regions to remain calm while following evacuation instructions issued by local authorities.
“And consciously and regularly take independent anticipatory measures by moving away from coastal areas to safe assembly points according to the threat level in their area,” said Abdul Muhari, Head of BNPB’s Disaster Data, Information and Communication Centre.
For areas under Alert status, local governments were instructed to immediately evacuate residents to higher ground. The warning covered parts of North Sulawesi, including the Sangihe Islands, Manado, North Minahasa, the Minahasa Islands and North Bolaang Mongondow, with estimated tsunami wave arrival times beginning shortly after 6:50 a.m. WIB.
Alert status was also issued for North Gorontalo, Buol and Toli-Toli in Central Sulawesi, as well as several coastal locations in North Sulawesi.
Meanwhile, residents in areas under Advisory status were instructed to stay away from beaches and river mouths and suspend marine activities until further notice. These areas included the Talaud Islands, Bitung, parts of North Maluku, East Kutai, Bulungan and Nunukan.
Tony Agus Wijaya, Head of the BMKG Manado Geophysics Station, said evacuation recommendations had been issued for several locations in North Sulawesi.
“The BMKG recommends evacuation for the Sangihe Islands Regional Government with a warning status of 7:51 a.m. WITA, Manado City with a warning status of 8:12 a.m. WITA, the northern part of North Minahasa at 8:12 a.m. WITA, and the northern part of Minahasa with a warning status of 8:14 a.m. WITA,” he said, as quoted from Kompas.com.
The earthquake triggered temporary panic among residents in Manado, Bitung, Minahasa, North Minahasa, Kotamobagu and several island districts. However, according to BNPB and local disaster management agencies, monitoring continues and no significant impacts have been reported so far.
“Until now, the joint BPBD teams in each region continue to conduct regular, close monitoring in the field to monitor any post-earthquake impacts and ensure coastal conditions remain safe,” Muhari said.