Three large earthquakes also rattled the region on 29 Aug. Based on the seismic activity, it seems that the earthquakes were triggered by a new opening in the previously locked fault plate.
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FABIO MARIA LOPES COSTA, YOLA SASTRA
·4 minutes read
DOKUMENTASI BNPB
Residents affected by the earthquake eat at a shelter in Simatalu Village, West Siberut District, Mentawai Islands, West Sumatra, on Tuesday (30/8/2022).
Earthquakes hit Mentawai, West Sumatra and Memberamo Raya, Papua. In Mentawai, the tremors over the past two weeks are feared to be followed by an 8.9 magnitude earthquake.
PADANG, KOMPAS - A series of quakes in the Mentawai-Siberut megathrust segment for the last two weeks until Sunday (11/9/2022) is feared to trigger an 8.9 magnitude earthquake in the Mentawai Islands and the west coast of West Sumatra.
Suaidi Ahadi, head of Padang Panjang geophysics station of the Meteorology, Climatology and Geophysics Agency (BMKG), said that seismic activity in the northern part of Siberut Island was detected to be increasing. The condition has prompted a worst-case scenario that a large earthquake may occur.
"There is new [tectonic] opening, and an 8.9 magnitude earthquake may occur. This is what we have detected. The distribution [of the opening] is even. It widens to the northern part of Siberut Island, from east to west," he said during a virtual-media conference on Sunday.
An analysis on faulting mechanism revealed that the earthquakes were caused by thrust fault.
Magnitude 6.1 and 5.4 earthquakes rocked Siberut Island and its surroundings on Sunday morning. Based on the location of the epicenter and the depth of the hypocenter, the magnitude 6.1 earthquake was a shallow quake caused by tectonic-plate-subduction activity in the Mentawai-Siberut megathrust zone. An analysis on faulting mechanism revealed that the earthquakes were caused by thrust fault.
Three large earthquakes also rattled the region on 29 Aug. Based on the seismic activity, it seems that the earthquakes were triggered by a new opening in the previously locked fault plate.
"Given the characteristics of the earthquakes on 29 Aug., the epicenters were vastly scattered. The aftershocks had long intervals, from 4, 6, up to 8 hours apart. Now [on Sunday], the earthquakes occurred again. What we fear is that these rattling quakes are part of a [fault] opening with an even more immense magnitude,” Suaidi said.
He said that the Mentawai-Siberut megathrust, compared to other fault segments on the west coast of Sumatra Island, had so far been void of large earthquakes, but this segment carried the potential for a magnitude 8.9 earthquake after all.
While calling for public concern and vigilance over the situation, Suaidi warned against building narratives that would cause fear among local people. He said the community must develop an awareness about potential disasters and knowledge about self-evacuation as mitigation efforts in the event of an earthquake.
DOKUMENTASI BPBD KEPULAUAN MENTAWAI
Mentawai Islands Regent Martinus Dahlan (third from left) receives assistance from BNPB representatives in Tuapejat, Mentawai Islands, West Sumatra, on Wednesday (31/8/2022), to be distributed to residents affected by the M 6.4 earthquake in West Siberut.
The Regional Disaster Mitigation Agency (BPBD) of Mentawai Islands reported the residents from three villages in West Siberut district were still evacuating as of Sunday afternoon. There are 5,756 people at evacuation shelters. The come from Sigapokna (2,429), Simatalu (975) and Simaleg (2,352). "Residents are still worried about aftershocks," Amir Ahmari, who heads the BPBD’s emergency and logistics division, said.
The disaster mitigation agency also reported that the earthquakes had caused three injuries in Simaleg village and damages to scores of houses, mosques and schools.
Memberamo Raya
An earthquake also hit Mamberamo Raya regency, Papua, on Sunday night. A total of 83 tremors were recorded from Saturday morning to Sunday evening, leaving a crack on the wall of a facility building belonging to the local state electricity company (PLN) at Kasonaweja, Mamberamo Raya. No victims were reported.
It began with four quakes and aftershocks with a magnitude of 5.5-6.2 on Saturday (10/9) between 8:31 a.m. to 9:05 a.m. The inland epicenter was 8 kilometers northeast of Mamberamo Raya at a depth of 19 km.
BMKG
Infographic of the location of the epicenter of the earthquake in Mamberamo Raya Regency, Papua on Saturday (10/9/2022).
Danang Pamuji, observation center coordinator for the Meteorology, Climatology and Geophysics of Jayapura Region V, appealed to the public not to panic. They were called to be vigilant. In the past, the Anjak Mamberamo fault triggered an earthquake in Sarmi and Mamberamo Raya in 2019, damaging 33 houses and the Kasonaweja regional general hospital.
BPBD Mamberamo Raya head Deden Sumantri said there had been no reports of casualties or substantial damages of buildings. "Our team has been deployed to the quake location to check on the condition of the residents," he said.
