M7.3 Earthquake in Mentawai May Trigger Other Fault Activities

TEMPO.CO, Jakarta - The Meteorology, Climatology, and Geophysics Agency (BMKG) keeps monitoring developments from the powerful earthquake that occurred on Tuesday, April 25, at 03:00:57 WIB (western Indonesia time), on the west coast of Sumatra. The quake was measured at a magnitude of 7.3 on the Richter scale which was then updated to 6.9.

The agency recorded 10 aftershocks after the main event. “As of 05:45 WIB, the BMKG’s monitoring results showed that there were 10 aftershocks with the largest magnitude of 5.0,” the agency head Dwikorita Karnawati said at a press conference, on Tuesday.

According to her, the main quake in the Mentawai Siberut segment was preceded by shakings a few days earlier. 

Can a strong earthquake trigger earthquakes on other fault segments?

Daryono, the BMKG’s head of the quake and tsunami center, argued that it may happen in certain conditions. He explained that when a large quake occurs, positive stress is released and may cause a disturbance to the stress field next to it. “That can happen if a nearby fault segment is already mature and unstable.”

He cited an example of the 2018 Lombok earthquake. “The quake segment triggered the right and left segments,” Daryono said.

Meanwhile, in this latest quake occurring in the Megathrust zone, the nearby segments did not have a maximum stress field. Besides, in the north, the energy in the Simeulue segment was released in 2004 with a magnitude of 8.5 which became known as the Aceh tsunami.

Maximum Potential Has Not Released Yet

Daryono explained that there had been no major quake since the 1700s in the Mentawai Siberut segment. “Based on the historical record in this zone, the last quake that ever occurred was on February 10, 1797, with a magnitude of 8.5.”

More than 300 people died in the event. “This means we have not had a major earthquake for more than 300 years, so it is reasonable that experts consider this the big one zone that is of their concern,” he added. It was expected that the quake was significant, but not destructive and did not cause a large tsunami.

Daryono thus asked residents to understand that the megathrust zone in western Sumatra is an active zone and has the potential for a powerful quake. He assessed that the government, residents, and related agencies must build a mitigation system.

He called on various parties to prepare matters related to infrastructure and community capacity, as well as regional disaster mitigation agency (BPBD) that respond to information and alerts including information preparation, dissemination of early warnings, and coordination in the regions to deal with the threat of an earthquake that could come at any time.

MARIA FRANSISCA LAHUR

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