Getting To Know Megathrust, A Potentially Powerful Earthquake Occurs In Indonesia

Map of Indonesian megathrust. (BMKG)

JAKARTA The Meteorology, Climatology and Geophysics Agency (BMKG) detected an earthquake of 5.8 magnitudes rocked Gunung Kidul, Yogyakarta Special Region, Monday (26/8/2024) night. The earthquake, which is 95 km from the southwest of Gunung Kidul, occurred in the midst of the public commotion about the megathrust earthquake.

The megathrust earthquake has indeed become a hot topic of conversation lately, after the BMKG said that the devastating earthquake in Indonesia was just a matter of time.

This was expressed by the Head of the BMKG Earthquake and Tsunami Center, Daryono when he mentioned the concerns of Indonesian scientists regarding the seismic gapmegathrust of the Sunda Strait and the Mentawai-Siberut megathrust.

The seismic gaparti vacuum of seismic activity for a very long time, generally more than 30 years, so it keeps energy large enough.

The Seismic gap in the Sunda Strait is 267 years and Mentawai-Siberut is 227 years, while other segments have experienced an earthquake. My job is to remind," said Daryono.

BMKG estimates that the Sunda Strait Megathrust could trigger a catastrophic earthquake with a maximum strength of M 8.7 and Megathrust Mentawai-Siberut M 8.9.

"The release of the earthquake in the two megathrust segments can be said to be 'a short time' because the two areas have not had a major earthquake for hundreds of years," Daryono said in his official statement, Sunday (11/8/2024).

Concerns by Indonesian scientists about a large earthquake emerged after an earthquake with a magnitude of 7.1 in Megathrust Nankai, in South Japan on August 8.

Gempa merupakan bencana alam yang sering terjadi di Indonesia. Dari 1907 hingga Agustus 2016, PuSGEN Mencatat lebih dari 51 ribu gempa telah terjadi di Indonesia dengan magnitudo di atas 4,5. Pada 2023. Indonesia tercatat sebagai negara dengan gempa bumi terbanyak (2,205 kejadian).

The reason why Indonesia often occurs earthquakes is because Indonesia's position is located along the jagged seismic lane called the Pacific ring of fire, as reported by Gov.uk.

This is the reason why earthquakes and volcanic eruptions occur regularly, which can present a potential tsunami. Indonesia is surrounded by four main plates, namely the Eurasian Plate, the Indo-Australian Plate, the Philippine Sea Plate, and the Pacific Plate.

When these plates push each other, pull, or slide, there is a shock called an earthquake. This phenomenon also often increases volcanic activity that leads to volcanic eruptions.

One of the sources of the earthquake that has been clearly identified is the active subduction zone (where one plate is tectonic, closing down other plates), the largest in western to eastern parts of Indonesia, as written in the 2017 book Map of the Source and Danger of the Indonesian Earthquake.

"In addition, the remaining energy from the collision process between plates will cause faults on land or oceans in several Indonesian islands and seas," the book wrote.

Meanwhile, regarding the megathrust earthquake which has recently been in the spotlight, it usually occurs on the seabed, and along this subduction zone. Pressure due to the movement of plates that have accumulated for hundreds of years, can then be released suddenly in the form of a devastating earthquake.

Antakan (2015) in his study entitled On the Origin of Mega-thrust Earthquakes said large earthquakes usually occur along the subduction zone with a generally magnitude of 8.5 or larger.

Several countries in the world have experienced devastating earthquakes, including Chile with a magnitude of 9.5 in 1960, Indonesia in 2004 (9.2 AD), Chile 2010 (8.8 AD), and Japan 2011 (9.1).

"Everything triggers a powerful tsunami and poses a great danger to the community," he explained.

Daryono's statement that the megathrust earthquake in Indonesia was just waiting for time to trigger a stir among netizens. Understandably, as mentioned earlier, Indonesia is one of the earthquake-prone countries because it is surrounded by a ring of fire.

Not to mention the bad memories of the 2004 Aceh tsunami, the 2006 Yogyakarta earthquake, the 2018 Sulawesi earthquake and tsunami still made an impression on the minds of the public.

In the midst of public concerns, the BMKG said that the discussion of the potential for a megathrust earthquake was not a form of early warning, which seemed to be happening in the near future.

"It is said that it is a matter of time because the segments of earthquake sources around it have released all major earthquakes, while the Sunda Strait and Mentawai-Siberut Strait have not yet happened," explained Daryono.

In fact, Daryono emphasized that until now there has been no precise and accurate science and technology able to predict the occurrence of earthquakes, both when, where, and how much power.

"So, we all also don't know when the earthquake will occur, even if we know its potential," he continued, quoted from the BMKG website.

Daryono's statement is in line with research by Funiciello and friends [2020], which states that a large subduction megathrust earthquake is an earthquake that shows a complex pattern.

"Whether an earthquake is predictable or not, it can be answered with hope in the future," he wrote.

However, thanks to advances in technology and data analysis methods, scientists are getting closer to uncovering the complex behavior of this earthquake. The researchers also suggested the importance of detecting early signals by monitoring surface deformation and seismic activity.

In line with Daryono, Researcher at the Center for Geological Disaster Research, National Research and Innovation Agency (BRIN) Nuraini Rahma Hanifa stated that there was no definite time when a megathrust earthquake occurred in Indonesia.

"If there is information about the date, month, and year when the earthquake will occur, it can be ascertained that it is a hoax, but if the Megathrust incident really exists. It can happen, when? Want five more minutes, 100 years, that can happen," said Nuraini, quoting Antara.