A 5.0-magnitude earthquake hit Jembrana regency in Bali on Aug. 12. The earthquake was not so powerful, but it was only one of the many earthquakes that have occurred in the past few months across the archipelago.

There were also earthquakes with greater magnitudes that occurred in the country, such as the 6.9-magnitude earthquake on the southern coast of Banten on Aug. 2 that killed four people. 

In the eastern part of Indonesia there was also the 7.3-magnitude earthquake that struck the Banda Sea, Maluku, and the 6.1-magnitude earthquake that hit Central Mamberamo Raya regency in Papua on the same day on June 24. 

The recent series of earthquakes has raised questions over whether there has been an increase in seismic activity in the country and whether it could continue in the months ahead. 

The head of the Meteorology, Climatology and Geophysics Agency’s (BMKG) earthquake information and early tsunami warning division, Daryono, told The Jakarta Post on Friday that there had indeed been a significant increase in earthquake activity across the country since 2013.

BMKG data recorded the number of earthquakes in the country had increased from 4,234 in 2013 to 5,299 in 2015 and doubled to 11,920 earthquakes in 2018. It was the largest number of earthquakes recorded by the BMKG since 2008. 

Although it showed a less significant rise, the earthquakes that measured larger than 5.0-magnitude also showed an increase. The BMKG recorded that there were 181 earthquakes larger than 5.0-magnitude in 2016. The number increased to 222 in 2017 and 312 in 2018. However, in recent years more powerful earthquakes have occurred more frequently, around 585 times in 2008 and 645 times in 2009.

“Since 2013 there has been an increase in earthquake activity. There was a trend of these activities from 2008 to 2013, and we can see that from 2013 to 2019 the number of earthquakes rose significantly,” Daryono said. 

Meanwhile for this year only there have been 6,881 earthquakes recorded by the BMKG. 

“There was an anomaly spike in April where there were 1,291 earthquakes recorded in that month,” Daryono added. 

The BMKG, however, cannot explain the cause of the increase in earthquakes in the past few years.

“This is the dynamic in the bowels of the earth, there is no definite pattern in its activities. There are many things about earthquakes that still leave us in the dark, especially the patterns of it,” he said. 

Indonesia experiences frequent seismic and volcanic activity because of its position in the Pacific Ring of Fire, where tectonic plates collide. The BMKG, however, detected that there are two active earthquake zones in the archipelago that have contributed to an increase in seismic activities in recent years. 

The first one is the Sunda megathrust zone that covers the western part of Sumatra, the southern part of Java, Bali, Lombok and Sumba island. 

The second one is the Northern Maluku Sea Plate, which includes the northern part of Maluku and North and Central Sulawesi.

Indonesian Geologists Association (IAGI) chairman Sukmandaru Prihatmoko, however, said the increase in earthquake activity was not an indication that there would be a massive earthquake. 

He was referring to the information that Java’s southern coast could experience an 8.8-magnitude earthquake and tsunami of up to 20 meters in height.

“Sometimes big earthquakes are not always preceded by a series of [small magnitude] earthquakes. So I think the most important thing is how we prepare people who live in the area of megathrust zones to anticipate possible earthquakes and tsunamis,” Sukmandaru told The Jakarta Post on Thursday.

President Joko “Jokowi” Widodo, in his annual state of the nation address on Aug. 16, also mentioned the importance of vigilance to face unpredictable natural disasters. 

“Indonesia is surrounded by the Ring of Fire and it can cause natural disasters that we cannot predict. Almost all of Indonesia is prone to natural disasters. Earthquakes, landslides, volcanic eruptions, tsunamis, forest fires, floods. That’s why it is very important to stay alert and maintain our vigilance to face these uncertainties,” Jokowi said. 

The National Disaster Mitigation Agency (BNPB) has recorded that in the past five years 112 massive earthquake and tsunami disasters have killed 4,276 people, while 721 others are still missing.

The number of casualties is higher than hydrometeorology disasters that occurred 11,040 times in the past five years and killed 1,548 people with 290 others missing.

“Most of us live in an area that is prone to earthquakes, that’s a fact. We can’t avoid it. And that doesn’t mean that we have to be scared, move or close our business. Instead, we have to be ready. Build earthquake resistant buildings and learn about self-help evacuation. We have to know where we should move to as soon as disaster strikes. That’s the most important part,” BMKG’s Daryono said.

Daryono further said that people could not only rely on warning systems as all technologies had their weaknesses.

“So we have to understand what to do when disaster strikes. For example, when we are on the beach when an earthquake happens, we must go further away from the beach. In Indonesia the megathrust zones are far from
the beach, so we still have 20 to 30 minutes to move before a possible tsunami hits,” Daryono added.

Meanwhile, BNPB head Doni Monardo said education and drills on earthquake mitigation and evacuation were with the involvement of institutions needed and people at the grassroots level.

“Training and drills must not only be held for agency members but also for the people in the community. Because they are the ones who have to save themselves during an earthquake,” Doni said.

Doni said when there was an earthquake with tsunami potential, people must remember the “333 pattern” which explains that when a more than 30-second earthquake happens, within three minutes people around the area must move to a higher area with a minimum height of 30 m.

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