Aftershocks following the strongest recorded quake on Sept. 12 will continue to take place in the Korean Peninsula for months to come, though there will be no more quakes stronger than 5.8 magnitude tremors, the Korea Meteorological Administration said Thursday.

The KMA said that it decided to install additional seismic monitors nationwide to detect earthquakes within 7 seconds of a disaster striking the county.

“It is very unlikely that a quake stronger than the magnitude 6.5 will hit the nation again,” said Koh Yoon-hwa, the chief of the KMA in a news briefing held on Thursday to inform the public of the interim result of analysis on the nation’s natural disaster warning system and what could have caused a string of earthquakes.

“It is possible to see aftershocks within the range of magnitude 3.0. to 4.0,” the KMA said. “It is difficult to predict when aftershocks will end and it is likely for them to last for weeks and months to come.”

The announcement came after South Korea experienced a 5.8 magnitude earthquake on Sept. 12 in Gyeongju, located some 370 kilometers southeast of Seoul. It was the strongest ever recorded by the KMA in the Korean Peninsula.

Among a total of 423 aftershocks recorded as of Wednesday afternoon since the Sept. 12 quake, most were assessed to be weaker than magnitude 3. Only two aftershocks recorded a magnitude of between 4 and 5, while 15 tremors have ranged from 3 to 4.

The historic city of Gyeongju in North Gyeongsang Province is set to be designated as a special disaster zone, which will grant the city state funds to help restore the area. Its residents will receive tax benefits and cuts in utility bills.

A 3.5 magnitude earthquake struck Gyeongju on Wednesday morning, two days after a magnitude 4.5 quake shook the nation Monday night.

The KMA added that the epicenter of the foreshock in Gyeongju was 0.7 to 0.8 kilometers away from that of the main quake. “We found out that foreshocks, major quakes and aftershocks were seen as moving in southwestern direction,” said the KMA. 

Nearly 90 percent of the aftershocks, including the most powerful ones with a magnitude of 4.0 and over took place with 2.5 kilometers from where the major 5.8 magnitude quake occurred, the KMA said. Nearly 70 percent of the aftershocks took place within two days after the quake rattled the country, with the quakes hitting a depth of 15.2 kilometers on average.

“Currently, it takes 50 seconds to detect earthquakes stronger than 5.0 magnitude and notify relevant agencies and areas of the tremors, but we will reduce it to 7 to 25 seconds,” said the KMA. “In order to do so, we will increase the number of seismic monitoring facilities from the current 206 to 314 by 2018.”

“Starting in November, the KMA will directly notify the public of the occurrence of natural disasters in association with Cell Broadcasting System,” the agency said. “We believe we can measure the seismic activity within 10 seconds and notify the public within 2 minutes through text messages by 2017.”

The current system of sending alert messages to the public has been criticized for failing to inform them in time. The weather agency sends mobile alert messages in times of natural disasters after going through the Ministry of Public Safety and Security.

When the 3.5 magnitude aftershock jolted the country Wednesday, warning messages were sent to the public some 10 minutes after residents felt the shaking. On Monday night, the website of the Public Safety Ministry as well as the weather agency, which provide information on how to evacuate in cases of quakes, also crashed due to heavy traffic.

The KMA also said that a team of eight relevant officials will be dispatched to Gyeongju to conduct an on-site investigation from Sept. 20 to March 31 in 2017 to investigate causes and impact of the series of quakes.

In regard to the latest earthquakes, President Park Geun-hye ordered a comprehensive overhaul of the country‘s national quake response system at a meeting with top aides in the presidential office on Thursday.

“It has been confirmed that the country had several problems in the process of responding to quakes because we have perceived our country as safe from such natural disasters,” she said.

“As it is possible that aftershocks continue to take place, the government should have more prompt and accurate readiness to promote the public safety,” she said.

Relevant ministries and state-run agencies are scrambling to assess, prevent and minimize the damage of quakes.

According to the Ministry of Strategy and Finance, it will revise relevant acts so that special subsidy tax of the interior ministry, the education ministry and the public safety ministry can be used to reinforce public facilities to make them more earthquake-resistant.

The Ministry of Land, Infrastructure and Transport announced Thursday that it will inspect all major social infrastructure including bridges, tunnels and airports in the quake-stricken southeastern region.

A team of more than 420 officials from relevant state-run agencies will be put on the field to inspect the safety of nearly 6,000 public facilities in the region by the end of this year. It also aims to make express trains, expressways and bridges earthquake-resistant by 2018, ordinary trains by 2019 and intake towers by 2020.

The ministry has already announced plans to revise construction codes to require all new structures that are two-stories high or higher to be earthquake-proof.

The Korea electric Power Corporation will also raise the level of safety of electric facilities as well as nuclear reactors by evaluating its ability to endure quakes in the face of the series of quakes.

By Ock Hyun-ju (laeticia.ock@heraldcorp.com)