Students participate in a quake drill at Seorabeol Girls Middle School in Gyeongju, North Gyeongsang Province, Thursday, after a magnitude 4.0 earthquake struck the southeastern city in the early hours of the day. Yonhap

In the early hours of Thursday, a 4.0 magnitude earthquake struck the southeastern city of Gyeongju in North Gyeongsang Province, triggering a blaring emergency alert from cell phones, which drew complaints from people who expressed frustration at being abruptly awoken at dawn by the disconcerting sound.

According to the Korea Meteorological Administration (KMA), the quake occurred at an estimated depth of 12 kilometers at around 4:55 a.m. Seven aftershocks followed, with the largest measuring 1.5 in magnitude and taking place at around 5 a.m.

While fire authorities received 107 reports of shaking until 5 a.m., no damage has been reported so far.

The KMA detected the earthquake within two seconds of its occurrence, and the emergency alert was disseminated nationwide through the Cell Broadcasting System (CBS), just eight seconds after the quake struck.

It was the second quake with a magnitude of 4.0 or higher on the Korean Peninsula or its waters this year. It also ranked eighth on the scale within 50 kilometers of the epicenter since instrument observation began in 1978, according to the KMA.

Concerns were heightened because within a 50-kilometer radius of the seismic center of this quake, 418 other earthquakes of magnitude 2 or stronger have been reported since 1978. This location is also close to where the country's strongest-ever earthquake, measuring 5.8 in magnitude, occurred on Sept. 12, 2016.

Responding to the situation, the Ministry of Interior and Safety elevated the alert level of its Central Disaster and Safety Countermeasures Headquarters to Level 1, the lowest in a three-stage system. An emergency meeting was also convened at 8 a.m., aiming to assess the aftermath of the quake.

During the meeting, Interior Minister Lee Sang-min emphasized the importance of promptly assessing the level of damage and implementing necessary measures, considering Gyeongju's significance as an area with major infrastructure and containing many historical assets.

Lee directed officials to uphold a state of emergency readiness, collaborating with the pertinent ministries and regional governments.

Meanwhile, the widespread alarm prompted a barrage of complaints on social media, with users questioning the necessity of a nationwide alert and suggesting a more subdued tone for earthquake notifications.

Some online users shared their annoyance at being roused from sleep, saying, "I thought a missile was launched or something."

Criticism also emerged about the alert being broadcast across the entire country instead of specifically targeting North Gyeongsang Province.

“I understand the importance of notifying the quake, but it was quite bothersome to be awakened early, especially after a late-night study session, despite residing at a considerable distance from Gyeongju,” said a university student surnamed Seo living in Gyeonggi Province.

This map shows the location of the seismic source, 19 kilometers southeast of Gyeongju, North Gyeongsang Province.

The KMA explained that the alert distribution adhered to cell broadcasting regulations. According to the rules, notifications should be sent to metropolitan cities and provinces within a radius of 50 kilometers for magnitudes 3.0 to 3.5, expanding to an 80-kilometer radius for magnitudes 3.5 to 4.0. Alerts for magnitudes 4.0 or higher must be broadcast nationwide.

This aims to prepare the public for potential evacuation and aftershocks, according to an official at the KMA.

In contrast, North Gyeongsang Province and Gyeongju faced criticism for their delayed response in sending emergency alerts, issued approximately 30 minutes after the earthquake.

At 5:29 a.m., the North Gyeongsang Provincial Office issued a cautionary alert to residents, urging vigilance against potential building collapses and large fires stemming from a magnitude 4.0 earthquake occurring 19 kilometers southeast of Gyeongju.

Subsequently, the Gyeongju City Government's alert message, notifying residents about the earthquake, reached them at 5:43 a.m. The message instructed individuals to take protective measures, such as seeking shelter under tables, using stairs when exiting buildings, and evacuating to outdoor areas.

Interior Minister Lee Sang-min, right, holds an emergency meeting with officials from the Central Disaster and Safety Countermeasures Headquarters at the Government Complex in Seoul, after a 4.0 magnitude earthquake struck Gyeongju, Thursday. Yonhap