(ATTN: UPDATES throughout with more info)
By Park Boram
SEOUL, May 15 (Yonhap) -- A 4.5 magnitude earthquake struck off the east coast city of Donghae on Monday, the 35th one the same area has experienced in about three weeks, leading to residents reporting shaking and sparking concerns it might signal a stronger temblor could be coming.
No damage has been reported after the quake occurred in waters 59 kilometers northeast of Donghae, 182 km east of Seoul, at 6:27 a.m., according to the Korea Meteorological Administration (KMA) and fire authorities.
But there were reports of shaking from residents of not just Donghae and the nearby cities of Samcheok and Gangneung but also from regions as far away as the southeastern cities of Yeongju and Andong, about 110 kilometers away from Donghae.
"My bed shook and thudded while I was sleeping, and I wondered what happened. I was surprised after getting a text message," a 60-year-old resident of Donghae said of the emergency message the government sends to residents in case of disasters and accidents.
"I went outside as the house shook," he said.
Some other Donghae residents said they ran out of their homes in fear when the buildings shook.
"With a thud, my bed shook from side to side at around 6:30 a.m.," a resident of the area said on an online community.
The quake was the strongest to hit the Korean Peninsula or waters around it so far this year. Its epicenter was at 37.99 degrees north latitude and 129.72 degrees east longitude, with the depth estimated at 32 km, the KMA said.
It was the 35th quake to hit the same region since April 23, and came a day after a 3.1 magnitude quake struck Sunday morning. Experts said they cannot rule out the possibility that a stronger quake could be coming.
The weather agency had initially put the scale of Monday's earthquake at 4 magnitude, based on the analysis of P waves that travel faster than other seismic waves, but shortly revised up the figure after further analysis.
The seismic intensity scale measuring the severity of ground shaking was 3 in Gangwon Province that houses Donghae and the nearby North Gyeongsang Province, meaning the quake could be felt "significantly" by those staying indoors, especially on upper floors.
So far this year, 44 earthquakes of 2 magnitude or stronger have hit the peninsula or its surrounding waters, but all but the Monday quake were under magnitude 4.
The previous earthquake of a similar size was the 4.9 magnitude quake that shook waters off Jeju Island on Dec. 14, 2021.
Since 1978, 28 earthquakes of 4.5 magnitude or stronger have occurred on the peninsula or its nearby waters, according to the agency's data.
The interior ministry upgraded its earthquake advisory level to "caution" from "attention," which had been in place since late April. South Korea has a four-level earthquake advisory system going from attention to caution, alert and grave.
Prime Minister Han Duck-soo instructed officials to be fully ready to evacuate residents in the event of danger and provide earthquake-related information correctly and promptly so as to ensure the public doesn't get too agitated.
Han also instructed officials to ensure state infrastructure, such as nuclear power plants, electricity or communication networks, operates without disruptions and stay ready to take emergency measures in the event of a contingency.
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