16 Earthquakes in Three Days in the Sea Northeast of Donghae... Crisis Alert Raised to 'Interest'

by Yoo Byeongdon

Published 25 Apr.2023 13:46(KST)

A series of earthquakes occurred in the northeastern offshore area of the East Sea, prompting the issuance of a crisis alert.

According to the Korea Meteorological Administration, at 12:02 PM on the 25th, a magnitude 3.1 earthquake occurred 52 km northeast offshore of Donghae-si, Gangwon Province. Previously, earthquake magnitudes had been below 3.0, but this afternoon an earthquake exceeding that magnitude occurred.

Data provided by the Korea Meteorological Administration

Earlier that day, at 5:03 AM, a magnitude 2.3 earthquake also occurred nearby (54 km northeast offshore of Donghae-si).

Since a magnitude 1.7 earthquake occurred at 12:52 AM on the 23rd in the nearby offshore area, a total of 16 earthquakes, including microearthquakes below magnitude 2.0, have been detected to date. Among these, six were magnitude 2.0 or higher.

It is known that no faults have been surveyed in the area. For now, the Ministry of the Interior and Safety issued an earthquake crisis alert at the "Interest" level at 5:30 AM on the same day to prepare for possible events.

Based on the epicenter of the magnitude 3.1 earthquake that day, there have been a total of 34 earthquakes of magnitude 2.0 or higher within a 50 km radius since 1978. Among these, 28 were between magnitude 2.0 and 3.0, four were between 3.0 and 4.0, and two were between 4.0 and 5.0.

Cases where earthquakes occur consecutively in a short period at a specific point have occasionally happened.

On July 12 last year, after a magnitude 2.1 earthquake occurred 102 km east offshore of Seogwipo-si, Jeju, five consecutive earthquakes of magnitude 2.0 or higher followed, culminating in a magnitude 3.1 earthquake on August 3, 104 km east offshore of Seogwipo-si.

In 2020, there was also a case where 76 earthquakes occurred from April 26 to June 11 about 21 km northwest offshore of Haenam-gun, Jeollanam-do. Most were microearthquakes below magnitude 2.0, but a magnitude 3.1 earthquake occurred on May 3.

Park Soon-cheon, head of the Earthquake and Volcano Research Division at the Korea Meteorological Administration, said, "There are often cases where earthquakes repeat in a specific area, like the Haenam case," but added, "This time, since earthquakes of magnitude 2.0 or higher have repeatedly occurred within a few days, we are carefully monitoring the situation."

Fortunately, the earthquakes continuing in the offshore area northeast of Donghae-si occurred in the middle of the sea and were relatively weak, so no damage was caused. Although a tsunami could be a concern, it is reported that an earthquake magnitude of at least 6.5 is required to generate a tsunami.