Magnitude 2.6 Earthquake Strikes Sea Off Yeongdeok, North Gyeongsang Province... Why 'Another One in the East Sea?' is Making People Uneasy

This afternoon (the 14th), the sea off the coast of Yeongdeok in North Gyeongsang Province experienced a slight tremor. A magnitude 2.6 earthquake struck 31km east of Yeongdeok-gun, North Gyeongsang Province. With its shallow epicentre, residents in Yeongdeok, as well as parts of Ulsan and Pohang, would have likely felt a sudden jolt. For those living along the east coast, these tremors are no longer something to simply ignore. The memory of the tsunami that struck following a major earthquake near Japan is still fresh in their minds.

Today's Tremors as Detected by Seismographs

This earthquake's epicentre was located on the East Sea bed, quite close to the landmass. It would have certainly registered a typical shallow earthquake pattern on seismographs, with distinct seismic waves. Given the likely negligible time difference between the arrival of P-waves (primary waves) and S-waves (secondary waves), anyone near the epicentre at the time might have experienced an instant shaking of buildings, accompanied by a dull thudding sound. Fortunately, no damage has been reported so far.

Why Does It Keep Happening in the East Sea? The Seismic Characteristics of This Body of Water

The East Sea has long been considered the most 'tectonically active zone' on the Korean Peninsula. From a plate tectonic perspective, it acts as a conduit directly transmitting the influence of the Pacific Plate as it subducts towards the Japanese archipelago. In fact, earthquakes with a magnitude around 3.0 are not uncommon along the east coast. Among these areas, the waters off Ulsan and the Yeongdeok coast are known to have particularly complex fault systems. It is accurate to view this latest earthquake as a natural event originating from this geological context.

How Was the Perceived Intensity in Different Regions?

Compiling on-site reports, this earthquake was felt across a wider area than initially anticipated.

• Yeongdeok-gun and Uljin-gun, North Gyeongsang Province: Intensity III (Felt noticeably indoors, especially on upper floors of buildings).
• Ulsan Metropolitan City and Gyeongju City: Intensity II (Felt by a few people at rest, or on upper floors of buildings).
• Parts of Pohang City and Daegu Metropolitan City: Intensity I (Not felt by people, but recorded by instruments).

Residents in high-rise apartments would have been particularly sensitive to this shaking. This is because seismic waves with longer periods can resonate with tall buildings, amplifying the motion.

Should We Worry About a Tsunami? Still Safe for Now

An earthquake of this magnitude naturally poses no threat of a tsunami. However, the underwater topography off Korea's east coast features areas that drop off sharply into deep water. This means that if a major earthquake occurs near Japan, a tsunami could reach the Korean coast within one to two hours. Even when things are quiet, every time the ground shakes here, the instinct for those living on the east coast is to consider the 'what if' scenario – it's a survival instinct born from experience.

The Yeongdeok coast previously experienced a magnitude 3.1 earthquake in 2023. Back then, the reaction was similar, 'Yeongdeok again?' Today's earthquake released slightly less energy than that one. However, among seasoned observers, it's seen as a sign that tectonic movements in the area haven't ceased. Considering the earthquake mechanism, the propagation speed of seismic waves, and epicentre analysis, it's highly likely that similar tremors will continue along the east coast in the future.

Late this afternoon, people who felt that sudden, brief jolt while alone in their offices probably pulled out their smartphones to confirm what had happened. Earthquakes are no longer a strange or unfamiliar disaster for us. We don't need to wait for research findings to know that the Korean Peninsula is no longer a safe zone from earthquakes – we feel it physically. Even with a small tremor like today's, we must continue to practice reading the movements of the peninsula's crust within these shakes.