"The magnitude is different from before?" The scientific reason why earthquake information is revised immediately after announcement

Citizens who encounter emergency disaster texts or breaking news immediately after an earthquake often feel confused. This is because the magnitude or epicenter location of the earthquake they just confirmed is sometimes revised and announced within just a few minutes. This situation, which may lead to questions like "Was the first announcement wrong?", is actually a systematic process of supplementing earthquake analysis to save lives.

A 5 to 10-second battle to secure the golden time, 'Rapid Information'

The National Earthquake and Volcano Situation Room of the Korea Meteorological Administration monitors and analyzes domestic and foreign earthquakes, volcanoes, and tsunamis 24 hours a day, 365 days a year. Since it is difficult to predict the timing of an earthquake, it is more important than anything else to secure the 'golden time' during which citizens can evacuate immediately after an occurrence. Even with modern science and technology, no one knows when and where an earthquake will occur, and earthquake precursors have not yet been proven.

According to Korea Meteorological Administration footage, when an earthquake occurs, seismic waves first reach approximately 400 earthquake observation stations installed throughout the country. At this time, the results automatically analyzed by the earthquake early warning system using only the P-wave (the fastest wave among seismic waves) are immediately delivered; this is what is called 'Rapid Information'.

Rapid Information is classified into two types depending on the magnitude. For earthquakes with a magnitude of 5.0 or higher, an 'Earthquake Early Warning' is announced within 5 to 10 seconds, and for earthquakes with a magnitude of 3.5 or higher on land or 4.0 or higher at sea, an 'Earthquake Bulletin' is announced. This measure is taken to buy evacuation time by informing the situation even a few seconds faster, rather than perfectly matching the accuracy.

The process of increasing precision by accumulating data, 'Detailed Information'

After the Rapid Information is delivered, a more precise analysis stage follows. While the initial judgment was made quickly using only the P-wave, the data from more observation stations is comprehensively analyzed, including the S-wave (the wave that arrives after the P-wave), which is relatively slower among seismic waves. The Korea Meteorological Administration utilizes not only data from nationwide observation stations but also shares and uses earthquake observation data from related agencies and neighboring countries such as Japan for analysis.

Through this process, earthquake analysts perform manual precise analysis, and the result of this is 'Detailed Information'. Even for earthquakes that were not part of the Rapid Information, Detailed Information is announced within 5 minutes for all earthquakes with a magnitude of 2.0 or higher.

Ultimately, the revision of earthquake information is not because the initial analysis was an error, but rather a 'precise supplementation process' that increases the accuracy of information based on more accumulated observational data as time passes. The video emphasizes that the change in information is not that the first analysis was wrong, but a process of continuously and sophisticatedly supplementing based on more data. In other words, it can be said to be a scientific step to catch both rabbits: speed and accuracy.

Summary of standards for Earthquake Early Warning and Earthquake Bulletin

The Korea Meteorological Administration video summarized the announcement standards for Rapid Information and the announcement system for Detailed Information, which can be confusing for the public, as follows:

• Earthquake Early Warning: Announcement of automatic analysis results within 5–10 seconds when an earthquake of magnitude 5.0 or higher occurs.
• Earthquake Bulletin: Announced when an earthquake of magnitude 3.5 or higher on land or 4.0 or higher at sea occurs.
• Detailed Information: Announced within 5 minutes after manual analysis for all earthquakes of magnitude 2.0 or higher.

The revision of earthquake information is the result of the 'Rapid Information' for quick response and the 'Detailed Information' for precise analysis being organically connected. The Korea Meteorological Administration continues the data supplementation process for public safety by monitoring earthquakes, volcanoes, and tsunamis 24 hours a day, 365 days a year, without stopping.