The Korea meteorological Administration will significantly improve the earthquake disaster text system to provide tailored guidance that matches what people feel. It will also work to improve technology to reduce magnitude prediction errors that have occurred in the initial automatic analysis of earthquakes.
The Korea meteorological Administration said on Dec. 4 that starting in December, it will introduce a new system that distinguishes between "emergency disaster texts" and "safety guidance texts" based on the perceived intensity of earthquakes by region, and apply technology to improve the accuracy of magnitude prediction in earthquake early warnings.
Until now, when an earthquake was analyzed as magnitude 3.5 or higher, an emergency disaster text was sent to regions with an expected intensity of II or higher if the maximum expected intensity was V or higher. As a result, there were cases where alarm tones sounded even in areas with almost no shaking, causing complaints. Intensity refers to the relative size of shaking, and emergency disaster texts are sent with a warning tone.
At 2:35 a.m. on Feb. 7, when a magnitude 3.1 earthquake struck Chungju, the initial automatic analysis estimated the magnitude at 4.2, prompting an emergency disaster text nationwide. However, in reality, only parts of Chungju recorded an intensity of 2 or higher, which is the threshold for sending an emergency disaster text.
Yeon Hyeok-jin, Director-General of the Korea meteorological Administration's Earthquake and Volcano Bureau, said at a policy briefing on the 4th, "The earthquake early warning is a system that automatically analyzes the faster P-waves among seismic waves to provide information, and even if it informs just 1 to 2 seconds before the stronger S-waves arrive, evacuation is possible," adding, "Because speed has been the top priority, there have been some limits to the accuracy of magnitude calculations. In particular, the difference from reality used to be about 0.5 to 0.7, but in the Chungju earthquake that gap grew to nearly double."
The Korea meteorological Administration explained that the difference in magnitude prediction arises as seismic waves reach observatories. When an earthquake occurs, the weaker P-waves arrive first, followed by the stronger S-waves. At observatories closer to the epicenter, the influence of these S-waves is captured more strongly, which can cause the calculated magnitude to be larger than it actually is.
Accordingly, since the end of last month, the Korea meteorological Administration has improved the analysis algorithm by adjusting the weights of data from observatories near the epicenter. Starting next year, it also plans to develop technology that automatically filters S-wave signals entering observation points to increase the precision of magnitude calculations.
The text dispatch system will also be further segmented. Going forward, emergency disaster texts with warning tones will be sent to regions with an expected intensity of III or higher, and safety guidance texts without warning tones will be sent to regions with an expected intensity of II, respectively, to reduce unnecessary confusion. The measure aims to minimize cases in which emergency disaster texts are sent to areas far from the epicenter where there is almost no seismic shaking. The epicenter refers to the point on the Earth's surface that is vertically above the point inside the ground where the earthquake occurred.
Director-General Yeon added, "The improved earthquake disaster text system has been coordinated with mobile carriers and testing is complete," noting, "Although revisions to related rules are necessary, we will push for early implementation within the year to minimize inconvenience to the public."
The tsunami forecast system will also add a special-report system that incorporates real-time observation data to the existing prediction-based special reports. It plans to provide detailed information at three-hour intervals by reflecting trends such as rise, fall, and end of tsunamis. Even if the expected tsunami height does not meet the special-report threshold, safety guidance texts will be sent when needed to strengthen the information delivery system so that the public can evacuate quickly.
Next year, the earthquake early warning service will be further advanced to deliver earthquake information faster than before to areas near the epicenter. Currently, it takes 5 to 10 seconds from detection to public notification, but starting next year, information is expected to be delivered up to 5 seconds faster to areas within a 40-kilometer radius of the epicenter.
To that end, the Korea meteorological Administration will integrate the on-site earthquake warning system, which is being piloted at 36 key national facilities such as nuclear power plants and railways, with the existing early warning system to operate a new early warning framework. The goal is to reduce by 70% the "earthquake warning blind spots," where warnings are received only after people first feel shaking.
Korea meteorological Administration chief Lee Mi-seon said, "Earthquakes and tsunamis occur without warning," adding, "With these system improvements, we will do our best to provide earthquake information quickly and accurately so people can recognize danger faster and evacuate safely."