A study on feasibility of earthquake early warning in Korea: Determination of locations and magnitudes of events

The fundamental purpose of an earthquake early warning (EEW) system is to provide an advance warning/alarm of strong ground shaking from large earthquakes that will help to mitigate earthquake damage. To accomplish this goal, both the location and the size of an earthquake must be automatically estimated as rapidly as possible, i.e., essentially in real-time. Given a sufficiently dense seismic array, such as in Korea, we have shown in a previous investigation that the location of potentially hazardous earthquakes can be quickly estimated from the arrival times of the P-waves at just two stations and the lack of arrivals at other nearby stations. Size, however, is difficult to estimate in a real-time environment where the implicit constraint is to use only several seconds of P-wave data to estimate earthquake source parameters. However, it is possible to predict the intensity of strong ground shaking from the damaging S-waves from the intensity of the observed P-waves. Here we investigate two methods for the rapid estimation of shaking intensity using the data from broadband sensors in the Korean seismic array. There is good agreement between methods for smaller events up to M∼5.2 but extrapolating the results to larger magnitudes is problematic; one method, however, may have an advantage in an EEW system.