Magnitude scaling relationships from the first 3 s of P-wave arrivals in South Korea

Two empirical magnitude scaling relationships, predominant period (t_p^max{\tau _p^{\max}}) and peak ground displacement (Pd) magnitudes, were investigated for the first 3 s after P-wave arrivals using 1,412 vertical waveforms recorded by the Korea National Seismic Network (KNSN) between 2001 and 2007. To evaluate the accuracy of the derived magnitude relationships, we simulated off-line ElarmS tests using 65 events occurring inside the KNSN. While the average magnitude error was ∼0.70 magnitude units when using only the closest station to the epicentre, the error dropped to ∼0.62 and ∼0.42 magnitude units when using the closest two and closest four stations, respectively. For events M _L ≥ 3.0, the average magnitude error was ∼0.33 and showed stable values when the closest four stations were available. Our magnitude scaling relationships may be useful for initial work in developing an earthquake early warning system in South Korea.