[J04-2] Geohazard early warning systems II

[J04-2-04] Determination of warning earthquake magnitude from the initial P-wave recordings based on half periods and characteristic periods

^○Dongwang Tao^{1, 2}, Qiang Ma^{1, 2}, Jindong Song^1,2, Haiying Yu^1,2, Jiang Wang^1,2, Shanyou Li^1,2 (1.Institute of Engineering Mechanics, China Earthquake Administration, Harbin, China, 2.Key Laboratory of Earthquake Engineering and Engineering Vibration, Harbin, China)

The determination of earthquake magnitude from the first several seconds of P-waves is fundamental in earthquake early warning (EEW) systems. There exist kinds of method to estimate the magnitude of ongoing earthquake, including peak displacements, characteristic periods and predominant periods. In this paper, the half period of the P-wave is implemented to determine the warning earthquake magnitude. Different seismic events in different regions of strong motion records is used to study the differences in the half periods of the first P waves. This paper discusses the characteristics at the beginning of waveforms in the Wenchuan mainshock and aftershock events and determines the correlation between the motion of moderately strong earthquakes in the early half cycle parameters and the earthquake magnitude. The effect of attenuation relations studied in the P wave seismic phase to S-wave phase time range, peak displacement with the time window length increases the variation characteristics, and different magnitude between peak displacement curve regularity is also investigated. Characteristics of cycle parameters in the P-waves for the records in the same time azimuth angle with the variation of the time window is also studies similarly. According to the research results, it is shown that there is a difference in the initial rupture of the earthquake with different sizes. In addition, this paper also discusses the relationship between the initial moving half period, the characteristic period and the source scale.