USING COMPLEX DEMODULATION TO RESOLVE P WAVE ACCELERATION SOURCE TIME FUNCTION

In order to study the acceleration characteristic of P wave, this research uses complex demodulation, attenuation structure and ray tracing method to resolve P wave’s acceleration source time function. The seismic waveform data recorded by Taiwan Strong Motion Instrumental Program (TSMIP) of Central Weather Bureau at Taichung, Tainan, Yilan and Taitung were used to resolve the source time function in this study. Data sampling length were chosen in nearly 10 seconds at the beginning of P wave and sampling rate at 4 ~ 10 Hz. The procedure of this study were divided into three parts: (I) complex demodulation, (II) calculate the amplitude value (gal) in the P wave acceleration of every frequency, and (III) resolve P wave’s acceleration source time function. The P wave’s acceleration source time function resolved from every area’s waveform data of the same earthquake reveal high positive linear correlation can prove this study is reliable. The variations in P wave’s acceleration resolved from earthquakes of each area correlate well with plate tectonics, seismicity, source rupture process and lithology. This study offer another reliable research method different from using seismic velocity structure to resolve source time function.