FILTER-M APPLICATION FOR AUTOMATIC COMPUTATION OF P WAVE DOMINANT PERIODS FOR TSUNAMI EARLY WARNING

The purposes of this research is to improve Indonesia Tsunami Early Warning System (InaTews), especially to improve result of automatic computation of P wave dominant period by applying filter-M to ignore noises signal. To reduce the effect of noise and signal defect on the calculation of the P wave dominant period automatically, this study used M-filter. The M-filter used the concept that the dominant period for small and moderate earthquakes is unlikely to exceed twice the maximum dominant period of the great earthquake. The automatic computation of P wave dominant period uses direct method, where the calculation uses time equation (τc) directly applied to seismogram, without inversion so that calculation process becomes faster. M- filter has been developed and used to filter out defective and high-null seismogram signals, so the seismogram is not used for the average computation of the P wave dominant period.