Disaster mitigation

[DM-04] The Importance of Reduction Noise of Earthquake Waveform to Get the Precision of "P and S Arrival Time"

*Wiji Raharjo¹, Indriati Retno Palupi¹, Nela Elisa¹, Arin Kuncahyani² (1. Universitas Pembangunan Nasional Veteran Yogyakarta (Indonesia), 2. BMKG Stasiun Yogyakarta (Indonesia))

Sometimes it is hard to decide in the P and S wave arrival time picking process of the earthquake waveform because of some factors. One of them is the noise factor. Noise can come from several parameters like human activity, seismograph mistaken of calibration, or other natural phenomena. Noise sometimes makes the difference between P and S waves is not clear like in volcanic earthquake waveform. Both of them are important in hypocentre location calculation. The mistake in the picking process of P and S can make the hypocentre location is incorrect or far from the earthquake source location. In this paper, some BMKG data of earthquakes located around Yogyakarta is used in this research. The noise is reduced using a low, band, or high pass filter. Then, the spectrogram process is applied to help in the picking process. Based on the spectrogram result, the earthquake waveform after noise reduction is more clear and it makes the user easier to decide about the arrival time of the P and S waves. The spectrogram can be processed in Python by a convolutional process between the waveform and the mother wavelet. When the spectrogram pattern is suitable with the waveform, the P and S wave arrival time determination will be easy.