[SSS15-P39] Estimation of P-wave arrival time differences using P-wave first motion similarity with sampling frequency of 10 kHz
Keywords:10 kHz waveform, cross-correlation, relative hypocenter determination, foreshock
In this study, we defined mainshocks and their foreshocks of small to moderate earthquakes spatiotemporally based on magnitudes, origin times, and distances between hypocenters. Then, we estimated P-wave arrival time differences of the earthquakes by cross-correlating their P-wave onset waveforms.
We use the vertical component of velocity waveforms. In some spatiotemporally defined foreshock activities, there were many earthquakes that were not similar in the whole waveform but similar in the P-wave initial rise recorded at an identical station. Therefore, we calculated the time differences that maximize cross-correlation coefficients of each pair of earthquakes in a series of foreshock activities, using only windows of a length of 0.01s around P-wave onsets. We treated such time differences as P-wave arrival time differences between two earthquakes at each station. Using these time differences, we will perform relative hypocenter determination with a few meters precision and elucidate the nucleation process of a series of foreshocks which is illustrated by preslip model or cascade model.