5:15 PM - 6:30 PM
[SSS30-P08] Quantification of the cross-correlation criteria for small foreshock detection
Keywords:foreshock, cross-correlation, detection criteria
In this study, we carried out foreshocks detection of the same earthquake in the same method as Toyomoto et al. (2015, SSJ) using the waveform record of N.MNYH (Hi-net) station (epicentral distance of main shock is 5.3km). In this case, the maximum correlation coefficients during one minute tended to be higher than those for records at N.MWDH station, and the result of detection strongly depends on a threshold employed in a cross-correlation method. This indicates that we should not use a universal threshold independent of data. One of alternative way is to use the standard deviation of cross-correlation coefficients. Then, we made a histogram of the cross-correlation coefficients of 1-day data. The histogram of N.MWDH data is Gaussian and the cross-correlation coefficients obey a normal distribution with the average of zero. Although the histogram of N.MNYH data is not Gaussian, so the cross-correlation coefficients have a large-deviation. In such a case, a criterion depending on the standard deviation is inadequate.
We used continuous waveform records of NIED high-sensitivity seismograph network in Japan (Hi-net) and the JMA unified hypocenter catalogs.