Vertical-vertical (ZZ) component cross-correlation database

This correlation function database is created for the application of the Rayleigh-wave focal spot imaging to the European Alps and surrounding areas in the period range of 20 to 200 s.

We apply a low-pass filter, decimate the daily records at 1 Hz, remove the instrument response, and apply a bandpass filter in the 2.2−400 s range. The vertical-component continuous waveforms are cut in four hour segments and normalised in the spectral and in the time domain. In the spectral domain, the data are whitened in the 2.2 s to 400 s period range. In the time domain, the data amplitude is clipped at three times the standard deviation of the distribution in each four hour window. We compute four hour time window cross correlations, which are normalised by the square root of energy in both traces, and apply a linear stack. The maximum lag time is 1000 s.