Analysis of temporal variation of earthquake occurrences in Caucasus from 1960 to 2011

Frequency of earthquake occurrences in Caucasus is investigated on hourly and daily time scales. The observation period is 51. years, which is sufficiently long to perform a reliable statistics. Several methods (power spectrum, wavelet and Hilbert-Huang transformation) are applied to earthquake time series. Our findings show that earthquakes hourly and daily occurrence is not characterized by the dominant frequencies. However, many different oscillations with periods from hours to years and longer contribute to the frequency content of the earthquake time distribution, although their amplitude is rather low. The variation of the power of cyclic components in the temporal features of earthquakes occurrence is not uniform, but their amplification corresponds to the decrease of released local seismic energy.