Using of modern seismological data to reveal the earthquake precursors G.A.Sobolev 1,2, A.A.Lyubushin 1 1.Institute of Physics of the Earth RAS, 2. Geophysical Center RAS

Typical Power spectra of the microseismic oscillations on the IRIS station ( BHZ – component) 12 h 24 h

We analysed the records of IRIS broadband stations that were obtained before the 5 strong earthquakes: Kronotskoe , M = 7.8, Neftegorskoe , M = 7.0, Simushirskoe , M = 8.2, Hokkaido , M = 8.3, Sumatra , M = 9.2

Simushirskoe Hokkaido

Sumatra

We used the various programs of processing and analysis of time series: revealing of hidden periodicities in the sequences of peak values; wavelet analysis of microseisms flow; search for multiple coherence effects based on Fourier and wavelet approaches; estimates of spectral coherence measures evolution of variations of multi-fractal singularity indexes and others

Asymmetric pulses on the Pet. station Before the Kronotskoe eq. on Kamchatka

Asymmetric pulses on the Pet. station Before the Kronotskoe eq. on Kamchatka

Asymmetric pulses on different stations before strong earthquakes

Asymmetric pulses on the Pet. station Before the Kronotskoe eq. on Kamchatka

In this research the method was used of detecting periodic components in the seismic process consisted of Poisson part and periodic oscillations by maximum likelihood approach. The maximums of  lnL yield frequencies of maximum increments of the logarithmic likelihood function compared to the purely Poisson sequence.

Evolution of  lnL on the Petropavlovsk station Before the Kronotskoe earthquake

Evolution of  lnL on the Petropavlovsk station Before the Simushirskoe earthquake

The spectral measure of coherence is based on the use of canonical coherences which extend the notion of the spectrum of coherence to the situation where, instead of a pair of scalar time series, it necessary to investigate the relationship between vector time series at various frequencies. We defined a frequency-dependent statistic q λ(ω) = Пν i (ω), i=1 characterizing the correlation at the frequency between variations in all components of the vector series, obtained on different stations. The closer the value of λ(ω) to 1, the stronger the correlation between variations of time series on on different stations.

Spectral measure of coherence before the Kronotskoe eq. on Kamchatka

Spectral measure of coherence before the Simushirskoe eq. on Kuril islands

Spectral measure of coherence before the Sumatra earthquake

Effect of synchronization and decreasing of period between pulses in dynamic nonlinear system

CONCLUSION Asymmetric pulses about 3-10 min long did arose several days before the Kronotskoe (M = 7.8), Neftegorskoe (M = 7.0), Simushirskoe (M=8.2) and Hokkaido (M = 8.5) earthquakes. Intervals of a stable manifestation of several periods (tens of minutes) of pulses were found before the Kronotskoe, Simushirskoe and Sumatra (M = 9.2) events. Synchronization of microseismic oscillations on different stations was detected starting several days before the Kronotskoe, Hokkaido and Sumatra earthquakes. It is assumed that the nature of these phenomena is related to self-organization properties of the seismic process. The asymmetric pulses, periodic vibrations and synchronization intervals are indicators of the unstable state of a seismically active region and could be regarded as earthquake precursors.