Abstract
The prognostic properties of four low-frequency seismic noise statistics are discussed: multi- fractal singularity spectrum support width, wavelet-based smoothness index of seismic noise waveforms, minimum normalized entropy of squared orthogonal wavelet coefficients and index of linear predictability. The proposed methods are illustrated by data analysis from broad-band seismic network F-net in Japan for more than 15 years of observation: since the beginning of 1997 up to 15 of May 2012. The previous analysis of multi-fractal properties of low-frequency seismic noise allowed a hypothesis about approaching Japan Islands to a future seismic catastrophe to be formulated at the middle of 2008. The base for such a hypothesis was statistically significant decreasing of multi-fractal singularity spectrum support width mean value. The peculiarities of correlation coefficient estimate within 1 year time window between median values of singularity spectra support width and generalized Hurst exponent allowed to make a decision that starting from July of 2010 Japan come to the state of waiting strong earthquake. This prediction of Tohoku mega-earthquake, initially with estimate of lower magnitude as 8.3 only (at the middle of 2008) and further on with estimate of the time beginning of waiting earthquake (from the middle of 2010) was published in advance in a number of scientific articles and abstracts on international conferences. It is shown that other 3 statistics (except singularity spectrum support width) could extract seismically danger domains as well. The analysis of seismic noise data after Tohoku mega-earthquake indicates increasing of probability of the 2nd strong earthquake within the region where the north part of Philippine sea plate is approaching island Honshu (Nankai Trough).
Highlights
The low-frequency microseismic oscillations and their correlation with the processes occurring in the hydrosphere and atmosphere of the Earth, which are the major sources of microseismic energy, are a common subject of research in geophysics [1,2,3,4]
As new data became available and after some new statistics of microseismic noise were included in joint analysis, we obtained some new results, indicating the facts that the parameters of the microseismic background had been increasingly synchronized and that the seismic danger had permanently grown [7,8,9,10]
Plotting the maps of different properties of low-frequency seismic noise within moving time window could present a new method of dynamic seismic hazard estimate
Summary
The low-frequency microseismic oscillations and their correlation with the processes occurring in the hydrosphere and atmosphere of the Earth, which are the major sources of microseismic energy, are a common subject of research in geophysics [1,2,3,4]. It is evident that the variations in the structure of the microseismic background may reflect the changes in the properties of the Earth’s crust, which is the medium where the microseismic signals propagate These changes in the parameters of microseisms in relation to Japan mega-earthquake 11 of March 2011, are the subject of the present paper. This paper presents results of analysis of properties of low-frequency seismic noise on the basis of more than 15 years of continuous observations, from the beginning of 1997 up to the middle of May 2012, at F-net (Japan) broad-band seismic stations including more than one year after the mega-earthquake 11 of March 2011. According to results of data analysis after 11 of March 2012 it is shown that there is a danger for occurring the 2nd mega-earthquake at the region to the south direction from Tokyo This danger was estimated in [13] using the singularity spectrum support width only.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
