Seismic catastrophe in Japan on March 11, 2011: Long-term prediction on the basis of low-frequency microseisms

This paper presents a software technique for analyzing the multidimensional time series of microseismic oscillations on the basis of over 14 years of continuous observations, from early 1997 to February 2011, at F-net (Japan) broadband seismic stations. An analysis of the multifractal parameters of low-frequency microseismic noise allowed us to hypothesize, in as early as 2008, that Japanese Islands were approaching a large seismic catastrophe, the signature of which was a statistically significant decrease in the support width of the multifractal singularity spectrum. Subsequently, as new data became available and after some new statistics of microseismic noise (such as a logarithm of noise variance and an index of linear predictability) were included in joint analysis, we obtained some new results, indicating the facts that the parameters of the microseismic background had been increasingly synchronized (the synchronization process was estimated to start in mid-2002) and that the seismic danger had permanently grown. A cluster analysis of background parameters led us to conclude that in mid-2010 the islands of Japan entered a critically dangerous developmental phase of seismic process. The prediction of the catastrophe, first in terms of approximate magnitude (mid-2008) and then in terms of approximate time (mid-2010), was documented in advance in a series of papers and in proceedings at international conferences.