## Multiple analysis of GPS signal fluctuation parameters before and after the megaearthquake in Japan on 11 March 2011

Category: 16-1

*UDC 550.334*

A.A.^{ }Lyubushin (1), P.V. Yakovlev (2), E.A. Rodionov (2)

^{(1) }*Schmidt Institute of Physics of the Earth, Russian Academy of Sciences, Moscow, Russia*

(2)* Ordzhonikidze Russian State Geological Prospecting University, Moscow, Russia*

**Abstract.** The field of GPS signals recorded at the net of 1203 stations in the Japanese archipelago from 30 January up to 26 March of 2011 is regarded. This time interval includes over 40 days before the mega-earthquake on 11 March 2011 (*M*=9.0) and almost 16 days after it. Signals from each station represent 3-component time series with a 30 minutes sampling time interval. Statistical properties of random fluctuations of GPS signals after linear trend removal and coming to increments before and after a seismic event are investigated. The maps of three noise waveform properties are regarded: maximum normalized eigenvalue of the correlation matrix and 2 smoothness indexes built by using orthogonal wavelets of Daubechies and Lang. The maps are constructed as values within nodes of a regular grid of the size 50´50 nodes which covers the investigated region by using information from 10 stations which are nearest to each node. Thus, 18 matrices of the noise properties within nodes of the grid are obtained: by 9 matrices before and after an event for three components of GPS signals (*N* – displacement northward, *E* – displacements eastward and *Z* – displacements upward). The final analysis consists in computing of the 1st principal components of investigated noise properties and constructing the maps of values of m* _{P}* – the maximum normalized eigenvalue of the correlation matrix of principal components within a sliding spatial rectangular window. These operations are performed separately using data before and after the earthquake.

The results of analysis reveal that before the earthquake the values of m* _{P}* exceeds significantly those after the event and the region of maximum values of m

*includes the epicenter of the future earthquake whereas after it the vicinity of the epicenter becomes a region of small correlations. These results confirm the hypothesis about increased correlations of geophysical field noises within zones of preparation of larger earthquakes and they could be used for seeking earthquakes precursors by GPS data.*

_{P}

**Keywords: **GPS signals, correlation analysis, principal component, wavelets, earthquake precursors.

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