[S11-2] Geo & space technologies to study pre–earthquake processes: Observation, modeling, forecasting II

[S11-2-01] Estimates of Seismic Danger in Japan by Coherence Properties of GPS Noise

^○Alexey Lyubushin (Institute of Physics of the Earth, Moscow, Russia)

invited

The dense GPS network at Japan islands (more than 1300 stations) provides the data for detail investigation of the Earth surface tremor. We used 3-components GPS data with sampling time step 5 minutes which were downloaded from the site of Nevada Geodetic Laboratory since 2015.03.03 up to the current time. Maps of kernel estimates of probability density functions are presented for nodes of the regular net sized 30x30, which are realized the spatial maximum of the frequency-dependent maximal values of the multiple spectral function of coherence of GPS time series from the nearest 10 workable stations for all 3 components of GPS time-series within moving time window of the length 5 days. The GPS station is considered workable in the time window if its registration interval includes the considered time window and the number of missing values does not exceed a predetermined maximum allowable proportion of the total length equal to 0.1. The missed values are filled using information about records from neighbor time interval of the same length as the length of gaps. Before calculating the coherence function in each window the trend is removed by polynomial of 4th order and 3-sigma winsorizing was performed. The map of most frequent positions of frequency-dependent maximum of multiple coherence of GPS noise extracts Nankai Trough with maximum at the vicinity of the point 34N and 138E. This result is an independent confirmation of the earlier conclusion made by the analysis of seismic noise (http://dx.doi.org/10.4236/ns.2013.58A1001).