Abstract: In view of the merits and drawbacks of strong motion (SM) and GPS, taking the Mw 6.0 Italy earthquake as a subject, the feasibility of Kalman filter to combine GPS and SM data, and then to conduct the real-time monitoring of instantaneous crustal deformation caused by moderate earthquake using fusion is discussed. The displacement waveform obtained by Kalman filtering uses GPS data as the overall trend, and the details are described by the SM displacement data. The combined displacement waveform has higher precision and can accurately and meticulously describe the coseismic ground dynamic deformation caused by earthquakes. At the same time, the Kalman filter displacement waveform can accurately detect the coseismic permanent offsets caused by moderate earthquake. The power spectrum density (PSD) of combined displacement waveform is similar to that of GPS displacement waveform in the low-frequency regions, while it is similar to the PSD of SM displacement waveform in the high-frequency regions, indicating that Kalman filtering can combine the advantages of GPS and SM. The spectral index of the displacement waveform obtained by Kalman filtering is different from that of GPS and SM displacement waveforms, indicating that the fused displacement waveform can better describe the variation of the noise characteristics of displacement waveform data caused by the earthquake. Cross-wavelet analysis shows that the displacement waveform obtained by Kalman filter has strong positive correlation with GPS and SM data, and the cross wavelet semblance is above 0.8. The above results show that the combined displacement waveform can combine the advantages of GPS and SM to make up for their defects. The combination of GPS and SM can effectively detect the transient crustal deformation induced by the earthquake with moderate magnitude.

Key words: GPS, strong motion instrument, Kalman filtering, fusion, crustal deformation