Determination of the Coseismic Displacement with PPP Wavelet Decomposition and InSAR

The 2019 northeast Ridgecrest earthquakes occurred on July 4th and July 6th with magnitudes of 6.3 and 7.1 on the Moment Magnitude Scale (Mw), respectively. Utilizing precise point positioning (PPP), coseismic displacement can be measured, which is crucial for understanding earthquake structures. Noises in PPP measurements must be mathematically modeled to mitigate these interferences and extract coseismic displacement. The PPP static method was employed to determine the coseismic displacements of ten high-rate (1 Hz) global navigation satellite system (GNSS) stations located near the earthquake epicenter. The precise orbit and clock corrections of the satellites were utilized in PPP processing, and the simulated time series were subjected to wavelet decomposition (WD). This method reconstructs the PPP signal by analyzing the time-frequency domain, effectively increasing the signal-to-noise ratio. The symlets 4 wavelet, characterized by near-symmetric, orthogonal, and biorthogonal properties, was used to determine the maximum decomposition level. The largest displacement was measured by the nearest P595 station, with the eastern component at 432.24 ± 3 mm and the northern component at -247.31 ± 2 mm. To validate the results, interferometric synthetic aperture radar (InSAR) processing was performed with two Sentinel-1 A descending images from July 4 to July 16, 2019. The significant correlation values between GNSS and InSAR displacement were 0.62 and 0.92 before and after WD, respectively, at a 95% confidence level.