Recent progress on wave gradiometry method

Wave gradiometry method is a data processing technique based on dense seismic arrays and is suitable for a variety of seismic signals/phases such as P-waves, S-waves, Rayleigh waves, Love waves, and ambient noise. Since both temporal and spatial differences within the wave field are fully considered by this method, more seismic wave propagation parameters and medium physical properties can be obtained; these include stress, rotation, seismic velocity, azimuth, geometrical spreading, radiation pattern, azimuthal anisotropy, and Q value. Since its introduction in 2007, wave gradiometry has been widely used to study strong ground motion in river valleys, shallow lunar crust, fault systems and the inversions of the velocity and anisotropy models of shallow Earth, crust, or mantle. Based on different signal processing techniques, wave gradiometry method has been developed into different branches such as the wave gradiometry analyses based on Fourier transform, wavelet transform and Hilbert transform. These methods have branched into further research based on different reference coordinate systems, network types, or seismic phases/signal sources. In this paper, the methodology, recent progress, developmental trend, and method comparisons of wave gradiometry are described in detail.