Ray-parameter based stacking and enhanced pre-conditioning for stable inversion of receiver function data

While inversion of seismic velocity from receiver function data could be instable due to intrinsic non-linearity and non-uniqueness, improper stacking of receiver function could introduce significant biases to the resulting velocity structure. In a distance section of functions, the Moho Ps conversion and the two reverberations possess a positive negative moveout, respectively. Stacking receiver functions without moveout correction significantly reduce and distort the amplitude and waveform of these phases. Inversion these incorrectly stacked receiver functions will thus inevitably introduce artefacts to the velocity structure. In this study, we have improved the inversion procedure in two. First, we introduce a ray-parameter based (RPB) stacking method to correctly construct function data for inversion. Specifically we develop a ‘four-pin’ method that accounts the moveout effect of the converted and reverberated phases in stacking individual receiver recorded at various distances. Secondly, we divide the receiver function trace into and reverberation windows and assign different weights between the two windows the inversion. More weight is given to the Ps conversion window in resolving the shallow, which can be nearly fixed in the successive inversion of deeper structure. We also other pre-conditioning proposed by previous studies, such as balancing the receiver data being filtered with different Gaussian filters, smoothing the velocity model and regulating the model based on existing information. We compute synthetic receiver at distances between 30◦ and 90◦ from a target model and then use the RPB stacking to generate the input data for various inversions (iterative linear) with different initial. Our inversions with enhanced pre-conditioning and RPB stacked data demonstrate a capability in recovering the target model from generally more stable iterations. Applying techniques to two broad-band stations in China indicates that the improvements on data and inversion can eliminate potential stacking-induced artefacts, and yield models consistent with surface geology.