P and S Wave Receiver Function Imaging of Subduction With Scattering Kernels

Abstract

A method for scattered wave imaging in 3‐D with both teleseismic P and S wave receiver function data is introduced. The approach relies on body‐wave scattering kernels that are derived from the adjoint data sensitivity kernels which are typically used for full waveform tomography. The forward problem is approximated using ray theory, yielding a computationally efficient imaging algorithm that can resolve dipping and discontinuous interfaces using both P and S wave receiver functions. Traveltime fields for the incident teleseismic arrivals and the receiver point‐sources are obtained by solving the Eikonal equation using a Fast Marching code which can handle a 3‐D reference velocity model. An energy stable finite‐difference method is used to simulate elastic wave propagation in a 2‐D hypothetical subduction zone model. The resulting synthetic P and S wave receiver function data sets are used to validate the imaging method. The kernel images are compared with those generated by the Generalized Radon Transform and Common Conversion Point Stacking methods. These results demonstrate the potential of the kernel imaging approach for constraining lithospheric structure in complex geologic environments with sufficiently dense recordings of teleseismic data. Potential imaging targets include short‐wavelength compositional variations in the mantle wedge and the slab's lithosphere‐asthenosphere boundary.

Multimode 3‐D Kirchhoff Migration of Receiver Functions at Continental Scale

“…Combining the information extracted from all the scattering modes by stacking the images linearly is an efficient tool to extract coherent information (Bostock et al, ; Hansen & Schmandt, ). In the case of GRT, the PS , PpS , and PsS modes are combined to create a composite result for δβ / β variations, and the PpP mode gives the result for the δα / α variations.…”

“…Our method projects and stacks teleseismic waveform data in the depth domain to recover scattering structure. Other methods have the same basic principle, ranging from fast 1-D CCP stacking (Dueker & Sheehan, 1997) to 2-D multimode CCP (Tauzin et al, 2016) and 3-D prestack techniques (this paper; Hansen & Schmandt, 2017). All these methods afford very high spatial resolution corresponding to one wavelength for PS scattering and ∕2 for multiple modes, and prestack techniques are able to image structures as shallow as two times the interstation spacing down to approximately the same depth as the array aperture (Miller et al, 1987;Rondenay, 2009).…”

“…Their method was tested using 2.5‐D synthetic data obtained from ray tracing (Raysum, Frederiksen & Bostock, ), as well as data from the Cascadia93, Mendocino, and USArray experiments. A similar method based on sensitivity kernels for P ‐to‐ S and S ‐to‐ P conversions has been devised by Hansen and Schmandt () and tested using 2‐D synthetics obtained from spectral element simulations (Specfem2D; Tromp et al, ). Both methods have the same order of computational cost as 2‐D GRT and can image laterally varying structures such as subducting slabs given a dense ray coverage of the region of interest.…”

Application of Ps Scattering Kernels to Imaging the Mantle Transition Zone With Receiver Functions

“…Under the Kirchoff migration framework, Cheng et al () proposed a method with 3‐D travel time calculations and 1‐D scattering coefficients and demonstrated resolution of dipping structures with correct polarities. Subsequently, Hansen and Schmandt () emphasized the advantages of applying multimode (Ps, Sp) scattering kernels with 3‐D travel times and scattering coefficients and tested the method with a subduction zone model. Here for the purpose of Ps scattered wave imaging at mantle transition zone depths on a continental scale, we implement a 3‐D migration framework that builds upon the approach of Cheng et al ().…”

Surface Imaging Functions for Elastic Reverse Time Migration

“…Alternatively, elastic RTM has been formulated for imaging specular reflectors using converted teleseismic waves from passive sources as described by Brytik et al (), Shang et al (), Hansen and Schmandt (), and Li et al () and related inverse scattering methods (e.g., Bostock et al, ; Poppeliers & Pavlis, ). These methods are based on back propagation using the elastic wave equation and involve the cross‐correlation of time‐reversed converted waves, that is, converted P to S , with time‐reversed transmitted waves, that is, direct P .…”