The spatial sensitivity of Sp converted waves—scattered-wave kernels and their applications to receiver-function migration and inversion

Mancinelli, N. J.; Fischer, K. M.

doi:10.1093/gji/ggx506

Cited by 10 publications

(31 citation statements)

References 20 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This is the expected model perturbation for recovery of a discontinuity relative to a homogeneous background and is typical for scattered wave kernel imaging and in agreement with several other studies (Mancinelli & Fischer, 2018;Pearce et al, 2012;Rondenay et al, 2001Rondenay et al, , 2008. Some studies apply a phase shift to the receiver functions in order to recover a single phase centered on the discontinuity for ease of visualisation and interpretation (Hansen & Schmandt, 2017;Hua et al, 2020), whereas other studies report that phase shifting results in further issues with side lobes and instability (Mancinelli & Fischer, 2018). Regardless of how presented, scattered wave kernels such as those presented here recover a change in velocity, rather than the absolute velocity of the layers.…”

Section: Recovery Resultssupporting

confidence: 91%

“…Alternatively, it could be related to the smaller number of stacked kernels at depth owing to the size of the array, which could be ameliorated by increasing the array aperture (Mancinelli & Fischer, 2018; Rondenay et al., 2005). Better recovery of shallow structures by S‐to‐P kernels is also reported in the work of Mancinelli and Fischer (2018) and the work of Hansen and Schmandt (2017).…”

Section: Discussionmentioning

confidence: 99%

“…Therefore, a different approach is needed to construct the kernel for a hypothetical discontinuity relative to a homogeneous background model, that is, the scenario under which our analytical kernels are constructed for scattered waves. The kernel for a hypothetical discontinuity can be constructed by running SPECFEM2D simulations for adjoint sources at many points throughout the model domain to populate the kernel for a given time delay and incidence angle, that is, essentially assuming that every point in the model is a scatterer (Mancinelli & Fischer, 2018). We use an alternative approach.…”

Section: Methodsmentioning

confidence: 99%

See 2 more Smart Citations

2‐D Analytical P‐to‐S and S‐to‐P Scattered Wave Finite Frequency Kernels

Harmon

Rychert

Xie

et al. 2022

Geochem Geophys Geosyst

View full text Add to dashboard Cite

Scattered wave imaging provides a powerful tool for understanding Earth's structure. The development of finite frequency kernels for scattered waves has the potential for improving the resolution of both the structure and magnitude of discontinuities in S‐wave velocity. Here we present a 2‐D analytical expression for teleseismic P‐to‐S and S‐to‐P scattered wave finite‐frequency kernels for a homogeneous medium. We verify the accuracy of the kernels by comparing to a spectral element method kernel calculated using SPECFEM2D. Finally, we demonstrate the ability of the kernels to recover seismic velocity discontinuities with a variety of shapes including a flat discontinuity, a discontinuity with a sharp step, a discontinuity with a smooth bump, and an undulating discontinuity. We compare the recovery using the kernel approach to expected recovery assuming the classical common conversion point (CCP) stacking approach. We find that the P‐to‐S kernel increases recovery of all discontinuity structures in comparison to CCP stacking especially for the shallowest discontinuity in the model. The S‐to‐P kernel is less successful but can be useful for recovering the curvature of shallow discontinuity undulations. Finally, although we observe some variability in the amplitude of the kernels along the discontinuities, the kernels show some potential for recovering the magnitude of the velocity contrast across a discontinuity.

show abstract

Section: Recovery Resultssupporting

confidence: 91%

Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

2‐D Analytical P‐to‐S and S‐to‐P Scattered Wave Finite Frequency Kernels

Harmon

Rychert

Xie

et al. 2022

Geochem Geophys Geosyst

View full text Add to dashboard Cite

show abstract

“…In prior studies, these spatial functions are either represented by geographic bins of conversion points (e.g., Dueker & Sheehan, 1997; Kind et al, 2012; Rondenay, 2009), or by empirically defined weighting functions that represent Fresnel zones for vertically incident waves (e.g., Lekic et al, 2011; Lekić & Fischer, 2017; Wittlinger & Farra, 2007). However, to incorporate the physics of wave scattering into CCP stacking, these spatial functions should be consistent with the sensitivity kernels that describe how scattering from a point on a velocity discontinuity contributes to an observed converted phase, for example the scattering kernels for Sp and Ps phases (e.g., Bostock et al, 2001; Bostock & Rondenay, 1999; Hansen & Schmandt, 2017; Hua et al, 2020; Mancinelli & Fischer, 2017). This condition is typically not met in prior CCP stacking approaches.…”

Section: Introductionmentioning

confidence: 99%

New Approaches to Multifrequency Sp Stacking Tested in the Anatolian Region

Hua

Fischer

et al. 2020

JGR Solid Earth

View full text Add to dashboard Cite

This study presents an improved approach to common-conversion point stacking of converted body waves that incorporates scattering kernels, accurate and efficient measurement of stack uncertainties, and an alternative method for estimating free surface seismic velocities. To better separate waveforms into the P and SV components to calculate receiver functions, we developed an alternative method to measure near-surface compressional and shear wave velocities from particle motions. To more accurately reflect converted phase scattering kernels in the common-conversion point stack, we defined new weighting functions to project receiver function amplitudes only to locations where sensitivities to horizontal discontinuities are high. To better quantify stack uncertainties, we derived an expression for the standard deviation of the stack amplitude that is more efficient than bootstrapping and can be used for any problem requiring the standard deviation of a weighted average. We tested these improved methods on Sp phase data from the Anatolian region, using multiple band-pass filters to image velocity gradients of varying depth extents. Common conversion point stacks of 23,787 Sp receiver functions demonstrate that the new weighting functions produce clearer and more continuous mantle phases, compared to previous approaches. The stacks reveal a positive velocity gradient at 80-150 km depth that is consistent with the base of an asthenospheric low-velocity layer. This feature is particularly strong in stacks of longer period data, indicating it represents a gradual velocity gradient. At shorter periods, a lithosphere-asthenosphere boundary phase is observed at 60-90 km depth, marking the top of the low-velocity layer. Plain Language Summary This paper presents a new method that more accurately incorporates the physics of seismic scattering into how the wave records are combined to form images of gradients in seismic velocity structure. This method was tested on data from the Anatolian region, where the asthenosphere is known to have low seismic wave velocities, consistent with high mantle temperatures and possibly small fractions of partial melt, as suggested by the presence of volcanic fields at the surface. However, the depth of the asthenospheric low-velocity layer is not well known. In this study, we locate this low-velocity mantle layer by applying the newly developed imaging method to seismic shear waves that convert to compressional waves at the velocity gradients that mark the layer boundaries. This study is the first to clearly resolve both the lower and upper margins of the asthenosphere for the whole region. The top of the layer corresponds to the lithosphere-asthenosphere boundary at 60-90 km depth, and this velocity gradient is localized in depth. However, the bottom boundary, which lies at depths of 80-150 km, occurs over a broader depth range.

show abstract

“…It is noteworthy that these suggestions are based on the curvature of the Ps kernel. For the Sp kernel, which curves downward, the Ricker will produce a reversed layer above the true interface (Mancinelli & Fischer, ).…”

Section: Discussionmentioning

confidence: 99%

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

Zhang

Schmandt

2019

JGR Solid Earth

View full text Add to dashboard Cite

Seismic imaging of the global boundaries of the mantle transition zone provides important constraints regarding mantle composition and convection. Additionally, modern hypotheses about mantle convection and increasing seismic data resources motivate attempts to image more complex regional transition zone structures such as dipping and discontinuous interfaces. Here we extend a 3-D prestack migration method to make it more applicable for transition zone imaging with Ps receiver functions. After validation with 1-D synthetic data, two types of hypothetical structures are adopted to demonstrate the strengths and weaknesses of different practical imaging parameters with 2-D synthetic tests. The results show that the method can resolve dipping anomalies and laterally discontinuous low velocity layers. However, receiver spacing of 0.5°is inadequate to accurately migrate scattering from all possible angles in the transition zone at~0.3 Hz. Application of a slowness cutoff window about the Ps raypath can mitigate artifacts due to low receiver density, but the tradeoff is a decrease in the maximum resolvable dip angle. Further synthetic tests evaluate source wavelet effects, addition of observed seismic noise to synthetic data, and imaging grid dimensions. Cumulatively, the tests indicate that generic application of migration algorithms to the limited source-receiver distributions relevant for the transition zone should be treated cautiously. Imaging parameters, such as the slowness cutoff and wavelet, should be chosen based on synthetic tests for hypothetical targets and realistic source-receiver geometries. Finally, observational Ps receiver functions from the USArray are migrated with the new method.Plain Language Summary This study extends a seismic imaging method to make it more applicable to the mantle transition zone depths (from 300 to 800 km) because seismic imaging of sharply defined structures in this layer of Earth provide important insights into mantle composition and convection. The method was tested with realistic combinations of synthetic earthquake sources and seismic network densities to evaluate how it would perform for hypothetical transition zone structures. The results are encouraging in that they show the possibility of detecting increasingly complex structures in this layer of Earth's interior, but they also show that realistic combinations of earthquakes and seismographs present challenges for generic application of imaging methods to the transition zone. Examples from a suite of synthetic tests outline how the new imaging method may be optimized to resolve some complex structures with realistic seismic data resources and avoid introducing artificial features that could confound structural interpretations.

show abstract

The spatial sensitivity of Sp converted waves—scattered-wave kernels and their applications to receiver-function migration and inversion

Cited by 10 publications

References 20 publications

2‐D Analytical P‐to‐S and S‐to‐P Scattered Wave Finite Frequency Kernels

2‐D Analytical P‐to‐S and S‐to‐P Scattered Wave Finite Frequency Kernels

New Approaches to Multifrequency Sp Stacking Tested in the Anatolian Region

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

Contact Info

Product

Resources

About