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SItomo – a New Matlab Toolbox for SKS Splitting Intensity Tomography and Application to the Dense SWATH-D Seismic Array in the European Alps

Description: 

The tomographic inversion of shear wave splitting data for upper mantle anisotropy has been a longstanding challenge for classical analysis techniques. This is due to the ray-based approximation of classical approaches and the near-vertical incidence of core-mantle converted phases that are often used. Recent developments involve the calculation of finite frequency sensitivity kernels for SKS splitting intensity observations, which allows us to take into account the laterally broadened sensitivity for the anisotropic structure with depth. A requirement of this tomographic technique is a dense station spacing, which results in overlapping sensitivity kernels at depth. This is satisfied by a growing number of temporary seismic deployments, which motivates the desire for an imaging of anisotropic complexities with depth.

Here, we introduce a toolbox for the MATLAB environment which facilitates the application of finite-frequency splitting intensity tomography (Mondal and Long 2019) to arbitrary 2D and 3D dense seismic arrays. Our implementation includes: 1) A forward calculation of splitting intensities and sensitivity kernels for a complex anisotropic model space. 2) The code takes into consideration the dominant period, allowing for multiple-frequency analysis, as well as a non-vertical incidence of the incoming wave. 3) The inversion can be based on a classical gradient descent or on a gradient-informed stochastic reversible jump algorithm, allowing for a data-driven parametrization of the model space. 4) An import of splitting intensities from waveforms processed in SplitRacer allows a fast pre-processing of large data sets due to its fully automatic design (Link et al. 2021).

We apply this inversion procedure to the SWATH-D network, which densely covers the transition of the Central to the Eastern Alps (Heit et al. 2017). Previous studies showed evidence for an abrupt lateral change of layered seismic anisotropy that had been attributed to an opening for a channeled asthenospheric flow. Here, we are able to confirm the previous observations while providing additional constraints on the anisotropic distribution.

Session: Earth’s Structure From the Crust to the Core [Poster]

Type: Poster

Date: 4/18/2023

Presentation Time: 08:00 AM (local time)

Presenting Author: Frederik Link

Student Presenter: No

Invited Presentation: 

Authors