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Converted-Wave Reverse Time Migration Imaging in Subduction Zone Settings

Description: 

We use a newly developed 2D elastic reverse time migration (RTM) imaging algorithm based on the Helmholtz decomposition to test approaches for imaging the descending slab in subduction zone regions using local earthquake sources. Our elastic RTM method is designed to reconstruct incident and scattered wavefields at depth, isolate constituent P and S wave components via Helmholtz decomposition, and evaluate normalized imaging functions that leverage dominant P and S signals. This method allows us to target particular converted-wave scattering geometries, e.g., incident S to scattered P, which may be expected to have dominant signals in any given dataset. We intend to apply this method to dense seismic array observations that adequately capture both incident and converted wavefields. We draw a direct connection between our imaging functions and the first-order contrasts in shear wave material properties across seismic discontinuities. Through tests on synthetic data using either S to P or P to S conversions, we find that our technique can successfully recover the structure of a subducting slab using data from a dense wide-angle array of surface stations. We also calculate images with seismic data from a small-aperture array to test the impact of array geometry on image resolution and interpretability. Finally, we demonstrate that our method successfully recovers the topographic shape of the surface of a subducting slab and yields high-resolution information even when the starting model is highly smoothed and does not include topography. We also discuss plans for an implementation of our method in 3D and explore regions that may be imaged via our method with existing seismic datasets.

Session: Subduction Zone Structure From Trench to Arc

Type: Oral

Date: 4/19/2023

Presentation Time: 10:30 AM (local time)

Presenting Author: Leah Langer

Student Presenter: No

Invited Presentation: 

Authors