AK112: Full Waveform Inversion Tomography of Alaska Improves Waveform Fits While Imaging Crustal, Mantle and Slab Structure
Description:
We present a new full waveform inversion (FWI) tomography model of Alaska and the surrounding regions. FWI tomography resolves seismic wavespeeds by minimizing the misfit between observed and simulated seismograms including the full volumetric finite frequency sensitivity of waveforms to Earth’s structure. For Alaska we solve for the radially anisotropic shear and isotropic compressional wavespeeds on a ~2000 km domain by fitting regional distance complete waveforms (body- and surface waves) from 120 MW 5.0 – 6.5 earthquakes from the Global Centroid Moment Tensor catalog. We inverted time-frequency (TF) phase misfits in 7 multiscale inversion stages and 112 total iterations starting with minimum period of 40 seconds and reducing to 20 seconds. The model was evaluated by computing the misfits for 40 independent validation events. We find that TF misfit reductions were about 55% for both the inversion and validation data sets providing confidence in the model. The model provides improved fits to complete waveforms compared to the starting model and other models of the region especially at far-regional distances. The resulting model images known crustal, upper mantle and slab structure but with new detail of radially anisotropic shear wavespeeds: sedimentary basins in the Gulf of Alaska, Cook Inlet, Northslope Foreland Basin; discontinuous crustal structure across major terranes boundaries; subducting slab geometry and back arc volcanics; and crustal and mantle signatures including anisotropy of the Yakutat Terrane. The new model has the advantage of specifying all parameters needed to simulate waveforms (anisotropic shear and isotropic compressional wavespeeds, attenuation and density) across a large domain spanning the coastlines, plate boundary and major terranes from the surface through the crust to the upper mantle. In addition to tectonic interpretations, the model could be used for full waveform simulations for long-period earthquake ground motions or source characterizations (e.g. moment tensor and finite fault inversions).
Session: Earth’s Structure from the Crust to the Core - III
Type: Oral
Date: 4/16/2025
Presentation Time: 02:45 PM (local time)
Presenting Author: Arthur
Student Presenter: No
Invited Presentation:
Poster Number:
Authors
Arthur Rodgers Presenting Author Corresponding Author rodgers7@llnl.gov Lawrence Livermore National Laboratory |
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AK112: Full Waveform Inversion Tomography of Alaska Improves Waveform Fits While Imaging Crustal, Mantle and Slab Structure
Category
Earth’s Structure from the Crust to the Core