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Next Generation, Waveform Based 3-Dimensional Models & Metrics to Improve Nuclear Explosion Monitoring in the Middle East
Final rept. 25 Jan 2008-25 Jan 2012
RHODE ISLAND UNIV KINGSTON
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Improvements to the current Middle East wave-speed model with full waveforms require confidence in sources and recordings, along with a methodology to iteratively improve the model and reduce its minimum period. The mismatch between recordings of seismic waves traversing the region from Tibet to the Red Sea compared to synthetics from the current iteration model is the principal metric in improving the current wave-speed model. After the sources were evaluated, regions requiring refinement were highlighted using adjoint tomography methods based on spectral-element simulations. Inversion results demonstrate that the iterative nature of the adjoint tomography primarily improves the travel-time variations between synthetics and data, with less of an improvement to the waveform amplitudes. Iterative improvements also significantly increase anomaly strength while sharpening the anomaly edges to create stronger and more pronounced tectonic structures. The results presented here, while accurate at intermediate periods, require the addition of attenuation tomography and transverse isotropy without a vertical symmetry axis to further reduce the minimum period to that of travel-time tomography models.
APPROVED FOR PUBLIC RELEASE