Improved Surface Wave Detection and Measurement Using Phase-Matched Filtering and Improved Regionalized Models

摘要

The goal of this project is to improve the capability to identify and detect surface waves under a Comprehensive Nuclear-Test-Ban Treaty. To date, we have concentrated on two tasks: development of improved regionalized earth models and dispersion curves, and improvements to surface wave processing through implementation of phase-matched filtering and path corrected spectral magnitudes. The first objective is to improve the dispersion curves that are now in use at the International Data Centre (IDC). The global dispersion data set has been expanded and now contains over 248,000 data points. Two global tomographic inversions were performed using this data set. The first inversion used the 149 IDC models as starting models. With the expanded data set regions such as Antarctica and Saudi Arabia where coverage was better were significantly improved. The second inversion increased the number of models to 399 to provide additional degrees of freedom in regions that required them. This inversion significantly improved the data fit in Eurasia and the Middle East. The standard deviation in the error of dispersion curves along paths from the former East Kazakh nuclear test site was reduced by almost a factor of two. We are continuing to make improvements to the models by adding new data, applying constraints where available, and adding models where the data requires them.