Improved Surface Wave Dispersion Models and Amplitude Measurements

Abstract

Abstract : The report describes the status and results to reduce the magnitude threshold for which surface waves can be identified and measured reliably, and to improve the accuracy of surface wave measurements, using phase-matched filtering, development of global regionalized earth and dispersion models, and other techniques. We have focused on improvements to global earth models and dispersion maps, and improved techniques for measuring surface wave amplitudes. Completed work on implementation and testing of azimuth estimation techniques at three component stations based on polarization analysis. Global regionalized earth and dispersion models are being developed by inversion of the very large data set of phase and group velocity dispersion measurements. The complete data set now contains over one million dispersion data pointS. The dispersion measurements are inverted for earth structure; the earth structure is then used to generate dispersion predictions. Improvement in the inversion procedure has been the introduction of the capability to vary damping and smoothing parameters for each model.