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Advanced Waveform Simulation for Seismic Monitoring
CALIFORNIA INST OF TECH PASADENA
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Earthquake source parameters underpin several aspects of nuclear explosion monitoring. Such aspects are calibration of moment magnitudes including coda magnitudes and magnitude and distance amplitude corrections MDAC source depths discrimination by isotropic moment tensor components and waveform modeling for structure including waveform tomography. This project seeks to improve methods for and broaden the applicability of estimating source parameters from broadband waveforms using the Cut-and-Paste CAP methodology. The CAP method uses a library of Greens functions for a one-dimensional 1D, depth-varying seismic velocity model. The method separates the main arrivals of the regional waveform into 5 windows Pnl vertical and radial components, Rayleigh vertical and radial components and Love transverse component. Source parameters are estimated by grid search over strike, dip, rake and depth and seismic moment or equivalently moment magnitude, MW, are adjusted to fit the amplitudes. Key to the CAP method is allowing the synthetic seismograms to shift in time relative to the data in order to account for path-propagation errors delays in the 1D seismic velocity model used to compute the Greens functions. The CAP method has been shown to improve estimates of source parameters, especially when delay and amplitude biases are calibrated using high signal-to-noise data from moderate earthquakes, CAP.
APPROVED FOR PUBLIC RELEASE