Next Generation Waveform Based Three-Dimensional Models and Metrics to Improve Nuclear Explosion Monitoring in the Middle East (Postprint)
Technical rept. 1 Sep 2010-31 Aug 2011
RHODE ISLAND UNIV KINGSTON
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Improving current Middle East wave speed models with full waveforms required confidence in sources and recordings, along with a methodology to iteratively improve models and reduce the minimum period of the waveforms used. A large, well recorded subset of 201 events 1997 2007 was reinterpreted through a direct comparison between data and synthetics based upon a centroid moment tensor inversion. Initial evaluations were done using a 1D reference model at periods greater than 80 seconds and a more stringent evaluation was done for a three-dimensional 3D model at periods of 25 seconds and longer. Final source reinterpretations within the 3D model define a source database and the initial starting point for tomography. Transitioning from a 1D to 3D wave speed model shows dramatic improvements when comparisons are done at shorter periods 25 s and even at longer periods 80 s. Updates of the wave speed model were accomplished using adjoint tomography. Initial attempts to update the wave speed model were hampered by the strong anisotropy in the mantle causing an unavoidable mismatch between Rayleigh and Love waves when using an isotropic mantle parameterization.
- Nuclear Warfare
- Nuclear Weapons