Model Development for Broad Area Event Identification and Yield Estimation

Models of laterally varying attenuation and site effects of regional phases are necessary to correct regional phase and coda amplitudes to reveal source effects of importance to identification and yield estimation procedures. We accomplish this using 2-D amplitude tomography, incorporating ground tr...

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Bibliographic Details
Main Authors: Phillips, W S, Yang, Xiaoning, Stead, Richard J, Begnaud, Michael L, Mayeda, Kevin M
Format: Report
Language:English
Subjects:
AMPLITUDE
AMPLITUDE TOMOGRAPHY
ATTENUATION
SEISMIC WAVES
Seismology
SPECTRAL GROUND TRUTH
SURFACE TRUTH
TOMOGRAPHY
YIELD ESTIMATION
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Summary:Models of laterally varying attenuation and site effects of regional phases are necessary to correct regional phase and coda amplitudes to reveal source effects of importance to identification and yield estimation procedures. We accomplish this using 2-D amplitude tomography, incorporating ground truth spectral estimates based on relative coda techniques and regional moment tensor inversion. The ground truth spectra allow calibration to absolute levels and can be used to validate amplitude prediction models. Ground truth spectra may also be used to improve resolution in the margins of raypath coverage where source-path tradeoffs would otherwise dominate. Initial studies using USArray amplitude data show that we can recover frequency dependent, laterally varying attenuation absolute site terms, moment and apparent stress using constraints based on ground truth spectra from the Wells Nevada sequence. Tomographic efforts in Asia rely on collections of temporary networks and permanent stations and preparation includes noise analysis for undocumented instrument changes, relative calibration of channels and array elements, and data culling using manual and automated methods. Network based Pg/Lg discriminants have confirmed earlier results showing that 2-D path calibration improves performance in intermediate bands (2-6 Hz) thus improves discrimination coverage. We applied relative coda methods to Asia sequences to obtain GT spectra. The method generalizes spectral ratio techniques by converting collections of high precision, pairwise relative coda measurements to absolute spectra assuming an omega-2 source model, allowing simultaneous analysis of large numbers of events. Apparent stress results vary significantly for smaller events, and for the Wenchuan sequence, is more heterogeneous over the southern, thrusting segment of the slip plane. Published in Proceedings of the 2010 Monitoring Research Review - Ground-Based Nuclear Explosion Monitoring Technologies, 21-23 September 2010, Orlando, FL. Volume I. Sponsored by the Air Force Research Laboratory (AFRL) and the National Nuclear Security Administration (NNSA). U.S. Government or Federal Rights License