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mb Bias and Regional Magnitude and Yield
LOS ALAMOS NATIONAL LAB NM
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Traditional seismic yield estimation is performed using body wave magnitude mb measured from compressional wave amplitudes recorded across the globe. Stability is obtained by averaging many measurements. These waves traverse the earths mantle, and are affected by mantle properties, particularly under the source region, as other variations are averaged out. To monitor individual test sites during the testing era, test site corrections were obtained by various means, most notably the Joint Verification Experiment, and applied to obtain yield. To extend yield estimation to broad areas, we must apply an upper mantle correction on the fly. We have investigated two methods to map upper mantle bias over broad areas. The first estimates the bias at individual stations by inverting for corrections that best fit the collection of amplitudes measured at all stations. These measurements were taken from global monitoring agencies, including the International Data Centre IDC and National Earthquake Information Center NEIC bulletins, examined separately. We augment bulletin amplitudes by replicating monitoring agency measurement techniques for non-reporting or temporary stations in regions of particular interest, such as the Korean Peninsula, including State University of New York SUNY Binghamtons northeast China and Lamonts Sinpo deployments. The second method compares mb to magnitude derived from regional Lg coda, which is not affected by mantle properties, producing a map of the upper mantle effects across broad areas where earthquakes occur. The station-based technique retains near-site effects that the event-based technique does not, thus, resolving any differences between the two techniques is of great importance.
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