# Sources of Error and the Statistical Formulation of *M* _{S}: *m* _{b} Seismic Event Screening Analysis

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## Abstract

The Comprehensive Nuclear-Test-Ban Treaty (CTBT), a global ban on nuclear explosions, is currently in a ratification phase. Under the CTBT, an International Monitoring System (IMS) of seismic, hydroacoustic, infrasonic and radionuclide sensors is operational, and the data from the IMS is analysed by the International Data Centre (IDC). The IDC provides CTBT signatories basic seismic event parameters and a screening analysis indicating whether an event exhibits explosion characteristics (for example, shallow depth). An important component of the screening analysis is a statistical test of the null hypothesis *H* _{0}: explosion characteristics using empirical measurements of seismic energy (magnitudes). The established magnitude used for event size is the body-wave magnitude (denoted *m* _{b}) computed from the initial segment of a seismic waveform. IDC screening analysis is applied to events with *m* _{b} greater than 3.5. The Rayleigh wave magnitude (denoted *M* _{S}) is a measure of later arriving surface wave energy. Magnitudes are measurements of seismic energy that include adjustments (physical correction model) for path and distance effects between event and station. Relative to *m* _{b}, earthquakes generally have a larger *M* _{S} magnitude than explosions. This article proposes a hypothesis test (screening analysis) using *M* _{S} and *m* _{b} that expressly accounts for physical correction model inadequacy in the standard error of the test statistic. With this hypothesis test formulation, the 2009 Democratic Peoples Republic of Korea announced nuclear weapon test fails to reject the null hypothesis *H* _{0}: explosion characteristics.

## Keywords

Seismic Event Nuclear Explosion Nuclear Weapon Test International Seismological Centre International Monitoring System## Notes

### Acknowledgments

The authors acknowledge the support of Ms. Leslie A. Casey and the National Nuclear Security Administration Office of Nonproliferation and Treaty Verification Research and Development for funding this work. This work was completed under the auspices of the US Department of Energy by Los Alamos National Laboratory under contract DE-AC52-06NA24596. We thank Dr. Dmitry Storchak, Director of the International Seismological Centre, for his support in the acquisition of the data used in this article. We also thank Dr. Ronan Le Bras, Head of the Software Integration Unit at the International Data Centre, for providing important context in regard to event screening.

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