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Detection and Identification of Small Regional Seismic Events,

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Many seismic events detected and located by the prototype International Data Center IDC at the Center for Monitoring Research CMR are small regional events. However, only very limited experience exists for regional seismic signals from small or decoupled nuclear explosions, which would be important in a CTBT monitoring environment. Furthermore, many of the events currently being reported by the lDC occur in geographical regions for which there is little or no previous seismic monitoring experience with underground nuclear explosion tests. The goal of this research has been to enhance the experience base for the IDC and to identify potential techniques and limitations of IDC seismic monitoring at the low magnitude levels appropriate to a CTBT. For these investigations we have focussed primarily on application of theoretical source scaling methods to the regional signals from observed underground nuclear explosions and, then, compared the behavior of the scaled regional signals to that from other source types with similar, small magnitudes. During the initial stages of this project, a test database of underground nuclear explosion tests recorded at the Fennoscandian regional arrays was identified. Mueller-Murphy theoretical source scaling was used to scale the array records down to the levels appropriate to CTBT monitoring goals e.g. 1-kt fully decoupled, and the scaled signals were re-embedded into normal background noise conditions. A copy of this scaled explosion database was provided to CMR for testing capabilities of the existing system, and we performed some independent signal analysis procedures on the waveforms to discern features which could be relevant in identification monitoring at the IDC. In a separate study under this contract, we also investigated seismic identification techniques for some specific events recently detected by the IDC.

Subject Categories:

  • Government and Political Science
  • Seismology
  • Seismic Detection and Detectors
  • Nuclear Weapons

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