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| Titel |
Body-wave magnitudes of underground nuclear explosions at major test sites derived by the maximum-likelihood method |
| VerfasserIn |
Sheila Peacock, Alan Douglas, David Bowers, Neil Selby |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250074693
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| Zusammenfassung |
| Body-wave magnitudes (mb) of ~600 underground nuclear tests have been derived from
station amplitudes collected by the International Seismological Centre (ISC), by a joint
inversion for mb and station-specific magnitude corrections (Lilwall 1986). The
maximum-likelihood method was used, to reduce the upward bias of network mean
magnitudes caused by data censoring for low-magnitude disturbances where stations do not
report arrivals that are hidden by the ambient noise at the time. Threshold noise levels at
each station were derived from the ISC amplitudes using the method of Kelly and
Lacoss (1969). The joint inversion is valid only for sites where enough explosions
occurred, and stations with enough arrivals (a minimum of three for both), for a
statistical treatment to be valid. It is used on the sites: Kazakhstan and Novaya Zemlya,
former Soviet Union; Singer, China; Mururoa and Fangataufa, French Polynesia;
and Nevada, USA. At sites where four or more arrivals could be used to derive
magnitudes and station terms for twenty-five or more explosions (Nevada, Kazakhstan
and Mururoa), the resulting magnitudes and station terms were fixed and a second
inversion carried out to derive magnitudes for additional explosions with as few
as three arrivals. A further ~90 magnitudes were derived thus, mostly of Nevada
explosions. |
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