DTIC ADA032699: Research in Seismology: Earthquake Magnitudes pdf

DTIC ADA032699: Research in Seismology: Earthquake Magnitudes

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This report presents results of a search for earthquakes in Eurasia that have anomalous ratios of body-wave magnitude to surface-wave magnitude values. Results of a study of mainshock-aftershock sequences are also provided. Earthquakes occurring along the plate margin of Eurasia were found to be non- anomalous. Anomalous earthquakes are confined to the continental interior, with about 18% of the intraplate earthquakes studied having anomalous (m sub b): (M sub S) values; the anomalus events extend from southern Europe to eastern Asia. Anomalous earthquakes are often found among the aftershocks of mainshock- aftershock intraplate earthquake sequences. Focal depth and focal mechanisms of anomalous and non-anomalous earthquakes were found to be the same, so that depth and mechanism variations do not explain the anomalies. It was also found that anomalous earthquakes had shorter P-wave spectral corner periods than non- anomalous earthquakes of the same surface-wave magnitude or seismic moment.

It appears to be especially difficult to discriminate between a small-magnitude aftershock of an intraplate earthquake and a small to intermediate yield explosion detonated within a few hours or days of the mainshock

• Creator/s: Defense Technical Information Center
• Date: 10/11/1976
• Year: 1976
• Book Topics/Themes: DTIC Archive, Nuttli, Otto W, Kim, So Gu, Wen, Huei-Yuin, Wagner, John A, SAINT LOUIS UNIV MO DEPT OF EARTH AND ATMOSPHERIC SCIENCES, *EARTHQUAKES, *NUCLEAR EXPLOSIONS, *SEISMIC DETECTION, *SEISMIC WAVES, ANOMALIES, ASIA, BOUNDARIES, CONCEALMENT, DEPTH, DISCRIMINATION, EPICENTERS, EUROPE, GEOGRAPHIC DISTRIBUTION, INTENSITY, NUCLEAR EXPLOSION TESTING, SEQUENCES, SPECTRUM ANALYSIS, SURFACE WAVES, TECTONICS

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