Research in Seismology: Earthquake Magnitudes
Abstract
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.
Document Details
- Document Type
- Technical Report
- Publication Date
- Oct 11, 1976
- Accession Number
- ADA032699
Entities
People
- Huei-yuin Wen
- John A. Wagner
- Otto W. Nuttli
- So Gu Kim
Organizations
- Saint Louis University