On the Existence, Magnitudes and Causes of Broad Regional Variations in Body-Wave Amplitude
Abstract
This report is a review of evidence for anomalous attenuation of short-period seismic body-waves in the upper mantle under the Western United States. The attenuation reduces the amplitudes of these waves by a factor of about two relative to those observed in stable, continental shield type areas. The magnitude of this amplitude anomaly is consistent with spectral differences of body-waves observed in the same region, assuming a simple exponential attenuation law with a constant quality factor Q. The most likely cause of the attenuation is partial melting in the upper mantle under the Western United States. This hypothesis is supported by measurements of travel-time delays, upper mantle conductivity and heat flow. The report also includes a considerable number of new results obtained recently at the Seismic Data Analysis Center.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 19, 1977
- Accession Number
- ADA054284
Entities
People
- Zoltan A. Der