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The attenuation of Fourier amplitudes for rock sites in eastern North America

Gail M. Atkinson and David M. Boore
The attenuation of Fourier amplitudes for rock sites in eastern North America
Bulletin of the Seismological Society of America (February 2014) 104 (1): 513-528

Abstract

We develop an empirical model of the decay of Fourier amplitudes for earthquakes of M 3-6 recorded on rock sites in eastern North America and discuss its implications for source parameters. Attenuation at distances from 10 to 500 km may be adequately described using a bilinear model with a geometric spreading of 1/R (super 1.3) to a transition distance of 50 km, with a geometric spreading of 1/R (super 0.5) at greater distances. For low frequencies and distances less than 50 km, the effective geometric spreading given by the model is perturbed using a frequency- and hypocentral depth-dependent factor defined in such a way as to increase amplitudes at lower frequencies near the epicenter but leave the 1 km source amplitudes unchanged. The associated anelastic attenuation is determined for each event, with an average value being given by a regional quality factor of Q=525f (super 0.45) . This model provides a match, on average, between the known seismic moment of events and the inferred low-frequency spectral amplitudes at R=1 km (obtained by correcting for the attenuation model). The inferred Brune stress parameters from the high-frequency source terms are about 600 bars (60 MPa), on average, for events of M>4.5.


ISSN: 0037-1106
EISSN: 1943-3573
Coden: BSSAAP
Serial Title: Bulletin of the Seismological Society of America
Serial Volume: 104
Serial Issue: 1
Title: The attenuation of Fourier amplitudes for rock sites in eastern North America
Affiliation: Western University, Department of Earth Sciences, London, ON, Canada
Pages: 513-528
Published: 201402
Text Language: English
Publisher: Seismological Society of America, Berkeley, CA, United States
References: 20
Accession Number: 2014-018592
Categories: Seismology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. sketch map
Secondary Affiliation: U. S. Geological Survey, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, Copyright, Seismological Society of America. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201412
Program Name: USGSOPNon-USGS publications with USGS authors
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