The Attenuation of Fourier Amplitudes for Rock Sites in Eastern North America

Research Article| November 26, 2013 The Attenuation of Fourier Amplitudes for Rock Sites in Eastern North America Gail M. Atkinson; Gail M. Atkinson aWestern University, Department of Earth Sciences, London, Ontario N6A 5B7gmatkinson@aol.com Search for other works by this author on: GSW Google Scholar David M. Boore David M. Boore bU.S. Geological Survey, 345 Middlefield Rd., Menlo Park, California 94205boore@usgs.gov Search for other works by this author on: GSW Google Scholar Bulletin of the Seismological Society of America (2014) 104 (1): 513–528. https://doi.org/10.1785/0120130136 Article history first online: 14 Jul 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Gail M. Atkinson, David M. Boore; The Attenuation of Fourier Amplitudes for Rock Sites in Eastern North America. Bulletin of the Seismological Society of America 2013;; 104 (1): 513–528. doi: https://doi.org/10.1785/0120130136 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyBulletin of the Seismological Society of America Search Advanced Search 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/R1.3 to a transition distance of 50 km, with a geometric spreading of 1/R0.5 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 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. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.