Some Problems With Using Magnitude Scales For Eastern North American Earthquakes

Research Article| July 01, 1976 Some Problems With Using Magnitude Scales For Eastern North American Earthquakes Ronald L. Street; Ronald L. Street *Weston Geophysical Research, Inc., Westboro, MA 01581 Search for other works by this author on: GSW Google Scholar Robert B. Herrmann Robert B. Herrmann **Dept. of Earth and Atmospheric Sciences, St. Louis, University, P. O. Box 8099, Laclede Station, St. Louis, MO 63156 Search for other works by this author on: GSW Google Scholar Author and Article Information Ronald L. Street *Weston Geophysical Research, Inc., Westboro, MA 01581 Robert B. Herrmann **Dept. of Earth and Atmospheric Sciences, St. Louis, University, P. O. Box 8099, Laclede Station, St. Louis, MO 63156 Publisher: Seismological Society of America First Online: 09 Mar 2017 Online Issn: 1938-2057 Print Issn: 0895-0695 © 1976 by the Seismological Society of America Seismological Research Letters (1976) 47 (3): 37–45. https://doi.org/10.1785/gssrl.47.3.37 Article history First Online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Ronald L. Street, Robert B. Herrmann; Some Problems With Using Magnitude Scales For Eastern North American Earthquakes. Seismological Research Letters 1976;; 47 (3): 37–45. doi: https://doi.org/10.1785/gssrl.47.3.37 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 SocietySeismological Research Letters Search Advanced Search Abstract Body wave magnitude scales are of the form mb=B+Clog10D+log10(A/T),where B and C are constants, D is the epicentral distance, and A is some measure of maximum ground motion amplitude at the period T. By accepted definition, mb applies to waves with periods of 1 second. However, the Lg wave amplitude data in eastern United states, typically within the period range of 0.6 to 1.5 seconds, are currently being used in determining mb magnitudes of eastern earthquakes. Implicit in the use of periods other than 1 second is the assumption that the ground velocity (A/T), is constant over that period range.This paper points out the errors introduced into the mb estimate of an earthquake when T is not restricted to lie relatively close to 1 second. These errors arise because of the shape of the seismic source spectrum and the relative scaling of 1 second period amplitudes with respect to other periods. As an example, it will be shown that the use of amplitudes with a period of 0.3 seconds can lead to error in the estimated mb magnitude by as much as 0.5 magnitude units. However, by using the known source spectrum scaling in a region, it will be shown how to obtain an equivalent mb magnitude from waves with periods other than 1 second. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.