A strategy to rapidly determine the magnitude of great earthquakes
Article first published online: 3 JUN 2011
©2005. American Geophysical Union. All Rights Reserved.
Eos, Transactions American Geophysical Union
Volume 86, Issue 19, pages 185–188, 10 May 2005
How to Cite
2005), A strategy to rapidly determine the magnitude of great earthquakes, Eos Trans. AGU, 86(19), 185–188, doi:10.1029/2005EO190002., and (
- Issue published online: 3 JUN 2011
- Article first published online: 3 JUN 2011
In the initial hours following the origin of the Sumatra-Andaman Islands earthquake at 0058:53 GMT on 26 December 2004, the event was widely reported as having a magnitude of about 8. Thus, its potential for generating a damaging teletsunami (ocean-crossing tsunami) was considered minimal.
The event's size later was shown to be approximately 10 times larger, but only after more than four and a half hours had passed, when a moment estimate based on 2.5 hours of data became available from Harvard University's Centroid-Moment Tensor (CMT) Project (M.Netties and G. Ekstrom, Quick CMT of the 2004 Sumatra-Andaman Islands earthquake, Seismoware FID: BR345, e-mailed announcement, 26 December 2004). This estimate placed its magnitude at Mw ≈9.0, in the range capable of generating a damaging teletsunami. Actually, the earthquake had caused a teletsunami, one that by that time had already killed more than a hundred thousand people. The magnitude estimate has been subsequently revised to at least 9.3 (Stein and Okal, http://www.earth.northwestern.edu/people/∼seth/research/sumatra.html), with the exact magnitude of the event likely to be a subject of further research in the coming years.