Decade-scale decrease inb value prior to the M9-class 2011 Tohoku and 2004 Sumatra quakes
Article first published online: 18 OCT 2012
©2012. American Geophysical Union. All Rights Reserved.
Geophysical Research Letters
Volume 39, Issue 20, 28 October 2012
How to Cite
2012), Decade-scale decrease in b value prior to the M9-class 2011 Tohoku and 2004 Sumatra quakes, Geophys. Res. Lett., 39, L20304, doi:10.1029/2012GL052997., , , and (
- Issue published online: 18 OCT 2012
- Article first published online: 18 OCT 2012
- Manuscript Accepted: 14 SEP 2012
- Manuscript Revised: 13 SEP 2012
- Manuscript Received: 4 JUL 2012
- 2011 M9 Tohoku earthquake;
- b value;
- data analysis;
 The Gutenberg-Richter frequency-magnitude distribution of earthquakes has become well established in seismology. The slope of the relation between frequency and magnitude (b value) is typically 1, but it often shows variations around 1. Based on an analysis of seismicity prior to the 2011 Tohoku and 2004 Sumatra earthquakes (both in magnitude (M) 9 class), we show that the pronounced decade-scale decrease inbvalue was a common precursor to both mega-quakes around their hypocenters. This is the first report onM9-class quakes to confirm a change inb value, which has been predicted based on the results of laboratory experiments. We propose that the b value is an important indicator of an impending great earthquake, and has great potential in terms of predicting a future large quake off the Pacific coast of Hokkaido, Japan.