A geometric frequency-magnitude scaling transition: Measuring b=1.5 for large earthquakes

We identify two distinct scaling regimes in the frequency-magnitude distribution of global earthquakes. Specifically, we measure the scaling exponent b=1.0 for "small" earthquakes with 5.5<m<7.6 and b = 1.5 for "large" earthquakes with 7.6<m<9.0. This transition at m(t)=7.6, can be explained by geometric constraints on the rupture. In conjunction with supporting literature, this corroborates theories in favor of fully self-similar and magnitude independent earthquake physics. We also show that the scaling behavior and abrupt transition between the scaling regimes imply that earthquake ruptures have compact shapes and smooth rupture-fronts. (C) 2012 Elsevier B.V. All rights reserved.