Stress drop as a criterion to differentiate subduction zones where Mw 9 earthquakes can occur

I propose a hypothesis that might be used to differentiate zones that produce M-w >=, 9 earthquakes from zones that do not. I calculate stress drop (Delta sigma) values, for M-w >= 7 thrust-type earthquakes over worldwide subduction zones, compiling the studies that obtained well-constrained slip distributions by inverting seismic, geodetic or tsunami data. Earthquakes are grouped into class 1: M-w >= 9 earthquakes, class 2: M-w < 9 earthquakes in a subduction zone segment in which at least one M-w >= 9 earthquake has occurred, and class 3: earthquakes in a subduction zone segment in which no M-w >= 9 earthquake has occurred. A total of 53 earthquakes are analyzed. The average stress drop (<(Delta sigma)over tilde>) values of the class I, 2, and 3 events are 4.6, 3.4 and 1.6 MPa, respectively. In individual subduction zones, (Delta sigma) over bar values of the class 2 events are by more than twice greater than those of the class 3 events, except Kuril-Hokkaido. Based on these results, I propose a hypothesis that if (Delta sigma) over bar is greater than 3 MPa in a subduction zone segment, this segment possibly produces M-w >= 9 earthquakes, and if (Delta sigma) over bar is less than 2 MPa, the segment would not produce Mw >= 9 earthquakes. I examine the fault parameters obtained in this study based on the newly derived scaling relations that take into account the variation in Delta sigma. The rupture of subduction zone earthquakes, from M-w >= 9 through M-w similar to 7, can be understood on the basis of the same scale-invariant physics, if M-o. is normalized by Delta sigma(1.5) in the scaling relation between L and M-o. Using this relation, I estimate the maximum magnitude of an earthquake which may rupture the entire Nankai-Suruga Trough off SW Japan, and obtain M-w = 8.6-8.4. (C) 2014 Elsevier B.V. All rights reserved.