Evidence for different scaling of earthquake source parameters for large earthquakes depending on faulting mechanism

Scaling relationships between seismic moment, rupture length, and rupture w idth have been examined. For this purpose, the data from several previous s tudies have been merged into a database containing more than 550 events. Fo r large earthquakes, a dependence of scaling on faulting mechanism has been found. Whereas small and large dip-slip earthquakes scale in the same way, the self-similarity of earthquakes breaks down for large strike-slip event s. Furthermore, no significant differences in scaling could be found betwee n normal and reverse earthquakes and between earthquakes from different reg ions. Since the thickness of the seismogenic layer limits fault widths, mos t strike-slip earthquakes are limited to rupture widths of between 15 and 3 0 km while the rupture length is not limited. The aspect ratio of dip-slip earthquakes is similar for all earthquake sizes. Hence, the limitation in r upture width seems to control the maximum possible rupture length for these events. The different behaviour of strike-slip and dip-slip earthquakes ca n be explained by rupture dynamics and geological fault growth. If faults a re segmented, with the thickness of the seismogenic layer controlling the l ength of each segment, strike-slip earthquakes might rupture connected segm ents more easily than dip-slip events, and thus could produce longer ruptur es than dip-slip events of the same width.