Physical characteristics of subduction-type seismogenic zones revisited

Based on both the Centennial earthquake catalog, the revised 1964-2007 EHB hypocenters and the 1976-2007 CMT Harvard catalog, we have extracted the hypocenters, nodal planes and seismic moments of worldwide subduction earthquakes for the period 1900-2007. For the period 1976-2007, we use the focal solutions provided by Harvard and the revised hypocenters from Engdahl et al. (1998). Older events are extracted from the Centennial catalogue (Engdahl and Villasenor, 2002) and they are used for the estimate of the cumulated seismic moment only. The criteria used to select the subduction earthquakes are similar to those used by Mc Caffrey (1994), i.e., we test if the focal mechanisms are consistent with 1/ shallow thrust events (positive slips, at least one nodal plane get dip < 45° and depth > 70 km), and, 2/ the plate interface local geometry and orientation (one nodal plane is oriented toward the volcanic arc, the azimut of this nodal plane is ± 45° with respect to the trench one, its dip is ± 20° with respect to the slab one and the epicenter is located seaward of the volcanic arc). Our study concerns segments of subduction zones that fit with estimated paleoruptures associated with major events (M > 8). We assume that the seismogenic zone coincides with the distribution of 5.5 < M < 7 subduction earthquakes. We then provide a map of the seismogenic zone for 36% of the oceanic subduction plates boundaries including dip, length, downdip and updip limits. The remnant 64% correspond to either weakly coupled oceanic subduction zones, slow subduction rates, or long recurrence period between earthquakes. We then revisit the statistical study done by Pacheco et al. (1993) and tested some empirical laws obtained for example by Kanamori (1986) in light of a more complete, more detailed, more accurate and more uniform description of the subduction interplate seismogenic zone. Since the subduction earthquakes result from stress accumulation along the interplate and that stress depends on plates kinematics, subduction zone geometry, thermal state and seismic coupling, we aim to isolate some correlations between parameters.