Publication Type:Journal Article
Source:Bulletin of the Seismological Society of America, Volume 102, Number 4, p.1693-1711 (2012)
Abstract:Wedges, such as accretionary prisms and thin-skinned fold-and-thrust belts, occur frequently in nature and can be the site of devastating earthquakes. Critical wedge theory can be applied to these settings, but this steady-state description of wedge deformation is at odds with the periodic occurrence of earthquakes. We discuss how critical wedge theory applies to the seismic cycle, and we use elastic wedge theory to constrain realistic stress states. Our goal is to determine the rupture behavior of an earthquake in a wedge. If rupture initiates on the basal sliding surface, will it stay confined to the basal surface, or will it propagate onto a fault branch interior to the wedge? This information can significantly alter the seismic hazard in areas where fault intersections occur. We answer this question using numerical models of dynamic rupture propagation through branched geometries for which the stress state is a pivotal input parameter. We apply wedge theory to constrain the stress state, but inherent to this theory is the assumption of a weak basal fault. We investigate the role of this assumption and determine that rupture is unlikely to propagate from a weak basal fault onto a strong branch fault without the aid of a physical process such as pore fluid migration along the branch. This framework is applied to the rupture of the 2008 Wenchuan earthquake. We find that we are able to reproduce the behavior at some fault intersections, but our 2D model is not able to reproduce all the behaviors, possibly due to the oblique nature of this event.
DeDontney, Nora Hubbard, Judith