Geometric Controls on Megathrust Earthquakes

Session: Earthquake Source Parameters: Theory, Observations and Interpretations [Poster]
Type: Poster
Date: 4/30/2020
Time: 08:00 AM
Room: Ballroom
Description: 

The role of subduction zone geometry in the nucleation and propagation of great-sized earthquake ruptures is an important topic for earthquake hazard, since it is of fundamental importance for hazard models to know how big an earthquake on a given fault can be. Past studies have shown subducting bathymetric features may help arrest a propagating rupture. Other studies have correlated the occurrence of great-sized earthquakes with flat megathrusts and homogenous stresses over large distances. It remains unclear, however, how subduction zone geometry and the potential for great-sized earthquake rupture are quantifiably linked - or indeed whether they can be. Here we examine the potential role of subduction zone geometry in limiting earthquake rupture by mapping out the planarity of seismogenic zones in the Slab2 subduction zone geometry database. We build from the observation that historic great-sized earthquakes have preferentially occurred where the surrounding megathrust is broadly planar and use this relationship to search for geometrically similar features elsewhere in subduction zones worldwide. If a seismogenic zone is flat enough over a large enough area, we assume it is capable of hosting a great-sized earthquake; in this way, we can estimate how large an earthquake a given megathrust can host. We show that it is possible, based on slab curvature alone, for most subduction zones to host great-sized earthquakes over much of their area. Many bathymetric features previously identified as barriers are indistinguishable from the surrounding megathrust from the perspective of slab curvature, meaning that they either do not play an important role in arresting earthquake rupture, or that their influence on slab geometry at depth is not resolvable at the spatial scale of our subduction zone geometry models.

Presenting Author: Gavin P. Hayes

Authors