Although subduction zones present significant seismic and volcanic hazards to an increasing number of population centers, the drivers and causes of faulting and permanent deformation in subduction zone forearcs remain an outstanding question. In this talk, I will begin by presenting results from lidar topography, structural-geomorphic mapping, and paleoseismic trenching to reveal evidence for a new Quaternary-active fault network in the forearc of the northern Cascadia subduction zone on Vancouver Island. Using compiled GNSS, geologic, and paleomagnetic data, I will argue that these faults accommodate active oroclinal bending of the entire Cascadia margin due to along-strike changes in subduction zone obliquity and local slab geometry. I will suggest that this oroclinal bending is related to the broad concave-outboard trench geometry observed across the Cascadia and Southern America subduction zones. Finally, I will discuss how emerging results from a global compilation of forearc faults suggest subduction zone obliquity may play a key first-order role in forearc rotation and the kinematics of forearc faulting across the world’s subduction zones. 

For the zoom information; please contact Rey Garduño (rgarduno@stanford.edu)