Investigation of Surface Deformation at Subduction Zones using a Finite Plate Model

Rensselaer Polytechnic Institute, Troy NY

Investigators

Abstract

Williams 0106798 Surface deformation at subduction zones is generally interpreted in terms of movement on the thrust boundary between the subducting slab and the overriding plate. Elastic half-space dislocation (EHSD) models are frequently used to infer a slip distribution on the fault from surface geodetic observations and seismic hazard is evaluated in terms of which portions of the fault are fully or partially locked. These models are appealing because of their simplicity, but the assumption that all surface deformation is due to movement on a fault embedded in a homogeneous elastic half-space leads to some unrealistic behavior. Rather than considering the entire system, this project will consider only the portion of the overriding plate that behaves elastically over the time period of interest. Surface deformation occurs as a result of stress changes or rates applied along the thrust fault boundary and along the base of a finite elastic region (the overriding plate). This approach offers a more promising means of understanding the physics of subduction zones and makes fewer implicit assumptions than do EHSD models. Inversion results using this method will be compared and contrasted with those using EHSD models. The investigators will initially examine the Cascadia subduction zone in Oregon and Washington, and the Kenai Peninsula in Alaska. Additional study areas will include Japan, Sumatra, the Himalayas, and New Zealand. The results of this study should have important implications in fault friction studies and earthquake hazard research, and in understanding plate driving and resistive forces.