HR: 16:45h
AN: S42I-04    [PDF]
TI: Inverse Modeling of Surface Deformation Data to Determine the Depth of Coupling at the Cascadia Subduction Zone
AU: * Verdonck, D
EM: dverdonck@eglab.org
AF: Eastern Geodynamics Lab, 60 Larchmont Road, Elmira, NY 14905
AB: Understanding the extent of seismic coupling along the Cascadia subduction zone is important in assessing earthquake hazards in the Pacific Northwest of the United States and southwestern Canada. Recently developed models suggest that surface deformation can be the result of seismic coupling deeper on the subduction interface than previously accepted models indicate. Models also indicate that the depth of coupling varies along the strike of the subduction zone. I use a two-dimensional, non-negative, least squares technique to model vertical and horizontal deformation data simultaneously. The inversion is based on a standard dislocation model, where the subduction interface is divided into small fault segments. The amount of slip deficit on each segment is determined by the inversion. In this study, horizontal surface deformation rates, derived from GPS data, are combined with surface uplift rates determined from historic leveling surveys. Adjustments to the leveling data are also calculated during the inversion. The data from two parallel profiles are inverted separately generating two independent models. The northern model, running through the southern Puget Sound region, indicates slip deficit is accumulating in two separate locations. A shallow locked region extends eastward from the toe of the wedge to beneath the coastline and a second distinct region is located down dip beneath the Puget Sound. The southern model, at the latitude of the Columbia River, indicates slip-deficit is only accumulating in a single shallow region.
DE: 7223 Seismic hazard assessment and prediction
DE: 7230 Seismicity and seismotectonics
DE: 8123 Dynamics, seismotectonics
SC: Seismology [S]
MN: 2003 Fall Meeting