Teleseismic Shear-Wave Splitting
|
|
Though subduction has long been explored as a kinematic
phenomenon, our understanding is still incomplete. We have an even more limited understanding of subduction dynamics. Subduction kinematics and dynamics has largely been explored with numerical modeling, and validation of existing subduction models still needs to be made with new data. Mantle flow patterns interpreted from seismic anisotropy can serve as such a validation. In my thesis work, I have been using data collected in 2000-2002 as a part of the CHARGE (Chile Argentina Geophysical Experiment) Passcal seismic deployment to analyze shear-wave splitting from both teleseismic and local s-waves. I am using these measurements to determine seismic fast direction both above and below the subducting slab in the South American subduction zone of Chile and Argentina, and from these observations, infer mantle strain and potential patterns of mantle flow. The station distribution in our study is such that we can see a change in seismic fast direction over several measurements across a slab-dip transition: the subducting slab dip changes along strike, from nearly flat in the north to normally- dipping in the southern part of our field area. The most important result so far is a correlation of seismic fast direction with slab geometry both above and below the slab. This observation demonstrates that the change in slab dip is likely affecting either mantle rheology, strain pattern, or both and therefore affecting mantle flow in a direction not parallel to either the direction of slab dip or strike of the trench. Such 3-D mantle flow, rheology, and dynamics could affect the path and nature of fluid fluxes through the mantle wedge, interaction of asthenospheric flow below the slab with deeper patterns of mantle convection, and the nature of deformation of the overriding crust through its interaction with flow (or lack of flow) in the mantle wedge. |
|
Publications and Recent Abstracts Anderson, M. L., Zandt, G., Triep, E., Fouch, M., Beck, S., 2004, Anisotropy and mantle flow in the Chile-Argentina
Anderson, M. L., Zandt, G., Triep, E., 2004, Mantle flow in the Chile-Argentina flat slab subduction zone from seismic
|
Last Updated: 01/2005