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Plume-Slab Interaction beneath Western US
Mathias Obrebski (UC Berkeley), Richard Allen (UC Berkeley), Mei Xue (Tongji University), Shu-Huei Hung (National
Taiwan University)
Using the Earthscope Transportable Array, Flexible Arrays in Cascadia, and regional seismic networks, we have constructed
3D P- and S-velocity models for the mantle structure beneath the western US. The DNA09-P and –S models use teleseismic
body-wave traveltime measurements that have been cross-correlated at a range of frequencies for relative arrival times and them
inverted for velocity structure using finite-frequency sensitivity kernels. The independent P- and S-velocity models show good
agreement in the structures imaged. The figure illustrates some of the more interesting features in the region. Panel (a) maps the
structures at 200 km depth and clearly shows the subducting Juan de Fuca slab high velocity anomaly (JdF) and the Yellowstone-
Snake River Plain low-velocity anomaly (YS). The three west-to-east cross-sections illustrate the variable nature of the subducting
slab. At its southern end (C-C’) the slab anomaly is strong, but at the latitude of Oregon it becomes weaker and shallower.
Further east a strong low-velocity anomaly is imaged beneath Yellowstone that can be tracked from the Caldera to the base of
model resolution at ~1000km depth. This is interpreted as the Yellowstone plume responsible for the hotspot rack at the surface.
Panel (e) shows a 3D view of the subducting slab (JdF) and the low-velocity Yellowstone anomaly. The DNA models are available
at http://dna.berkeley.edu.
References
Obrebski, M., R.M. Allen, M. Xue, S.-H. Hung, Slab-plume interaction beneath the Pacific Northwest, Geophys. Res. Lett., 37,
doi:10.1029/2010GL043489, 2010.
Acknowledgements: This work was funded by NSF EAR-0745934 and EAR-0643077. The work was facilitated by the IRIS-PASSCAL program
through the loan of seismic equipment, USArray for providing data and the IRIS-DMS for delivering it.
Figure. Slices through the DNA09-P velocity model. See text for description.
II-220 | 2010 IRIS Core Programs Proposal | Volume II | Upper Mantle Structure and Dynamics